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Guide to Optimizing Room Acoustics with Porous Absorbers

Step 1: Initial Measurement of Room Acoustics

Before you begin optimizing your room acoustics, it is important to measure and analyze the current acoustic conditions in your room. This can be done in 3 ways:

1. Ear and Sine Signal Method:

   • Play a sine signal across a broad frequency range (e.g., 20 Hz to 200 Hz).
   • Move around the room and listen attentively to identify areas where certain frequencies appear louder, quieter, or even completely canceled.
   • Note these problematic frequencies and their positions in the room.

2. Measurement with Software and Microphone:

   • Use an application like REW (Room EQ Wizard) and a measurement microphone.
   • Place the microphone at the listening position and conduct a frequency response measurement.
   • Analyze the data to identify the problematic frequencies and positions in the room (room modes).

3. Room Modes Calculation by Wall Distances

   Use our free Frequency Calculator tool to determine the frequency based on the parallel walls.

   Note the frequency for each set of parallel side walls, front and back walls, and ceiling and floor.

   Calculate the highest possible efficiency for your absorber using a calculator with frequency representation for the noted frequencies. Efficiencies over 0.6 should be considered.

*The calculated frequency is the first reflection and potentially the strongest mode in the room. By knowing this, you can plan appropriate measures and diameters for bass traps to efficiently reduce this and subsequent modes.

Step 2: Identifying Room Modes

Based on the collected data, you can identify the room modes of your space. Room modes are specific frequencies where standing waves occur, leading to peaks or nulls in sound energy. These modes mainly occur in the bass range and need targeted treatment.

Step 3: Construction and Placement of Bass Traps

Bass traps are specially designed absorbers that effectively absorb low-frequency sound energy. There are various types of bass traps, with porous absorbers and resonant panel absorbers being the most common.

1. Porous Bass Traps:

   • Porous bass traps should have a minimum thickness of 1/4 of the wavelength of the frequency being treated.
   • The airflow resistance of the material used is crucial. Here are some examples:
     • WLG 045: 3000 Pa·s/m²
     • WLG 040: 5000 Pa·s/m²
     • WLG 035: 10,000 Pa·s/m²

2. Placement of Bass Traps:

   • Bass traps should ideally be placed in the corners of the room where pressure maxima (highest sound pressure) occur.
   • Placing them in the corners allows you to treat two walls simultaneously, increasing efficiency.
   • Other possible placements include along wall edges or at points where the problematic frequencies are most pronounced.

Example of a successful calculation in a room with standard size. For the treatment you can see plate absorbers and porouse absorbers were used in the most efficient way. The parallel walls were calculated and the bass traps are choosen to treat those first reflection frequencies on the corresponding walls:

Step 4: Construction and Placement of Resonant Panel Absorbers

Resonant panel absorbers are another effective method for absorbing low frequencies. They consist of a thin panel mounted in front of a cavity that vibrates due to sound energy.

1. Construction of Resonant Panel Absorbers:

   • The thickness and material of the panel, as well as the cavity behind it, must be carefully tuned to the frequencies being treated.
   • The resonant frequency of the panel absorber should match the problematic frequencies.

2. Placement of Resonant Panel Absorbers:

   • Like bass traps, resonant panel absorbers should be placed in the corners or at points in the room where the problematic frequencies are most pronounced.

Step 5: Re-measurement and Fine-tuning

After installing the absorbers, conduct measurements again using the same method as before. Check if the problematic frequencies are now better controlled. If necessary, adjust the positioning or number of absorbers to further optimize the acoustic balance.

By following these steps, you can significantly improve the acoustics in your room, achieving clearer and more balanced sound reproduction.

For construction knowledge about perfect room size please read the following guide for golden room size for acoustic rooms.