We have the opportunity to build a new laboratory for our psychological experiments with eye-trackers, emotion recognition, psychophysiological parameters, virtual reality devices and so on.
To get a real good laboratory, we want it to be soundproof, to have light control, temperature control, and moisture control. Especially, the to build it soundproof seems to be a bigger problem.
Does somebody know about a soundproof laboratory for psychological experiments?
Does somebody know about a analogous structure that could be adapted to an optimal psychological laboratory?
Thank you very much for every useful hint and detailed information.
Best regards
Egon Werlen
Hi,
I have built many sound-proofing rooms for both human and animal (rats) subjects.
I have also built Faraday cages with built-in sound proof rooms.
Ideally what you want to have is a so called "acoustic anechoic chamber":
https://en.wikipedia.org/wiki/Anechoic_chamber
but in practice is difficult to have because it's too big and expensive.
The idea is that you want to have an internal layer of a material able to absorb the sound waves generated inside the room without giving too much (possible zero) back-scattering. You can do this by using special panels that breaks the acoustic wave-front. Such panels, like these ones:
https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=acoustic+insulator+panels&rh=i%3Aaps%2Ck%3Aacoustic+insulator+panels
makes a so called "impedance matched" acoustical load: because the wave reaching those surfaces will be, ideally, not reflected by them this simulates an infinitively big environment with no echoes. Proceeding describing the room from the inside to the outside, next you want you want to put some (at least one or two, more is usually not necessary) layers of foamy + heavy sandwhich of phono-absorbant materials, like soft foam and lead. Those layers will work as an acoustical filter: in a simple model, the compliance of the foam and its damping coefficient plus the inertia of the lead will damp the acoustical waves as a 1st order filter. The reason for putting more layers of these sandwiches is to increase the order of the filter, so you filter more. If you put, for instance, such symmetric sequence of layers: foam - lead - foam - lead - foam, then this filter is also bi-directional, therefore you guarantee the acoustic attenuation from inside to outside and viceversa:
http://alphacoustic.com/en/product/sound-insulating-panels-with-intermediate-lead-sheet-layer/
Read the datasheet of the product to find out the acoustical attenuation and transfer function suitable to your problem. In the end, you can verify the attenuation with a phono-meter.
You don't need the cone-like or wedge panel outside.
You can easily build the mechanical structure holding all this by means of Rexroth bars or similar modular structures:
https://www.boschrexroth.com/en/us/products/product-groups/assembly-technology/aluminum-structural-framing/index
You can put plywood panel as last, external, layer in order to use it to anchor the sound-proof panel. You can also use some gross metal mesh (e.g. mesh size = 1cm) in order to keep all the foamy and soft layers together (otherwise they are so soft they will fall down). Do not enclose the foamy layers between two rigid layers (e.g. two rigid layers of plywood or metal) otherwise they are useless.
This is, in short, a general guideline to start from in order to make a simple but effective acoustic chamber.
Hi Erik
Thank you very much, your general guidelines are a very helpful answer.
Best regards
Egon
Errata: compliance + damping + inertia = 2^nd order filter, so one should expect ad attenuation of -40dB/dec per sandwich. While usually, in practice, this is around -30dB/dec per sandwich. So two sandwiches is series gives about -60dB/dec in the cut band.
