Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – Adjacent ear
Patent
1996-01-05
1997-10-14
Isen, Forester W.
Electrical audio signal processing systems and devices
Acoustical noise or sound cancellation
Adjacent ear
181206, G10K 1116
Patent
active
056779585
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an active sound damper for compensating interference noise radiated by an interference noise source.
BACKGROUND OF THE INVENTION
Sound dampers of the above kind are used in sound damping systems and reduce the sound level of a sound field, experienced as annoying. The overall sound damping system in principle has a sound damper as well as a sensor for providing information about the interference noise to be expected and/or a control sensor for receiving the already damped or canceled-out interference noise. The sensor signal corresponding to the noise level is supplied to a control unit for further processing. The processed sensor signal thereafter reaches a speaker in the form of an electrical signal. The speaker is a component of the sound damper and radiates compensation sound or (anti-sound), The electrical signal supplied to the speaker is calculated so that the two sound fields corresponding to the compensation sound and the interference noise overlap in antiphase according to the principle of interference known from physics. As a result, the interference noise is cancelled out or at least considerably reduced.
WO 91/15666 and U.S. Pat. No. 5,097,923 disclose active noise dampers for reducing exhaust noise in motor vehicles which have one or a plurality of speakers. Each speaker is disposed in a compensation sound chamber. Compensation sound chambers are disposed diametrically opposite one another on the pipe jacket of the exhaust pipe so that the radiation direction of the speaker runs radially to the exhaust pipe. Due to the lateral disposition of the speakers, the compensation sound waves must travel a certain distance to the pipe opening, which constitutes the radiation opening of the noise, in order to generate a homogeneous compensation sound field at that location. To this end, the compensation sound field generated in the sound chamber is supplied to the exhaust opening via a conduit disposed concentrically around the exhaust pipe. As a result, the sound damper takes up a great deal of space and has a structurally complex design. Due to the complex outer contour of the sound dampers of the prior art, their manufacture is difficult from a technical manufacturing viewpoint, and can consequently be very cost intensive.
Moreover, since installation conditions according to the prior art are often very cramped, and since the sound damper should therefore take up as little installation space as possible, a further volume enlargement of the sound damper, which already takes up a great deal of space, is possible, if at all, only in a limited manner. However, it is desirable to provide as large as possible a chamber particularly at the back end of the speaker in order to produce low-frequency tuning of the speaker. Therefore since, as pointed out above, it is impractical to provide more space for sound dampers of the prior art the efficiency of the speaker in prior art sound dampers is low. Furthermore, the exact coupling between the control sensor and the speaker is impeded due to the large transmission path between the speaker and the radiation opening of the exhaust pipe. The damping of interference noise according to the prior art is therefore insufficient.
An active sound damping system is known from EP-A-227 372, in which the radiation directions of interference noise and compensation sound are aligned approximately parallel to one another. However, the particular disposition of the speaker which generates the compensation sound requires a sound damper, which is structurally very complex and takes up a great deal of space, in order to be able to damp the noise.
The object of the invention is to embody a sound damper of the above mentioned kind in a space saving manner, and to produce an antiphase overlapping of interference noise and compensation sound in a geometrically simple manner.
SUMMARY OF THE INVENTION
The above object is attained by the invention, according to which, the speaker cone radially surrounds the radiation opening. As a res
REFERENCES:
patent: 3936606 (1976-02-01), Wanke
patent: 4665549 (1987-05-01), Eriksson et al.
patent: 5097923 (1992-03-01), Ziegler et al.
patent: 5257316 (1993-10-01), Takeyama et al.
Technology!. vol. 3, 1990, Copyright Visation, pp. 21-29.
Isen Forester W.
Leistritz AG & Co Abgastechnik
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