Human Hearing

Human hearingHuman hearing

Limits, the human ear, and Limits, the human ear, and issues of perceptionissues of perception

Physical CharacteristicsPhysical Characteristics

Frequency range: 20 Hz … 20 kHzFrequency range: 20 Hz … 20 kHz Factor of 1000Factor of 1000

Intensity range: 10Intensity range: 10-12-12 to 1 W/m to 1 W/m22

Factor of 10Factor of 101212

Filtering of informationFiltering of information

Physical characteristicsPhysical characteristics

Graphics: Rossing, Moore & Wheeler, The Science of Sound, 3rd Ed.

Psychophysics:Psychophysics:

objective and quantitative study of the objective and quantitative study of the relation of physical stimuli and sensory relation of physical stimuli and sensory perceptionsperceptions

Pressure fluctuations

Middle Ear:

Transformation into mechanical and then electrical signals

Processing: sorting, selection,recognition

StructureStructure of the of the human human

ear ear

Important parts of the earImportant parts of the earOuter Ear:Outer Ear:

Auditory canalAuditory canal Ear drumEar drum

Middle ear:Middle ear: Ossicles: hammer (malleus), anvil Ossicles: hammer (malleus), anvil

(incus), stirrup (stapes)(incus), stirrup (stapes)

Inner EarInner Ear CochleaCochlea Auditory nerveAuditory nerve

Important parts of the Important parts of the CochleaCochlea

Oval windowOval window Scala vestibuli (filled Scala vestibuli (filled

with fluid)with fluid) Scala timpaniScala timpani Round windowRound window Basiliar membraneBasiliar membrane Organ of CortiOrgan of Corti Auditory nerveAuditory nerve

Mechanism of signal Mechanism of signal transporttransport

Hall, Musical Acoustics, 3rd Ed.

Lever action of ossiclesLever action of ossicles

Small displacement over large area Small displacement over large area becomes large displacement over becomes large displacement over

small areasmall area

Hearing lossHearing loss

Conduction deafness: reduced Conduction deafness: reduced mobility of ossicles due to vibrous mobility of ossicles due to vibrous tissue (i. e. from repeated otitis)tissue (i. e. from repeated otitis)

Nerve deafness: deterioration of hair Nerve deafness: deterioration of hair cells or nerve (also age-related cells or nerve (also age-related presbycusis)presbycusis)

Can be distinguished through bone Can be distinguished through bone conductionconduction

Just noticable differencesJust noticable differences At which frequency difference do two At which frequency difference do two

tones sound different to us?tones sound different to us?200/201 Hz200/202 Hz200/203 Hz

2000/2002 Hz2000/2003 Hz2000/2004 Hz2000/2006 Hz2000/2008 Hz

2000/2002 Hz2000/2003 Hz2000/2004 Hz2000/2006 Hz2000/2008 Hz

Simultaneous soundsSimultaneous sounds

At which difference in frequency can At which difference in frequency can we hear two distinct sounds?we hear two distinct sounds?

1000 Hz combined with …

990 Hz 1010 Hz

980 Hz 1020 Hz950 Hz 1050 Hz

900 Hz 1100 Hz 1200 Hz 1300 Hz800 Hz700 Hz

How are sounds resolved?How are sounds resolved?

How are sounds resolved?How are sounds resolved?

Critical band: region on basiliar Critical band: region on basiliar membrane for reception of a pure membrane for reception of a pure tonetone

If critical bands overlap, only a single If critical bands overlap, only a single tone is heardtone is heard

The critical band is larger at low The critical band is larger at low frequencies.frequencies.