Sound Therapy for Tinnitus Management: Practicable Options

Review

Sound Therapy for TinnitusManagement: PracticableOptionsDOI: 10.3766/jaaa.25.1.5

Derek J. Hoare*†

Grant D. Searchfield‡

Amr El Refaie§

James A. Henry**††

Abstract

Background: The authors reviewed practicable options of sound therapy for tinnitus, the evidence base

for each option, and the implications of each option for the patient and for clinical practice.

Purpose: To provide a general guide to selecting sound therapy options in clinical practice.

Intervention: Practicable sound therapy options.

Data Collection and Analysis:Where available, peer-reviewed empirical studies, conference proceedings,

and review studies were examined. Material relevant to the purpose was summarized in a narrative.

Results: The number of peer-reviewed publications pertaining to each sound therapy option reviewed

varied significantly (from none to over 10). Overall there is currently insufficient evidence to support orrefute the routine use of individual sound therapy options. It is likely, however, that sound therapy com-

bined with education and counseling is generally helpful to patients.

Conclusions: Clinicians need to be guided by the patient’s point of care, patient motivation and expect-

ations of sound therapy, and the acceptability of the intervention both in terms of the sound stimuli theyare to use and whether they are willing to use sound extensively or intermittently. Clinicians should also

clarify to patients the role sound therapy is expected to play in the management plan.

Key Words: Habituation, masking, neuromodulation, progressive management, residual inhibition

Abbreviations: EEG5 electroencephalography; MEG5magnetoencephalography; PTM5 Progressive

Tinnitus Management; RCT 5 randomized controlled trial; RI 5 residual inhibition; THI 5 TinnitusHandicap Inventory; TRT 5 Tinnitus Retraining Therapy

Theobservation that sounds can effect changes inthe nature or intrusiveness of tinnitus has a long

history. Indeed, the earliest recording of this

practice in the medico-scientific literature comes from

Jean-Marie Itard, a French writer who in 1821 notedin his medical textbook that running water or wood

crackling on the fire can help those suffering with tin-

nitus (Stephens, 2000). Fast-forward to 1976, and

*National Institute for Health Research (NIHR), Nottingham Hearing Biomedical Research Unit, University of Nottingham, Nottingham, UnitedKingdom; †Otology and Hearing Group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, United Kingdom;‡Section of Audiology and Centre for Brain Research, University of Auckland, New Zealand; §Human Communication Sciences, La Trobe University,Melbourne, Australia; **VA RR&D National Center for Rehabilitative Auditory Research (NCRAR), VA Medical Center, Portland, OR; ††Department ofOtolaryngology/Head and Neck Surgery, Oregon Health and Science University, Portland, OR

Dr. Derek Hoare, NIHR Nottingham Hearing Biomedical Research Unit, Ropewalk House, 113 The Ropewalk, Nottingham, UK, NG5 1DU;E-mail: [email protected]

Author D.J.H. is funded by the National Institute for Health Research (NIHR) Biomedical Research Unit Program. The views expressed are those ofthe authors and not necessarily those of the UK National Health Service, the NIHR, or the UK Department of Health.

Author D.J.H. is PI on the current clinical trial of CR Neuromodulation, referred to in this manuscript.

J Am Acad Audiol 25:62–75 (2014)

62

sound therapy devices were introduced on essentially

the same principal of distraction, turning total masking

with white noise into a clinical management technique

(Vernon, 1976).The founder of the “masking” method (J. Vernon)

described its purpose as rendering the tinnitus inaudible

with a more acceptable sound (Vernon, 1976, 1977). Soon

thereafter, combination instruments (combinationhearing

aid and masking device) became available, and “partial

masking” became an objective of treatment. Vernon

(1981) stated “masking that is incomplete can be never-

theless acceptable” (p. 17). He later noted that combina-tion instruments sometimes resulted in “only a partial

reduction in the tinnitus: it is still perceivable but in a

suppressed form” (Vernon, 1988) (p. 101). Vernon (1988)

reported that combination instruments were recom-

mended to 67% of his patients, while tinnitus maskers

were recommended to 21%. Thus, in the early years

of sound therapy using ear-level devices, combination

instruments were the preferred device, and partialmasking was most often the objective of treatment.

Further developments in the 1990s led to the con-

cept that, to promote “habituation” to the tinnitus,

therapeutic sound should be used “below the mixing

point,” that is, at a level low enough to maintain the

usual perception of the tinnitus (Jastreboff and Jastreboff,

2000). The term sound generator emerged to distinguish

devices used for partial masking/sound enrichment asopposed to maskers used for total masking. Unfortu-

nately, the termsmasker andmasking continue to be used

to refer to sound therapy in general.

Currently, sound therapy may refer to a specific

treatment approach or be used as a catch-all phrase

for the clinical use of sound.Even the term sound therapy

can lead to confusion. One recent review of sound ther-

apy (McKenna and Irwin, 2008) excluded maskingtherapy, while another (Hobson et al, 2010) included

masking (citing Mehlum et al, 1984; Hazell et al, 1985;

Vernon and Meikle, 2000; Henry et al, 2006) and sound

used to attempt tinnitus habituation (citing Jastreboff

and Hazell, 1993; Bauer and Brozoski, 2011). Sound

therapy is defined in the present review as any use

of sound where the intention is to alter the tinnitus

perception and/or the reactions to tinnitus in a clini-cally meaningful way.

Traditional approaches to tinnitus management

typically constitute a complex intervention involving

education and counseling, stress reduction and relaxa-

tion, and use of therapeutic sound, as in Tinnitus

Retraining Therapy (TRT; Jastreboff and Jastreboff,

2000) or other less protocol-driven habituation thera-

pies. The use of sound or sound enrichment is now coreto many tinnitus management programs, whether the

intention is to make tinnitus less noticeable, provide

immediate relief, promote control, promote habituation,

provide a distraction of attention, or promote plastic

change in the central auditory system (Newman and

Sandridge, 2012). But there is a great deal of debate

as to its usefulness and modes of effect of different

approaches (McKenna and Irwin, 2008; Hobson et al,2010). The purpose of this review is to provide clinicians

with a general guide to using sound in tinnitusmanage-

ment and so to inform decisionmaking for effective indi-

vidualized patient care. Appreciating that hearing aids

(with or without a sound generator component) are a

current mainstay of the audiological management of

tinnitus and indicated for the management of hearing

loss in any case, this review has more focus on recentlydeveloped device technologies and all published reports

relating to these devices. The evidence base for different

sound-based interventions, factors that may influence

success or failure, and potential neurophysiological bases

are discussed.

