Alternative Assessments for Musicians Marshall Chasin, AuD., M.Sc., Reg. CASLPO, Aud(C) Musicians’ Clinics of Canada

Why do any tests?  Hearing loss prevention  Assessment of hearing aids for music  (Assessment of musicians)

Hearing Loss Prevention  Audiometric High frequency testing High frequency testing Actual bandwidth of hearingActual bandwidth of hearing Notches in hearingNotches in hearing Up to 12kHz vs. higher…Up to 12kHz vs. higher…  Non-audiometric OAE (TTS analog) OAE (TTS analog) Speech in noise tests Speech in noise tests

Audiometric  High frequency artifacts Stinson (1988, JASA): minimal artifacts up to 12kHz but large variance above this. Stinson (1988, JASA): minimal artifacts up to 12kHz but large variance above this. Minimized with proper earphones that have both a smooth frequency response and wide bandwidth. Minimized with proper earphones that have both a smooth frequency response and wide bandwidth. Monitor at TM with probe microphone to verify calibration. Monitor at TM with probe microphone to verify calibration. Good test-retest reliability WITHIN subjects… Good test-retest reliability WITHIN subjects…

From: Nancy E. Vaughan, et al. 2002, Journal of Res. Rehab. Development (within subjects)

The right earphone for the right frequency…

The 4000 Hz notch  Results from a 28 mm long ear canal that functions as a quarter wavelength resonator…  F = (2k-1) v/4L  Odd number multiples of 4000 Hz… 12kHz, 20kHz,… 12kHz, 20kHz,…

The 4000 Hz notch  Even though the ear canal is on average, 28 mm… F = 340,000 mm/sec/4x28 mm = 3035 Hz But… F = 2700 Hz But… F = 2700 Hz The eardrum adds several mm of acoustic length because of its compliance. (3-4 mm) The eardrum adds several mm of acoustic length because of its compliance. (3-4 mm)

The 4000 Hz notch  BUT, for higher frequencies, the eardrum does not supply the extra several mm of acoustic length, so that odd number multiples of the 4000 Hz notch is really higher than 12kHz (… more like kHz).

High frequency audiometry  So,…. With the proper earphones and within subjects, one can reliably test in the higher frequency range.  (1) higher frequency notches (14k-15kHz) may occur prior to the Hz notches.  (2) 10k-12k thresholds may help identify etiology. (eg. Violins have an 8kHz notch).  (3) good reliability within subjects (longitudinal).

Ear Q software  Ear Q is one of many software products that can allow your lap top to become a (high frequency) audiometer…

High frequency audiometry  Interesting trivia…  Ashihara (2007) JASA: humans can hear up to 28kHz. As long as presentation level is 100 dB SPL. As long as presentation level is 100 dB SPL.

Non-audiometric tests  OAE Poor test-retest reliability between subjects. Poor test-retest reliability between subjects. But, good test-retest reliability within subjects. But, good test-retest reliability within subjects. Like high frequency audiometry, can be used for longitudinal testing of differences within subjects.Like high frequency audiometry, can be used for longitudinal testing of differences within subjects.

OAEs  Can be used to assess temporary changes (eg. TTS).  Can be used to assess deterioration over the years.  Can be used to test non-audiometric frequencies.

Otoacoustic Emissions (Drummer - symmetrical “hearing”)

Otoacoustic Emissions (Lead singer moved away from drummer)

OAE “notch” at 5000 Hz and not measured on audiometry...

What about assessment of hearing aids for music?  “Traditionally” one looks at pre-selection… Wide bandwidth Wide bandwidth WDRC WDRC Appropriate compression Appropriate compression High input limiting level or equivalent High input limiting level or equivalent Disabled feedback and noise management Disabled feedback and noise management 6 dB lower gain and output for same level 6 dB lower gain and output for same level

but,… how do you evaluate aids?  (1) Ensure that electro-acoustic settings and parameters are correct.  (2) An assessment scale (like the AI)….

Development of an assessment scale…  Gabrielsson et al. (1974, 1991)  Cox and Alexander (1983)  Chasin and Russo (2004)

Development of an assessment scale…  Loudness- music is sufficiently loud  Fullness- music is full (vs. thin)  Crispness-music is clear and distinct (vs. blurred or diffuse)  Naturalness- as I remember it (as if there was no aid there)  Overall fidelity- dynamics not constrained

Development of an assessment scale…  Cannot develop an AI (or SII) for music since there is no long term spectrum as there is for speech.  Can develop correlations (and regressions) between these five outcomes measures and various bands of music. Successive low pass filtering and the five perceptional parameters will be assessed at each of the cutoff frequencies of the LP filters.

Development of an assessment scale…  Goal: determine which perceptual parameters (or combination of parameters) correlates with which frequency band, similar to an SII measure.