Natural Science Forum / Physics / Acoustics / December 2003

In lieu of an anechoic chamber for testing microphones over
their full frequency range I've been wondering if it would
be possible to make a variant of the impedence tube with
absorbant walls (to catch reflections off the microphone

When testing a person's/patient's sense of hearing in general a method is
used where this subject has to verbally indicate when a tone stimulus can
be heard. These tone stimuli are usually presented sequentially from loud
to soft (in steps of a few dBs) in one frequency. When the ...

If I have a sound field with a certain SPL at a point and I put a
helmholtz resonator there, how do I calculate how much the air in the
resonator's neck will move?

had once  seen an old late 50's sci-fi program where the announcer did
experiments with light, sound, radiation that would e consider insane these
days.
But one in particular intrigued me: the guy set up an oscillator connected

For different books and articles, the wave equations and their solutions are
representated by sound pressure field.  But there are also many articles
refering those equtaions and solutions in term of velocity potential.
(Basically, these two quanties are linked by a constant.)

I am working on an audiovisual installation and I need to obtain
*acoustically* the same result one obtains by electrically summing two
180 deg. out-of-phase signals - i.e. silence.
Somehow the results of my first experiments are somewhat frustrating,

This is my first time to this news group, thanks in advance for your help.
Has anyone had any experience or knowledge about how to quiet a DC gear
motor.     Our staff is stumped on how to quiet the motors to an
acceptable level. Silent being the most acceptable.  Any help would ...

I am moving my lab to another building, and among other things I am
inheriting a former cold room. They want to install an air feed to it, but I
am concerned that in the process of installing a register (air exhaust) I
will wind up with a major source of noise, as is the case in my ...

Many speech recognition system users use a headset microphone, which
in addition to the advantages it offers, also presents some
challenges, one of which is the importance of positioning the
microphone to the side of the mouth, out of the breath stream.

Does anyone have detailed specs for the RPG Skyline diffusors?
Pete

I'm not fluent in english, so I do not know if the terms i will use
are the correct one. Hope you will understand me ! :o)
I have a digital system plug to a microphone. I would like to measure
sound pressure level :

A paper I am just reading refers to J. Acoust. Soc. Am.
47(1970)3, 676-682, but without any other bibliographical
information.
ASA on line service has only volumes starting from 1975.

Does anyone have a sound power spectrum for tap dancing ... suggestions where I might find such a
noise spectrum.

Does anyone know of a complete reference(or an ISO norm) that provides
detailed  material of the calculations of the length, the tip angle of the
wedges for a desired absorption coefficient and a lower cut-off frequency.

Now as long ago as ten years ago there were some protests in BC
on the effect or marine seismic airguns on marine life, and now
there is a fair bit more in Nova Scotia.   So what is the
latest on the effect of such airguns on marine mammals