PUTATIVE MECHANISMS OF TINNITUS

AMENABLE TO SOUND THERAPY

Current consensus is that damage to the afferent

input to the auditory pathway initiates events that

result in plastic changes at the central level giving rise

to the percept of tinnitus (Norena, 2011). Models of

these plastic changes describe changes in specificity

or functional organization of the auditory nerve fibers

and central auditory neurons, or hyperactivity withincreases in cortical neural synchrony, or increases in

central gain. These models account for the percept of

tinnitus (hearing the tinnitus sound) but do not account

for the reactions to tinnitus, which can include psycho-

logical effects including anxiety, depression, and insom-

nia, which impair quality of life (Langguth, 2011).

Cortical and Tonotopic Reorganization

The reorganizational model of tinnitus generation

proposes that as peripheral hearing loss deprives

central auditory neurons of their normal input, the

deprived neurons begin to show responsiveness to the

characteristic frequency of neighboring neurons that

have retained their original place in the tonotopic

map (for a review see Eggermont and Roberts, 2004).This process may involve either neuronal rewiring or

be the result of unmasking or disinhibition of latent

cochlear inputs to those regions newly deprived of direct

inputs. The resulting overrepresentation of certain

characteristic frequencies, all of which will show spon-

taneous activity, is proposed as amechanism of tinnitus

generation. Inducing reorganization is therefore a

potential mechanism for reducing overrepresentationand interrupting tinnitus. Long-term exposure to a

spectrally enhanced acoustic environment was observed

to induce tonotopic map reorganization in juvenile cat

auditory cortex, without inducing hearing loss (Norena

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Tinnitus Sound Therapy/Hoare et al

et al, 2006), and compensatory sound enrichment can

interrupt the tonotopic cortical changes normally asso-

ciated with noise-induced hearing loss (Norena and

Eggermont, 2005). Extensive tonotopic reorganization asa result of auditory perceptual learning for pure tones

has also been reported in the animal literature (Recanzone

et al, 1993). There are currently no commercial sound ther-

apy devices that explicitly target this mechanism of tinni-

tus, although behavioral data from Moffat et al (2009)

show a change in the low-frequency components of tinni-

tus after hearing-aid fitting, suggestive of some level of

reorganization at the cortical level.

Hyperactivity, Neural Synchrony, Increased

Central Gain

As well as functional reorganization, hearing loss has

been shown to significantly increase spontaneous neuro-

nal activity at various points in the auditory pathway, to

increase evoked responses in the hearing brain, and toincrease synchrony in auditory cortex (Norena, 2011).

Overall hyperactivity could result from increases in cen-

tral gain where the central system is trying to stabilize

mean firing in response to reduced afferent input

(Norena, 2011). Tinnitus has been linked to decreased

oscillatory brain rhythm activity in the alpha band (8–13

Hz) and increased activity in the delta band (1.5–4 Hz)

and the gamma band (e.g., 25–80 Hz) (Weisz et al, 2007;Adjamian et al, 2012). Gamma activity in particular has

been associated with synchronization of neural firing both

within and between neural ensembles (Gray et al, 1989,

Singer, 1999), and from a clinical perspective, enhanced

neuronal activity in the gamma frequency range in the

resting state has been linked to symptoms in tinnitus

and other neuropsychiatric disorders (Llinas et al, 1999).

Sound therapy devices that reputedly target thebreakdown of neural hyperactivity or pathological syn-

chronous activity are reviewed further below.

Emotional Disturbance

The mechanisms of emotional disturbance associated

with tinnitus define the “reaction” to hearing the tinni-

tus sound, as opposed to the “perception” of the sound.Recent models propose a role for the emotional centers

of the brain in tinnitus maintenance. The presence of a

salient signal out of context creates focus and com-

mands attentional resources feeding into nonsensory

cognitive processes that are strongly associated with

tinnitus distress (De Ridder et al, 2011). This process

should be influenced by sound therapy if it trains atten-

tion and the new auditory activity introduced by thesound therapy becomes the focal stimulus forcing tinni-

tus to become a background sound (Searchfield et al, 2012).

Electroencephalography (EEG) measures of resting-

state oscillatory electrical activity in the tinnitus brain

suggest that there is enhanced activity in the amyg-

dala (Vanneste et al, 2010). However, there is mixed

anatomical evidence to suggest a difference in the

brain of those with and without tinnitus. While somestudies report differences in graymatter in the emotional

centers (subcallosal area) between those with tinni-

tus and those without it (e.g., Muhlau et al, 2006),

Melcher et al (2013) demonstrated that this effect

could be due to differences in hearing thresholds between

subjects, irrespective of thepresence or absence of tinnitus.

Emotional disturbance generally refers to the “stress

response,” which is a constellation of physiologicalevents that occurs in response to some stress-inducing

stimulus (Iversen et al, 2000). The use ofmusic has been

shown in numerous studies to reduce the stress of

patients in clinical settings (Salamon et al, 2003).

Relaxing music lowers blood pressure, reduces heart

rate, and creates a sense of well-being (Steelman,

1990; Krumhansl, 1997). The mechanisms underlying

these effects have been extensively studied (Chrousosand Gold, 1992). Physiological and behavioral reactions

to tinnitus can be mitigated through the use of music.

More generally, any sound that is perceived as relaxing

can reduce stress; thus, sound therapy targeting the

relaxation response can be an important component

of any tinnitus management program (Henry, Zaugg,

Myers, Schechter, 2008).

