SU939795A1 - Noise silencer - Google Patents

Description

one

The invention relates to acoustics, in particular, to the technique of damping airborne noise in ventilation systems and air conditioning systems.

A noise suppressor is known, comprising a housing lined with sound-absorbing material and mounted wedge-shaped plates of sound-absorbing material whose cross-section decreases in the direction of sound propagation ll.

The silencer reduces the noise level of the working machines.

The disadvantage of the known silencer is a significant reduction in the efficiency of sound attenuation on you. soki frequencies.

The purpose of the invention is to increase the efficiency of noise attenuation at high frequencies.

This goal is achieved by the fact that in front of the wedge-shaped plates at a distance L - -t-b /, a perforated metal partition is installed perpendicular to the channel walls with a perforation hole diameter equal to 2r: c / fefni, where c is the speed of sound in air ; fyy, is the upper limiting frequency of the muffled frequency range, the perforation step is equal to Р - С / 4f.

ten

Figure 1 shows the proposed muffler, General view; fig 2 is a perforated partition.

The silencer consists of the face 5 of the sound-absorbing material of the housing 1, the wedge-shaped plates 2 made of the sound-absorbing material, and a perforated metal partition 3.

20

The muffler works as follows.

Claims (2)

The sound waves propagate through the channel and pass through the perforated partition 3, at the same time, the zak energy transferred by paraxial rays is transformed into the energy of oblique rays, i.e. decreases the coefficient of axial concentration of sound energy in the channel. Thus, the sound energy transmitted by paraxial rays (and not attenuated by absorption in the channel) in the proposed silencer constitutes a small part of the total energy, therefore the effect of the radiation effect on the sound attenuation efficiency is significantly reduced, the main part of the sound energy is transferred by oblique rays which are well absorbed in sound-absorbing material channels formed by wedge-shaped plates. 2. Since the distance between the perforated partition 3 and the wedge-shaped plates 2 is equal to the length of the near field of the sound field for the entire muffled range, the chosen diameter of the holes in the perforated plate 3 and the perforation pitch provide for the far zone of the sound field a uniform angular spectrum of the sound beams the floor within the entire spatial angle from 0 to 180 relative to the perforated plate, a uniform angular spectrum of sound rays is created in the channels between the wedge-shaped plates 2 (. There is an effective noise absorption in the sound-absorbing lining of the channels J. As the width of the wedge-shaped plates 2 decreases smoothly and monotonously along the channel axis in the direction of sound propagation, the proposed silencer has a set of efficiency peaks with a monotonous and smoothly changing frequency, and this set of peaks covers the frequency range : C ... / zfvrAe 1i, ti - maximum and W / l l minimum width of wedge-shaped plates, respectively. The proposed muffler effectively works in a wide range of frequencies. Claims The muffler comprises a housing lined with sound-absorbing material and installed in wedge-shaped plates of sound-absorbing material whose cross section decreases in the direction of sound propagation, characterized in that, in order to increase the sound attenuation at high frequencies, a perforated metal partition is installed in front of the wedge-shaped plates, perpendicular to the walls of the body at a distance of L-tEyn with the diameter of the perforation holes being equal to / di and the perforation step is equal to P-C / 4f, where c is the speed of sound in air; - upper limit frequency of the muted frequency range. Sources of information taken into account during the examination 1. Reference book on ship acoustics. L., Shipbuilding, 1978, p.121, fig.5,1a. ) (KKH) ) fig 2