musicians and hearing aids marshall chasin aud, m.sc., reg. caslpo, aud(c ) musicians’ clinics of...

Musicians and Musicians and Hearing AidsHearing Aids

Marshall ChasinMarshall Chasin

AuD, M.Sc., Reg. CASLPO, Aud(CAuD, M.Sc., Reg. CASLPO, Aud(C))

Musicians’ Clinics of CanadaMusicians’ Clinics of Canada

Musicians’ Clinics of CanadaMusicians’ Clinics of Canada

Some recent publications…Some recent publications…

Canadian Hearing Report, May/June 2007Canadian Hearing Report, May/June 2007 M. ChasinM. Chasin

Hearing Journal, July 2004Hearing Journal, July 2004 M. ChasinM. Chasin

Trends in Amplification, Trends in Amplification, 77, 3, 2004, 3, 2004 M. Chasin and F. RussoM. Chasin and F. Russo

Trends in Amplification, Trends in Amplification, 88, 3 and 4, 2005, 3 and 4, 2005 King ChungKing Chung

Special issue on musicians…Special issue on musicians…

Hearing Review March 2006Hearing Review March 2006 Edited by Marshall ChasinEdited by Marshall Chasin www.hearingreview.comwww.hearingreview.com (archives) (archives)

A new book….A new book….

Musicians and Hearing Loss (2008) from Musicians and Hearing Loss (2008) from Plural Publishing.Plural Publishing.

Replaces my original Musicians and the Replaces my original Musicians and the Prevention of Hearing Loss (1996), Prevention of Hearing Loss (1996), Singular Publishing Group.Singular Publishing Group.

……. Two websites…. Two websites…

www.chasin.ca/musicwww.chasin.ca/music

www.musiciansclinics.comwww.musiciansclinics.com

(Five) differences …(Five) differences …

Speech vs. Music SpectraSpeech vs. Music Spectra Phonemic vs. phonetic requirementsPhonemic vs. phonetic requirements Differing intensitiesDiffering intensities Crest factorsCrest factors (Loudness and intensity)(Loudness and intensity)

Five differences …Five differences …

(1) Speech vs. Music Spectra:(1) Speech vs. Music Spectra:

Speech has a relatively uniform spectrumSpeech has a relatively uniform spectrum• Human vocal tract sourceHuman vocal tract source• Long-term speech spectrum “target”Long-term speech spectrum “target”

Music has many sourcesMusic has many sources• Highly variableHighly variable• No “music target”No “music target”


(2) Phonemic vs. phonetic requirements:(2) Phonemic vs. phonetic requirements:

Speech is mostly low-frequency energy and high Speech is mostly low-frequency energy and high frequency clarity (AI).frequency clarity (AI).

Music perceptual requirements depends on the Music perceptual requirements depends on the instrument…. Highly variable.instrument…. Highly variable.

• Violins need to hear the balance between low and high Violins need to hear the balance between low and high frequencies.frequencies.

• Clarinets only need to hear the lower frequency energy.Clarinets only need to hear the lower frequency energy.


(3) Differing intensities:(3) Differing intensities:

Speech is 65 dB SPL Speech is 65 dB SPL ± 12 dB ± 12 dB • (53 dB SPL to 77 dB SPL)(53 dB SPL to 77 dB SPL)• Shouted speech can be 82 dB SPL Shouted speech can be 82 dB SPL

Music can reach 105 dBA; peaks of 120 dBAMusic can reach 105 dBA; peaks of 120 dBA


(4) Crest factor: (peak – RMS)(4) Crest factor: (peak – RMS)

Speech has a crest factor of 12 dBSpeech has a crest factor of 12 dB

Music has a crest factor of up to 18 dB.Music has a crest factor of up to 18 dB.• Less damping.Less damping.

(Five) differences …(Five) differences …

(5) Loudness and intensity:(5) Loudness and intensity:

Speech has a well-defined relationship since Speech has a well-defined relationship since harmonics are in different critical bands.harmonics are in different critical bands.

Bass instruments have some harmonics within the Bass instruments have some harmonics within the same critical bandwidth… same critical bandwidth…

• Loudness and intensity mismatch with some instruments Loudness and intensity mismatch with some instruments (intensity increases and no change in loudness)(intensity increases and no change in loudness)

• Bass instruments “suffer” from this mismatch… underplay…. Bass instruments “suffer” from this mismatch… underplay…. Less low frequency gain needed…Less low frequency gain needed…

What about hard of hearing What about hard of hearing musicians … or non-musicians musicians … or non-musicians

who like to listen to louder who like to listen to louder music?music?