PUTATIVE EFFECTS OF SOUND ON TINNITUS

PERCEPTION AND REACTION

Many types of sound (generation of noise, environ-

mental sounds, music, or the amplification of nat-

urally occurring sounds by hearing aids) have been

applied to the task of tinnitus treatment (Jastreboff,

2007a; Henry, Zaugg, Myers, Schechter, 2008). Soundtherapy has been proposed to exert its benefits through

tinnitus masking by reducing audibility (Vernon, 1977)

or by inducing a sense of relief (Vernon and Meikle,

2000), through habituation (Jastreboff and Hazell,

1993), by reversing abnormal cortical reorganization

or activity thought to contribute to tinnitus (Norena

and Eggermont, 2005; Tass et al, 2012), or through

the promotion of relaxation (Sweetow and Sabes, 2010).

Masking

In psychoacoustic terms, masking can be categorized

as either “energetic” or “informational” (Bennett et al,

2012). With energetic masking, interference of auditory

signals takes place within the cochlea, resulting in

suppression of the resultant neural activity. Whereasenergetic masking can be thought of as a “bottom-up”

peripheral process, informational masking is more of

a “top-down” central process. Specific psychoacoustic

protocols have been developed to test informational

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Journal of the American Academy of Audiology/Volume 25, Number 1, 2014

masking (e.g., Kidd et al, 1994; Durlach et al, 2003,

Richards and Neff, 2004), but for our purposes we

can consider it to be a process of neural interference

that occurs at more central levels.A great deal has been written about the speculated

mechanisms of tinnitusmasking, starting with the semi-

nal paper by Feldmann (1971), who described data sup-

porting a retrocochlear origin of the tinnitus signal.

Indeed, the prevailing view has been that tinnitus has

a central origin. This view has been challenged, however,

by alternative explanations that tinnitus canbe generated

in the cochlea or auditory nerve (Penner and Bilger, 1995;Nouvian et al, 2012). Until the physiological origin(s) of

tinnitus are confirmed,wemust rely on phenomenological

data to generate reasonable hypotheses upon which to

base rational therapies involving sound.

In practical terms, “total” tinnitus masking involves

the use of sufficient external sound to make tinnitus

inaudible. “Partial” masking is the interference of the

perception of tinnitus through sound where both thetinnitus and masker sound are audible at the same

time. Masking for any given individual or clinician

may range across a signal (tinnitus) to noise (sound

therapy) continuum from the minimum effective level

to total masking (Tyler, 2006). Masking is sometimes

thought of as a relief therapy (Henry et al, 2006), pro-

viding a sense of relief from stress or anxiety caused by

tinnitus. It should be emphasized that the primary pur-pose of Vernon’s method of “tinnitus masking” is to

induce a sense of relief (Vernon andMeikle, 2000), with

the actual effect on the perception of tinnitus usually

being partial masking.

In a Cochrane review, Hobson et al (2010) evaluated

the effectiveness of sound-generating devices for man-

aging tinnitus. These authors used the terms sound

therapy and masking interchangeably, thus any refer-ence to masking did not imply total masking. The

review identified six randomized controlled trials

(RCTs) that met their inclusion criteria, three of which

(Mehlum et al, 1984; Hazell et al, 1985; Henry et al,

2006) included sound in a masking manner (the other

studies used a TRT-like approach or the Neuromonics

treatment, both discussed later). Only one study (Hazell

et al, 1985) compared the effect of masking to a no-sound control, finding that a reduction in the effects

of tinnitus on sleep and overall quality of life was

greater for those who used maskers (ear-level sound

generators). It was concluded that masking/sound ther-

apy was a useful approach, but it was acknowledged

that counseling was important to overall therapy suc-

cess (Hazell et al, 1985).

One potential outcome of high-intensity masking isresidual inhibition (RI), a partial or total suppression

of tinnitus typically lasting seconds to minutes follow-

ing the presentation of relatively intense sound (Roberts

et al, 2006). RI has been used clinically as an aid for

counseling and to demonstrate that broadband noise

can impart a beneficial effect (Vernon and Meikle,

2000). The finding that RI occurs with most patients

who receive the appropriate type of auditory stimula-tion (Vernon, 1981, 1988; Tyler et al, 1983; Meikle

andWalsh, 1984) makes it surprising that this phenom-

enon has received little investigation with regard to

specific parameters of acoustic stimuli that are respon-

sible for its occurrence. At least one company (Tipa

Tinnitus Corporation) is marketing a device that is

claimed to produce prolonged RI (reviewed further

below). Recent magnetoencephalography (MEG) datafrom Adjamian et al (2012) further suggests that there

is a physiological effect of tinnitus masking: they

reported a reduction in delta band activity when partic-

ipants experienced tinnitus masking, demonstrating a

possible neuronal marker for the effect of masking.

Habituation

A decline in the reactions to and the perception of tin-

nitus over time is often described as being the result of

habituation (McKenna, 2004). Habituation is the basis

of common tinnitus treatment methods used in psychol-

ogy (Hallam et al, 1984) and audiology (Jastreboff and

Hazell, 1993).

The original habituation model of tinnitus was based

on the hypothesis that most people naturally habituateto tinnitus, that is, they come to classify tinnitus as a

meaningless sound, and their negative reactions to tin-

nitus consequently decline with time (Hallam et al,

1984). According to this model, people with chronic

intrusive tinnitus are those who fail to habituate.

The most established and protocol-driven tinnitus

management strategy to promote habituation is

TRT (Jastreboff and Hazell, 1993). TRT aims to facil-itate habituation of reaction to tinnitus, primarily

through counseling, and habituation of perception

through use of sound.

All TRT patients are advised to continuously “enrich

their sound environment” with low-level, relatively

benign sound, thus creating a constant “passive listening”

environment that promotes habituation (Jastreboff and

Hazell, 2004). Patients with more severe tinnitus areadvised to wear ear-level sound generators during all

waking hours to optimize the sound therapy protocol.

An important concept relevant to sound therapy with

TRT is that the external sound should always be per-

ceived “below the mixing point.” The rationale for this

requirement is that habituation is stimulus specific

(Thompson and Donegan, 1987). Sound therapy below

the mixing point means that the external sound doesnot alter the tinnitus percept; that is, the spectral char-

acteristics of the tinnitus percept should not be altered

so that habituation can take place to the “usual tinni-

tus” (Jastreboff and Hazell, 2004).

