Determination of parameters of vibroacoustic noise systems.

Апр 27, 2024
opredelenie parametrov sistem vibroakusticheskogo zashuml

Determination of parameters of vibroacoustic noise systems

Tests were carried out by «Engineering and Commercial Multidisciplinary Center (IKMC-1)»

1. The purpose of the tests.

Determination of parameters of vibroacoustic noise systems ANG-2000, VNG-1020, GSh-01, WALL, VAG-66, VNG-006 when installing their vibration exciters on various elements of building structures of the room.

2. Estimated parameters.

2.1 Spectral characteristics of vibration vibrations of various elements of building structures when excited by vibration transducers of systems in the frequency range 0.25 — 6.3 kHz relative to the zero vibration level a0=3*10-5 g

2.2 Integral values ​​of vibration oscillations au of various elements of building structures in the frequency range 0.25-6.3 kHz relative to a0=3*10-5 g when excited by vibration transducers of the systems.

2.3 Spectral characteristics of acoustic noise emitted by vibration exciters of noise systems installed on various elements of building structures, in the frequency range 0.25-6.3 kHz relative to the zero sound pressure level p0=2*10-5 Pa.

2.4 Integral values ​​of acoustic noise Lp emitted by vibration exciters of systems installed on various elements of building structures, in the frequency range 0.25-6.3 kHz relative to p0=2*10-5 Pa.

3. Test method.

3.1 Measurement of the parameters of noise systems was carried out in a room with internal dimensions of 6.7 m x 5.4 m x 3 m. The wall area with thickness h=0.5 m was ~ 20 m2, thickness h=0.25 m ~ 16 m2, ceiling area, formed by floor slabs with a thickness of h=0.25 m ~ 36 m2. Window noise parameters were measured on a window opening measuring 2m x 1.5m.

3.2 To carry out measurements, vibration exciters of the noise system were installed on various elements of building structures in the following sequence.

3.2.1 In accordance with the operating instructions for each system, fasteners for vibration exciters were installed on each of the building structure elements: brick wall h=0.5 m, brick wall h=0.25 m, floor slab h=0.25 m . Then the vibration exciters were installed on the fastening elements.

3.2.2 The vibration exciter was also installed on the window opening (glass thickness h=4 mm) in accordance with the instructions for each system.

3.3 Parameter measurements according to pp. 2.1, 2.2 were produced in accordance with the block diagram presented in Fig. 1 in the following sequence.

3.3.1 The measuring accelerometer was installed on the elements building structures at a distance of 3 m from the vibration exciter. The system turned on.

3.3.2 Using a spectrum analyzer, the accelerometer signal level was recorded at the accelerometer installation sites in each 1/3-octave band in the frequency range 0.254-6.3 kHz.

3.3. 3 Measurement of the spectral characteristics of vibration oscillations of window glass was carried out in accordance with clause 3.3.2 according to the block diagram in Fig. 1. In this case, the distance from the measuring accelerometer to the vibration exciter was 2 m.

3.3.4 The measurement of the integral values ​​of vibration oscillations au was carried out at the installation point of the measuring accelerometer. In this case, the spectrum analyzer recorded signal levels in octave bands in the frequency range 0.254-6.3 kHz.

3.4 To assess the level of vibration oscillations, arising in elements of building structures from a speech-like acoustic signal, the following was done.

3.4.1 At the installation site of the measuring accelerometer, on each of the elements of building structures, a speech-like noise signal with an integral level of 75 dB(A) relative to P0=2*10-5 Pa was reproduced.

3.4.2 Speech-like signal levels were recorded and established using a microphone with an acoustic sensitivity of 50 mV/Pa. Then, in accordance with clauses 3.3.2 and 3.3.4, measurements were taken from the output of the accelerometer path.

3.5 Measurement of parameters according to clause. P. 2.3, 2.4 were produced according to the block diagram presented in Fig. 1 in the following sequence.

3.5.1 Vibration exciters were sequentially installed on each element of the building structure and the noise system was turned on.

