Acoustics 101 - and the NZ Building Code - New … · Acoustics 101 - and the NZ Building Code NZAS 39th Annual Conference 2-4 July 2015 George Dodd and James Whitlock on behalf of

Acoustics 101 - and the NZ Building Code

NZAS 39th Annual Conference 2-4 July 2015

George Dodd and James Whitlock on behalf of ASNZ

To cover –

• What is an acoustician?

• Phenomena and techniques used in the control of

sound

• The special case of dwellings and the New Zealand

Building Code requirements

• Some current research and a look to the future.

The job of an Acoustician

– TO CONTROL OBJECTIVE SOUND SO THAT THE

ASSOCIATED SUBJECTIVE SOUND BENEFITS PEOPLE

Formal noise complaints - Christchurch

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Residential noise

Commercial noise

Total cmplaints

Christchurch complaints – analysed by source

12000

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20000

2002

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Auckland City

Noise complaints investigated for Auckland City - data only available since 2002

(Courtesy of Armourguard)

More recent data only provided if requested under OIA and time paid for!

Noise arising from activities within zones Residential zones Except where other more specific controls apply, the LAeq(15 min) noise level and maximum noise level (LAFmax) arising from any activity in the residential zones measured at or within the boundary of an adjacent property site in the residential zones must not exceed the following levels limits. Monday to Saturday 7am-10pm 50dB LAeq(15 min) Sunday 9am-6pm 50dB LAeq(15 min) All other times 40dB LAeq(15 min)

75dB LAFmax

An example of the form of a ‘noise limit’ from the Auckland Council submission to the Unitary Plan Hearings where the objectives include – 1. People and activities sensitive to noise are protected from unreasonable levels of noise. 2. The amenity of residential areas is protected from unreasonable noise, particularly at night.

What is the purpose for a dwelling?

The fact that it is PRIVATE makes it different from a hotel,

hostel, hospital, or other building providing amenities for

humans.

What do we mean by PRIVACY – and especially what

acoustical conditions are required to give you Acoustic

Privacy?

A Definition for Acoustic Privacy –

The condition where no information about you or your

neighbour (including your, or their, presence!) is

communicated by sound.

Tools/Techniques acousticians use for controlling noise –

DISSIPATION =

REFLECTION

DIFFRACTION =

REFRACTION

SPECTRUM CHANGE =

REDIRECTING THE SOUND

ENERGY AWAY FROM A SPACE

SHIFTING THE FREQUENCY

CONTENT SO WE CAN’T HEAR IT

CHANGING THE SOUND

ENERGY INTO HEAT

What would be a good material to insulate sound?

Neighbour’s Noise CAC 1

CAC 2

CAC 3

Shouting Voice intelligible generally intelligible generally unintelligible

Raised Voice generally intelligible generally unintelligible unintelligible

Normal Voice generally unintelligible unintelligible inaudible

Footsteps generally annoying generally not annoying not annoying

Sanitary Noise unacceptable annoyance generally avoided

occasionally annoying not or seldom annoying

Home Music, Loud Radio/TV , Parties

clearly audible clearly audible

generally audible

Subjective Response to Noise from Neighbours

Subjective Response to Noise from Neighbours for the “Classes of Acoustical Comfort (CAC)” in German Guideline VDI 4100 “Noise Control in Housing”

assumimg background level of 20 dB(A) and normal size rooms

NZ’s current Building Code requirements match those of CAC 1

NB: safeguard from loss of

AMENITY as a result of undue

noise …..

Amenity means an attribute of a building

which contributes to the health, physical

independence, and well being of the

building's users but which is not associated

with disease or a specific illness.

Insulating material A material that has a thermal conductivity of less than 0.07W/mK.

Health is a state of complete physical,

mental and social well-being and not merely

the absence of disease or infirmity.

Sound Insulation

• Transmission Loss (TL) is a measure of the energy loss through an element

• Indicates the Sound Insulation value

• Normally quoted as Sound Transmission Class (STC)

TL = 55 dB

50 dB

STC – Sound Transmission Class

• Transmission Loss is measured over a frequency range (low sounds and high sounds)

• STC enables a single figure rating • Obtained by comparison with a

standardized ‘curve’

• Emphasis of curve is on the ‘speech’ frequencies

Transmission Loss vs Noise Reduction

• TL is a property of a building element

e.g. “This wall has a TL of 57 dB”

• NR is the difference in sound level either side of a building element

e.g. “This wall has an NR of 57 dB… when it is X m2 and has room Y with a reverb time of Z on the other side of it.”

