Simple Dynamic Acoustic Absorber

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Simple Dynamic Acoustic Absorber


Postby Soundman2020 » Fri, 2019-Sep-20, 13:48

Another free tool for studio designers! (The same disclaimers as for the Raytrace Assistant tool applies to this one as well)

This is a simple acoustic absorber, but it is fully dynamic, meaning that you can reshape it and resize it in different ways to fit whatever it is you need to do in your own room. It also has automatic dimensioning on it, where the dimensions update as you change the parameters. Like the raytracing aid, this is not an earth-shattering component: just something that I developed to be helpful in quickly trying out treatment options in the SketchUp model of studios.

Here's what it looks like:


Nothing fancy. Just your basic porous absorber panel. A wood frame with insulation inside it, and plastic mesh front and back to hold the insulation in place. That view shows it without the fabric cover visible, so you can see the inner parts. Here's what it looks like if you make the fabric visible:


Boring! But useful. What makes it useful is the ability to re-size it quickly and change the options, to help speed up the layout of your room. Instead of needing to manually create and re-size each part of each absorber, this component does it all automatically.

Here's the Dynamic Component options control panel:


This lets you set several options, such as:

- Choosing the frame dimensions in three different ways: 1) A list of nominal lumber sizes, such as 2x4, or 1x8 etc. 2) A list of metric sized panels, or 3) manually entering the exact size you want. If you choose #1 or #2 then the manual dimensions are ignored, as they are set automatically by the lumber size. There are sensible limits on how big or small you can make the framing, and those are shown, along with the current width and thickness of the frame members.

- Set the overall height and width of the device. Limits apply here as well.

- Set the insulation thickness: you can select to have that set automatically based on the lumber size, or to enter it manually yourself, or choose from a list of common sizes.

- Air temperature: needed for the acoustic calculations.

- Projected lowest useful absorption frequency. This is presented in three different ways: first as the traditional "quarter-wave length" old-school theory, which has been proven to be wrong but you still find it in some texts that aren't yet up to date. Then as the more correct " 1/16 wave length " theory, which has been shown to be correct. This theory states that an absorber provides useful absorption down to the wavelength that is 1/16th of the thickness of the absorber for normally incident sound (sound waves that hit the panel head-on, hitting the face at a 90° angle), and down to one octave lower for randomly incident sound waves (arriving at the panel face from all angles at once). Be warned that the "randomly incident" number makes a number of assumptions that probably are not true in your room, unless it is VERY large! The "normal incidence" number is more realistic, and shows the lowest frequency where your panel will have some usable effect. The 1/4 wavelength number shows the lowest frequency where maximum absorption can be expected (assuming that the type of absorption is optimum).

- Acoustic data: shows the frontal area of the insulation (does not take into account the parts of the insulation exposed through the side slots - maybe in the next version...), along with the number of sabins of absorption (both imperial and metric) that this panel will provide, assuming that the coefficient of absorption is 1.

- Display controls: the final section provides a set of controls for making some parts of the absorber invisible, so you can see what's going on better. One of these controls the visibility of the dimensions, in case you don't want to see them all the time. The dimensions will still update automatically every time you change something, even if the visibility is turned off: you'll be able to see the new dimensions once you turn it on again.

And that's it! Nothing fancy, really. Just a useful component you can insert into your SketchUp model of your studio, for quickly placing and sizing acoustic absorbers in your room.

Hopefully you'll find it worthwhile.

- Stuart -

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