RU47979U1 - SOUND-PROTECTING CASING - Google Patents

Abstract

The invention relates to a technique for damping noise and can be used for soundproofing electrical machines. The purpose of creating a utility model is to increase the efficiency of sound insulation. The soundproof casing is a box-shaped structure, the walls 1 of which are made of duralumin with a thickness of 1 mm. A layer of ShVIM-18 2 vibration-absorbing material with a thickness of 5 mm and a sound-absorbing lining 3 of Schumanet-BM mineral wool material 50 mm thick are applied to the inner surface of the casing walls. Ventilation of the internal volume of the casing is carried out through ducts 4, lined with a similar sound-absorbing material. For access to parts of an insulated electric machine, when inspecting and monitoring its components, a removable cover is provided 5. Electrical cables are laid inside the casing through special “glands”. The use of the proposed device can improve the efficiency of sound insulation.

Description

The invention relates to a technique for damping noise and can be used for soundproofing electrical machines.

Sound-insulating enclosures of sizes not exceeding 1-1.5 meters are known, the walls of which consist of a metal shell and vibration-absorbing coating (A. Pogodin, Sound-attenuating devices. M., "Mechanical Engineering", 1973, p. 73.).

Known casings do not fully isolate noise sources.

The purpose of creating a utility model is to increase the efficiency of sound insulation.

To achieve this goal, a 50 mm thick sound-absorbing cladding has been added to the soundproof casing from the inside of the wall.

The proposed soundproof casing is shown in FIG.

The soundproof casing is a box-shaped structure, the walls 1 of which are made of duralumin with a thickness of 1 mm. A layer of ShVIM-18 2 vibration-absorbing material with a thickness of 5 mm and a sound-absorbing lining 3 of Schumanet-BM mineral wool material 50 mm thick are applied to the inner surface of the casing walls. Ventilation of the internal volume of the casing is carried out through ducts 4, lined with a similar sound-absorbing material. For access to the parts of the insulated electric machine during inspection and control of its components, a removable cover 5 is provided.

A soundproof casing hermetically seals a noisy electric machine (for example, a PT-200 Ts current converter). To increase efficiency

the casing inside is lined with a layer of ShVIM-18 2 vibration-absorbing material with a thickness of 5 mm and a layer of Shumanet-BM 3 sound-absorbing material with a thickness of 50 mm, selected taking into account technological and fire-fighting requirements for the material of the absorber. In order to reduce the transmission of oscillations from the current transducer to the casing, there is no rigid connection between them. The casing is mounted on vibration-isolating gaskets made of soft rubber, designed to attenuate vibrations that occur on an electric machine during its operation. Electric cables are introduced under the casing through sealing devices - soundproofing “glands”. The casing is equipped with air ducts 4 lined with the same sound-absorbing material. Excess heat is removed from the internal volume of the casing through these channels by natural convection.

To determine the average soundproofing ability of the casing is the formula:

R = 13.51gQ + 13 dB, (1)

where R is the soundproofing ability of the casing, dB;

Q - weight of 1 m ² fencing in kg (weight 1 m ^{2 of} duralumin with a thickness of 1 mm - 3.6 kg).

The average soundproofing ability corresponds to the soundproofing ability at a medium frequency, which is considered to be 500 Hz.

Having determined the sound-insulating ability at a frequency of 500 Hz, it is possible to construct the frequency response of the sound-insulating ability at other frequencies by introducing the amendments presented in Table 1 into the calculated value (Alekseev S.P., Kazakov AM, Kolotilov N.N. Struggling with noise and vibration in mechanical engineering . M., "Engineering", 1970, p.208).

Table 1.
Corrections to the calculated value of R Frequency in Hz Correction Amount 125 -8 250 -4 500 0 1000 +4 2000 +8 4000 +12

The soundproofing ability of the casing at the geometric mean frequencies of the octave bands, determined by the formula (1), is presented in table 2.

Table 2.
Soundproofing ability of the casing Geometric mean frequency, Hz 125 250 500 1000 2000 4000 Sound insulating ability, dB 12 16 twenty 24 28 32

The values of noise reduction during casing lining with SHVIM-18 vibration-absorbing material are presented in Table 3 (Alekseev S.P., Kazakov A.M., Kolotilov N.N. Fighting noise and vibration in mechanical engineering. M., "Mechanical Engineering", 1970 p.208).

Table 3.
Noise reduction with a vibration absorber Geometric mean frequency, Hz 125 250 500 1000 2000 4000 Decrease in level, dB 0 0 1 8 10 12

To calculate the sound absorption of a layer of mineral wool material “Schumanet-BM” with a thickness of 50 mm, it is necessary to use the values of the sound absorption coefficient a as a function of frequency (table 4), determined using an acoustic interferometer.

Table 4.
Sound Absorption Ratings Geometric mean frequency, Hz 125 250 500 1000 2000 4000 Sound absorption coefficient 0.53 0.66 0.75 0.96 0.89 0.89

Noise attenuation by the casing (level difference inside and outside the casing) is calculated by the following formula:

(2)

where L _In - the noise level inside the casing;

L _H - noise level outside;

R - soundproof ability of the casing, dB;

α is the sound absorption coefficient of the material.

The effectiveness of the casing is presented in table 5.

Table 5.
The effectiveness of the casing. Geometric mean frequency, Hz Sound insulation, dB Level difference Vibration absorption, dB The effect of the use of the casing, dB 125 12 nine 0 nine 250 16 14 0 14 500 twenty 19 1 twenty 1000 24 24 8 32 2000 28 27 10 37 4000 32 31 12 43

Thus, the use of the proposed soundproof casing can improve the efficiency of sound insulation.

Claims (1)

The soundproof casing, mainly of electrical machines, is a box-shaped structure, the walls of which are made of duralumin with a thickness of 1 mm with a layer of ShVIM-18 vibration-absorbing material 5 mm thick deposited on them, equipped with air ducts for ventilation of the internal volume of the casing and a removable cover for access to parts of the insulated electric machines during the inspection and control of its components, characterized in that, in order to improve the sound insulation efficiency, the inner surface of the casing walls is sound-absorbing lining of mineral wool material "Schumanet-BM" with a thickness of 50 mm.