acoustics i: hearing - eth z · 2019-08-18 · acoustics i: hearing kurt heutschi 2013-01-25....

hearing

structure of the ear

hearing threshold

loudness

frequencydiscrimination

critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase

binaural hearing:localization

precedence effect

back

Acoustics I:hearing

Kurt Heutschi2013-01-25

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

structure and principleof operation of the ear

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

structure of the earouter ear external air

middle ear air, closed airtight

inner ear filled with fluid

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

inner ear: principle of operationI excitation by oval window → traveling wave along

basilar membrane

I maximum amplitude depends on frequency →frequency y location transformation

I movement of basilar membrane detected by haircells → electrical pulses to brain

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

frequency dependency of thehearing threshold

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

frequency dependency of the hearing

threshold

demo Nr. 6, Tracks 17,18, preparation of a protocol:

125 250 500 1 k 2 k 4 k 8 k0 dB-5 dB

-10 dB-15 dB-20 dB-25 dB-30 dB-35 dB-40 dB-45 dB

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back


threshold

demo Nr. 6, Track 18, procedure:

I new frequencyI tones with decreasing level (-5 dB steps)I count the number of stepsI staircase is repeatedI mark in the table

I new frequency, ...

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back


threshold

typical hearing threshold:

125 250 500 1 k 2 k 4 k 8 k0 dB-5 dB

-10 dB-15 dB-20 dB x-25 dB x-30 dB x-35 dB x x-40 dB x-45 dB x1

1resonance of the ear canal

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness in phon LN

I description of the intensity of the sensation in phon

I subjective determination:I adjust a 1 kHz reference signal for equal loudness

as the test signalI phontest.signal = dBreference.signal

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness in phon LNequal loudness contours for tones:

→ loudness filter in pre-amplifiers

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness in sone N

I description of the intensity of the sensation in sone

I sone scale is proportional to sensation

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness in sone N

demo Nr. 7, Tracks 19,20, preparation of a protocol:

Nr. Nref Nsignal Nr. Nref Nsignal

1 10 11 102 10 12 103 10 13 104 10 14 105 10 15 106 10 16 107 10 17 108 10 18 109 10 19 10

10 10 20 10

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness in sone N

subjective evaluation of the loudness in sone for testsignals relative to a referencedemo Nr. 7, track 20, procedure:

I reference signal (= loudness 10 sone)

I loudest test signal

I most silent test signal

I loop:I reference signalI test signal

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness in sone N

solution:

Nr. Nref Nsignal Nr. Nref Nsignal

1 10 30 11 10 52 10 7 12 10 303 10 2.5 13 10 404 10 10 14 10 75 10 5 15 10 206 10 40 16 10 3.57 10 14 17 10 78 10 20 18 10 2.59 10 3.5 19 10 14

10 10 10 20 10 30

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

relation between LN and N

I definition: LN = 40 phon → N = 1 sone

I above 40 phon:I LN+10 phon → N · 2 sone

I N = 2LN−40

10

I LN ≈ 40 + 33 · log(N)

I below 40 phon the sone number cuts half for phonereduction steps < 10.

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

frequency discrimination

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

frequency discrimination

I frequency range of hearing (16. . .16’000 Hz):around 620 frequency steps

I maximal resolution for a frequency modulation with4 Hz:

I f < 500 Hz → ∆f = 3.5 HzI f ≥ 500 Hz → ∆f = f · 0.007 Hz

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

critical bands

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

critical bandsinner ear: blurred frequency y location transformation

I even in case of pure tone excitation, an extendedzone on the basilar membrane is put to motion

I this zone can be expressed as frequency range →critical band

I f < 500 Hz → width = 100 HzI f ≥ 500 Hz → width = f · 0.2 Hz (≈ third octave

band)

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

critical bands - loudness summation

two cases:

I two signals with overlapping critical bandsI summation of intensitiesI 40 phon + 40 phon = 43 phon

I two signals clearly separated in frequency nooverlapping critical bands

I summation of loudnessI 1 sone + 1 sone = 2 soneI 40 phon + 40 phon = 50 phon

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

critical bands - loudness summation

loudness comparison of test signals of differentbandwidth ∆B but equal power:demo nr. 3, track 7, procedure:reference (∆B 145 Hz) and test signal in alternatingsequence

I test signal 1: narrow band noise ∆B 145 Hz








hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

masking

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

maskingpresentation of a tone lifts the hearing threshold →frequency components in the vicinity may be masked.

I masking effect more pronounced towards higherfrequencies

I the higher the level of the masker, the wider themasking range

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

virtual pitch

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

virtual pitcha missing fundamental in a complex sound can becomplemented by the brain.demo nr. 20, track 37:

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

virtual pitch

possible applications:

I virtual bass in organsI pipe with frequency f1I pipe with frequency f2 = 3

2 f1I → virtually audible f = 1

2 f1

I reproduction of low frequencies with smallloudspeakers

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

nonlinear distortions

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

nonlinear distortions of the ear

I nonlinear transfer function from the tympanicmembrane to the inner ear

I frequencies are generated that are not contained inthe original signal

I sum-tones: f1 and f2 → f1 + f2I difference-tones: f1 and f2 → f2 − f1

I difference-tones are especially critical as they arenot masked

I level of difference-tone:L(f2 − f1) ≈ L(f1) + L(f2)− 130dB

I e.g. L(f1) = L(f2) = 80dB → L(f2 − f1) ≈ 30dB

I distortion factor:

excitation[dB] 70 80 90 100 110 120distortion[%] 0.05 0.2 0.5 1.5 5 16

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness as a function ofsignal duration

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

loudness as a function of signal durationI hearing process shows a certain delay

I full loudness is reached for signal length > 0.5 s

I below 100 ms → loudness corresponds to signalenergy

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

temporal masking

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

temporal masking

pre and post masking:

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

phase

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

sensitivity with respect to phase

?

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

binaural hearing: localization

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

binaural hearing: localization in the

horizontal plane

I evaluation of the two ear signals yields:I interaural level differencesI interaural time differences

I maximum resolution: 1 degree

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back


horizontal plane

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back


vertical plane

detection of elevation:

I evaluation of the frequency response

I resolution: 10. . .45 degrees

detection of distance:

I evaluation of the loudness (the more silent, themore distant)

I reverberation (the more reverberant, the moredistant)

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

precedence effect

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

precedence effect

capability of the ear to merge direct sound and echoesand to localize the direction of the direct sound

hearing


hearing threshold

loudness


critical bands

masking

virtual pitch

distortions

loudness(t)

temporal masking

phase


precedence effect

back

eth-acoustics-1

acoustics i: hearing - eth z · 2019-08-18 · acoustics i: hearing kurt heutschi 2013-01-25....

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