The anechoic chamber is not designed to completely isolate the outside sound, but is designed to simulate a place with no reflection acoustic environment. The characteristic of the anechoic chamber is that it can absorb almost all the sounds generated inside to reduce or eliminate echoes and reflections, thereby providing an ideal environment for acoustic measurement. However, the anechoic chamber cannot completely isolate the outside sound.

Characteristics of the anechoic chamber:
Internal acoustic characteristics: The interior of the anechoic chamber is covered with sound-absorbing materials, usually pyramid-shaped or wedge-shaped sound-absorbing spikes, which can absorb most of the sound waves and make the interior almost non-existent.

Simulation of free field conditions: The anechoic chamber can provide an acoustic environment close to the free field, which is very important for accurate acoustic measurement.

Sound insulation performance:
Although the design of the anechoic chamber focuses mainly on the internal acoustic environment, they usually take measures to reduce the impact of external noise. The internal background noise is generally below 20 decibels, and the lower can be below 5 decibels. Microsoft's anechoic chamber even has a negative value.

Still, anechoic chambers cannot guarantee complete isolation of all external sounds. Especially for low-frequency sounds, they tend to be more difficult to isolate. Low-frequency sounds have longer wavelengths and are able to travel around obstacles or through tiny cracks in walls. Therefore, even the most advanced anechoic chambers may allow a certain amount of external sound to enter.

In general, anechoic chambers are mainly used to provide a non-reflective acoustic environment, rather than to completely isolate external sounds. Measures are usually taken to reduce the impact of external noise, but absolute sound insulation cannot be guaranteed. Anechoic chambers are mainly used for precise acoustic measurements and research and development, and for those scenarios that require complete isolation of external sounds, additional sound insulation measures may be required.