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Helping Apple get iPod hearing protection right

Hi John Lazzaro,

Thanks for the news item.  I guess putting a volume limiter in the iPod is a 
start, but they tried that with Walkmans in times past.  But it's a bit like 
advertising low-strength heroin, quiet vacuum cleaners, or a Ferrari with a 
speed governor.   It's the power buzz which sells things - at least to the 
group least likely to listen to warnings.

At least if Apple has raised awareness of the risks to hearing it's a good start.
SONY also issued a throw-away (red) slip with their products.

I've added to my webpage (below) a section on our research on the effects 
of Walkmans on hearing... or more specifically the effect upon click-evoked 
otoacoustic emissions.  It was originally published (1998) in the Medical 
Journal of Australia (alas not very mainstream or accessible) but is now 
available in pdf format or by going directly to the eMJA site.

The article shows two things.  
1)   Walkmans (particularly with button earphones), with only up to 6 hours 
use per week, can be as damaging to hearing as working in noisy industry; 
over 6 hrs per week produces are larger effect, while both kinds of 
exposure can be at least twice as damaging), and 
2)   Click-evoked otoacoustic emissions are good at revealing hidden 
accumulated damage, since none of the 900+ users tested had a 
hearing loss.  

OAEs are mostly used as a quick predictor of hearing thresholds, but 
in our hands they can do much better than that; our measure of 
emission strength declines by 80 percent of its range before hearing 
levels START to shift.  i.e. a "1 percent hearing loss" constitutes a 
large amount of outer hair cell damage.

This work was quite controversial at the time, but several groups have
duplicated the idea of using OAEs for early warning of hearing loss.  Our
methodology now gets a mention as an appendix in the new Australian/NZ
Noise Standard (AS/NZS 1269.4:2005 Occupational noise management 
- Auditory assessment)

Eric LePage