Hearing Aids and MusiciansHearing Aids and Musicians

1. Peak input limiting level of most hearing aids limits sound 1. Peak input limiting level of most hearing aids limits sound above 85 dB SPL.above 85 dB SPL.

… … great for speech… bad for music.great for speech… bad for music.

- shouted [a] is about 82 dB SPL peak- shouted [a] is about 82 dB SPL peak- music can be >110 dB SPL- music can be >110 dB SPL

An Experiment:An Experiment:

Traditional measures of distortion in the industry Traditional measures of distortion in the industry involve:involve: AutocorrelationAutocorrelation Harmonic relationshipsHarmonic relationships

- total harmonic distortion- total harmonic distortion

- intermodulation distortion- intermodulation distortion

Problem:Problem: Works best for linear systemsWorks best for linear systems


Kates (1990, 1991)Kates (1990, 1991) Notch filter paradigm (can work for non-linear Notch filter paradigm (can work for non-linear

systems)systems)• Comb filterComb filter

With current technology(eg. Adobe Audition), a With current technology(eg. Adobe Audition), a square notch was removed from the input spectrumsquare notch was removed from the input spectrum

• ““debris” in the notch is a measure of distortiondebris” in the notch is a measure of distortion• An output spectrum with a perfectly square notch is An output spectrum with a perfectly square notch is

representative of perfect fidelity.representative of perfect fidelity.

An Experiment: An Experiment: Unfiltered and Filtered MusicUnfiltered and Filtered Music


A hearing aid was constructed where the A hearing aid was constructed where the peak input limiting level can be peak input limiting level can be successively reduced from 115 dB SPL, to successively reduced from 115 dB SPL, to 105 dB SPL, to 96 dB SPL to 92 dB SPL, 105 dB SPL, to 96 dB SPL to 92 dB SPL, … and back to 115 dB SPL. … and back to 115 dB SPL.

Acknowledgments: Mead Killion, Russ Acknowledgments: Mead Killion, Russ Tomas, Norm Matzen, Mark Schmidt, Tomas, Norm Matzen, Mark Schmidt, Steve Aitken.Steve Aitken.

Unfiltered and Filtered MusicUnfiltered and Filtered Music

-90

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Filtered 2-3 kHz notch

Unfiltered

Two Input Limiting Levels Two Input Limiting Levels (115 dB and 105 dB SPL)(115 dB and 105 dB SPL)

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Unfiltered Input

Output for 115 dBlimiting level

Output for 105 dBlimiting level

Two Input Limiting LevelsTwo Input Limiting Levels(96 dB and 92 dB SPL)(96 dB and 92 dB SPL)

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Output for 92 dB limitinglevel

““Signal/Distortion – 30 dB” ratio Signal/Distortion – 30 dB” ratio (0 dB =best)(0 dB =best)

115

105

9692

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dB

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Preference ScalesPreference Scales

Gabrielsson et al. (1974; 1991)Gabrielsson et al. (1974; 1991) Cox and Alexander (1983)Cox and Alexander (1983)

LoudnessLoudness (vs. “faint”) (vs. “faint”) FullnessFullness (vs. “thin”) (vs. “thin”) CrispnessCrispness (vs. “blurred”) (vs. “blurred”) NaturalnessNaturalness (…“as I remember it”) (…“as I remember it”) Overall fidelity (…“dynamics not too narrow”)Overall fidelity (…“dynamics not too narrow”)

Signal/Distortion ratio vs. Signal/Distortion ratio vs. Preference Scale Totals Preference Scale Totals (n=138)(n=138)

0

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Signal/Distortion Ratio (dB)

Pre

fere

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25)

Therefore ….Therefore ….

Peak Input Limiting Level Peak Input Limiting Level should be at least 105 dB SPLshould be at least 105 dB SPL

If you are stuck with a low peak If you are stuck with a low peak input limiting level ….input limiting level ….

Lower volume on stereo or other input and Lower volume on stereo or other input and increase gain on aid.increase gain on aid.

Depending on the manufacturer, you can use an Depending on the manufacturer, you can use an FM system as input.FM system as input.

