session 2 7 - grøndal k - hearing test - seafarers ver2
DESCRIPTION
The Norwegian Sea Health Conference 2014, Bergen, 27-28th August 2014TRANSCRIPT
NMA/NCMM Approved Doctors' Meeting 2014
Kjell Grøndahl, M.Sc. Dept of Medical Engineering
Haukeland University Hospital Bergen, Norway
TESTING SEAFARERS HEARING CAPACITY WHILE USING HEARING AIDS
INTERNATIONAL LABOUR OFFICE / INTERNATIONAL MARITIME ORGANIZATION, 2013
APPENDIX B: HEARING STANDARDS
UNAIDED HEARING
PTA «Pure Tone Average» max:
30 dB in the better ear and
40 dB in the less good ear
Measured at the frequencies 500, 1000, 2000 and 3000 Hz.
AUDIOGRAM
Left
Right
Is this an acceptable hearing loss?
PURE TONE AUDIOMETRY
• Independent of language
• Standardized equipment and methods
• Not suitable for testing with hearing aids
• Does not measure speech recognition
SPEECH AUDIOMETRY
SPEECH AUDIOMETRY
• Routine test in many countries
• Calibration issues: Values for sound field (loudspeaker) may not be available.
• Difficult to compare across languages
• Speech without background noise is not representative for normal working conditions
AIDED HEARING
Appendix B: ”Alternative assessment methods using validated and standardized tests that measure impairment to speech recognition are also acceptable.”
AIDED HEARING
Testing with headphones not possible
We want to test speech recognition in realistic conditions (background noise)
Speech Noise
SPEECH-IN-NOISE (SIN) TEST
Result: The speech/noise ratio (SNR) where 50% of the words are repeated correctly
Speech Noise
SPEECH-IN-NOISE (SIN) TEST
Example:
67 dB 65 dB
SNR: + 2 dB Sound examples: people.kth.se/~e99_ehe/project.html
SPEECH-IN-NOISE (SIN) TEST
Many different methods in use. Manual, adaptive, single-speaker, multi-speaker, different types of noise. But they all measure the SNR at 50 %.
AVAILABLE TESTS
• Validated tests are available in many languages
• A few tests are standardized and available in more than one language. One of the most common is HINT (Hearing In Noise Test) from House Ear Institute.
• Some require proprietary equipment
• Often used to evaluate the fitting of hearing aids
• Main users: University hospitals, hearing aid dispensers
WHAT SHOULD BE AN ACCEPTABLE RESULT?
According to the guidelines:
“Hearing aids are only acceptable in serving seafarers where it has been confirmed that the individual will be capable of safely and effectively performing the specific routine and emergency duties required of them”
WHAT SHOULD BE AN ACCEPTABLE RESULT?
SIN tests are validated using young, normal-hearing subjects. We can compare the results to this reference (similar to the audiogram) We assume that the validation measurements follow a normal distribution. A reasonable «rule of thumb» may be using the 5 % percentile or 2 standard deviations (= 2.3 % percentile). The requirements of the actual workplace must be taken into consideration.
WHAT SHOULD BE AN ACCEPTABLE RESULT?
REFERENCES
Audiogram figure: Public Domain (Wikipedia / User:Carnildo). Hearing loss example by Kjell Grøndahl
Hearing aid image: Oticon
Speaker setup illustration: HINT test, House Ear Institute
Sound examples: people.kth.se/~e99_ehe/project.html
(Dept. of Speech, Music and Hearing, KTH, Sweden)