3.5.2 The measuring microphone was located opposite the place of their installation at a distance of 1 m .

3.5.3 Using a spectrum analyzer, the signal levels from the measuring microphone in each 1/3-octave band, as well as the integral value of the signal, were recorded.

3.5.4 In the mode of the noise system turned off, in accordance with clause 3.5.3, the level of background noise in the room was recorded.

Note: for all measurements, the regulators of the levels and frequency characteristics of the generators were set to the maximum position.

4 Test results.

The test results of vibroacoustic noise systems are presented in Fig. 2,4, 5 in the form of graphs of the spectral characteristics of vibrations of various elements of building structures and in Fig. 6 in the form of spectral characteristics of acoustic noise produced by a vibration exciter on the same elements. The integral values ​​of these characteristics are also presented there.

5 Conclusions.

5.1 The studied vibroacoustic noise systems have approximately the same values ​​of integral levels but, at the same time, a significant spread in frequency characteristics. Conventionally, according to the type of spectral vibrations of building structures, they can be divided into three groups:

  • first: VNG-006, ANG-2000;

  • second: VNG-1020;

  • third: GSH-01, VAG66, WALL.

5.2 Products of the first group, for all types of building structures used in testing, provide a noise/signal ratio of 20dB in almost the entire range of speech frequencies: 0.254 -5 kHz.

5.3 Products of the second group provide a ratio noisesignal is 20dB in the lower and upper parts of the speech range, but has a “dip” at mid-frequencies 1-3 kHz.

5.4 Products of the third group provide effective blocking of the speech signal at frequencies above 2 kHz. The interference generated by these devices may qualify as out-of-band.

5.5 When choosing a vibration noise system and determining the radius of guaranteed noise, you should pay attention not only to the integral values ​​of the output levels, but also to their spectral characteristics

 

Fig. 1

Block diagram of measurements of vibration and acoustic characteristics of vibroacoustic protection systems.

  1. — vibration exciter;

  2. — electronic unit for vibration-acoustic protection;

  3. — measuring accelerometer;

  4. — measuring amplifier;

  5. — measuring microphone “Brühl and Kjær”, type 4155;

  6. — measuring amplifier “Brühl and Kjær”, type 2610;

  7. — digital frequency spectrum analyzer “Brühl and Kjær”, type 2131;

  8. — acoustic speaker, type 10 AC-401;

  9. — power amplifier “Brühl and Kjer” ”, type 2706;

  10. — specialized noise generator block with equalizer

 

 

.Fig. 2

Spectral characteristics of vibrations of a brick wall with a thickness of h=0.5 m, excited by vibration exciters of various systems and acoustic speech-like noise with a level of 75 dB(A).

opredelenie parametrov sistem vibroakusticheskogo zashuml 2
opredelenie parametrov sistem vibroakusticheskogo zashuml 3

 

Fig. 3

Spectral characteristics of vibrations of a brick wall thickness h=0.25 m, excited by vibration exciters of various systems and acoustic speech-like noise with a level of 75 dB(A).

opredelenie parametrov sistem vibroakusticheskogo zashuml 4
opredelenie parametrov sistem vibroakusticheskogo zashuml 3

 

Fig. 4

Spectral characteristics of vibrations of a thick concrete wall h=0.25 m, excited by vibration exciters of various systems and acoustic speech-like noise with a level of 75 dB(A).

opredelenie parametrov sistem vibroakusticheskogo zashuml 5
opredelenie parametrov sistem vibroakusticheskogo zashuml 6

 

Fig.5

Spectral characteristics of vibrations of window glass 4 mm thick, excited by vibration exciters of various systems and acoustic speech-like noise with a level of 75 dB(A).

opredelenie parametrov sistem vibroakusticheskogo zashuml 7
opredelenie parametrov sistem vibroakusticheskogo zashuml 8

 

Fig. 6

Spectral characteristics of acoustic noise created by vibration exciters of various systems on a thick concrete wall h=0.25

opredelenie parametrov sistem vibroakusticheskogo zashuml 9
opredelenie parametrov sistem vibroakusticheskogo zashuml 10
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