Use (creative) microphone attenuators (Adhear), Use (creative) microphone attenuators (Adhear), or Scotch tape. Tape will provide 7 dB of flat or Scotch tape. Tape will provide 7 dB of flat attenuation up to 4000 Hz. (Can also do it attenuation up to 4000 Hz. (Can also do it electronically- resistive network).electronically- resistive network).

Reducing output (not gain)Reducing output (not gain)

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100

0 2000 4000 6000 8000 10000

Frequency (Hz)

Out

put (

dB S

PL)

Unattenuated output Adhear or Scotch Tape Adhear and Whiteout

A quick way to determine the A quick way to determine the peak input limiting levelpeak input limiting level

In a test box, set the stimulus level to 100 dB. (may need In a test box, set the stimulus level to 100 dB. (may need to move the reference mic).to move the reference mic).

Set the gain of the aid to about 5-10 dB, and the Set the gain of the aid to about 5-10 dB, and the OSLP90 is set >110dB .OSLP90 is set >110dB .

(The output is less than the OSPL-90)(The output is less than the OSPL-90)

If distortion is >10%, then this is “front end” clipping and If distortion is >10%, then this is “front end” clipping and the peak input limiting level is too low. the peak input limiting level is too low.

Ref: Chasin, 2006, Hearing Journal.Ref: Chasin, 2006, Hearing Journal.

Music is intense so…Music is intense so…

A useful hearing aid fitting for listening to A useful hearing aid fitting for listening to and playing loud music, even for those and playing loud music, even for those with a moderate to severe loss, is a non-with a moderate to severe loss, is a non-occluding BTE fitting.occluding BTE fitting.

At higher input levels, less gain and output At higher input levels, less gain and output is required and all that may be needed is is required and all that may be needed is 15-20 dB of mid and high frequency 15-20 dB of mid and high frequency gain…gain…

A non-occluding BTE mod’n…A non-occluding BTE mod’n…

Non-occluding BTE provide gain above Non-occluding BTE provide gain above 1000 Hz and do not occlude the ear canal.1000 Hz and do not occlude the ear canal.

Useful for those with a high frequency lossUseful for those with a high frequency loss

BUT still has a front end peak limiting BUT still has a front end peak limiting problem…problem…

A non-occluding BTE mod’n…A non-occluding BTE mod’n…

SO…. We can use a desensitized SO…. We can use a desensitized microphone.microphone.

Use a high frequency emphasis (-6 dB low Use a high frequency emphasis (-6 dB low frequency roll-off) microphone.frequency roll-off) microphone.

Same frequency response but less front Same frequency response but less front end distortion.end distortion.


2. One channel is best.2. One channel is best.

- relationship between low frequency - relationship between low frequency fundamental and higher frequency fundamental and higher frequency harmonics is maintained (similar CR). harmonics is maintained (similar CR).

- may not be useful in some bass-heavy - may not be useful in some bass-heavy noisy situations (modification of multi- noisy situations (modification of multi- band?) band?)

(L. Revit)(L. Revit)


… … Two channels may be better (?) with one Two channels may be better (?) with one below 500 Hz set to have a higher CR below 500 Hz set to have a higher CR than the higher frequency channel (CR = than the higher frequency channel (CR = 1.7:1). 1.7:1).

This will cut the low frequency gain for all This will cut the low frequency gain for all bass sounds.bass sounds.

Hearing Aids and MusiciansHearing Aids and Musicians(hearing aids and music)(hearing aids and music)

3. Compression issue.3. Compression issue.- speech has a crest factor of 12 dB.- speech has a crest factor of 12 dB.- music has a crest factor of 18-20 dB.- music has a crest factor of 18-20 dB.

……. Detector should be set 5 dB . Detector should be set 5 dB higher?higher?

Depends whether the compression system Depends whether the compression system is based on RMS or peak.is based on RMS or peak.

WDRC?WDRC?

WDRC with a higher compression WDRC with a higher compression threshold (if it uses a peak detector) may threshold (if it uses a peak detector) may be quite useful…??be quite useful…??

Most of damage for mild to moderate loss Most of damage for mild to moderate loss is OHC… WDRC?is OHC… WDRC?

Crest factor and outputCrest factor and output

Music has an 18-20 dB crest factorMusic has an 18-20 dB crest factor Speech has a 12 dB crest factorSpeech has a 12 dB crest factor

Therefore the output (OSPL90) of a “music program” Therefore the output (OSPL90) of a “music program” in a hearing aid should be 6 dB lower than the in a hearing aid should be 6 dB lower than the program for “speech in quiet”.program for “speech in quiet”.

