Design requirements for semi anechoic chambers
 
In the design of semi anechoic chambers, ground treatment is an important consideration factor. The ground of a semi anechoic chamber needs to be a hard and rigid reflective surface to ensure that the sound waves between the sound source and receiver only have direct sound and no reflected sound, thus forming a free field similar to that in a fully anechoic chamber in the half space on the ground. This design is suitable for measuring the noise power of equipment or machines that require measurement of large weight and size, such as vehicles and large machines.
 
The impact of measuring height
 
When conducting acoustic testing, if the equivalent sound center or receiver of the tested device is significantly higher than the ground, the impact of sound reflection can cause the sound field to deviate significantly from the free field, which is particularly evident at high frequencies. Therefore, in some cases, it may be necessary to reduce the impact of sound reflection by raising the height of the device to ensure the accuracy of the test results.
 
Selection of Structure and Materials
 
The ground treatment of anechoic chambers usually uses special sound-absorbing or shock-absorbing materials to reduce vibration and sound reflection. If the need for direct placement of the product is considered in the design, it can be placed directly on the ground. However, in order to ensure the stability of the product and prevent vibration, it may be necessary to use support frames or washers to lift the product and maintain a certain distance from the ground.
 
Conclusion
 
In summary, the anechoic chamber may need to be raised above the ground in the following situations:
 
1. Design requirements for semi anechoic chambers: When measuring the noise power of equipment or machines with large weight and size, due to the need for a hard and rigid reflective surface on the ground, it may be necessary to raise the height of the equipment to meet the design requirements.
2. Requirements for acoustic testing: When the equivalent sound center or receiver of the tested equipment is much higher than the ground, in order to reduce the impact of sound reflection on the test results, it may be necessary to raise the height of the equipment to ensure the accuracy of the test.
 
These situations indicate that the treatment of the ground and the height of the equipment are important factors affecting the acoustic performance when designing and using anechoic chambers. Proper handling of the ground and reasonable arrangement of equipment height can ensure that the anechoic chamber can meet the needs of various acoustic tests.