Natural Science Forum / Physics / Acoustics / November 2003

I will be helping my church with improving and replacing their sound system.
There is lots of echo due to the high "A"frame ceiling and all glass front
and rear walls.
I am looking for resources like books, room acoustic  calculators/formulas

I had an idea the other day and I am wondering if anyone has every
proposed it or looked into the idea that the Pyramids of Egypt might be
some sort of Heat Sink to organize the way the day's heat is released to
allow for better observations at night?

I've got a commissioning test coming up with a big air horn rated at
140dB at 1m at the top of a 15m mast.
Would I be right in thinking that I should measure around 120 dB at
10m and 100 dB at 100m from the mast and an 85 dB hearing protection

I'm not a physics expert, so I want to see if I have this right.  
Hopefully this should be easy for some of you.  I read that a passenger
jet engine can produce 150db at 10 meters away.  According to the
formulas I've found this db intensity is relative to a standard reference

If you have seen my earlier post, you know that I have failed to find a
study that even in the most elementary way has explored how individual
harmonics color a complex sound.
Angelo Campenella has suggested that I carry out such a study for myself,

What could be the absorption coefficients for grass ?
I would say for a soccer field as example:
(125 - 4000 Hz)
0.20 0.22 0.30 0.40 0.45 0.45

this may be a FAQ but anyway
A pub where I frequent has a dance club upstairs such that
the pounding (low frequency) monotonous beat comes down
though.   Now sometimes it seems to magically mesh well

I have searched the internet, examined Diana Deutsch's book, "Psychology of
Music" and have failed to find the information I need.  Let's suppose you
have a musical note--how does the perceived timbre change as you add more
and more harmonics, what if you increase the intensity of ...

While reading a chart of approximate db ratings for typical noises (e.g.,
noisy office = 70 db, jet engine = 120 db, etc) I noticed someting
strange.  The chart listed "the loudest sound that can occur" at 187 dbs,
or some number close to that.

If I have one sound source generating 10 decibels and a second source also
generating 10 decibels and I put the two together do I get 10 decibels, 20
decibels or something else - 15?
Thanks, Peter.

Anyone know - do silicone joints in high performance glazing (heavy acoustic
laminated glass) significantly affect the sound insulation performance,
other than as would be predicted from the small joint area?
Tony Woolf

Now I´m deaf!

Can anyone help me?
I'm from the UK and I need some help with my studio. It is a room 8ft high x
8ft wide and approx. 12ft long. the trouble is that when I record drums in
this space it sounds boxy. I've tried dampening the walls with packing

I'm looking for good vibro-acoustics simulation softwares. I've heared of
SYSNOISE, NASTRAN and ACTRAN and they seem to be the cream of such
softwares. Does anyone own them ? What would you advise me to use ? I'm
trying to design a muffler for a small r/c helicopter engine (15cc). ...

Could someone let me know the equation for SEL, sound exposure level?
Thanks,
Daniel Cloke