Also, given similar compression characteristics, the Also, given similar compression characteristics, the gain should also be 6 dB less intense.gain should also be 6 dB less intense.

K-AMP or “K-AMP-like” is the K-AMP or “K-AMP-like” is the best hearing aid for music…best hearing aid for music…

High input limiting level or “equivalent”High input limiting level or “equivalent” One channelOne channel Appropriate compressionAppropriate compression WDRC WDRC

Digital Hearing Aids and MusicDigital Hearing Aids and Music

Greater dynamic range than 96 dB? (need to be Greater dynamic range than 96 dB? (need to be able to transduce inputs >110 dB SPL). able to transduce inputs >110 dB SPL). Perhaps 20 dB SPL to 116 dB SPL??Perhaps 20 dB SPL to 116 dB SPL??

16 bit limitation?16 bit limitation? A/D converter limitations?A/D converter limitations? … … other solutions?other solutions?

Music and a flat response…Music and a flat response…

I have always “assumed” that a flat I have always “assumed” that a flat frequency response was needed in order frequency response was needed in order to maintain the balance of the low-to maintain the balance of the low-frequency fundamental energy with the frequency fundamental energy with the higher frequency harmonic energy….higher frequency harmonic energy….

… … This may be secondary…This may be secondary…

Music and a flat response…Music and a flat response…

A flat frequency response means a better A flat frequency response means a better transient response.transient response.

More important for music than for speech.More important for music than for speech. Speech has some transients such as [t]…Speech has some transients such as [t]… Some forms of music have many transients.Some forms of music have many transients.

Frequency Transpostion?Frequency Transpostion?

Decreasing high-frequencies by about a Decreasing high-frequencies by about a fifth (eg. G to C) may be usefulfifth (eg. G to C) may be useful

Like changing from a violin to a viola…Like changing from a violin to a viola…

Examples: Examples: Sonovation (non-linear)Sonovation (non-linear)

Widex Inteo Audibility extender Widex Inteo Audibility extender (linear)(linear)

Noise and Feedback ReductionNoise and Feedback Reduction

Disable these functions for music??Disable these functions for music??

A few slides on feedback A few slides on feedback reduction techniques…reduction techniques…

In general, all approaches use aIn general, all approaches use a

Fixed slow acting component for static noiseFixed slow acting component for static noise Adaptive fast acting component for dynamic Adaptive fast acting component for dynamic

noises.noises.


Three major approaches:Three major approaches: (1) adaptive gain reduction(1) adaptive gain reduction

• eg. Phonak Perseo, Phonak Verve, (Widex Diva/Inteo)eg. Phonak Perseo, Phonak Verve, (Widex Diva/Inteo) (2) adaptive notch filters(2) adaptive notch filters

• eg. Siemens Triano, Unitron Liaisoneg. Siemens Triano, Unitron Liaison (3) phase cancellation(3) phase cancellation

• eg. Oticon Syncro/Safron, Resound Canta, Bernafon eg. Oticon Syncro/Safron, Resound Canta, Bernafon Symbio, Phonak Savia/Verve, (Widex Diva/Inteo), Symbio, Phonak Savia/Verve, (Widex Diva/Inteo), Unitron Indigo, ... Unitron Indigo, ...


Negative issues for each approach:Negative issues for each approach:

Gain reduction: undesirable gain reductionGain reduction: undesirable gain reduction Notch filter: Frequency-hopping artifact Notch filter: Frequency-hopping artifact

resulting in a “blurry sound”.resulting in a “blurry sound”. Phase cancellation: Chirping- there is no Phase cancellation: Chirping- there is no

feedback signal for the feedback signal for the generated generated signal to cancel.signal to cancel.

Six feedback reduction Six feedback reduction techniques and music…techniques and music…

For music…. Since a feedback reduction For music…. Since a feedback reduction system may confuse the pure tones of system may confuse the pure tones of music (and of microwaves, etc) with music (and of microwaves, etc) with feedback…feedback…

(1) Limit the frequency range that activates (1) Limit the frequency range that activates the feedback reductionthe feedback reduction Oticon Syncro and Safron (>1.5 kHz)Oticon Syncro and Safron (>1.5 kHz) Siemens Triano (>2 kHz)Siemens Triano (>2 kHz)


(2) Long signal detection (10 sec) with (2) Long signal detection (10 sec) with pattern recognition AND a slow adaptive pattern recognition AND a slow adaptive time constant for filter… time constant for filter… … … short signals are not cancelled.short signals are not cancelled.

