Natural Science Forum / Physics / Acoustics / August 2005

Hey all,
Does anyone have or know of reference to a table of C-weighted values
for typical noise sources (car @50mph/50ft= xx dBC, vacuum cleaner at
5ft= yy dBC, etc)?

Have I got it right? An earth bank makes no difference to transmitted noise?
Also foliage the same?
yours
Richard

Nowadays i work for acoustic enclosure design used for compressor.
Is there any standard such as ISO for enclosure design ?
It will be better if the contents of thermal insulation are included.
Thank you.

I've been playing around with ultrasonic transducers. I generated two
waves of differing frequencies (ex. 75 kHz and 80 kHz) and multiplied
them and I heard the 5 kHz tone in the air, which was great, especially
since it was directional.

I am going to measure RT of a large auditorium.  I am facing a problem that
how to place the loudspeaker in a right position. I dont have an
omi-directional speaker but a cube-like loudspeaker (speaker diameter about
14" ).

Dear Acoustikers:
    For some decades, I have been using a barrier attenuation model to
predict the height required for effectively screening housing sites from
highway noise. Land developers have usually gone along with the required

Friends:
my question now is about the technical diference between measure power
level of a source with an intensity probe and using a survey method
like iso 3744 or iso 3746 for example. Is clear the economic diference

Hi ... When I played with my cat today, suddenly I rasied up a question
in my mind.  Why cats walk and jump so quietly ? Does this relate to the
pads on foot, the body flexibility .... etc ? When a 15lbs cat jumps up
onto a table, sound should be generated, where does this sound go ...

I'm reading that sound can be made coherent like light beams (Lasers)-
focusing light trough a ruby, etc.
anyone know HOW this done?
Tip:

I am trying to implement an adaptive beamforming algorithm using
artificial delayed two channel data for my class project.
The sampling rate of signal is 8000Hz, I assumed the spacing between
microphones are 17cm. The target speech signal comes from the center of

Not exactly "acoustics" but might be of interest to those concerned
about the hearing damage sound reinforcement can inflict.
http://www.stevehoffman.tv/forums/showthread.php?t=55342&page=1&pp=20
WVK

Hi, All;
A couple of years ago I bought over a dozen ceramic disks that I tucked away into
a drawer and forgotten, that may either be PZT-5H or PZT-8; I honestly don't
remember

In a duct with a side - branch, would the amount of sound in the branch
depend on constant sum of volume velocity in the duct system?
yours
Richard

A well-known technique for measuring flow in a pipe is comparing the
time-of-flight or phase of a sound signal (propagating in the
longitudinal direction) from point A to point B with that from point B
to point A. The difference in phase or time-of-flight is a measure of