65

Tinnitus Sound Therapy/Hoare et al

Trials of TRT suggest benefits but have been

criticized for the difficulties disassociating sound stim-

ulation effects from counseling effects (McKenna and

Irwin, 2008). A controlled study comparing TRT and“tinnitus masking” showed that both methods could

provide significant benefit to a large majority of individ-

uals with severely bothersome tinnitus (Henry et al,

2006). TRT, however, achieved greater benefit in the

long term, and patients with more severe tinnitus

improvedmore with TRT. Amore recent RCT compared

classical TRT to counseling with a reduced sound compo-

nent (Bauer and Brozoski, 2011). Although tinnitushandicap progressively improved for both the placebo

and sound therapy groups over the 18 mo trial, at 18

mo the clinical effect size was greater for the group

receiving the full sound component of TRT. Psychoacous-

tic loudness did not change in this trial suggesting no

effect of the interventions on the neural activity respon-

sible for the tinnitus signal (Bauer and Brozoski, 2011).

Questions remain as to the effectiveness of differentcomponents of TRT. For example, the developers of TRT

stated that “If tinnitus is suppressed (“masked”) habitu-

ation will never occur” (Jastreboff and Hazell, 2004).

This claim was tested by Tyler et al (2012), who random-

ized subjects into three groups: total masking, TRT, and

counseling only. All three groups showed improvement

on a tinnitus outcome questionnaire, and there was no

significant difference between groups. The results of thisstudy call into question the premise that total masking

precludes habituation but do not definitively answer the

question due to limitations of the study (e.g., small group

design, hearing aid users excluded, no intent-to-treat

analysis) and the need to replicate these results. It is

imperative that well-designed, well-controlled studies

be conducted to answer basic questions about the optimal

use of sound as therapy for tinnitus.

Sound to Target Both Tinnitus Percept

and Reaction

There are conflicting accounts for the putative action

of many practicable sound therapy options as to whether

they target the tinnitus reaction to promote relaxation

and reduce stress or whether they are actually targetingneuromodulation through plastic change. The correla-

tion between habituation of reaction and habituation

of perception, and if achieving the first will lead to the

latter, was also an important concept arising from

Jastreboff’s (1990) neurophysiological model. Complex

tones or music have certainly been demonstrated to

modulate attention, emotion, cognition, behavior,

and communication and are consequently believedto have benefits for health (Koelsch, 2009; Attanasio

et al, 2012). And, as a tinnitus therapy, music has been

used both singularly (Argstatter et al, 2012) or as part of

a multifaceted intervention (Davis, 2006).

Music has been manipulated in an attempt to

enhance treatment by accounting for the frequency

spectrum of music relative to auditory threshold and

tinnitus, or to promote lateral inhibition between tinni-tus and nontinnitus areas of the auditory cortex (Davis,

2006; Okamoto et al, 2010). Okamoto et al (2010) modi-

fied music with a one-octave notch at the individual’s

tinnitus pitch. Music was used because of its emotional

and motivational benefit and was notched at the puta-

tive tinnitus frequency in an attempt to achieve lateral

inhibition and reverse maladaptive activity. In this

study, after 12 mo of daily listening, participants’ tinni-tus annoyance and handicap were reduced relative to a

placebo music (notch distant from tinnitus pitch) con-

trol group. MEG further indicated significantly reduced

auditory steady state andN1m responses in the notched

music group but not controls (Okamoto et al, 2010), pos-

sibly due to a reduced neural population and/or less syn-

chrony in response to tinnitus matched tones (Stracke

et al, 2010). More recently, Vanneste et al (2013) exam-ined the relative efficacy of listening to music that

either compensated for hearing loss, overcompensated

for hearing loss, or unmodified music, for 3 hr per day

over 1 mo. In this shorter study, there was no change

in visual analog scale scores for tinnitus annoyance

across the three groups. There was, however, an increase

in gammaband activity in the auditory cortex aftermusic

exposure for the group receiving the overcompensatedstimulus, suggesting that this form of modulated music

could actually worsen tinnitus-related brain activity.

CURRENT PRACTICABLE OPTIONS FOR

SOUND THERAPY

A summary of the options reviewed here and the

highest level of research evidence identified foreach option are given in Table 1.

Acoustic Coordinated Reset

(CR) Neuromodulation

This method was developed by Adaptive Neuromodu-

lation GmbH (ANM) (www.anm-medical.com/) and

explicitly targets pathological neural synchrony thatmay be responsible for tinnitus generation. Sound stimuli

are individualized to span a frequency range centered

on the dominant tinnitus pitch. Patients are required

to listen to sequences of tones presented at a low volume

over open-fit headphones for up to 8 hr daily. The pat-

tern of sound stimuli is predicted to force asynchronous

firing of neurons from within a pathologically firing

population through a reduction of mean synaptic weight(Hauptmann and Tass, 2007), an effect measurable

using EEG. Indeed, in their exploratory trial, Tass

et al (2012)measured EEG activity at baseline and again

after 12 weeks of Acoustic CR Neuromodulation

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Journal of the American Academy of Audiology/Volume 25, Number 1, 2014

treatment, most notably finding there to be an increase

in alpha band power (strongest in temporal and pre-

frontal cortex), a reduction in delta (strongest in auditorycortices), and a general reduction in gamma power after

treatment. Tass et al (2012) also reported clinically sig-

nificant improvements in tinnitus handicap (reduction

on the Goebel Hiller Tinnitus Questionnaire, GHTQ

score; Goebel and Hiller, 1994) after treatment. This trial

was exploratory, however, and so the efficacy of the

device has yet to be demonstrated. An independent

Phase 2 clinical trial is currently underway in the UK(clinicaltrials.gov identifier: NCT01541969).

SoundCure

The Serenade device was developed in the United

States by SoundCure Inc. (www.soundcure.com). The

device delivers programs of sounds, recently described

by the provider in an industry magazine as “corticallyinteresting,” that are designed to effect highly synchro-

nous cortical responses (Strom, 2012). This approach

stems from the work of Zeng et al (2011), who reported

a single-case study of electrical stimulation delivered by

a unilateral cochlear implant to relieve tinnitus. Zeng

et al (2011) found that whereas high-rate (2–5 kHz)

electrical stimulation had no effect on tinnitus, a 100

Hz electrical stimulation pulse delivered to an apicalelectrode provided total tinnitus suppression and led

to an increase in alpha band (7–9 Hz) power. More

recently, the same group examined tinnitus suppression

during and after exposure to a series of modulated

sounds at different modulation rates and carrier fre-

quencies, and unmodulated sounds at different carrierfrequencies (Reavis et al, 2012). A 40 Hz amplitude-

modulated tone with carrier frequencies near the tin-

nitus pitch generated the best tinnitus suppression (up

to total suppression during stimulation, with residual

inhibition lasting up to 90 sec after stimulation ended).