(Siemens Acuris/Centra, Bernafon Symbio, (Siemens Acuris/Centra, Bernafon Symbio, Oticon Syncro & Delta, Unitron Indigo, ….)Oticon Syncro & Delta, Unitron Indigo, ….)


BUT both (1) and (2) may cause a listener BUT both (1) and (2) may cause a listener or a player to miss out on the first few bars or a player to miss out on the first few bars of music or miss out on the tuning of their of music or miss out on the tuning of their instrument.instrument.

Six feedback reduction techniques Six feedback reduction techniques and music…and music…

(3) Harmonics in the 3000 Hz region will (3) Harmonics in the 3000 Hz region will also have a lower frequency harmonic in also have a lower frequency harmonic in the 1500-2000 Hz region, whereas the 1500-2000 Hz region, whereas feedback would not (ie., it would be only at feedback would not (ie., it would be only at 3000 Hz)3000 Hz)

Can use a broadly tuned band pass filter Can use a broadly tuned band pass filter from 1000-2500 Hz. If energy, then from 1000-2500 Hz. If energy, then harmonic; else feedback…..harmonic; else feedback…..


(4) Limit the amount of filter adaptation(4) Limit the amount of filter adaptation Create a poorer model of the feedback Create a poorer model of the feedback

transmission line so that the feedback transmission line so that the feedback reduction technique would be less effective reduction technique would be less effective overall.overall.


(5) Siemens Acuris/Centra.(5) Siemens Acuris/Centra. CLAIM: this circuit can distinguish between CLAIM: this circuit can distinguish between

music and non-music 75-80% of the time.music and non-music 75-80% of the time.• ……. It is a two stage phase cancellation approach.. It is a two stage phase cancellation approach.

• Distinguishes between internal feedback and an Distinguishes between internal feedback and an external “feedback-like” tone.external “feedback-like” tone.

• Mitigated by a slow vs. a fast attack time.Mitigated by a slow vs. a fast attack time.


(6) Turn off feedback reduction (and noise (6) Turn off feedback reduction (and noise management) systems.management) systems.

My “gut feeling” regarding My “gut feeling” regarding music….music….

If the feedback/noise reduction systems If the feedback/noise reduction systems cannot be disabled, the best approach is cannot be disabled, the best approach is the adaptive gain reduction since it is the the adaptive gain reduction since it is the one that is less susceptible to artifacts (eg. one that is less susceptible to artifacts (eg. Chirping, and frequency-hopping)…Chirping, and frequency-hopping)… (eg. Phonak Perseo, Phonak Verve, Widex (eg. Phonak Perseo, Phonak Verve, Widex

Inteo) Inteo)

My “gut feeling” regarding My “gut feeling” regarding music….music….

… … OR …OR …

A feed-forward phase cancellation system A feed-forward phase cancellation system with SLOW time constants in order to with SLOW time constants in order to differentiate long lasting feedback from differentiate long lasting feedback from shorter, intermittent musical harmonics.shorter, intermittent musical harmonics.• (eg. Bernafon Symbio, Siemens Acuris/Centra, …)(eg. Bernafon Symbio, Siemens Acuris/Centra, …)

Some thoughts on noise Some thoughts on noise reduction systems…reduction systems…

DON’T!DON’T!


Best noise reduction system (other than a Best noise reduction system (other than a binaural hearing aid fitting) is one that uses a binaural hearing aid fitting) is one that uses a directional microphone.directional microphone.

BUT, musicians are so aware of how they are BUT, musicians are so aware of how they are perceived, it is rare to find someone who will perceived, it is rare to find someone who will wear anything but a SMALL CIC aid.wear anything but a SMALL CIC aid.

May be useful for non-musician listeners …May be useful for non-musician listeners …


Many manufacturers have tried frequency Many manufacturers have tried frequency response changes. This may take the response changes. This may take the effect of a low cut, a low frequency boost, effect of a low cut, a low frequency boost, a high cut, a high frequency boost, or a high cut, a high frequency boost, or alterations to the mid-frequencies.alterations to the mid-frequencies.

None work well, and are probably of None work well, and are probably of minimal use in real life situations.minimal use in real life situations.


Modulation rate analysis may offer some Modulation rate analysis may offer some hope?hope? The modulation rate is the rate in Hz of the The modulation rate is the rate in Hz of the

time based waveform increasing and time based waveform increasing and decreasing in intensity. For speech it is decreasing in intensity. For speech it is typically 4-6 Hz.typically 4-6 Hz.

