Membrane absorbers, also known as panel and diaphragmatic absorbers, use the resonant qualities of a membrane to take in sound over a narrow frequency range.
Their composition is of pressed wood fibers and soft panels, as well as rigid or semi-rigid materials like plastic. When mounted on a solid wall and separated by a narrow air space, the panel will vibrate. Additionally, it’ll produce sound waves. In this instance, the fibers will bend, thus losing some friction. All these parts of the process result in the absorption of the sound energy. The resonant system includes both the springiness of the air and the mass of the fibers, so absorption occurs exactly at the resonance frequency.
The Composition of Membrane Absorbers
The most common use of membrane absorbers is to control particular resonant modes inside small rooms. For this to be successful, you must be place these on the appropriate surfaces at maximum modal pressure. Porous absorption inside the space will dampen the resonance and broaden the bandwidth. Experts also call this bandwidth the Q factor of the absorber; it’s effective even when the desired frequency is not achieved. It’s extremely important to take good care of membrane absorbers because small modifications can alter the overall performance. Keep in mind, too, that people frequently customize theirs for specific tasks.
The Sound Absorption Coefficient
The sound absorption coefficient is around 15 to 20 per cent and has a significant effect when the components join together. Typical examples include large glass areas of many modern buildings for they ensure that the reverberation time does not increase excessively for bass tones. These glass areas help balance the room’s acoustics. The glass is absorbent due to the frequency range.
As a final note, it’s worth mentioning that membrane absorbers work exclusively for bass tones, so they tend to reflect high-frequency sounds. Also, glass windows can produce echo effects, while wooden floors can produce drum sounds.
Membrane Absorbers: Conclusions
As you can tell from this description, these absorbers are part of soundproofing. If you want to lear more on this topic, you can consult other entries, such as reflection filters, ceiling clouds, the Helmholtz Resonator, and acoustic fiberglass and foam.