The Serenade device delivers two tracks of tempo-

rally patterned sounds (“S tones”) that are determined

according to the span of hearing loss and the dominanttinnitus pitch. It also delivers a customized narrowband

sound and a broadband sound. The manufacturer rec-

ommends its use on an “as needed” basis to gain relief,

for example, before going to bed. But whereas the sound

element of the intervention is considered to target the

neural activity associated with tinnitus, it is stressed

that the treatment process relies on counseling to

address the psychological reaction to tinnitus. The clin-ical effectiveness and neurophysiological effects of Ser-

enade have yet to be demonstrated.

Neuromonics

Neuromonics uses modified music that compensates

for hearing loss and provides less low-frequency bias

than unmodifiedmusic (www.neuromonics.com). Musicis delivered using a lightweight Oasis device with head-

phones in a two-stage process startingwith high tinnitus

interaction (total masking) for about 2 hr per day (stage

Table 1. Practicable Sound Options

Sound Device Putative Mechanism of Action Indications/Requirements Highest Supporting Evidence

Acoustic CR

Neuromodulation

Neuromodulation—disruption

of pathological neural

synchrony

41 hr daily over several months Safety of the device demonstrated

in an exploratory study

Serenade Relaxation, neuromodulation z1 hr per day for short-term relief,

e.g., to support sleep

No clinical trials or other evidence

identified

Oasis Relaxation 21 hr per day for 6 mo Clinical trials but of limited quality

Hearing Aids Masking, neuromodulation Aid a hearing loss, functional hearing

difficulties; to be worn maximally

during waking hours

Number of open trials and cohort

studies: inconclusive

Wearable White Noise

Generators

Masking, habituation Used variably to provide acute relief

or maximally during waking hours

as per therapy plan

Cochrane review of clinical trials:

inconclusive of effect of masking

independent of counseling

Combi-Devices: Hearing

Aid with White Noise

Generator

Masking, relaxation Hearing loss and tinnitus; devices to

be worn maximally throughout

waking hours

Low-level evidence of improvement

in tinnitus handicap for some

patients from one small-scale

cohort study

Phase-Out/Phase-Shift Noise cancellation 30 min sessions for short-lasting

relief repeated as required

Randomized double-blind crossover

study showed no specific effect

Tipa Tinnitus Device Extended residual inhibition 10 min sessions for short-term relief

repeated as required

No clinical trials identified

Table-Top Devices Relaxation Intermittent use for immediate relief

such as at night

No clinical trials identified

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Tinnitus Sound Therapy/Hoare et al

1), followed by a lower level of music in which the tin-

nitus is intermittently masked through the natural

dynamics (peaks and troughs) of the music (stage 2).

Considered from the perspective of an acoustic desensi-tization theory (Yulis et al, 1975), tinnitus creates a

negative “phobic-like” reaction in patients. The gradual

exposure of patients to their tinnitus in a controlled and

supportive manner (through counseling and relaxing

music) is claimed to lead to a decrease in reaction (Davis

et al, 2008), which is, in essence, a systematic desensi-

tization approach (Yulis et al, 1975).

Neuromonics has been the subject of a number of clin-ical investigation papers and reviews (Davis et al, 2007;

Davis et al, 2008; Hanley and Davis, 2008; Hanley et al,

2008; Henry, Zaugg, Myers, Schechter, 2008; Goddard

et al, 2009; Henry and Istvan, 2010; Jang et al, 2010;

Seidman et al, 2010; Tavora-Vieira et al, 2011; Wazen

et al, 2011). Most studies show there to be significant

improvements in tinnitus questionnaire scores occur-

ring across 6 to 24mo of therapy, particularly if patientsmeet the majority of the developer’s clinical selection

criteria (Davis et al, 2008). However, few studies used

a controlled comparison. Davis et al (2008) compared (a)

2 hr daily use of Neuromonics with (b) 2 hr daily use of

the device playing broadband noise at the mixing point

and (c) a no sound control. All groups received coun-

seling. In the Neuromonics group, 86% reported a clin-

ically significant improvement (40% reduction inTinnitus Reaction Questionnaire), and 47% met the

same criteria in the broadband noise group, while

23% in the no sound control group reported significantly

reduced tinnitus handicap (Davis et al, 2008). This

result suggests that the provision of the device and

the type of sound used influenced treatment outcome.

In a more recent retrospective between-subjects clinical

study, Newman and Sandridge (2012) compared thecost-effectiveness and cost utility of Neuromonics versus

ear-level sound generators. While both interventions

resulted in reduced tinnitus handicap score, there was

no difference in improvement between groups. Sound

generators, therefore, as the less expensiveoption, emerged

as the preferred choice in terms of cost-effectiveness and

utility.

General reviews ofNeuromonics trials also cast doubton our confidence in the published data. Henry and

Istvan (2010) were critical of the lack of methodological

rigor in the three controlled studies published at the

point of their review.

Potential physiological mechanisms affected by the

interventions have not been defined. However, one

aspect of auditory processing that may count against

the intermittent masking (stage 2) used by Neuromonicsis the ability of the auditory system to fill gaps, so-called

continuity or auditory restoration (Petkov and Sutter,

2011). Tinnitusmay appear continuous even if at certain

points in time the tinnitus is obscured. This continuity

effect may contribute to the need to maintain a higher

level ofmasking and limit or delay intermittentmasking.

Such effects require further study.

