A microphone will measure the acoustic pressure in front of an acoustic resistance. The acoustic resistance is designed to let air through but reducing significantly the pressure. Behind the acoustic resistance, a transducer membrane is driven to absorb the volume of air going through the acoustic resistance as well as ensuring a specific acoustic impedance in front of this acoustic resistance. When in function, this acoustic impedance in front of the acoustic resistance is significantly lower than in ambient air and therefore acts as a pressure sink. The acoustic impedance of the air is affected typically over a radius of 1 to 1.5 m around the AVAA. This explains how the AVAA can be more absorbent that its actual surface of perfect absorber. It is designed to absorb frequencies between15 and 150 Hz and is most effective on room modes that are the result of multiple reflections.
It will do so just like passive absorbers but in a much more efficient way and using up much less space. Each operating AVAA will have the same effect as a hole in the wall much larger than the dimensions of the AVAA (that is 0.2 m2). The exact ratio will depend on the frequency and environment but typically range between 5 and 20.
The AVAA will affect the impedance of the air and “suck” low frequencies around it. Therefore the best position to place an AVAA is in the most rigid corners as that is where all room modes will be most present. It is important to work on the positioning of loudspeakers and listening, as the AVAA will have little effect on inevitable first reflections.