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The Use and Construction of Acoustic Laboratory

Acoustics laboratory as the name suggests, its main role is to carry out acoustic research or environmental acoustics research experimental sites. In addition, such as speaker manufacturers, acoustics processing companies in the development of new products also need to meet the appropriate standards in the environment of the various parameters of the product to test. Acoustics laboratory as the name suggests, its main role is to carry out acoustic research or environmental acoustics research experimental sites. In addition, such as speaker manufacturers, acoustics processing companies in the development of new products also need to meet the appropriate standards in the environment of the various parameters of the product to test. From the total to the points, acoustics laboratory can be divided into three categories, namely reverberation room, sound insulation room, anechoic chamber. For the laboratory, the surrounding environment should have a good sound insulation and isolation performance, the purpose of doing so is very obvious, is to avoid the experimental work in the external noise generated by the interference. From the structural point of view, the general practice is to make the room into a separate concrete box, on the basis of the spring, the spring foundation is divided into several types, such as: steel springs, air springs, cork, etc., the specific use of which According to the actual situation to determine. In the room quality and spring system composed of the resonant frequency also has strict requirements. Usually the resonant frequency is lower than the lower frequency used in the laboratory for testing, the ratio is usually 1/20, which can ensure that the outside vibration does not affect the indoor test work. Laboratory sound insulation generally use double-wall structure, usually the external walls of the brick wall plaster, the wall is a concrete structure. Door to use a special sound barrier door, made around the exact meet the seam, deposited to wool, to ensure strict and seamless; or in the door frame with rubber air cushion, so that inflatable seal. In general, the acoustics laboratory comes with a control room for placing test equipment and control instructions. In the reverberation chamber can measure the sound absorption coefficient of the material, the sound absorption in the air, the sound source and the sound power spectrum of the machine, measure the efficiency of the speaker, etc., but also can do sensitive noise test and produce artificial reverberation The The volume of the reverberation chamber is generally between 100 and 500 m and for the upper reverberation time, the high frequency is determined by the absorption of cheap beats headphones molecules in the air, and the low frequency depends on the viscous absorption on the wall. For different areas of the reverberation chamber, the use is also different. The reverberation chamber of the Institute of Acoustics, Chinese Academy of Sciences, for example, is divided into three categories: the volume of 425m and the large reverberation chamber can be studied specifically; the volume is 191m and the standard reverberation chamber can be Used as a regular absorption of material testing; volume of 100m and about three small reverberation chamber can be used to measure the wall and ceiling insulation or general test.

Reverberation room requirements: 1, plus the empty room reverberation time; 2, to ensure that the proliferation of indoor sound field state.

Second, the sound insulation room can be used to measure the floor, wall panels, doors and windows on the structure and air sound insulation characteristics. From the structure of the sound insulation chamber, usually by the vibration pad (spring), sound insulation panels, sound barriers, sound insulation windows, ventilation muffler and other components. According to the different sound insulation, will use a single layer of sound insulation and double-layer sound insulation room.

1, vibration pad: According to the design requirements of the polarization coefficient, load and other parameters to select the appropriate vibration isolation pad or vibration isolation spring. The number of selected groups was 4 or 5 groups;

2, the assembly of soundproof panels: sound insulation room of the main sound insulation panels are usually assembled structure, the sound insulation board thickness of 50,75,100 mm and so on. The outer layer of the soundproof plate is galvanized steel, the inner layer is perforated plate, the middle of the sound-absorbing material with rock wool, glass wool and other fibrous materials. When the sound insulation room for the double structure, two acoustic board between the gap about 100mm;

3, acoustic doors, windows: doors, windows of the sound insulation is usually required higher, mostly 30,35 or 40dB. The sound insulation of the soundproofing chamber depends on the comprehensive sound insulation of each component, beats headphones cheap so the sound insulation of the door and the window and the combination of the sound insulation board Way, the sealing method is reasonable, the sound insulation of the sound insulation room plays a key role. The sound insulation chamber is based on the indoor and outdoor sound level difference as its evaluation index, according to the use of the sound insulation room or indoor sound source noise to determine the noise level of the sound insulation room, usually ranging from 20 to 45dB. When higher than 35dB above, usually need double-layer sound insulation structure can be achieved.

