The anechoic chamber is a free sound field created by humans. It is not a completely free sound field and can only absorb about 99% of the sound.

First of all, let’s understand what a free sound field is. A free sound field refers to a sound field formed when sound waves propagate freely in an open space. In a free sound field, the path of sound wave propagation is free and does not encounter any obstacles or reflection surface restrictions. The propagation direction and speed of sound waves are also uniform and irregular. The sound pressure level in this sound field shows a square attenuation law as the distance increases, that is, the sound pressure level is inversely proportional to the square of the distance. Free sound fields are frequently used in acoustic experiments and measurements and are the basis for many acoustic models and theories.

So how does the anechoic chamber achieve a free sound field?

An anechoic chamber is a closed space whose internal surface is filled with sound-absorbing materials, which can absorb most of the sound wave energy, thereby reducing indoor noise levels. In order to achieve a free sound field, the anechoic chamber requires multiple designs to achieve the desired effect, including overall structural design, vibration and sound isolation design, sound absorption design, etc. (For specific plans, please consult Static Environmental Protection). Sound-absorbing spikes are an essential material for an anechoic chamber. In order to achieve a free sound field, multiple evenly distributed sound-absorbing spikes need to be arranged inside the anechoic chamber to form a free sound field.