Hearing Aids

Hearing aids amplify external sounds, which reduces

the contrast between tinnitus perception and the exter-

nal sounds, thereby reducing the relative salience of tin-

nitus (McNeill et al, 2012). Alternatively, amplification

by hearing aids may simply help to refocus attention on

sounds that are different from the tinnitus sound. Hear-ing aids also improve communication (Surr et al, 1985;

Carmen and Uram, 2002), which alone may indirectly

lead to improved tinnitus self-report. It can also be

hypothesized that hearing aids act as a form of sound

enrichment, decreasing the possibility of sensory depri-

vation and thus decreasing neuroplastic changes within

the central auditory system that contribute to tinnitus

generation. Despite being recommended as a poten-tially useful intervention for tinnitus since the 1940s,

hearing aids have been the subject of many open trials

and cohort studies (beyond our scope but recently

reviewed by Shekhawat et al, 2013) but trials of hearing

aids for tinnitus have only recently been systematically

reviewed (Hoare et al, 2014). It is uncertain what benefit

from hearing aids results from a change in reactions to

tinnitus as opposed to improvement in hearing function.

Wearable White Noise Generators

A number of studies have explored the efficacy or rel-

ative efficacy of ear-level white noise generators (also

referred to as sound generators and maskers). In their

systematic review of masking for tinnitus, Hobson et al

(2010) reported that there was little current evidence toindicate the effectiveness of maskers. Indeed, sound

therapy usingmasking appeared to be nomore effective

than education or relaxation training (Dineen et al,

1999), the provision of hearing aids (Mehlum et al,

1984; Hazell et al, 1985), or a waiting list control (Goebel

et al, 1999). Where recorded, masking did not effect

changes in tinnitus quality (Dineen et al, 1999), suggest-

ing that the changes to occur during tinnitus maskingare likely habituations rather thanmodulation of the tin-

nitus generating activity. Hobson et al (2010) concluded

“the absence of conclusive evidence should not be inter-

preted as evidence of lack of effectiveness,” and “optimal

management may involve multiple strategies” (p. 2).

Combination Instruments—Examples

Widex Zen

The Widex Zen combines a hearing aid and sound

generator using an alternative to conventionally composed

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Journal of the American Academy of Audiology/Volume 25, Number 1, 2014

and performed music in the form of fractal “music” or

tones (www.widex.co.uk/en/products/thewidexsound/zen/).

A fractal is a mathematical algorithm that generates

a series of sounds, and, like music, fractal tones havebeen proposed to promote relaxation, which might in

turn have some benefits for persons with tinnitus. In

an industry magazine article Kuk et al (2010) reported

a survey of patients who had been fitted with the device

by clinicians with some training in tinnitus manage-

ment. Forty-three patients participated, but only 26

completed a tinnitus quality of life measure (the Tinni-

tus Reaction Questionnaire—TRQ; Wilson et al, 1991)both pre- and post-fitting. Of the 26 patients, 18 (69%)

had TRQ improvements of greater than 20 points. At

the same time, a research study from Sweetow and

Sabes (2010) monitored changes in Tinnitus Handicap

Inventory (THI; Newman et al 1996) questionnaire

score and TRQ score over a 6 mo period following the

fitting of the fractal combination aids to 14 participants.

Five participants (36%) had a 20-point THI improve-ment, and four (29%) had a 40% or greater TRQ

improvement at the 6 mo follow-up. The most widely

preferred fractal sounds in both studies were those with

slow-medium tempos and restricted dynamic range,

which were also found to be the most relaxing (Sweetow

and Sabes, 2010). It is difficult to ascertain from these

studies whether the fractal tones were beneficial

because of their relaxation effect or masking or theextent of benefit from concurrent background amplifica-

tion relative to the fractal sounds. No physiological mea-

sures have been undertaken toward identifying the

effect of fractals on putative tinnitus mechanisms.

Danalogic iFIT Tinnitus

The Danalogic iFIT Tinnitus is another example of a

combination instrument. This device offers sound gen-

erator options of broadband signals, a narrowband sig-

nal focused on the frequency of the tinnitus, and the

option of using amplitude modulation (AM; fluctuationin the level of noise signal while all other spectral com-

ponents remain uniform). The stated purpose from the

company is to provide options to personalize the sounds

to those preferred or most acceptable to the individual

(www.danalogic-ifit.com).

ReSound Live TS

ReSound Live TS is another combination instrument

providing options for the use of broadband or narrow-

band noise, with additional options for amplitude mod-

ulation and environmental steering (www.gnresound.

com). The suggested mechanism of action is the diver-sion of attention away from tinnitus, thereby promoting

habituation. AM and the speed at which AM fluctua-

tions occur are used as “comfort settings.” The Environ-

mental Steering option allows automatic volume

control and has seven different environmental settings,

negating the need to manually adjust the device when

moving between different noise and listening environ-ments. Piskosz and Kulkarni (2010) provided an indus-

try magazine report on two studies using the Live TS in

combination with counseling over a 6 mo period. Study

A was a cohort study that found significant improve-

ment in tinnitus handicap (mean reduction in THI score

of 20 points) at the end of the 6mo. StudyB looked at the

preferences for broadband or narrowband sound, the

environmental steering feature versus volume control,and AM versus continuous noise. In their sample of

24 patients, 82% preferred the broadband noise option,

68% preferred the volume control feature over Environ-

mental Steering, and 73% preferred unmodulated sound

to AM sounds.

Summary of Combination Instruments

Combination instruments have been available since

the 1980s. Until fairly recently, however, these devices

tended to provide limited hearing aid options and/or

quality. Within the past few years, most major hearing

aid companies have developed combination instru-

ments that offer full-featured hearing aids. Some of

these are described above. Other combination instru-

ments currently available include devices producedby Starkey (Xino Tinnitus) and Siemens (Life and Pure

Carat). Although data are not definitive, the addition of

noise or other sounds to hearing aids seems to benefit

many patients with tinnitus. Provided there is no sac-

rifice to the amplification needs of the patient, fitting

combination instruments rather than hearing aids

may be the preferred option when reactions to tinnitus

are a concern. These instruments, without amplifica-tion, can also be employed in the management of tinni-

tus for people with normal hearing.

Phase-Shift and Phase-Out

Phase-Out therapy is based on the principle of noise-

cancellation; Choy et al (2010) hypothesized that if a

sound was pitch and volume matched to tinnitus, andthen phase shifted sequentially by 6° at intervals of

30 sec (i.e., 360° over a 30 min intervention), the neuro-

nal complex in the auditory cortex responsible for that

tinnitus tone would be cancelled at least temporarily.

