JPH0659690A - Noise reducer in vehicle cabin - Google Patents

Abstract

PURPOSE:To provide a noise reducer for cabin noise reduction which is improved to efficiently reduce noise in a high frequency band. CONSTITUTION:A noise reducer, which generates a signal in the same amplitude and the opposite phase of noise input to a microphone 1 by using an applicable filter 5 to reduce cabin noise, is provided with a microphone 1 set up on a ceiling above a seat to output a control signal to the applicable filter 5, a low- band 3 set up under the seat to generate low-band noise from the applicable filter 5 and a high-band speaker 3 set up on the ceiling above the seat to generate high-band noise from the applicable filter 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle interior noise reduction device for reducing noise in the vehicle interior.

[0002]

2. Description of the Related Art In the interior of a vehicle, noise is generated by the rotation of the engine, which causes an unpleasant feeling.
As a method of reducing such noise, for example, as described in Japanese Patent Application Laid-Open No. 1-178846 (vehicle interior noise reduction device) and Japanese Patent Application No. 4-195462 (noise reduction device), A method is used in which a signal having the same amplitude and the opposite phase is generated by an adaptive filter to cancel it.

A conventional example will be described below with reference to FIG.
In FIG. 3, 1 is a microphone installed at a point where noise is desired to be reduced, 4 is a noise signal pickup for picking up a noise signal, 5 is an adaptive filter, and 8 is a speaker.

The adaptive filter 5 corrects a portion where the signal picked up by the noise signal pickup 4 is different from the noise input to the microphone 1 and sends it out from the speaker 8, and the signal reaching the microphone 1 is the same as the noise. Generates a signal with amplitude and opposite phase.

When the signal corrected by the adaptive filter 5 and transmitted from the speaker 8 has the same amplitude as the noise and is not in the opposite phase at the point where the microphone 1 is installed, the output of the microphone 1 has a difference. Signal appears and is fed back to the adaptive filter 5. The adaptive filter 5 is composed of a digital filter including a delay line with a tap (not shown) and a transfer characteristic compensator.

A signal of any waveform can be decomposed into a frequency spectrum by Fourier transform.
If the frequency spectra are the same, the same waveform can be obtained by performing the Fourier inverse transform. Therefore, the tap value of the digital filter is changed by the feedback signal from the microphone 1, and the filtering characteristic is created so as to have the same spectrum as the noise spectrum.

Further, the transfer characteristic compensator compensates for the influence of the time delay until the signal generated by the digital filter reaches the microphone 1 and the band limitation so that the input of the microphone 1 has the same amplitude as the noise. In addition, compensation is performed so that signals with opposite phases are output.

[0008]

As described above, the conventional vehicle interior noise reduction device is composed of the microphone 1, the noise pickup 4, the adaptive filter 5 and the speaker 8. The speaker 8 outputs a signal having the same spectrum as noise. Since the noise frequency spectrum includes low-frequency components to high-frequency components, the speaker becomes large in order to efficiently transmit the low-frequency components.

Therefore, the speaker is installed under the seat as shown in FIG. 3, for example, in combination with the aesthetics of the passenger compartment. On the other hand, the microphone 1 is installed at a point where noise is desired to be reduced. That is, it is installed near the ears of the passenger, for example, on the ceiling of the seat as shown in FIG.

As described above, the noise reduction effect when the speaker and the microphone are installed apart from each other is great for the low frequency noise as shown in FIG. The result is that the reduction effect is lost. It is considered that this is because, when a sound wave propagates in a closed space such as a vehicle interior, the transmission characteristic fluctuates due to the fact that the propagation of a high frequency sound wave rather than a low frequency causes a greater number of reflections. That is, the proportion of the passenger in the space (when the passenger is fat or thin)
It is considered that the transfer characteristic set in the adaptive filter and the actual transfer characteristic differ with respect to the high frequency signal due to the change of the signal and the riding position.

An object of the present invention is to provide a vehicle interior noise reduction device which is improved so as to have a great reduction effect on high frequency noise.

[0012]

Means adopted by the present invention for solving the above-mentioned problems will be described. A noise reduction device for reducing a noise in a vehicle compartment by generating a signal having the same amplitude and a reverse phase as a noise input to a microphone by an adaptive filter, (a) being installed on a ceiling of a seat, A microphone that outputs a control signal, (b) a low-range speaker that is installed under the seat and that generates a low-range noise having a signal that has the same amplitude and opposite phase as the noise from the adaptive filter, and (c) the seat And a high-frequency speaker that generates high-frequency noise of a signal having the same amplitude and opposite phase as the noise from the adaptive filter.

