JPH0622389A - Sound field reproducing device - Google Patents

Abstract

PURPOSE:To efficiently reduce a noise such as an engine noise without reducing a sound desirable to a person, and to produce a sound field space with a sense of expanse by providing two music source adaptive type and noise adaptive type digital filters. CONSTITUTION:This device is equipped with a speaker 2 which reproduces a signal generated from a music source 1, and a microphone 5 which detects the noise and a music signal. And also, the device is equipped with two speakers 8 which control the noise, and two microphones 3 which monitor the state of a noise control and a sound field reproduction. A music source adaptive digital filter 4 generates a signal so that a difference between the signals of the speaker 2 and the monitor microphones 3 arranged near the person, and the music source 1 can be the minimum. In a noise adaptive digital filter 7, a filter coefficient is updated so that a difference signal (a), that is, a signal allowed to approach only the noise by the digital filter 4 can be the minimum. Thus, the noise components at the monitor microphone 3 can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound field reproducing device for actively controlling noise and reproducing a sound field, and is propagated from a noise source such as engine sound in a narrow space such as a passenger compartment. The present invention relates to a device that generates control sounds having different phases with respect to noise and creates a sound field with a sense of spaciousness.

[0002]

2. Description of the Related Art There is an active noise control device for reducing control noise by generating control sounds having different phases with respect to noise transmitted from a noise source.

Conventionally, as an active noise control device, Japanese Patent Laid-Open No. 3-40598 (International Patent Classification H04R 3
/ 00), it is known that a control sound having a phase opposite to that of the noise and having the same amplitude as that of the noise is generated and emitted, and the noise is suppressed by mutual interference between the noise and the control sound.

An active noise control device of this type is disclosed in Japanese Patent Laid-Open No. 3-203792 (International Patent Classification G10K).
11/16), as shown in 3
It is also applied to dimensional space. This three-dimensional noise control device emits control sound from a speaker so that the noise level at the control point is minimized based on the means for detecting noise at a plurality of points and the means for detecting a mute state at a plurality of control points. , Reduce noise. As noise detecting means, noise is detected directly by using a microphone, and an acceleration sensor, a rotation monitor, or the like is used for noise of a rotating sound of a motor, a compressor, an engine, or the like.

On the other hand, when listening to music in a narrow space such as a vehicle compartment, the reverberation sound is generally shorter than in a listening space such as a listening room, and the sound field has a sense of spaciousness. In this case, by adding the reflected sound / reverberation sound to the music signal using a digital filter based on the desired acoustic data (data related to the reflected sound / reverberation sound) previously obtained by measurement, etc. Can be given.

[0006]

However, in the above-mentioned conventional noise control device, the method of detecting noise with an acceleration sensor or the like cannot be used when the noise source cannot be identified, and the noise source cannot be used by humans. When the propagation path reaching both ears is complicated, the correlation between the signal detected by the sensor and the actual noise signal is significantly reduced, and the noise reduction effect is reduced.

By the way, when the noise is directly detected by the microphone, it is not necessary to identify the sound source, and it is possible to detect a signal having a strong correlation with the noise signal in both ears of a person. In a space containing signals, there is a problem that music signals that are not noise are also reduced.

On the other hand, as a method of adding a reverberation sound to a music signal and reproducing a sound field in a narrow space with a high noise level such as a vehicle interior, a method using a fixed digital filter and a method using an adaptive digital filter are used. There is.
In the case of adding the early reflection sound and the reverberation sound by using the fixed digital filter, the optimal control is impossible because it cannot adapt to the changes of the person's position and environment, and when the adaptive digital filter is used. However, there is a problem in that the system may become unstable due to the influence of noise and control may be difficult.

The present invention solves the above-mentioned problems of the conventional device, and in a narrow space such as a passenger compartment,
When the signal is known in advance from a cassette tape recorder or CD player, sound field reproduction that effectively reduces engine noise and other noise without reducing the preferred sound for humans and creates a spacious sound field space The purpose is to provide a device.

[0010]

In order to achieve the above object, according to the present invention, a portion for adaptively controlling a music source such as a CD player / cassette tape recorder and the like are transmitted by a vibration of an engine or a road surface. It has a part that adaptively controls incoming noise, and controls the music source signal and noise signal based on the monitor microphone input signal provided at the control point to reduce noise and create a spacious sound field space. Reproduce. That is, a speaker that radiates a music source and a first adaptive digital filter that adaptively generates a signal so that the difference between the signal from the monitor microphone installed near a person and the music source is minimized, and a speaker. And a digital filter simulating a transfer function between a microphone that detects noise in which music signals are mixed, and a second adaptive digital that adaptively generates a signal in a monitor microphone to minimize noise. It includes a digital filter and a speaker that emits a control signal for controlling noise.

[0011]

With the above construction, the first adaptive digital filter updates the filter coefficient so as to minimize the difference between the signal convolving the desired transfer characteristic of the music source and the input signal of the monitor microphone. As a result, the monitor microphone eventually converges to a desired signal including the initial reflected sound and reverberant sound. Also, the difference signal approaches only the noise signal in the monitor microphone. The second adaptive digital filter updates the filter coefficient by the first adaptive digital filter so that the signal approaching only noise is minimized, and as a result, the noise component in the monitor microphone is reduced.