However, in a large population study, Choy et al

(2010) found that only 1% of patients had what was

defined as a long-term total resolution of their tinnitus.

Various lesser reductions were reported, but with thelack of appropriate control data, spontaneous improve-

ments in tinnitus or placebo effects are not accounted

for. In an earlier open prospective clinical trial of Phase-

Out, Vermeire et al (2007) reported a mean improvement

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Tinnitus Sound Therapy/Hoare et al

of 5.5 points on the Tinnitus Questionnaire (TQ;

Hallam, 1996; minimum clinically important difference

is 5 points). Although clinically significant, a shift of

5 points has been reported elsewhere as a test-retesteffect in tinnitus studies (Dohrmann et al, 2007), so

we can have little confidence in the estimate of the

effect.

Phase-shift is another device based on the same prin-

ciple of noise cancellation. Produced by Tinnitus Care

(London), this device delivers a stimulus that is of

the same amplitude and frequency as the tinnitus

sound butwith an inverted phase. The stimulus is deliv-ered over a 30 min session. Lipman and Lipman (2007)

reported the results of 61 participants who underwent 2

wk of phase-shift treatment. One in five reported a clin-

ically significant reduction in THI score (20 points or

more). Most participants reported a reduction in tinni-

tus loudness induced by the stimulus (41% had com-

plete residual inhibition for some period). Tinnitus

loudness increased for 22% of participants. While thisresult looks more promising than that for Phase-Out,

when the use of the inverted phase tone was compared

to noninverted phase tone in a randomized double-blind

crossover study, therewas no difference in effect between

groups in terms of change in handicap questionnaire

score, tinnitus quality, or loudness or annoyance ratings

(Heijneman et al, 2012). So the effect of the phase-

inverted signal was no greater than its best control.The concept of noise cancellation with tinnitus war-

rants some comment. Noise cancellation headphones

available commercially are designed to detect a contin-

uous signal and to add the same signal but phase shifted

by 180°. Combining these two signals cancels the orig-

inal signal. This effect is limited to low-frequency

sounds such as the constant roar from inside an air-

plane. It is tempting to think that the same approachcould be used with tinnitus, which is also a continuous

signal. Tinnitus, however, is not an acoustic signal and

therefore does not have an acoustic phase. It is theoret-

ically impossible to cancel tinnitus through noise can-

cellation procedures. Any benefit from such devices

may be attributed to sound therapy effects in general

or to nonspecific effects.

Tipa Tinnitus Device

The Tipa Tinnitus Device reputedly works through

the induction of extended periods of residual inhibition

“probably through inhibitory pathways using digital

non sinusoidal low frequency sounds” (http://tipatinnitus.

com/). The system uses three different complex tones

each presented for 3 min and played in the order1,2,1,3 (12 min stimulus in total per day). Case studies

presented at conference by Winkler (2009) claim that

the signal can induce RI lasting many hours. Although

some anecdotal evidence of the effects are presented on

the Tipa Web site, the effect has yet to be tested in con-

trolled and peer-reviewed studies.

Non-Ear-Level Sound Options

Alternatives to ear-level devices in sound therapy

include sound therapy Web sites (e.g., beyondtinnitus.

com), the use of music from a speaker system, or the

use of bedside or table-top sound generators. Bedside

or table-top sound generators typically deliver a variety

of simple or natural sounds to choose from. Indeed,

Handscomb (2006) found that the choice of soundselected for use with bedside sound generators was influ-

enced more by emotional than sensory factors. Thera-

peutic sounds delivered in this way may elicit positive

responses due to positive memory associations (Henry

et al, 2004).

RECOMMENDATIONS FOR THE CLINICAL

MANAGEMENT OF TINNITUS USING SOUNDAS PART OF INDIVIDUALIZED,

MULTIDISCIPLINARY CARE

There are many different models of tinnitus man-

agement in use and under investigation worldwide

(Henry, Zaugg, Myers, Kendall, 2008; Department of

Health, 2009; Biesinger et al, 2010; Cima et al, 2012).

All of thesemodels advocate amultidisciplinary approach(Daugherty and Wazen, 2010). The introduction of sound

therapy to care therefore needs to follow a pragmatic line.

Is the Patient at the Right Stage of Care to

Introduce Sound Therapy?

For successful engagement with sound therapy, it is

essential that the patient is sufficiently informed oftheir sound therapy options, motivated to try sound

therapy, and has expressed realistic expectations

of the effects of the proposed therapy. Henry, Zaugg,

Myers, and Kendall (2008) describe a Progressive Tin-

nitus Management (PTM) approach using a hierar-

chical (stepped-care) program of triage, audiological

evaluation, skills education, interdisciplinary evalua-

tion, and individual patient management. Within thisprogram it is envisaged that the patient reaches auton-

omous decisions on their choice of sound therapy, for

example, whether soothing (to calm anxiety or nervous-

ness), background (for contrast reduction), or interesting

(to shift attention) sounds are going to be of benefit to

them in different situations. With PTM, the goal is for

patients to achieve self-efficacy in managing their reac-

tions to tinnitus. The skills education level of PTM isdesigned to provide patients with coping and sound ther-

apy skills. The philosophy with PTM is to provide these

skills at the earliest level of intervention so as to

empower patients with the ability to self-manage their

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Journal of the American Academy of Audiology/Volume 25, Number 1, 2014

tinnitus and tomake informed choices regarding specific

forms of treatment that might be available.

