Acoustics: Measurement vs. Trial & Error

[andrebrito]

Has anyone else actually tried an ECM8000 and tested or calibrated it?

I have used this mic. It works ok and it is usable for most applications apart from environmental acoustics where you need to have an accurate value of sound pressure level (you really need to know that for instance the value of Ln at night is 44.0 dB and not 46.0 dB).

For room acoustics in terms of room modes, rt60 etc.. is in my opinion enough... unless you are a bit paranoid and pretend to have a completely flat room !

[DanDan]

The following is the 'Conclusion' from a recent Project/Thesis I did as part of a Diploma in Acoustics from the I o A in England. The Project Name was 'Abbey Road in a Semi- D' I think that is self explanatory. My conclusion is I hope enhanced by the final quote from a Master of these topics.

It is interesting to consider the contributions of the various techniques and tools used. One may have noted that I chose not to use Sabine or Eyering calculations. In research there was plenty of this activity found. However the SoundSound room could hardly be farther from the definition of a Sabine space; predominant modes, alcoves, flutter. It was everything but diffuse. I believe any attempts at calculating the required absorption would have been of little use. Prediction of room behaviour by calculation was of limited value, and inaccurate. However, it became useful when aided by the Sine Sweeps. FuzzMeasure requires quite a bit of interpretation. The EDT, T20, T30, measurements are difficult to make, and quite variable, with zero figures etc. appearing inexplicably. Spatial averaging will need some experimental work. The ‘Grunt’ method and Handclapping were invaluable. The magic tool, the Batt of fibre used to intercept flutter paths was also invaluable. The single most useful and cheapest asset was LabMeter, the software frequency meter .
The holistic approach used was clearly the safest way to tackle such a task. The various different approaches to analysis conflicted and confused. Taken together though, they work well. I intend investigating other software, mostly PC based. ETF by AcoustiSoft is highly regarded by some. I have not yet used Ray Tracing software, and look forward to it. I would like to conclude with some words from the late Alton Everest Ref 1
“ The pioneer scientist was right when he said ‘to measure is to know’. Only in this way can subjective factors be controlled. However the very act of hearing is subjective, a trained listener might detect flaws in a studio, elegant graphs and sophisticated measurements to the contrary. This does not mean that measurements are useless. It only means that if one is processing programs for ultimate consumption by the human ear, a trained ear and measurements must supplement each other. The science of acoustics has grown to maturity during the past 100 years but there is still something of an art about it’s practice”.

DanDan FitzGerald www.soundsound.ie

[andrebrito]

ETF by AcoustiSoft is highly regarded by some

I have tested in the same space (large cafetaria) ETF and EASERA and I must ETF gave me very unreliable results. When I have another change for measurements in a large room I will try to test a bunch of measurement software.

[Glenn Kuras]

Originally Posted by andrebrito

I have tested in the same space (large cafetaria) ETF and EASERA and I must ETF gave me very unreliable results. When I have another change for measurements in a large room I will try to test a bunch of measurement software.

Please tell more.

Glenn

[Ethan Winer]

Originally Posted by andrebrito

I have tested in the same space (large cafetaria) ETF and EASERA and I must ETF gave me very unreliable results.

I can believe that. ETF is meant for small rooms. I once asked ETF author Doug Plumb about using ETF in the reverb chamber at IBM's acoustics lab, and he said it won't work because ETF can't handle reverb times longer than 3 seconds.

--Ethan

[jwl]

Just to add to this thread, in terms of how easy acoustics is to understand.

I agree that the finer details of acoustics -- like any other science -- require serious math and training to understand.

But the reason forums like this take off is because the BASICS are really pretty straightforward.... the point is NOT that anyone can learn as much as a PhD about acoustics by reading a forum, but anyone can DEFINITELY learn enough to make their rooms sound better by understanding a few of the basic principles that many of us tend to repeat a lot.