Masonry vs Plasterboard

150mm Concrete 2 x 10mm Noiseline

STC 55 200mm cavity with insulation

1 x 10mm Noiseline

STC 55

IIC – Impact Insulation Class

Not measured as a TL

The actual sound level is measured over a frequency range

Standardised Impact Source

Tapping Machine

The New G6

There is change in Philosophy from;

Performance of the materials to

Performance of the building

Change from TL to NR - from STC to Rw and DnTw

… and more.

The New G6

Overall improvement of 3 – 8 dB

stay tuned…

Neighbour’s Noise CAC 1

CAC 2

CAC 3

Shouting Voice intelligible generally intelligible generally unintelligible

Raised Voice generally intelligible generally unintelligible unintelligible

Normal Voice generally unintelligible unintelligible inaudible

Footsteps generally annoying generally not annoying not annoying

Sanitary Noise unacceptable annoyance generally avoided

occasionally annoying not or seldom annoying

Home Music, Loud Radio/TV , Parties

clearly audible clearly audible

generally audible

Subjective Response to Noise from Neighbours

Subjective Response to Noise from Neighbours for the “Classes of Acoustical Comfort (CAC)” in German Guideline VDI 4100 “Noise Control in Housing”

assumimg background level of 20 dB(A) and normal size rooms

NZ’s current Building Code requirements match those of CAC 1

Elastic Meta-Materials are materials which are internally engineered to create -

• Properties not available in nature

e.g.Negative density and/or stiffness

• Properties which are determined by their

internal structure rather than their chemical

composition

(so the fundamental equations governing their

behaviour need modifications to Newton’s

Law!!)

Application: sound barrier

• Changing the effective density of wall or partition

• First practical application!

• Exceptional performance but limited frequency band (for

now)

Acoustic Invisibility and Black Holes with ‘Indefinite Materials’

• Cloaking: guiding waves around an object

• Super-absorbers: guiding waves in a lossy object

July 8, 2013

Redesigned Window Stops Sound But Not

Air, Say Materials Scientists By exploiting some exotic acoustic techniques, researchers have

built a window that allows the passage of air but not sound

Wind Turbine Syndrome (Pierpont, 2009)

• Sleep disturbance, • Headache, • Dizziness, vertigo, unsteadiness • Tinnitus • Ear pressure or pain • External auditory canal sensation • Nausea • Memory and Concentration deficits • Irritability, Anger • Panic episodes • Fatigue • Loss of motivation

What could be causing health effects?

• Dominant source of sound is the aerodynamic noise caused by the flow of air past the turbine blades

• Sound produced is a broadband sound present across a range of frequencies, from the audible to the sub-audible.

• Audible sound limit set in New Zealand by wind farm noise standard NZS 6808:2010 (recommended limit of 40dB).

• Symptom reporting has coincided with public

speculation about alleged health effects (Chapman et

al., 2013).

• Media reporting about wind farms and health effects

contain factors likely to induce fear, anxiety and

concern (Diegnan et al., 2013).

What could be causing health effects?

Negative health information

and symptom reporting Warnings about health effects may

trigger health complaints even when no

actual risk is posed (Faasse et al., 2012)

Such information can create anxiety,

health concerns and related symptom

expectations, priming people to notice

and negatively interpret common

physical sensations and symptoms (Petrie

et al., 2005)

The Role of Expectations

Might symptom expectations created from negative

health information explain the link between wind

turbines and health effects?

A sham double-blind provocation study

54 participants

High infrasound symptom

expectations video

Low infrasound symptom

expectations video

Infrasound (<40db at 5Hz)

Sham infrasound (no sound)

counterbalanced

10 mins

10 mins

Number of symptoms

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Before Infrasound During Infrasound Before Sham During Sham

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Low Expectancy

High Expectancy

Symptom Intensity

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Before Infra During Infra Before Sham During Sham

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Low Expectancy

High Expectancy

Perceived effect on physical symptoms G

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Experience of Annoyance

Conclusions

• Negative health information readily available to people living in the vicinity of wind farms may create symptom expectations, providing a possible pathway for symptoms attributed to operating wind turbines.

• Framing health information in a positive way may provide a way to reverse, reduce, or protect against the experience of noise annoyance and symptom reporting.

The design is relatively simple and relies on two exotic acoustic phenomenon. The first is to

create a material with a negative bulk modulus.

A material’s bulk modulus is essentially its resistance to compression and this is an

important factor in determining the speed at which sound moves through it. A material with a

negative bulk modulus exponentially attenuates any sound passing through it.

Kima and Lee’s idea is to design a sound resonance chamber in which the resonant forces

oppose any compression. With careful design, this leads to a negative bulk modulus for a

certain range of frequencies.

Their resonance chamber is actually very simple—it consists of two parallel plates of

transparent acrylic plastic about 150 millimetres square and separated by 40 millimetres,

rather like a section of double-glazing about the size of a paperback book.