Anechoic chamber simply refers to a room that does not have acoustic reflex capability. The principle is in the anechoic chamber on the laying of sound-absorbing sound-absorbing material, in order to achieve the effect of removing acoustic reflection. Its main purpose is: to test the anti-noise to send, receiver sensitivity, frequency response and directivity and other electro-acoustic performance. (Such as: test speakers, speakers and other equipment, the specific parameters and performance.)

From the sound-absorbing material used in the anechoic chamber, the sound absorption coefficient is greater than 0.99. Generally use the gradient absorption layer, commonly used wedge or cone structure, glass wool for sound-absorbing material, but also useful soft foam. When tested in the anechoic chamber, the object or sound source to be tested is placed on the center of the nylon mesh or wire mesh. cheap beats Since the weight of the mesh can be limited, it can only be tested for light weight and small volume Wait.

Four, semi-anechoic chamber and divination room

The semi-anechoic chamber and the divination chamber are constructed on the basis of the general anechoic chamber, using the two adjacent walls of the rectangular tube to do the sound absorbing treatment to double the effective size of the tube. The divination chamber is an adjacent three-sided hard-reflective surface, and the other three sides are equipped with sound-absorbing spikes. The three reflecting surfaces form three mirrors, such as a sound source or a receiver placed at the intersection of the three reflecting surfaces, so that the sound source and the receiver are the same as the semi-anechoic chamber and have only a direct sound without sound Forming a free field. As the sound source or receiver can only be placed at the intersection, so in actual use will be greatly limited. Semi-anechoic chamber is the floor as a mirror, the other are equipped with a split room.

Five, high sound strong laboratory

High sound strength laboratory is mainly used for high noise environment simulation experiment, high sound under the sound absorption material and structure research, large amplitude sound wave research, metal sheet in the strong sound field fatigue test.

High sound strength laboratory usually includes the sound pressure level of 160dB small reverberation chamber and a set of different cross-section, the sound pressure level of 170dB of the wave tube. A sound source that produces a high sound field can use a whistle or airflow speaker. The efficiency of the whistle is high, but the spectrum can not be changed, the airflow speaker can produce arbitrary spectrum of random noise, easy to use.

Six, acoustic wind tunnel

The acoustic wind tunnel can be understood as an anechoic chamber with airflow, or a low noise, low turbulence in the anechoic chamber, and a wind tunnel from the open working section. It is a ground device that can be used to study flight speed Fan airflow noise and propeller noise, and to study the noise flowing through the object. It has the characteristics of conventional wind tunnel, with suitable pipeline and air flow control device, with the minimum energy loss in the test section to produce experimental requirements of the air flow; also has acoustic requirements; to meet the free field conditions, sufficient size conditions (can be far Measured) and very low test section background noise. In order to achieve a small turbulence, the nozzle should be formed in the form of shrinkage. While the low noise is by using low noise fan and before and after the installation of muffler method is not more than 60 ~ 70dB noise.

At present, China's more standardized, comprehensive acoustic laboratory was undoubtedly Tsinghua Building Physics Laboratory. The laboratory for many years engaged in architectural acoustics in scientific research, experimental testing and engineering design work, strong technical force, by professors, lecturers, engineers composed of professional acoustics team, and a doctorate or master of the reserve echelon, Theater, the beats solo Olympic Games and many other construction projects to provide acoustic design and measurement.

Conclusion: Although the presence of acoustic laboratories is more to detect sound-related products or acoustics-related experiments. However, the acoustics laboratory to promote the development of acoustic technology has a role can not be ignored. With a simple example to describe it as a monitor speaker in general, if the music in the post-production without a real sound to restore the reference equipment, it will be difficult to produce a high-quality music, which is probably the relationship The