John Sayers' Recording Studio Design Forum Archive

I've searched many times and get no definitive threads on this.

1. How do you calculate the resonant frequency of pegboard?

2. Will it become more broadband with varying hole sizes?

2. Is it anywhere near as effective in a corner as a slot resonator?

TIA,
jim

[quote="jimlongo"]I've searched many times and get no definitive threads on this.

1. How do you calculate the resonant frequency of pegboard?

Using he helmholtz absorber formula with a hole correction facor.

2. Will it become more broadband with varying hole sizes?

If you mean just changing the hole size, no.

2. Is it anywhere near as effective in a corner as a slot resonator?

Amazingly vague.

Pegboard, given the only variable being using pegboard, will have roughly the same peak absorption and aborption width. So yes it is as effective.

Pegboard, because of how thin it is, will be a MF/HF absorber, not LF. So no, it is not as effective.

Andre

AVare wrote:

jimlongo wrote:
2. Is it anywhere near as effective in a corner as a slot resonator?

Amazingly vague.

Pegboard, given the only variable being using pegboard, will have roughly the same peak absorption and aborption width. So yes it is as effective.

Sorry
If I have a corner resonator of a certain size (36X24X43 inches) filled with OC703 and neutral cloth behind the covering. How would covering it with pegboard differ in results from covering it in slats.

Pegboard, because of how thin it is, will be a MF/HF absorber, not LF. So no, it is not as effective.

Andre

jimlongo wrote: How would covering it with pegboard differ in results from covering it in slats.

If you would have quoted me completely, you would have seen the answer. I wrote in my first post, trying answer your vague question:

avare wrote:Pegboard, given the only variable being using pegboard, will have roughly the same peak absorption and aborption width. So yes it is as effective.

Pegboard, because of how thin it is, will be a MF/HF absorber, not LF. So no, it is not as effective.

The pegboard will create a mid frequency absorber, not low frequency. The slats would create a low frequency absorber.

That is assuming all other factors remainig the same.

Andre

I guess I'm somewhat vaguely thankful for your response.


Jim

Jim, to get a little less vague - there is about a 10-page discussion of pegboard and helmholtz absorbers in Everes'ts Master Handbook of Acoustics, starting on page 218 - if you're serious about acoustics and DON'T already have at LEAST this one book, you need to get it. The electronic version (about the only electronic version of any acoustics book I've found to date) is much more useful than the print version, and either can be had from Amazon.

There are a few mistakes in the book, but overall it's a good primer on a wide range of acoustic subjects.

Standard 1/8" pegboard, with 1/8" holes on 1" centers, has a perforation percentage of just under 1.3%, and mounted on 3-1/2" depth from wall would have a resonance of around 240 hZ - 1/4" holes on 1/4" centers would raise the percentage of perf. to 4.9%, which (on 3-1/2" space from wall) would move the resonance to around 400 hZ (not calculated, but interpolated from chart in the book)

The angle of incidence will also change results (partially due to increased effective depth), unless you are willing to build an "eggcrate" divider that causes each hole in the pegboard to have its own separate air cavity - this would get expensive enough to make hiring a pro seem cheap...

For slat type absorbers, the calculators posted on this forum are using the correct Helmholtz formula - most of the others on the web have an incorrect formula and will NOT return the right values; they will be off more than an octave in most cases.

I've not yet found time to do a similar search for the OTHER helmholtz formula, the one used for perforated absorbers - odds are that there are more wrong than right postings for that one as well.

For starters, I would go buy the Everest book; there is enough useful info in it to make it more than worth the relatively low price... Steve