This chamber is designed to ensure that any sound resonating inside it acts against the way

the same sound compresses the chamber. When this happens the bulk modulus of the entire

chamber is negative.

An important factor in this is how efficiently the sound can get into the chamber and here

Kima and Lee have another trick. To maximise this efficiency, they drill a 50 millimetre hole

through each piece of acrylic. This acts as a diffraction element causing any sound that hits

the chamber to diffract strongly into it.

The result is a double-glazed window with a negative bulk modulus that strongly attenuates

the sound hitting it.

Kima and Lee use their double-glazing unit as a building block to create larger windows. In

tests with a 3x4x3 “wall” of building blocks, they say their window reduces sound levels by

20-35 decibels over a sound range of 700 Hz to 2,200 Hz. That’s a significant reduction.

9th International Conference on Advanced Building Skins, 28-29 October 2014, Bressanone, Italy The main objective of the conference is to contribute to a multidisciplinary, integrated planning approach among architects, engineers, scientists, energy managers, manufacturers and the building industry, with the aim to reduce energy consumption while improving the comfort of the building's occupants. This year's topics include: - Design Methods for Sustainable, High-Performance Building Facades - The Future of Advanced Building Skin Design - High-Tech, Low-Tech, Lightweight Building Envelopes - Thermal Performance of Phase Change Materials for the Building Skin - Thermal and Environmental Performance of Eco Materials for the Building Skin - Smart Materials for Intelligent Building Skins - Architectural Membranes for High Performance Building Skins - Shading Systems for Enhanced Daylight Control - Building Skins for Tropical Climates - Adaptive Hortitecture: Building Envelopes as Micro Climates and Productive Environments - Integrating Photovoltaics into the Building Envelope - Cost Optimization for Solar Energy Systems, NZEB and Façade Renovation - Optimization Techniques for the Refurbishment of Building Envelopes - Performance Simulation of the Building Envelope

“So close? Cooper wondered if the Chadwicks knew what

it was actually like to have neighbours living practically

on top of you, packed in cheek by jowl, so close that you

could hear them clearly through the walls on either side of

you. There were lots of people … who knew what that

was like. His own ground-floor flat in Welbeck Street

sometimes echoed to the slam of a door from the tenant

upstairs, the clatter of feet on the stairs, the blare of old

Mrs Shelley’s TV set next door.”

“Many of these people would have come here from the

city seeking peace and quiet, looking for a refuge from

noise and traffic ..”

Excerpt from The Devil’s Edge, by Stephen Booth, Sphere Books, 2011

CASE STUDY: NOISE COMPLAINTS IN NORTHERN IRELAND

There has been a 5.25% increase in the total number of complaints received this year

compared to last year and a 45.21% increase since 2003/04 when numbers of complaints were

first recorded.

Many neighbour noise problems are a result of incompatible lifestyles and a lack of

consideration for the rights of others. The Department of the Environment considers that

better education is one way of tackling the problem and is keen for the councils to continue

their efforts to raise noise on local agendas.

Factors Influencing IIC

The IIC is dependent on:

• The floor structure (material, thickness, etc.)

• The floor covering (carpet, vinyl, parquet tiles)

• The ceiling beneath (isolated, layers etc.)

The acoustic benefit of each factor can be separated.

IIC factors

Concrete Floor

Thickness (mm) IIC

75 16

100 21

150 28 Unlike airborne sound, we cannot

achieve Building Code G6 requirement using mass alone

Improvements: Floor Coverings

Vinyl +4 Cushioned Vinyl +15 Parquet +16 Cork +18 Tiles with underlay +0 to +24 Carpet +44

Improvements: Ceilings

Ceiling fixed directly to slab +4 13mm Gib suspended ceiling on battens +13 Gib on resilient hangers +20

[nothing beats carpet]

The NZ Building Code

Clause G6 addresses

Airborne and Impact Sound

• Airborne Sound: STC 55 for walls and

floors/ceilings

• Impact Sound : IIC 55 for floors/ceilings

• 5 point relaxation for field testing on site i.e. FSTC 50 and FIIC 50.

• Both laboratory performance and field performance must be complied with.

Scope of G6

Performance requirements are for habitable spaces of household units.

Habitable spaces are: Bedrooms

Living rooms and lounges Kitchens

Studies

Is Compliance Enough?

• G6 is the Building Code minimum. Often not sufficient for owners expecting high quality

• Complaints received with FSTC 55 & FIIC 57 i.e. 5 - 7 points above G6

• Owner expectations, neighbours’ behaviour and background noise all have an influence on satisfaction

• STC and IIC are rather old criteria, based on 1950 noise sources and brick walls

• Modern entertainment systems produce significant low frequency energy, which is not catered for by STC