JPS6256995A - Active silencer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active silencer, and more particularly to an active silencer that can be suitably used in a closed space such as a vehicle interior.

[Prior Art] An active silencing device has a sound source for silencing, and outputs a sound having a phase opposite to the noise from the sound source, thereby canceling out the noise. While conventional resonant silencers are large due to the long wavelength of low frequencies, the active silencer described above has no relation to the wavelength of the noise, so it has a compact shape and can be used at low frequencies. It is capable of effectively muffling wave noise, and is attracting attention as a silencer for use in vehicles where it is difficult to secure installation space.

[Problems to be solved by the invention] Normally, a speaker is used as the sound source for silencing, but in a closed space such as a vehicle interior, the sound is emitted from a high-output silencing speaker installed near the noise source such as an air conditioning duct. Sound may be transmitted or reflected in a complex manner, resulting in secondary noise.

The present invention is intended to solve such problems, and aims to provide an active muffling device in which a muffling speaker installed in a closed space does not become a secondary noise source.

[Means for solving the problem] In the figure, A1 is a noise source that generates noise in a closed space S, and a microphone 1, which is a sound collection means for noise detection, is installed near the noise source A. .

On the other hand, the speakers 2A and 2B, which are noise-muffling sound generating means, are provided near the noise receiving position S1 in the closed space S, and emit a sound having a phase opposite to that of the noise in order to eliminate the noise that has arrived there.

The output signal of the microphone 1 is input to the sounding means 3,
The calculation means 3 calculates the noise waveform at the sound receiving position S1 from the output signal. The output signal of the itching means 3 is input to the speaker driving means 4, where the phase is inverted and applied to the speakers 2A and 2B.

[Effect] The noise that has reached the sound receiving position S1 is transmitted through the silencing speakers 2Δ, 2
It is effectively extinguished by the sound of the opposite phase emitted from B.

According to the present invention, since the speakers 2A and 2B are provided near the noise receiving position, the speaker output required to cancel out the noise may be small, and therefore there is no problem that the speakers 2A and 2B become a secondary noise source. Furthermore, the speakers 2A and 2B can be small and inexpensive (for example, headphone speakers).

Roughly speaking, it takes longer time for the noise to reach the speakers 2A and 2B installed near the sound receiving position 81 than when the speakers 2A and 2B are installed near the noise source A1.
Another advantage is that it is easy to secure the calculation time.

Embodiment] In the figure, S is a sealed vehicle interior, and a seating seat (not shown) is provided in the vehicle interior S, and a passenger seat 0M is located therein. There are noise-reducing speakers 2 on the left and right positions of the noise receiving position S2 on the seat near both ears of the occupant M.
A and 2B are buried.

An air conditioning duct A is installed inside the instrument panel P. In the figure, A1 is the inside air intake port, A2 is the 10-a motor, and A
3 is an evaporator, A4 is an air mix damper, and A5 is a heater core. Air suction sound is emitted into the vehicle interior S from the suction port A1, and this is directed toward the occupant M as indicated by the arrow in the figure. A noise detection microphone 1 is provided near the opening of the suction port A1.

The microphone 1 is connected to a computing device 3, and its output signal 1a is input to a preamplifier 31 of the computing device 3. The arithmetic device 3 has a memory 32, and the memory 32 stores sound transmission characteristics from the inside air intake port Δ1 to the binaural ears S1 of ΩM,
Impulse response data of the sound propagation space represented by the ratio of the sound transmission characteristics from the silencing speakers 2A, 2B to both ears S1 of the occupant M are preset as S1 to S1.

The signal 1a that has passed through the preamplifier 31 is input to an integrating circuit 33, where it is convoluted and integrated with the impulse response data. This integral output 3a is the passenger M's both ears S1
This shows the noise waveform at .

The integral output 3a is the power amplifier 41 of the speaker drive circuit 4.
Then, the phase of the signal is inverted by the phase inverting circuit 42 and outputted to both the speakers 2A and 2B.

As a result, from the speakers 2A and 2B, the above-mentioned Ellf
A sound having a phase opposite to the noise reaching S1 is output to eliminate the noise.

According to the present invention, the noise-reducing speakers are installed near both ears, which are the noise receiving positions, so it is possible to use speakers with low output, and to avoid problems such as the sound of the current speakers leaking to the adjacent seat. There is no risk of noise generation. Moreover, the speaker can be made small and inexpensive. Furthermore, it is easy to secure the calculation time of the calculation device.

In the above embodiment, the case where there is a single noise source is explained.
Noise source is +! If there are two, a microphone and an arithmetic circuit are provided for each, and the outputs of the respective arithmetic circuits are added together by a mixer and given to the speaker.

[Brief explanation of the drawing]

The figure is a plan view of a single room equipped with the device of the invention. S... Vehicle interior (closed space) A1... Inside air intake (noise source) Sl...
・Ear (&I sound receiving position) 1...Microphone (
Sound collection means) 2△, 2B...Speaker (sound generation means) 3...Arithmetic circuit 32...Memory 33...Integrator circuit 4... ... Speaker drive circuit 42 ... Phase inversion circuit

Claims (3)

[Claims] (1) What is the noise detection sound collection means installed near the noise source that emits noise into the closed space, and the noise that is installed near the noise receiving position in the closed space and reaches the sound receiving position? silencing sounding means for emitting sound with an opposite phase to eliminate it; a calculating means for inputting the output signal of the sound collecting means to calculate a noise waveform at the sound receiving position; and calculating means for calculating the phase of the output signal of the calculating means. and a driving means for inverting the signal and outputting it as a driving signal to the sounding means. (2) The active noise reduction device according to claim 1, wherein the sealed space is a vehicle interior, and the sound generating means is embedded in a headrest of a vehicle seat near the ears of a vehicle occupant. (3) The calculation means convolutes and integrates the output signal of the sound collection means and the impulse response data with a memory in which impulse response data of the sound propagation space from the noise source to the sound receiving position is stored in advance. 2. The active muffling device according to claim 1, further comprising an integrating circuit for obtaining a noise waveform at the sound receiving position.