Acoustic laboratory

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Acoustic laboratory

DATE: 2018-10-26 21:22:28
Item
Acoustic laboratory is comply with CNAS standards,An experimental site designed to test the acoustic specifications of products according to ISO 3745, GB6882 and related industry standards.It is mainly suitable for the testing of product acoustic indicators and can be compared with the data tested in the acoustic laboratory of any third-party authority.
The acoustic laboratory can be divided into a full anechoic chamber (full silence chamber), a semi-anechoic chamber, an anechoic chamber, a muffler chamber, a silent chamber, a silent chamber, a reverberation chamber, etc.
Its main function is to provide a free sound field or semi-free sound field space that meets the requirements of CNAS, ISO3745, GB6882 and industry standards, and its main function is:
Provides acoustic free field or semi-free field environment
Low noise measurement environment
The propagation of sound waves in free field space is defined as:
The sound pressure of the point source is attenuated with distance, which is the inverse square law of sound energy;
The sound pressure level is equal to the sound intensity level at normal temperature. This is the theoretical basis for measuring sound power in an anechoic chamber.
Background noise
ISO3745  Acoustics-Determination of sound power levels of noise sources using sound pressure. Precision methods for anechoic and hemi-anechoic rooms、.ANSI S12.55 Acoustics - Determination of sound power levels of noise sources using sound pressure - Precision methods for anechoic and hemi-anechoic rooms.
According to .ISO3745 and GB6882 "Acoustic noise source sound power level measurement anechoic chamber and semi-anechoic chamber precision method", in the test frequency range, the background noise sound pressure level is at least lower than the sound pressure level of the measured sound source 6dB, preferably 12dB lower.
Cutoff Frequency
It mainly depends on the acoustic spectrum analysis of the noise emitted by the product under test. It is impossible to design a sound absorber that can achieve 100% of the half-band (20hz-20000hz).Because general-purpose materials are easily absorbed by high-frequency sound waves, low-frequency absorption is related to the thickness of the material (the length of the tip).The cutoff frequency means that above this frequency, the sound absorption system of the wall can guarantee a sound absorption coefficient of 99%. The semi-free sound field space in actual engineering refers to the sound wave above the cutoff frequency. The lower the cutoff frequency, the greater the length requirement of the tip. In general, the length of the tip is applicable to the 1/4 wavelength theory. Free field correction is required according to GB 6882 when measuring.
size
The internal volume of the acoustic laboratory (acoustic laboratory) depends mainly on the size of the object being measured and the specific measurement method. As recommended by ISO 3745 or GB6882, the acoustic laboratory (acoustic laboratory) should have an internal volume of at least 200 times the effective volume of the object being measured.
Component
In the design of Acoustic Laboratory (acoustic Lab), door is a very important factor. A good sound insulation door should have good sound insulation and optimized edge effects.It adopts 1.5mm thick cold-rolled steel plate, and internally forms sound-absorbing cotton. The hinge adopts imported products, and the whole door floats when the door is opened. The high-density magnetic edge banding is semi-closed when returning to the door, ensuring that its acoustic treatment can be matched with the acoustic treatment of other surrounding components to eliminate edge leakage as much as possible, the strength meets the operational requirements, and the deformation is not used for long-term use, while the outer surface is sprayed. Plastic treatment makes the color consistent with the sharpness.
Interior wall
The structure of the inner wall and ceiling can be designed according to user requirements. The commonly used structures are:
●Concrete structure---This structure has good sound insulation effect, but it has a large weight. High requirements for floating ground.
● "Noise Shield" composite sound insulation structure - patented design, consisting of two layers of steel plate, the inner layer is perforated, and the interlayer is filled with a high sound absorption coefficient sound absorber to ensure the sound insulation effect. Lighter weight, but at a slightly more expensive price.
Float up the ground
In the case of high external noise or required vibration measurement, floatation structure is usually adopted to isolate the external influence. Vibration damping materials that play a key role in floatation structure are provided with the following methods:
Spring structure: vibration isolation frequency can be achieved (1Hz, which is adopted when low noise is required. But the disadvantages are: high cost, difficult maintenance, spring rust prevention.
Rubber shock absorber structure: the vibration isolation frequency can be achieved (7Hz).
Glass cotton felt vibration damping structure: the vibration isolation frequency can be less than 15Hz. This kind of structure has low cost. In practical engineering, what kind of vibration reduction is adopted depends on:
Background noise as request
Surrounding environment, noise sources, and vibration sources  
illuminate
Provide incandescent lamp that can satisfy indoor lighting, the requirement of the background noise and sound reflection of incandescent lamp is smallest, also want to consider the consistency of lamp and interior integral design and beautiful sex at the same time.
The circuit system
In addition to the illuminator, all circuit conduits, wires, and controls are required to be mounted on the tip to avoid acoustic reflections.
Walk line pipe                                                  
The routing pipeline meets the required line passing without any impact on the test.
Control room
The design of the control room should take into account the user’s aspects and functions, and the installation of the monitoring system can be chosen to reduce the human impact of the measurement.
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