Acoustics – Sound-modifying means – By wave interference
Patent
1989-05-22
1991-10-22
Brown, Brian W.
Acoustics
Sound-modifying means
By wave interference
381 71, F01N 106
Patent
active
050587021
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a silencer device for exhausts of motorcycles, vehicles, air conditioners, air compressors and all other acoustic pollution sources.
Until today the attempt of reducing the noise, which is one of the most serious components of the pollution in the industrial society, has been developed with sound-absorbing means suited for reducing the intensity thereof.
In particular for what concerns the reduction of the noises produced by the exhausts of motors of any kind, the outlet gases are forced to pass through winding passages and hurt against absorbing walls which however do not determine a sound reduction level that makes the civic centers, the working ambients and places like autodromes and the like more comfortable.
It is the aim of the present invention to completely eliminate the noises produced by the exhausts of motors, conditioners, compressors and similar by means of a process different that absorption.
It is already known that the physical phenomenon of interference allows in case of overlaying of acoustic waves in phase opposition, to anul a sound with a "counter-sound", characterized in a phase-displacement corresponding to a displacement of 1/2 wave length.
It is the aim of the present invention to realize an active silencer device that will produce for each sound passing through the exhaust pipe of any kind of motor, a corresponding counter-sound in phase opposition that will be superimposed to the primary sound in correspondence to the noise's outlet, thus anulling it.
The evident advantage of the present invention consists in the capacity of the device to make any noise source with localized outlet noiseless, without therefore causing any reduction in the efficiency of the motor itself but, on the contrary, improving the functioning of the same.
The present invention will be explained more in detail hereinbelow relating to the enclosed drawings in which a preferred embodiment is shown.
FIG. 1 shows a vertical section of a silencer device for exhausts of motors and similar with acoustic interference.
FIG. 2 shows an axonometric exploded view of the device according to FIG. 1.
FIG. 3 shows a scheme of a mechanical variant of the device according to the present invention.
FIG. 4 shows a scheme of a variant of the device according to the present invention provided with external springs.
The figures show a silencer device for exhausts of motors and similar with acoustic interference, consisting of a pipe 1 with walls being insulating against heat and sounds with amianthus, that may be applied, in a well known manner, to exhaust pipes of any kind, or that may be obtained inside the end part of said pipes.
To said first pipe 1 a second pipe 2 is applied parallel and out of one piece, being closed at the end of the semispherical cap 3 with hole(s) 4 for the air from the outside.
Said parts 1 and 2 converge in the same outlet end 5 being preferably outwardly tapered.
A main feature of the device according to the present invention consists in the rigid rod 6 passing through an opening 11 provided in said parts 1 and 2, and provided with end blades 7 and 8 having its fulcrum on the spherical knot 9 or similar, placed in the point of contact of said parts of the pipes 1 and 2 and that will elastically vibrate due to the presence of springs or similar applied on both sides, under the impulse of the acoustic waves spreading in the exhausts in part 1 and acting onto blade 7 so that the corresponding blade 8 produces vibrations in the air entering pipe 2 through hole 4, in perfect phase opposition with respect to the exhaust waves.
In fact, to each compression phase of said blade 7 an opposite phase of rarefaction of the coupled blade 8 corresponds and vice versa, so that blade 8 in turn produces a sound in phase opposition to the one spreading in the exhaust and acting on said blade 7.
Said two composed sounds, or noises, now reach outlet end 5 overlapping and therefore reciprocally anulling themselves according to the aim set forth.
For what concerns the variant according to FIG.
REFERENCES:
patent: 3396812 (1968-08-01), Wilcox et al.
patent: 4109108 (1978-08-01), Coxon et al.
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