What are the requirements for the design process of anechoic chamber for noise testing?

Anechoic room is a special laboratory for acoustic testing and an important part of the testing system. In fact, it is also one of the acoustic detection equipment, and its acoustic performance index directly affects the detection accuracy. The main purpose of anechoic room is to test the electro-acoustic performance of anti-noise transmitter and receiver, such as sensitivity, frequency response and directivity. The frequency range of this transmitter and receiver should ensure clear language communication, generally around 200-4000 Hz. The following is a specific case.

According to the use of Ayffre anechoic room and the original room conditions, the acoustic design indicators are as follows:

The anechoic chamber designed by (1) is full anechoic chamber, which needs working grounding net.

(2) The lower frequency is 150Hz.

(3) In the horizontal diagonal direction, the free field range with allowable deviation of theoretical value of 1.55dB should be greater than1m..

(4) The background noise in the anechoic room is not more than 30 decibels.

Building an acoustic anechoic chamber with anechoic structure;

(1) Sound insulation and vibration isolation Because the anechoic room is located in the ground floor room of the test building, the west side is close to the stairs and elevators, and the south side is close to the building walkway, it is greatly disturbed by noise, especially the footsteps going up and down the stairs and the solid sound generated when the elevator is running. In order to improve the sound insulation effect of anechoic room on solid sound and air sound, the sound insulation structure of "room in the room" which is completely isolated from the original building is adopted. (2) Floating ground In order to isolate the solid sound generated by impact, floating ground with elastic pad is used for vibration isolation. Its method is to lay a layer of glass wool insulation board (10cm after compaction) with a thickness of10 cm on the original ground as an elastic cushion for vibration isolation, and then make a layer of reinforced concrete floor with a thickness of 20cm on it, leaving a gap of 5cm with the external wall to prevent rigid connection with the external wall and isolate the introduction of solid sound inside and outside the building.

(3) The partition wall should be built with a brick wall with a thickness of 24cm on the floating ground as the inner wall, with a gap of 20cm between it and the outer wall. Masonry joint mortar should be full to prevent sound leakage.