SU884586A3 - Plate structure for noise reduction - Google Patents

Description

The invention relates to mechanical engineering and can be used mainly in trucks, industrial and airborne plants, and building structures.

Known plate design to reduce the noise of trucks, air installations and building structures, in which there is mixed noise with a frequency of from 20 to 20,000 Hz, containing three plates fixed at separate points, the middle plate having a lower modulus of elasticity in bending and a lower elastic constant and made in the form of a plastic film, and at least one of the plates having a higher modulus of elasticity is in contact with the vibration excitation source [1].

However, the known design does not provide sufficient noise reduction.

The purpose of the invention is to increase the efficiency of noise reduction by using interference.

This goal is achieved in that the fastening points of the plates are arranged so that the distance between two adjacent points in the direction of the sides of the plate and the maximum distance of the points from the edge of the plate are from 10'1 / 1.5 to 1/50 of the length of the plate or are multiples of this value moreover, at the attachment points of the plate are in adhesive contact.

In FIG. 1 shows, as an example, a plate structure in perspective; in FIG. 2 - layers of plate structure; in FIG. 3 - = segment of the air channel; in FIG. 4, the radiating plate of the air channel in FIG. 3; in FIG. 5 is a graph of the air channel noise level.

The lamellar structure contains excitation 1 and radiating 2 plates, between which there is a plastic25 foil (plate) 3. All three plates are fastened at separate points 4 between themselves, for example, by spot welding or in another way (Figs. 1 and 2).

The distance between two adjacent attachment points in the direction of the lateral sides of the plate and the maximum distance of points from the edge of the plate is 1 / 1.5 to 1/50 of the length of the plate or is a multiple of this value, and at the attachment points of the plate are in adhesive contact.

The thickness of the plates 1 and 2 are the same or may be different.

The connection has such an arrangement that coherent waves excited by waves of damped frequency are well damped on the outer surface of the radiating plate or are either damped, or their radiation is significantly reduced.

The contact points 3 foil melts and fills the ring-shaped intermediate space between the plates 1 and 2. Foil aligns transverse waves arising at the bending of plates 1 and 2, and eliminate sliding _parts as- _mp: ting relative to each other and constantly separates plas7 ^t different from each other.

In addition, the foil prevents the formation of waves of large amplitude.

A section of the air channel (frt. 3) is made entirely of a plate design. The wall 5 of the channel 6 is bent from one sheet and closed by welding along the edge 6. A soft plastic foil 7 and a radiating plate 8, which is glued or welded on the sides, are superimposed or wound on the thus-made channel wall 5. The outer plate is as sized to fit the edges of the channel as required by the edge loss coefficient, but the edge plate is always fixed.

When determining the distance between the attachment points, it should be taken into account, on the one hand, that a uniform fit should be ensured on the foil, on the other hand, that such local concentrated concentrated progressive waves carry out excited by a frequency that it is desirable to damp, bending transformed onto a radiating plate which are coherent and can be interfered.

The distance between the attachment points should be set as follows (according to Fig. 4), the rectangular channel has a size A x B and a length L, the dimensions of the radiating plate, mm:

A | = A —10

B = B —10

L - L -50

Dimensions of distance between points

fastenings, mm:  L.4 L * J A ¹ ' ⁼ 30' ^L x ’7’ 20 8' ^l a ts - »·· - · 7.

In FIG. 5 is a diagram showing the noise level of the air passage of FIG. 3.

The solid line represents the noise level of an air channel made of a normal plate, measured by a microphone located 1 mm from the channel and excited by a pump speed of 1000 rpm.

The dashed line shows the noise level of the air channel (of similar dimensions) made of the described noise-reducing plate structure.

The graph clearly shows how much the noise level is reduced.

Claims (1)

1. Skurndin A. A. and Mikheev E. M. Fighting the noise and vibration of shipboard two .. Shipbuilding, 1970, p. 196-197, rice, 101. / / / Fig 2 (tkie.fi 9 3 J / S6 89tO S 5 4y5 iDa & S at S678ff}