Acoustic panels

There are basically two different ways to build acoustic in a room : the absorption and the diffusion.

The diffusion :
The diffusion of a sound in a room must distribute uniformly the sound energy in the field. The direction of propagation is random.

The absorption :
There are many different ways to absorb the sound energy, but the result is always the same:

• Transform or dissipate the energy in heat.
• Reduce the reverberation time in the frequency bandwidth of the material used.

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• Quadratic-Residue Diffusers or Schroeder Diffusers
• Rounded slats
• Ceiling cylinder
• Corner cylinder
• The foam
• The rockwool
• Helmholtz Resonator
• Resonant panel
• Bass trap
• Panel combinations

Quadratic-Residue Diffusers or Schroeder Diffusers.

It is a periodic slot of equal width but with different and determined depth. The slots are usually separated by a thin separator.

To make it easy:

• The depth gives the lowest frequency efficiency.
• The width and the quantity of slots per length give the random and the quantity of diffusion.

Qualities:

The Schroeder diffuser is very efficient because the sound is distributed both in space and in time.

• Space: this means that the sound is distributed throughout 180° or 360° with 2D Schroeder panels.
• Time: this means that the energy will be slightly delayed. Limitations: Real random means great quantities of elements.

Limitations:

Real random means great quantities of elements.

So if you want to get good efficiency with Schroeder Diffusers, you must always install a large quantity close to each others.

Rounded slats.

The shape of this panel is another way to scatter the sound waves in different directions. This panel must be placed at the back center of the room.

Qualities: This panel is very efficient in small rooms. The shape and the build in Helmholtz Resonator will absorb low and low mid frequencies.

Limitation: It must be placed only in the center.

Ceiling cylinder.

This structure is made to diffuse the sound from the highest position of the room.

Indeed, quite often we forget that the first reflexions from the ceiling are as destructive as the reflexions from the walls.

The shape and the structure of this panel is built to resonate.

Corner cylinder.

The corner cylinder is very helpful to trap the low-mid frequencies and to diffuse the high mid frequencies.

Such panels are both attractive and effective.

The foam.

Different sizes and depths are available. In any case the absorption is limited to the high mid and high frequencies.

The rockwool.

Covered with fabric this type of panel is similar in performance to the foam. Aesthetically, it is much nicer.

Helmholtz Resonator.

Is the most impressive way to trap the frequencies.
The bandwidth is often quite narrow but really very highly efficient.

There are hundred ways to build Helmoltz Resonators and they are used everywhere.

The principle is easy:

• holes on a panel are connected to a cavity covered with absorbent.
• The resistance of the air flow in the neck of the perforation gives the frequency tuning.
• The mass of the material and the springless of the air determine the resonant system.

Resonant panel.

• a. With plywood:
  In order to get good results, absorbent material must be placed on both sides of the plywood.
  This will increase the level of absorption. If it is not done, the vibration of the plywood will shift the phase in the room itself. Maximum tuned frequency is around 200 Hz.
• b. With amorphous material:
  The maximum of absorption occurs when placed at a ¼ wave length.
  Maximum tuned frequency is around 90 Hz. Resonant panel is the most effective method of controlling modal resonances.

Bass trap.

This panel is made to trap the bass frequencies. The bass trap must introduce significant absorption down to 30 Hz. The size must be ¼ wave length.

The most effective one is the corner bass trap. It is of prime importance to place bass trap in the corners because the distribution of the own modes in a standard room are always concentrated in the corners.

Panel combinations.

1. Helmholtz and absorbent:
   The combination of an Helmholtz or perforated panels with an absorbent on the front covered with a nice fabric.
2. Resonant and absorbent:
   This combination unsure a maximum absorption from the lowest frequencies up to the highest one.

FAR manufacture your panels according to your individual project specifications.

Any of these are available in virtually any combination of sizes, shapes, core materials, frames, fabrics and attachment methods.