Natural Science Forum / Physics / Acoustics / February 2007

Friends:
Exist any recomendation, like ISO, ANSI, ASTM, or other that give a
ranges for background noise in a give room. I know about books about
that, but this ranges are in any standard.

DOes anyone know how I can get/buy a CD of an anechoic music
recording? I know there was an orchestra recording in an anechoic
chamber, how can I get it? I'm trying to find something like drum
recording with a lot of transient although music in general will be

I am looking for a closed form solution for the distribution of sound
pressure across the surface of a rigid piston vibrating in water.  The
diameter of the piston is 15mm and the frequency of vibration is 50KHz.  I
can measure the surface vlocity and need the pressure ...

I am looking into active noise control of car exhausts.  I understand
some work has been done in this field, but cannot find anything recent.
 A lot of websites have closed down.  Can anyone point me in the
direction of recent work (especially in the uk) on this.

Dear Acoustikers:
For those computer savvy, here's a way to let Windows do your work in
coping with new daylight savings time date settings;
Following is self-explanatory (Thanks to one Russell Childers)

The Material World - BBC science programme in a an hour and a half
(16.30 GMT), looking at techniques for recreating the acoustic space
of old or distant buildings by acoustic mapping.
May be quite interesting  - listen online.

I'm not really familiar with rigid fiberglass or where to buy it.
I really need it for insulating my basement, and unprotected foam
sheets it not permitted. I would like some foil on top of the sheet
or both sides. Since many here work with this kind of stuff,

It's been brought to my attention recently that the forms dB(A) etc. are
considered incorrect by the AES and the IEC, who prefer dB A-weighted, or dB
A-wtd, etc.
They say that an abbreviation in brackets after dB must only indicate the

I'm trying to get the best possible SNR from emitting broadband chirps
in a tank filled with water.  I'm limited by the maximum power that
the transducer can output, but I also know that increasing the chirp
length will improve the SNR.  But is there some sort of equation or

I currently have a version of the UK DoE Advisory Leaflet 72 "Noise
control on building sites" (published 1976) which appears to be a pdf
version of a scanned copy such that some of it is almost illegible;
can any one assist with a more legible copy please?

I have a problem trying to do acoustic measurements in a water tank
(the tank is only a simulation of the environment containing the DUT).
One easy way of doing this is transmitting short bursts of a single
frequency. The problem arises (of course) for low frequencies where

I ended up double-posting this because I wasn't really sure which
group I should ask the question in.
I am curious about those ultrasound emitting devices that are supposed
to repel insects or other pests. I did not want to spend money on

I've been watching the commercials for the movie Messengers with
interest because of the so-called message only kids can hear. I can
hear up to 15 kHz and I didn't hear squat and I'm wondering if there
really is such a highpitched message in the commercial. Does anyone

Hi,  when performing frequency spectrum analysis, do various octave
settings produce frequency response curves at different dB levels, if
the audio being measured does not change?  As a test, I output pink
noise at my laptop headphone output, and run that through a quality

Coarsely shredded or cut into random size chunks anywhere from
1" to 4" across; what might I expect if used as a sound insulating
packing?  Fireproof with boric acid or similar, or use where fire
isn't a hazard.