Natural Science Forum / Physics / Acoustics / February 2006

I am a beginner of acoustics.
I understand frequency for periodic sound waves, since they repeat a
certain pattern.
But in the power spectrum of an aperiodic sound wave, for example, [s],

Hi everyone. We are led to believe that humans can only hear
frequencies between approx. 20Hz -20,000Hz or there abouts depending on
how good ones hearing is. If this is so why do we hear the difference
in timbre between a triangular wave who's fundamental frequency is

What is the most unusual event you have been paid to measure a sound level
of?
I have just done the most unusual for me.  It was a milk float (electric
delivery vehicle for non UK readers) being dropped 100 feet on to a hard

How do we go about getting more than 45 dB attenuation for noise
isolation?
rajag

I have finally had time to put some web pages together that show the
stages I went through to build my drum practice room.
I started with an empty garage, and ended up with a drum practice room
and a home office rolled into one.

As part of due diligence I am searching for references to published
articles about what is commonly called a "phase plug" as a part of a
loudspeaker or "acoustical" transducer.  (I did read the thread on
acoustic v. acoustical.)

Does anyone have any experience in setting up a type 1 recording
system.
We are considering using a marantz pmd671 to record sound from the AC
output of our type-1 sound level meter.

Dear colleagues,
I've got to measure vibration levels for vibrating feeders to a
controll rom. The feeders are more or less pipes which are vibrating i
2 axes by means of excentric rotating masses fixed on an electric

Bonjour,
I am looking for sound absorption coeff.of HELMOLTZ resonator.
Thank you very much.

I read some of the old posts (5-6 years ago) in this group about
acoustic cameras. (Especially by Optel). Has there been any new
developments in these devices recently? I need to measure and record
holograms in water using Ultrasound frequencies. Which companies should

Anybody know the formulas for ring vibrations? Seems like a simple
device, but the stuff out there, at least in older literature is very
confusing. One paper sid theory, even when modified for all know
anomalies can predict frequencies considerably in error- up tp 50%.

I'm looking for low-cost ultrasonic piezoeelectric transducers (i.e., <
$30). that couple to solids for sound speed measurement experiments.  Does
anyone know of a supplier?  (Note this is for coupling to solids, not air)
Thank you

I attend a mobile church that meets weekly in a grade school gym.  It's not
as bad as it sounds; the school is fairly new, and was built with a bit of
acoustics in mind.  So it's not the hardwood echo-chamber that one normally
associates with school gyms.  Another advantage, the ...

Hi ... I want to measure sound absorption coeff. of larger surfaces.
However, those surfaces cannot be cut in to pieces and tested in normal
impedance tube in lab.
Now, I am looking for a portable equipment (commerical products) which is

I just want to understand exactly how the speed of sound would be
affected by currents underwater? Does the current speed add linearly to
the speed of sound based on other water characteristics such as
temperature, salinity and pressure?