
Acoustics and Vibration Animations - speednoise
http://www.acs.psu.edu/drussell/demos.html
======
robomartin
Many years ago I was involved in the design of several very high end listening
environments. At that time I built a series Excel-based tools to analyze room
acoustics and design wall, ceiling and floor treatments in order to fix
problems.

I remember one room where we ended-up custom fabricating 150 Helmholtz
resonators to tame the beast. If I remember correctly it had a 2,000 W sound
system with an array of various speakers. The walls has six layers of drywall
glued and screwed together. The concrete floor was isolated from walls and
floated on hard rubber.

We ran impulse tests with specialized software as we went along to fine tune
the resonators and other treatments. The speaker system manufacturer sent
their acoustics expert to help. As an EE you sometimes get to work on projects
far outside your area of expertise. I have always embraced those opportunities
and usually come of of them having learned a ton of new and interesting stuff.

Interestingly enough I was showing these Excel tools to my oldest son the
other day. He is getting into Excel and this workbook has examples of doing
things with VBA one does not normally see on normal Excel spreadsheets. At
that time I thought it could be interesting to re-code this with Python and
build a neat little website around it. The comment on this thread by acqq made
me come back to that thought. Could be interesting.

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quarterwave
This is superb stuff, e.g; phase change at hard/soft boundaries is explained
nicely. EE's may recognize the conformal map leading to the Smith chart; since
EM waves are E+M we can have both 'open-circuit' and 'short-circuit' hard
boundaries (duals of each other).

The section on reverberation reminds me of Dr.Cooper at the cinema, conducting
impulse response tests.

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acqq
That inspired me to try to evaluate the acoustic of my room. I've landed on:

[http://realtraps.com/modecalc.htm](http://realtraps.com/modecalc.htm)

Anybody has better links to the programs and material which would let an
amateur (but still with a technical background) evaluate and experiment with
the acoustic conditions of the room?

~~~
robmiller
I maintain a detailed reverberation (RT60) calculator at
[http://threedb.com/rt.php](http://threedb.com/rt.php) and a primitive, but
realtime 2D room beamtracer at
[http://threedb.com/2d-viewer.php](http://threedb.com/2d-viewer.php). You'll
also find my large database of absorption coefficients there.

As an enthusiast, would you pay some modest amount for access to more related
calculators and analysis tools?

~~~
acqq
Hello, thanks! As I've said, I have a technical background, such that I have
the basic understanding of how the sound works, what decibels are and that
basic stuff, but I've never had any acoustic classes. I'm just trying to
figure out what's happening in my living room and how I can improve the sound.
I know that the shape and the minimal furniture are far from any ideal, but I
have the problems of even hearing the clear dialogues when watching the movies
and I hope I can do something about that. The room acoustics at the moment is
such that even talking to the other people there is for me harder than in some
better setting.

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fizixer
As a game-development/simulation enthusiast, I'm disappointed at the utter
relative lack of interest in computer-generated acoustics (CGA?) compared to
computer-generated imagery (CGI).

I hope CGA gets attention because there is a lot of work to be done before a
fully synthetic world simulation could be realized.

~~~
robmiller
There is work being done in this. I saw some Microsoft demos during the 2011
Acoustical Society of America meeting in Seattle where they showed realtime
room reverberation for characters as they move through rooms. There are some
European universities working on this too. Sorry, I can't find any links at
the moment. There is also some promise that GPUs will be able to handle some
of the processing needed to do this quickly.

Consider the challenges with modelling acoustics. The audible spectrum spans
from 2E1 to 2E4 Hz and those difference in wavelenghts make for different
behaviors in rooms, not to mention the challenges of accurately modeling
diffraction and diffusion. Computer modelling largely is still brute force,
where rays are randomly drawn from a source in hopes of eventually finding a
receiver's location in the room before reaching inaudibility. Recently some
algorithms that were developed for computer graphics have been introduced in
acoustics to make room reflections not brute force anymore. I've created an
early implementation of this based on the work of another HNer, kabla.
Realtime raytracer
[http://threedb.com/2d-viewer.php](http://threedb.com/2d-viewer.php)

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anigbrowl
I have this page bookmarked, it's a great resource. I wish he'd add more stuff
on cymatics though - it seems there's still a lot of work ot do in that area,
but researching it through the internet requires strong pseudoscience filters.

~~~
Anechoic
_I wish he 'd add more stuff on cymatics though_

Have you asked him? Prof Russell is quite approachable:
[https://twitter.com/drussellpsu](https://twitter.com/drussellpsu)

