Natural Science Forum / Physics / Acoustics / May 2004

I know this may sound dumb but would canvas punching bags work as bass
traps? They are not filled with corning 70X but they gotta be better
than the foam crap you buy for $50.
Besides, being a boxing fan I think it would look really cool in my

My theory on space and matter is presently on the following URL:
http://www.geocities.com/garyforbat  It is called Dialogues on Matter.
This theory is embedded in a fictional framework. Chapter one deals
with micromatter, chapter 2 with macro (astro) matter.

Folks,
Apologies if this is OT
Do you know of any inexpensive products employing active noise reduction
(forward feedback) to reduce the noise of a large industrial fan and

Are there any standards or reference materials to specify the NC level
of the spa area? What's the common practice to specify the NC level of
the spa? NC20/25/30? I think over NC30 is not acceptable to me. In
addition, where can I find the NC level for special activity space,

In response to comments from the reviewers and some user questions, I
have reworked my Helmholtz calculation spreadsheet - particularly the
sheet for slotted absorbers.
This tool can be downloaded from

Hi everyone, what characteristics should I seek in a decoupler?
I would like to block noise through my hardwood bedroom floor.  I bought
some 1/8th-inch-thich mass-loaded vinyl to put beneath my fake Persian
rug, but the MLV didn't do much.  

I have just completed V1.0 of a spreadsheet to calculate the absorption
curve of a slotted or perforated Helmholtz absorber.
This type of calculation is more useful (IMHO) than simply calculating
the resonant frequency of a Helmholtz resonator, because the absorption

good moorning.
Do you know a web link where it's possible download setup file of larson
davis 2900? or a web link for this instrument?
(another that www.larsondavis.com)

    Just received my ASA NY meetings announcement.
    In it was included a brochure about the microflown 'scanning probe'.
This does the acoustic pressure and velocity measurements needed to fond
acoustic intensity. It seems to have a good sensitivity and a remarkable

I would like some evidence that the "just noticeable difference" in
sound level is lower than 1 under certain conditions.
I work with player pianos and I think that I am able to tell when the
volume of a repeating note changes by 1/4 of a db.  Furthermore it

For those who have downloaded my acoustic calculation spreadsheet, there
has been a problem with the use of the spin buttons.
This was caused by the spreadsheet containing a reference to a
non-Microsoft OCX extension, which in turn produced either a compile

I am determining the reverberation time (T60) for a chamber
experimentally. I am using ASTM C 423 - 90a as a guideline  (Standard
test method for sound absorption and sound absorption coefficients by
the reverberation room method). But I'm mainly interested in the reverb

I'd like to know if anyone can point me toward a source of information
about the acoustic power output of brass and/or percussion
instruments. The published information I have is for a symphony
orchestra as a whole. I can interpolate from that, but I'm trying to

I am having a discussion with some blacksmiths regarding triangles.
These are made by some blacksmiths to sell for backyard barbequers
etc.
Some feel that making the triangles out of high carbon steel (rather

I'm trying to compute the 1/3 octave spectrum of a microphone signal saved
in a file. Computing the traditional spectrum (psd) I can obtain the same
plot of Spectralab but the I do not have the same 1/3 octave spectrum. As
anyone any idea about the right algorithm?