Silencer Type

* Full Anechoic Chamber, Semi-Anechoic Chamber, Simple Anechoic Chamber

Acoustic Material Types

Glass Wool Wedges, Metal Wedges, Flat Acoustic Chambers

Soundproofing panel types

Mixed brick and concrete construction with metal soundproof and absorbent panels

Vibration Isolator Types

Spring Isolators, Rubber Isolators

Full-Acoustic Shielding Ground Mesh Type

Wire Soft Ground Mesh, Reinforced Steel Hard Ground Mesh

2. Acoustic Chamber Function

Primarily used for standard testing and experiments in the automotive, electromechanical, household appliance, and communication product industries.

3. Acoustic Chamber Size:

For example: External dimensions approximately 5600mm x 3200mm x 4500mm, internal dimensions approximately 3000mm x 2500mm x 3000mm.

4. Anechoic Chamber Performance:

Example: Base noise less than 5dB, cutoff frequency 80Hz

5. Acoustic Chamber Features:

Standard acoustic free-field space for acoustic testing, providing third-party testing and calibration reports. The sound absorption chamber (semi-anechoic chamber) is an indispensable testing environment for various noise tests and acoustic research. Inheriting the research achievements in the field of acoustics for many years and combining practical engineering experience, we have designed and constructed several characteristic sound absorption chambers domestically.

Design

After fully understanding the customer's requirements, the anechoic chamber is designed according to the standards. The acoustic criteria in the design include background noise, cutoff frequency, available space, vibration reduction, etc. While meeting the acoustic criteria, the design also considers ease of use, wedge doors, installation and handling of specimens (products), ventilation conditions, instrument wiring, monitoring conditions, and indoor environment.

Construction

During construction, the company strictly controls the selection of materials to ensure that indoor environmental pollution meets national standard requirements. Basic concept of an acoustic chamber (or semi-acoustic chamber)

Open space

The main function of an anechoic chamber is to provide a free-field or semi-free-field space for acoustic testing. A free-field refers to the propagation of sound waves in an infinite space without any reflective surfaces. In nature, a free-field space is achieved by suspending the sound source in the air, far from any reflective objects, allowing sound waves to propagate freely in all 360 degrees. A semi-free-field space is one with a full reflective surface within the free space, where sound waves can only propagate freely in a 180-degree hemispherical direction. Common semi-free-field spaces include large outdoor parking lots with concrete surfaces, outdoor basketball courts, runways, and so on.

The propagation of waves in free or semi-free field spaces has a specific physical definition.

(1) The sound pressure of a point source decreases with distance, which is known as the inverse square law of sound energy.

(2) The sound pressure level is equal to the sound intensity level under normal temperature and pressure. This is the theoretical basis for measuring sound power in an anechoic chamber.

Background noise

Despite large outdoor parking lots with concrete surfaces, outdoor basketball courts, and runways, etc., which can also provide semi-open spaces, measurements are affected by background noise. Imagine, the noise from a refrigerator is at 30dB(A) while the environmental background noise is at 45dB(A); it's impossible to measure the refrigerator's noise. Therefore, another function of the soundproof room is to provide a low background noise environment to meet the requirements of the testing environment.

Based on National Standard GB6882-86 "Acoustics," within the test frequency range, the sound pressure level of the background noise is at least 6 dB lower than that of the measured sound source, preferably 12 dB lower.

Cutoff Frequency

An anechoic chamber is designed to simulate a free field or semi-free field space indoors. The reflection coefficient of the semi-free field surface is over 95%. It is impossible to design a 100% absorbent material that can achieve full frequency range (20 Hz - 2000 Hz) because common materials are easily absorbed by high-frequency sound waves, while low-frequency absorption is related to the thickness (or length) of the material. The cutoff frequency refers to the frequency above which the wall's acoustic system can ensure a certain level of absorption coefficient. In actual engineering, the (semi-)free field space refers to the space within the anechoic chamber that is (semi-)free field for frequencies above the cutoff frequency. The lower the cutoff frequency, the longer the length of the wedges required. Generally speaking, the length of the wedges is applicable to the 1/4 wavelength theory.

Acoustic chamber qualification methods

In practical engineering, the free field of the acoustic field is a key criterion for assessing the quality of an anechoic chamber. The national standard ISO 4744 and GB 6882-86 provide methods for evaluating the free space of anechoic chambers.

Additionally, the background noise is another important indicator of the anechoic chamber. The measured background noise is the sum of the instrument's background noise and the anechoic chamber's background noise.