[WARC] Nice Net Tonight!

[Leslie Hittner]

The article is very clear about one thing: The passive (acoustic isolating)=
 features block or reduce high frequency sound waves. The active noise redu=
ction is effective on low frequency sound waves. I do not get a sense from =
this site that the active response is "instantaneous" and not throughout th=
e article that the motivation - at lease for Bose - was jetliner noise.

I think for the active reduction to be effective in an office it would have=
 to be a very large office indeed (unless there was a bothersome window-mou=
nted air conditioner accross the room). It would be interesting to try them=
 against the thousands of conversations in an auditorium before the event b=
egins.

-Les


----- Original Message ----- =

  From: Len Litvan =

  To: Leslie Hittner =

  Cc: Winona Amateur Radio Club general discussion =

  Sent: Monday, December 31, 2007 09:04
  Subject: Re: [WARC] Nice Net Tonight!


  Hi Les,

  Here is a site about noise-canceling headphones:  http://electronics.hows=
tuffworks.com/noise-canceling-headphone.htm

  It looks like the active types are "instantaneous" in response to outside=
 noise and would quiet irregular noises as well as stable noise sources.

  HNY & 73,
  Len KC0RSX

  Leslie Hittner wrote: =

What kind of "noise" do noise cancelling headphones eliminate?
These devices integrate noise over time and eliminate the noise
by producing out-of-phase counterparts and linearly adding the
two waves. That means they are most effective on stable noise
sources, such as jet engine noise in airliners, components of
vehicle road noise, etc. They are less effective on short
duration pulse noise and sounds whose spectra vary with time
(like speech.)

In addition to the electronic noise elimination, noise canceling
headsets usually feature very effective acoustic isolation from
outside noise sources. I suspect such isolation, rather than the
electronic DSP systems, is most effective in communications
center environments.

I admit, I haven't listened to every noise canceling headset on
the market, but this has been my experience. I actually decided
not to purchase a pair but then I just got one from my son for
Christmas. My experience with that set so far bears out my other
observations and I believe I will most often use the headset
when flying.

I know that Clare has a set of noise canceling headphones and
would be interested in his observations, since I was unable to
be in the net tonight.

-Les

----- Original Message ----- =

From: "Len Litvan" <Litvan at acegroup.cc>
To: "W0NE Listserv" <warc at lists.w0ne.org>
Sent: Sunday, December 30, 2007 21:32
Subject: [WARC] Nic Net Tonight!


  Hi folks,

That was a good net tonight--very informative.

I especially liked the info about noise-canceling headphones.
    I was
  about to buy a conventional headset (to replace the Radio
    Shack and
  assortment of other earphones around) but was not considering
    noise
  canceling types.

The comments about noise canceling at emergency sites was a
    big factor
  in persuading me to go upscale and get a noise-canceling set.
    Thanks
  for helping me spend our money wisely!

73,
Len KC0RSX
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