If the Shure buds seal the ear canal, I wonder if they create a pressure condition where the eardrum
or bones are flexing more or less than normal for a given SPL. The idea is very appealing if it
allows even lower volume levels from an iPod, but it would be very bad to do worse damage due to
unnatural air-pressure/air movement situations inside the ear.
I expect we'll see plenty of research on all this soon enough since there are already some worrying
stats about how much hearing damage the "iPod generation" is doing to themselves at a much younger
age than previous generations.
----- Original Message -----
From: "Mike Richter" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, May 15, 2006 9:47 PM
Subject: Re: [ARSCLIST] headphones revisited
> Tom Fine wrote:
>> Is there any science on the hearing-damage ramifications of these noise-cancelling phones? Do
>> they allow lower-SPL listening or are they putting out more SPL to cancel outside noises?
> I've seen no science on the subject and do not use Shure's product, but perhaps my experience with
> other models will be helpful.
> The Philips phones I use provide both noise cancellation and signal boost. The boost seems to be
> frequency-dependent, reaching perhaps 2 db in the upper midrange. Noise reduction varies with the
> ambient noise but seems to be in the neighborhood of 5 db. The phones begin a few db less
> sensitive than typical over-the-ear models; I have not tried earbuds.
> I suggest that on the bottom line these phones allow several db lower SPL without sacrificing
> intelligibility. Since high fidelity and a noisy environment are not consistent, the frequency
> shaping is not a drawback. At the same time, they offer the opportunity for higher SPL due to
> their signal boost, though like most players they run on a single 1.5-volt cell so cannot peak
> higher than another headset of the same efficiency.
> [log in to unmask]