Tinnitus and reactions to tinnitus may be altered by

the specific sound chosen, which can have effects involv-ing different levels of processing: encoding (tinnitus

and sound interact such that tinnitus is totally sup-

pressed, i.e., energetic masking), central analysis (where

tinnitus and sound—distractor—are similar but distin-

guishable, i.e., informationalmasking),mood and arousal

(e.g., music), and psychosocial (e.g., hearing aids). These

stages in processing involve both bottom-up and top-

down auditory modulation of activity. It has beenhypothesized that bottom-up adaptation processes are

major contributors to determining the signal strength

of tinnitus (Searchfield et al, 2012); a significant top-down

contribution is an individual’s detection thresholds

(Welch and Dawes, 2008). For the full benefits of any

sound therapy, an effective intervention may initially

require management of residual and psychological factors,

such as arousal, through effective counseling and providingrelief through higher levels of sound; once the individual

has some level of control (i.e., they have adjusted to tinni-

tus), a second stage of lower sound might facilitate adapta-

tion. This is countered by an argument from Pineda et al

(2008), however, who propose that combining customized

sound therapy (designed to draw attention away from

the tinnitus sound) with directive counseling (which ulti-

mately draws attention to tinnitus) could be counterproduc-tive. Such an effect, if actual, might be acute but recurring

in the case of a therapy where sound is used continuously

and directive counseling is delivered in a limited series of

educational interactions. The choice of an individualized

patient counseling or psychoeducation approach that is

complementary to the sound therapy intended (and vice

versa) is consequently an important consideration.

What Is the Patient’s Hearing Like?

As hearing loss is a high risk factor for tinnitus

(Sindhusake et al, 2004) it should be addressed with

all tinnitus patients. In most circumstances hearing loss

will require hearing aids or, occasionally, cochlear

implants. The use of hearing aids may have strong psy-

chosocial benefits as well as influencing most of the pro-cesses postulated in the model to drive tinnitus, that is,

sound enrichment. Combination instruments provide a

further option for those with an aidable hearing loss,

with further technology options of environmental steer-

ing and modulated masking sounds available with some

devices. This provides a range of options to explore and

individualize the device to particular preferences.

What Sound Therapy Options Are Acceptable?

When assessing the suitability of sound therapy for a

particular patient, there is a need to understand from

the outset what sort of tinnitus exacerbating factors

there are and whether the patient has identified any fac-

tors that reduce the tinnitus (perception or reactions)

such as particular sound situations. In terms of self-management, patients could be advised on the potential

benefit of using sound-producing devices at their disposal

such as personal music players or radios, electric fans,

table fountains, and so on. Assessment for the presence

of hyperacusis, which is not an uncommon association

with tinnitus, might be an important first step if the

patient expresses abnormal reactions to everyday sounds.

Acceptability of the sound to be used is essential. Forexample, if sound level needs to be raised to an uncom-

fortable level to mask tinnitus, then the patient is not a

good candidate for that intervention. Henry, Zaugg,

Myers, and Kendall (2008) examined the relative accept-

ance of dynamic reproduced environmental sound as

masking sounds finding that the more dynamic (water,

nature) sounds reduced tinnitus annoyance more than

the less dynamic (air) sounds, although only 11 of their21 participants reported any relief from tinnitus, and for

four participants the sounds increased tinnitus annoy-

ance. Mental imagery techniques may be used to enhance

the effect of positive sounds on tinnitus (e.g., imagining

sitting on a beach). Once learned, associated relaxation

may persist on cessation of therapeutic sound.

The Cleveland Clinic Sound Therapy Option Profile

(STOP) tool contains a number of questions on issuesthat are likely to influence a patient’s preference or

aversion to particular sound therapies (available at

audiologyonline.com). The questionnaire probes the

issues of patient motivation to use sound therapy, the

amount of intervention they are willing to accept (hours

per day, months of continued therapy), expectations

and confidence in sound therapy, acceptability of differ-

ent sounds, and willingness to pay. This tool may beuseful in particular when a number of sound therapy

options are available to the patient.

RESEARCH THAT IS NEEDED

Most sound therapy interventions focus on a single

putative mechanism. The complex nature of tin-

nitus however (Roberts et al, 2010; De Ridder et al,

2011), suggests thatwe should either use sound therapy

that targets a broad range of potential tinnitus mech-

anisms or identify subgroups of tinnitus patients that,

based on their symptom profile would be predicted to

benefit from a specific therapy. It is also important tounderstand those subgroups for which sound therapy

is wholly ineffective or indeed exacerbates tinnitus.

The current body of research available on sound ther-

apy is insufficient for us to do that. Many research

reports also fail to distinguish between individuals

who do not seek help for tinnitus and those who do.

It is possible that those two groups might have different

71

Tinnitus Sound Therapy/Hoare et al

underlying mechanisms and hence would respond dif-

ferently to the same intervention.

Although sound therapy is commonly used, we still

know very few details about its specific benefits andmodes of effect. Consequently, any model of sound ther-

apy needs to be open for critique andmodification as evi-

dence becomes available. The absence of RCTs for sound

therapy has been bemoaned (McKenna and Irwin, 2008;

Hoare et al, 2011); however, to support the design of

large-scale trials there is also a need for small-scale

heuristic orwell-designed single-subject studies to exam-

ine the components of sound therapy that likely contrib-ute to treatment success. As we report here, while some

sound therapies have been the subject of a number of

clinical trials (e.g., masking, TRT, Neuromonics), most

have received little investigation. Proponents of sound

therapy need to systematically evaluate both behavioral

effects in a more rigorous manner and exploit the devel-

opments in auditory electrophysiology and neuro-

imaging to elucidate mechanisms that contribute toany improvement in tinnitus (perception and/or reac-

tions) that is reliably demonstrated. The inclusion of

objective measures in an attempt to understand contri-

buting mechanisms is highly desirable (e.g., MEG

studies undertaken alongside behavioral measures

of notched music effects by Okamoto et al, 2010).

CONCLUSIONS

Sound therapy on its own is of unproven benefit;

equally, there is little to suggest it is of potential

harm to patients. In particular there is limited evidence

of the benefit of sound therapy independent from other

concomitant treatment factors such as counseling(McKenna and Irwin, 2008). Our understanding of

the neuroscience of tinnitus has made great strides

and gathered momentum particularly with the use of

advanced imaging techniques (Lanting et al, 2009;

Adjamian et al, 2012; Melcher et al, 2013), and while

sound therapy research has been rooted largely in

the behavioral domain, studies of the neurophysiologi-

cal consequences of sound therapies are beginning toemerge (Tass et al, 2012). There are few large-scale

controlled studies to support or refute many of the

sound therapy options currently in use, amounting

to considerable gaps in our evidence base, and there-

fore opportunities to design and run exciting explan-

atory trials. Despite the current lack of explanatory

evidence, sound therapy should be considered an

essential component of any clinical program of tinni-tus management.

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