[Don Pearce[_3_]]

On Fri, 5 Jun 2009 14:55:55 +1000, "Mr.T" MrT@home wrote:


"Don Pearce" wrote in message
news:4a2c020b.558504156@localhost...
On Thu, 04 Jun 2009 13:04:08 -0400, Harlan Messinger
wrote:

I've got a pair of Sony MDR-NC6 noise-canceling headphones. They do a
great job of removing the low, rumbling sounds, like the office copier
or the continuous roar on a plane. On the other hand, on a plane, they
do virtually nothing about the higher-frequency airplane sounds
(hissing, whining), and they add their own hiss.

I asked someone selling expensive Bose headphones at Denver Airport
about whether their phones cover the higher frequency ranges, but he
turned out not to be informed on such a technical topic.

Is this issue with my Sony phones normal--are only the lower frequencies
targeted by today's noise-canceling products? Or are there products that
I can rely on to cancel a wider range of frequencies and, ideally don't
introduce significant noise of their own?

It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.


I don't own any NC headphones, but surely anything designed properly, rather
than just for marketing hype, would use a combination of both NC to combat
LF noise where simple isolation is difficult and less affective, and use
good insulation/isolation of the higher frequencies where NC is impossible.

I imagine there are some that do meet the criteria, but you may need to look
past Sony and Bose, and put up with bigger, heavier headphones.

MrT.


Phones that isolate the HF well also tend to deal with the bottom end
without resort to active cancelling. Where active phones work well is
in situations like light aircraft where there is a great deal of throb
and drone to get rid of, which is well taken care of with FFTs and
multiple band generators. Then, because the headshells are lightweight
and not particularly padded, all the other external sounds that you do
want to hear - radios, beacons, your passenger etc, which are not
repetitive - are far better heard than without them. That, as far as I
can see, is the true raison d'etre for active phones.

d