[0013]

The microphone for outputting the control signal to the adaptive filter is installed on the ceiling of the seat near the ears of the passenger as a point where noise is desired to be reduced. A low-frequency speaker that outputs low-frequency signals from the adaptive filter is installed under the seat.

Further, a high frequency speaker for transmitting a high frequency band signal from the adaptive filter is installed on the ceiling of the seat. Since the high-frequency speaker is small, even if it is installed on the ceiling of the seat, the distance from the microphone can be shortened without impairing the appearance. For this reason, the level of the main wave of the signal in the high frequency band becomes much higher than the level of the reflected wave, fluctuations in the transfer characteristic are reduced, and the noise reduction effect in the high frequency range is increased.

FIG. 2 shows an example of noise reduction characteristics when a microphone is installed on the ceiling of the seat, a reduction speaker is installed under the seat, and a high frequency speaker is installed on the seat ceiling. As compared with FIG. 4, it can be seen that the reduction effect in the high frequency range is great.
As described above, a low-frequency speaker and a high-frequency speaker that separately transmit the signal from the adaptive filter to the low-frequency range and the high-frequency range are provided, and the low-frequency speaker is under the seat and the high-frequency speaker is close to the microphone. Since it is installed on the ceiling, it is possible to efficiently reduce not only low frequency noise but also high frequency noise.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, the microphone 1, the adaptive filter 5, and the noise pickup 4 are as described in FIG.

Reference numeral 2 is a low frequency speaker that converts an electric signal in a low frequency band into a sound wave, 3 is a high frequency speaker that converts an electric signal in a high frequency band into a sound wave, and 6 is a low pass filter (LP).
F) and 7 are high-pass filters (HPF). The microphone 1 is installed on the ceiling of the seat near the ears of the passenger. Since the low range speaker 2 is large, it is installed under the seat. The high frequency speaker 3 is small and is installed on the ceiling of the seat near the microphone 1.

By installing the microphone 1, the low-frequency speaker 2, and the high-frequency speaker 3 as described above, the distance between the high-frequency speaker 3 and the microphone 1 becomes short, and the main wave at high frequency is higher than the reflected wave. It becomes extremely large, and fluctuations in transfer characteristics are eliminated, and noise in the high frequency band is efficiently reduced.

Since the operation of the adaptive filter 5 is the same as that described in the conventional example, its description is omitted. In the embodiment, the microphone is installed on the seat ceiling, the low range speaker is installed under the seat, and the high range speaker is installed on the seat ceiling. However, either the microphone or the high range speaker is installed on the side of the seat back of the seat. It may be installed.

Further, although the low frequency speaker is installed under the seat in the embodiment, it can be shared with the speaker of the car radio installed in the vehicle compartment. Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications can be made according to the gist of the invention.

[0021]

As described above, according to the present invention, the following effects can be obtained. A low-frequency speaker and a high-frequency speaker that separately transmit the signal from the adaptive filter to the low-frequency range and the high-frequency range are provided, and the low-frequency speaker is installed under the seat and the high-frequency speaker is installed on the ceiling of the seat close to the microphone. Since this is done, it is possible to efficiently reduce noise in the high range as well as in the low range.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of noise reduction characteristics in the case of the two-division band speaker of the same embodiment.

FIG. 3 is a configuration diagram of a conventional example.

FIG. 4 is a diagram showing an example of noise reduction characteristics of a conventional example.

[Explanation of symbols]

 1 Microphone 2 Low-pass speaker 3 High-pass speaker 4 Noise signal pickup 5 Adaptive filter 6 Low-pass filter 7 High-pass filter 8 Speaker

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Nohara 1 25 Nishimachi, Yamada character, Kawagoe City, Saitama Prefecture Pioneer Co., Ltd. Kawagoe Factory

Claims (1)

[Claims] 1. A noise reduction device for reducing noise in a vehicle compartment by generating a signal having the same amplitude and opposite phase as noise input to a microphone by an adaptive filter,
(A) A microphone that is installed on the ceiling of the seat and outputs a control signal to the adaptive filter; and (b) a microphone that is installed under the seat and has the same amplitude as the noise from the adaptive filter but a low phase signal. A low-frequency speaker that generates local noise,
(C) A vehicle interior noise reduction device provided with a high-frequency speaker installed on the ceiling of a seat and generating high-frequency noise of a signal having the same amplitude and opposite phase as the noise from the adaptive filter. .