The modulation depth is the amount of The modulation depth is the amount of decibels between the quietest and loudest decibels between the quietest and loudest elements. For speech this is typically about elements. For speech this is typically about 30 dB.30 dB.


If the modulation rate is greater than 2-3 If the modulation rate is greater than 2-3 Hz it is speech or speech-like.Hz it is speech or speech-like.

If the modulation rate is less than 2 Hz, it If the modulation rate is less than 2 Hz, it is noise or noise-like.is noise or noise-like.

If the modulation rate is 50 Hz…. ???If the modulation rate is 50 Hz…. ???

[a] as in ‘father’[a] as in ‘father’


Speech has modulation rates 4-6 HzSpeech has modulation rates 4-6 Hz

Noise has modulation rates <1 HzNoise has modulation rates <1 Hz

Music has modulation rates of up to 100 Music has modulation rates of up to 100 HzHz


There are two commonly used types of There are two commonly used types of modulation rate analysis:modulation rate analysis: Multi-channel adaptive modulation rate Multi-channel adaptive modulation rate

algorithms. (eg. Siemens, Phonak, Widex, algorithms. (eg. Siemens, Phonak, Widex, Resound, Oticon, Unitron, Bernafon Neo)Resound, Oticon, Unitron, Bernafon Neo)

Synchrony detection co-modulation rate Synchrony detection co-modulation rate algorithms. (eg. Oticon Syncro)algorithms. (eg. Oticon Syncro)


Co-modulation rate detection is based on the Co-modulation rate detection is based on the fundamental frequency (ffundamental frequency (foo) of speech ) of speech

(100 Hz to 250 Hz).(100 Hz to 250 Hz).

Noise has no co-modulation rate (ie., it is not Noise has no co-modulation rate (ie., it is not periodic).periodic).

Music may or may not have a co-modulation Music may or may not have a co-modulation rate… so…?rate… so…?

A FINAL thought on noise A FINAL thought on noise reduction systems…reduction systems…

SpeechSpeech Instrument Instrument MusicMusic

NoiseNoise

Modulation Modulation Rate (Hz)Rate (Hz)

4-6 Hz4-6 Hz 10-100 Hz10-100 Hz <2 Hz<2 Hz

Modulation Modulation Depth (dB)Depth (dB)

30 dB30 dB 60 dB60 dB <15 dB<15 dB

Something else we can do with Something else we can do with music and hearing aids…music and hearing aids…

Many hard of hearing people, especially Many hard of hearing people, especially children cannot enjoy music.children cannot enjoy music.

Instead of conditioning hearing aids to Instead of conditioning hearing aids to accept music, one can change the input.accept music, one can change the input.

Many hard of hearing adult musicians Many hard of hearing adult musicians have been known to change from violin to have been known to change from violin to viola.viola.


We can transpose music down to a We can transpose music down to a frequency region with better auditory frequency region with better auditory function.function.

Frequency transposing hearing aids are Frequency transposing hearing aids are one solution.one solution.

Another is to change the music …Another is to change the music …


Using software, such as Adobe Audition, Using software, such as Adobe Audition, music can be transposed without affecting music can be transposed without affecting the temporal characteristics.the temporal characteristics.

For example, one can use the “stretch” For example, one can use the “stretch” function while preserving “tempo”.function while preserving “tempo”.

A Plan …A Plan …

People can bring in pre-purchased CDs with People can bring in pre-purchased CDs with their favorite music.their favorite music.

This can be ripped onto the computer and using This can be ripped onto the computer and using Adobe Audition, the frequency of the songs can Adobe Audition, the frequency of the songs can be reduced/transposed.be reduced/transposed.

They can walk away with the original CD and the They can walk away with the original CD and the new transposed CD, with more intelligible music.new transposed CD, with more intelligible music.

www.chasin.ca/musicwww.chasin.ca/music

www.chasin.ca/musicandhearingaidswww.chasin.ca/musicandhearingaids


Musicians and Hearing AidsMusicians and Hearing Aids

[email protected]@rogers.com


musicians and hearing aids marshall chasin aud, m.sc., reg. caslpo, aud(c ) musicians’ clinics of...

Documents

db speech

db music

differences speech

db spl music

db splshouted speech

intensity slide

dba slide

db spl53 db spl