Acoustics and Vibration Animations | Hacker News Reader

Acoustics and Vibration Animations

acs.psu.edu

29 pointsspeednoise9 comments

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.

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.

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

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?

I maintain a detailed reverberation (RT60) calculator at http://threedb.com/rt.php and a primitive, but realtime 2D room beamtracer at 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?

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.

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.

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

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.

I wish he'd add more stuff on cymatics though

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

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