On Mon, 04 Sep 2006 10:57:37 +0100, wrote:

On Mon, 04 Sep 2006 05:14:25 -0400, Roger
wrote:

On Sat, 02 Sep 2006 20:50:46 +0100, wrote:

On Sat, 02 Sep 2006 14:25:05 -0400, "Roger (K8RI)"
wrote:

On Sat, 02 Sep 2006 18:22:41 +0100, wrote:

On Thu, 31 Aug 2006 21:19:11 -0400, Roger
wrote:

snip

I've been looking at headsets recently and came to the conclusion that
the QFR XCC clone is a good compromise at $240. Compared to other ANR
headsets it has some of the highest passive attenuation though only
~10db electronic. If the electronics fail it should still be very
good.

By the way Roger you mentioned in a previous post that 3db was
half/double. I think you're still thinking of power not volts.
I assume ANR refers to volts so think 6db = half/double, or am I
getting rusty with all this?

Sound (and our hearing) is logarithmic so I'm pretty sure that the 3
db holds for sound as it does for power.




David
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger, now you've got me thinking:-) As you say it's logarithmic but
if I'm not mistaken 10w to 100w =10dbw, 10v to 20v = 20dbv. I don't

That is correct, but sound is analogous to power not volts.


know how ANR is measured so I'm guessing dba but it looks like double
= 6db. In an expample I found on the web and you compare say the Rifle
& Threshold of Pain there's 6db difference. That would suggest
headphones with say 26db passive attenuation would reduce the sound
level by a factor of 40. If you use 3db then it would be a factor well
over 500 which I think would be unrealistic.

Source of sound Sound pressure Sound pressure level
pascal dB re 20 µPa
=============================================
Rifle being fired at 1 m: 200 Pa = 140 dB
Threshold of pain: 100 Pa = 134 dB
Hearing damage during short term effect: 20 Pa = approx. 120 dB
Jet, 100 m distant: 6 – 200 Pa = 110 – 140 dB
Jack hammer, 1 m distant / discotheque: 2 Pa approx. 100 dB
Hearing damage during long-term effect: 6×10-1 Pa = approx. 90 dB

When I had a two blade prop on the Deb is was measured at 93 db at a
distance of one city block and full RPM. So you can see why the
neighbors off the end of 18 complained when I'd go over at roughly 300
feet on climb out at full power. :-))

David (GM3RFA)
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

I'm not qualified to comment further on this topic so will let it lie
and await somebody better qualified to chip in.

Ok on the Deb, it sounds much louder than the PA28 I fly. Perhaps you
need some 'Stealth bomber paint' so they don't know who you are?

And unfortunately I have those great big numbers on the side. sigh

One *hot* afternoon, the wind was out of the SSE and gusty. That
meant even the high performance stuff was using 18. Unfortunately that
same subdivision fought lengthening 18/36 so *everyone* was going over
their houses at 200 to 300 feet. I made three takes offs and
landings that afternoon. We had a pair of Navions, a 310, two 210s, a
couple of Bonanzas, some 182s and I don't remember what else.

It was a busy day at the airport and I have no doubt they were telling
the truth when they said they couldn't even carry on a conversation
when one of us went over. To the non flying we all sound alike and
the one guy wrote down my N number. He said I went over every five
minutes. I can't take off, fly the pattern, land, taxi back and take
off again in less than twice that. Fortunately he lost sympathy and
credibility when accusing one plane of doing all that when the pattern
was full most of the afternoon.

I wasn't one of those paint jobs that changes color depending on your
angle to the viewer and sun. That way no two people will give the same
story. :-))

When we took off, loaded to gross for the day and I could see the
grass under the picnic table through the gaps in the top I told my
passengers "I'll bet we hear about this one!":-))

Which reminds me. That subdivision just popped up. One day I was on
final for 36 and some guys were putting up a tall TV antenna. I
noticed it was gone the next day. I had the gear down and full flaps
with lots of power when I went directly over the top of it. I'll
bet it was a bit drafty on top of that tower. Apparently they didn't
know they are not allowed to go above the tree line around there.
Actually I think it may be less than that.

If you ever visit 3BS and land using the VASIs on 36 you'll know what
I mean. Take a look just south of the expressway.



David
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com