On the other hand, in the input signal of the adaptive digital filter for noise control, the difference between the signal input from the microphone and the signal obtained by convolving the transfer function 6 between the speaker and the microphone with the signal output to the speaker. Since the signal is used, the speaker does not radiate a signal correlated with the music signal, and operates to minimize only noise.

As described above, according to the present invention, the adaptive digital filters operate so as to minimize signals (noise and music signals) due to instability of their operations, and have a sense of spread with less noise. Realizes a certain sound field stably and at high speed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is roughly divided into a part for adaptively controlling a music source such as a CD player and a cassette tape recorder, and a part for adaptively controlling noise transmitted due to engine and road surface vibrations. , A music source signal and a noise signal are controlled based on a monitor microphone input signal provided at a control point to reduce noise and reproduce a sound field space with a sense of spaciousness.

FIG. 1 is a block diagram showing an embodiment of the present invention. In this embodiment, as shown in FIG.
A speaker 2 for reproducing a signal generated from a music source 1 such as a player / cassette tape recorder, a microphone 5 for detecting noise and a music signal, a speaker 8 for controlling noise, and a noise control / sound field reproduction state monitor. One microphone 3 is set for each.

The part for adaptively controlling the music source includes a speaker 2 radiating the music source 1, a monitor microphone 3 installed near a person, and a desired sound field characteristic digital for simulating a transfer function of a desired sound field. The filter 9 and the adaptive digital filter 4 that minimizes the difference between the signal obtained by convoluting the desired transfer characteristic 9 in the music source 1 and the input signal of the monitor microphone 3.

The adaptive digital filter 4 adaptively generates a signal so that the difference between the signal from the speaker 2 radiating the music source 1 and the monitor microphone 3 installed near the person and the music source 1 is minimized. To do. That is,
A signal obtained by convoluting the characteristics of the desired sound field characteristic digital filter 9 into the music source 1 and the input signal of the monitor microphone 3 are given to the adder 10, and based on the difference output a, the adaptive digital filter 4 determines the difference. The filter coefficients are updated to minimize As a result, the monitor microphone 3 converges on a desired signal including the initial reflected sound and reverberant sound, and the difference signal a changes to the monitor microphone 3
Approaching only the noise signal at.

On the other hand, the part for adaptively controlling the noise is the speaker 2, the microphone 5 for detecting the noise mixed with the music signal, and the transfer function between the speaker 2 and the microphone 5 detecting the noise mixed with the music signal. A spatial correction digital filter 6, an adaptive digital filter 7 that adaptively generates a signal in the monitor microphone 3 so as to minimize noise, and a speaker that emits a control signal for controlling noise. 8 and.

In this adaptive digital filter 7, the filter coefficient is updated so that the difference signal a, that is, the signal that approaches only noise by the adaptive digital filter 4 is minimized. As a result, the noise component in the monitor microphone 3 is reduced.

A signal obtained by convolving the signal input from the microphone 5 and the signal output to the speaker 2 with the transfer function 6 of the spatial correction digital filter 6 simulating the space between the speaker 2 and the microphone 5. And are adders 1
The difference is taken by 1. Since the difference signal between the two signals is used as the input signal of the noise control adaptive digital filter 7, a signal correlated with the music signal is not emitted from the speaker 8, and only noise is minimized. To work.

Further, the adaptive control algorithm of the adaptive digital filters 4 and 7 described above, in this embodiment, is fi
The lteredX algorithm was used. This algorithm is
As shown in FIG. 2, the filter coefficient is updated so that the root mean square of the error signal is minimized by the equation in the figure.
In the present invention, the error signal in FIG. 2 corresponds to the signal a in FIG. 1, and the root mean square of the signal a approaches zero as the filter coefficient is updated.

As described above, in the present system, the adaptive digital filters 4 and 7 operate so as to minimize signals (noise and music signals) due to instability of operation, and have little noise. A stable and high-speed sound field with a sense of spaciousness is realized.

Further, according to the present invention, the speaker 2 for reproducing the music source, the microphone 5 for detecting the noise signal including the music signal, the speaker 8 for controlling the noise and the noise control /
It is possible to receive a plurality of microphones 3 that monitor the effect of creating a sound field, and a wider range of control is possible.

[0024]

As described above, the sound field creating apparatus of the present invention has a low noise and a desired desired expansive sound in a sound field space where there is no noise and there is no expansive feeling. It is possible to create a space.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of an adaptive control algorithm used in the embodiment of the present invention.

[Explanation of symbols]

 1 Music Source Source 2 Music Playback Speaker 3 Monitor Microphone 4 Sound Field Playback Adaptive Digital Filter 5 Noise Detection Microphone 6 Spatial Correction Digital Filter 7 Noise Control Adaptive Digital Filter 8 Noise Control Speaker 9 Digital filter for desired sound field characteristics

Claims (1)

[Claims] 1. A speaker that emits a music source, a monitor microphone that is installed in the vicinity of a person and that detects the state of noise control and sound field characteristics, and is adapted to minimize the difference between the signal from the monitor microphone and the music source. First adaptive digital filter for dynamically generating a signal, a microphone for detecting noise in which a speaker and a music signal are mixed, and a digital filter for simulating a transfer function between the speaker and the microphone, Sound field reproduction including a second adaptive digital filter that adaptively generates a signal in the monitor microphone so that noise is minimized, and a speaker that emits a control signal for controlling noise. apparatus.