NEW bass traps range & detailed selection table

This article is an analysis about bass traps, explaining its use but also its major differences with other acoustic materials.

More technical information about our advanced range of bass traps available here.

There are two very different and unrelated aspects of acoustic treatment used in recording and music studios, that are often confused and mixed with each other.

One is sound isolation (or sounfproofing or noise control), which attempts to minimize the sound and vibration transmission between rooms and also between a room and the environment. More information regarding building noise isolation can be found here. For building vibration control products additional information is available here.

The other parameter that is very different to building soundproofing is acoustic treatment or architectural acoustics within a room, to minimize reflections that cause reverb, echoes, and standing waves. That is often not only applicable in music studios but also in auditoriums, restaurants, bars or even offices.

The specific article is about the second parameter considered above ie acoustic treatment and more specifically low frequency sound absorption.

When bass frequencies bounce around in a room they generate standing waves. Standing waves are pressure nodes created when a sound wave reflected from a wall collides with the direct sound emanating from the loudspeaker. At some frequencies the reflections reinforce/regenerate the direct sound, creating an increase in sound level at that specific location of the space. In contrary in some other frequencies the reflections tend to cancel the direct sound, lowering the volume or in some cases eliminating it altogether.  There are many building strategies to avoid standing waves from the construction stage. The most critical and widely spread is by building non-parallel walls and angled ceiling (not parallel to the floor).

The difference between a bass trap and a sound absorption panel is that absorbers usually absorb the middle to high frequencies. Bass traps absorb much lower frequencies due to their thickness and often because of their membrane.

So even though an absorption panel on a studio wall or ceiling works well with mid to high frequencies, due to reduced thickness and different composition is not as sufficient in low frequency sound absorption which often causes flatter echo compare to bass traps.

Following our research presented at the National Conference of Acoustics in Corfu in 2012 by Mr. Theodore Argoudelis entitled “Experimental research and development of low-frequency sound absorption” we are pleased to announce our commercial bass traps selection catalog with detailed tables, graphs and technical acoustic specifications.

More information about the National conference of acoustics can be obtained here

Indicative selection tables are presented below.

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In order to create a reliable product which can effectively absorb low frequencies, our R&D department studied different types and sound- absorbent combinations for optimizing absorbing low frequencies. Then we constructed a large number of specimens, which were tested in the laboratory’s reverberation chamber of Athens Technical University and were measured in accordance with the principles of ISO 354: «Acoustics-Measurement of Sound absorption in a reverberation room».

Before presenting the outcome of our acoustic research on bass traps, it will be beneficial to mention some more key acoustic characteristics and some critical details on low frequency sound absorption.

There are generally two types of bass traps: diaphragmatic/membrane absorbers and porous absorbers. By their nature resonating absorbers tend toward narrow band action [absorb only a narrow range of sound frequencies] and porous absorbers tend toward broadband action (absorbing sound all the way across the audible band but less effectively in low frequencies). Our research concentrated primarily in membrane bass traps, as our aim was to target music studios that have carried out acoustic measurements and know exactly the frequency they intend to isolate.

Resonating absorbers can be made from membranes stiff enough to be susceptible to being induced to vibrations by impinging sound.

Porous absorbers are most commonly made from fiberglassmineral wool or open cell foam, and function through the existence of interstices in the medium which present small captured pockets of air to the room which when excited by sound pressure waves in the room’s air space.

Due to the nature of the membrane bass trap, a targeted awareness of the frequencies that need to be absorbed is needed before designing and constructing a resonating bass trap. This can be done by calculation of the room’s modes or by direct measurement of the room itself. For more information regarding room acoustic measurements, architectural acoustics and acoustic simulations please visit below links:

https://alphacoustic.com/en/showcase/architectural-acoustic-consultancy/

https://alphacoustic.com/en/showcase/building-sound-level-measurements/

Resonating bass traps will absorb sound with high efficiency at their fundamental frequency of resonance. Resonating absorbers can be broadened in the frequency range of efficacy to some degree by either introducing porous absorptive material to the interior of the acoustic bass trap, by constraining the vibrations of the panel or membrane, or by installing an array of resonating devices each tuned to adjacent frequency ranges so that collectively the array functions over a broadened range of sounds.

Positioning of bass traps

Since low frequency resonances in a room have their points of maximum or minimum pressure in the corners of the room, bass traps mounted in these positions will be the most efficient. Bass traps are typically used to attenuate modal resonances and so exact placement depends on which room mode that are targeted. For more information regarding the positioning of your bass trap and technical clarifications regarding its installation, do not hesitate to contact us further at tech@alphacoustic.com. If you have carried out some acoustic measurements we would be happy to see them so we can carry out the acoustic bass trap selection for you.

 Acoustic Performance of bass traps

The key concepts to efficiently building a high performance broadband Bass Trap are to choose the right material for the bass trap core, using a sufficient thickness of acoustic materials, choosing an appropriate (sound-transparent) fabric. Very critical for ergonomic purposes in the overall weight of the bass trap to be relatively low so that it is acoustically sufficient, but ease to move and carry around a room.

 Outcome of R&D on bass traps

We are very proud of the outcome of our long research in low frequency absorption and we strongly believe that our developed range of bass traps will resolve acoustic problems that professional or amateur audio engineers are currently facing. Our approach was to not just produce a product that will look pretty in a wide range of spaces, but will also resolve target acoustic problems and will deliver high end acoustic results.

For the complete pdf file that summarizes the , click on the below link:

https://alphacoustic.com/wp-content/uploads/2014/05/ALPHAcoustic_TRAP-Bass-Traps-Sound-Absorption-Coefficient.pdf

 

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