From: "Chris Haynes" <chaynes@sunfish.cs.indiana.edu>
Subject: Re: ANC Headsets
Keywords: ANC, Headsets
Organization: Indiana University, Bloomington
Date: Sat, 19 Dec 1992 17:17:54 -0500

>Has anyone had addtional experience with the Evolution ANC Headsets?

I've had only a couple of flights with mine, and I'm very impressed.  In
the cord there's a rectangular power module containing nicads, charger,
volume control, jack for cig lighter power cord, power switch, two LEDs
(power and charging--goes out when charged).  Otherwise it looks very much
like conventional sets of high quality, including a modern-style flexible
mic boom.  The head band is almost identical to the one on my Dave Clark
10-40, not the flimzy looking one of the prototype pictured in their adds.
The cords are somewhat beefier than Dave Clark's.  The power switch, volume
control, and external power jack are all the sort you'd find on a Walkman.
For reliability and ease of use I wish they were more substantial -- a
minor gripe.

With the power off it functions much like other headsets, greatly reducing
high frequency noise and doing precious little to the low-end noise.  (The
passive attenuation is said to be 21db instead of the 24db of the better
traditional headsets like the 10-40, but I couldn't tell the difference.)
Turn the power on, and in a couple of seconds the low-end noise DISAPPEARS!
(My plane is a Grumman AA1C, which has the same engine as a 152 but is
somewhat noisier since it has a canopy.)  The high-end noise remains -- in
fact even seemed to me to be slightly greater, but that's probably a
psychological effect due to lack of competition with low-end noise.  Of
course the passive attenuation has greatly reduced the high-end noise, so
the overall impression is comparative silence.  I believe hearing loss is
mostly from high frequency noise, so

Communications are MUCH easier to hear in that silence.  So is electronic
and microphone noise, so you'll really be lucky if you have a high quality
intercom such as the PM1000 and you'll wish you had one if you don't.  The
difference between the PM1000 and a Telex intercom was dramatic.  You just
have to get used to hearing every buz and squak on the com channels and in
your plane's electrical system (unless you get the latter fixed).  

You also have to get used to a quite different engine sound.  Enough
high-end noise gets through to hear RPM changes and such things as
over-leaning roughness, although the latter I sensed more in my seat than
my ear.  (Could engine experts suggest problems that can be heard in
low-end noise but not felt or heard in high-end noise?)  It was also easier
than with my old headset to hear someone next to me speak w/o the intercom.

This is purely subjective, but the amount and quality of noise that gets
through reminds me of road noise in my Subaru (which has a somewhat noisier
than average engine but is fairly typical of small cars) when the road is
smooth.  Overall I'm very impressed with ANC technology of the Evolution
headset.

>Anyone had a chance to compare them to the other major brands?

I'd also be interested in hearing from anyone who has.  My impression is
that the other ANC units are better, though still imperfect, at cancelling
high-end noise.  (They couldn't be noticeably better at the low-end --
silence is silent.)  More high-end attenuation wouldn't necessarily be an
advantage if you want to clearly hear the engine and passengers speaking
without an intercom.  The only reason I can think of for spending 2 to 4
times the $300 Evolution price for one of the competing brands is if you're
so devoted to hi-fi music that you've got to have the best in the air.  The
difference could be like listening to music in an economy vs. a luxury car.

Chris Haynes
N30NA

-- 
     Chris Haynes -- Computer Science Department -- Indiana University
     Bloomington, IN 47405 -- 812-855-3376 -- FAX 812-855-4829
Newsgroups: rec.aviation.products