JPH02161900A - Vehicle mounted acoustic apparatus - Google Patents

Abstract

PURPOSE:To obtain a satisfactory stereophonic reproducing sound field by converting an output signal of an acoustic apparatus so that a both-ear response of a listener in a car room becomes equal to a both-ear response in a desired sound field being an object. CONSTITUTION:An output (sound signal) of an acoustic apparatus is selected by an input/output switching circuit 19 of a sound field converter 26. A coefficient of a digital filter for constituting sound field conversion matrix elements 9-12 is stored in a memory 25 in accordance with a characteristic of several kinds of sound fields being an object, read out of the memory 25 by a central arithmetic processor 24 in accordance with a kind or choice of a music source, and the coefficient of the digital filter can be reset again. In such a way, a asymmetrical sound field, and a sound field having turbulence in a transfer characteristic can be converted to a desired sound field, therefore, even in a car room of an automobile, a satisfactory sound field can be reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to audio equipment, and particularly to a sound field correction creation device suitable for vehicle-mounted audio equipment that targets an asymmetric sound field.

[Prior Art] As described in Japanese Unexamined Patent Publication No. 114999/1982, a conventional device delays and attenuates a sound source closer to the listening position to create a virtual image sound source, and then uses the virtual image sound source as a distant sound source. By making it symmetrical with respect to the listening position, it was configured so that natural stereo reproduction sound could be heard even at an asymmetrical stereo listening position.

[Problems to be Solved by the Invention] The above-mentioned prior art solves the problem of disturbances in frequency characteristics caused by the shape of the vehicle interior, the mounting position of the speakers, and asymmetry in the frequency response of the left and right ears of the received sound caused by the asymmetric speaker arrangement. However, no consideration has been given to this, and it has not been possible to obtain a good stereo playback sound field.

The purpose of the present invention is to correct disturbances in frequency characteristics caused by the shape of the vehicle interior and speaker mounting positions, and also to correct asymmetries in binaural time and frequency responses caused by asymmetrical speaker placement. The objective is to obtain a stereo reproduction sound field and further create a desired sound field.

[Means for Solving the Problems] The above object is to provide a sound field conversion means, such as a digital filter, a memory, and a controller, for converting the binaural response in the vehicle interior to be equal to the binaural response in the desired sound field. This is achieved by installing a sound field conversion network configured by the following in front of the vehicle interior speakers.

[Operation] The sound field conversion network operates to convert an asymmetric sound field or a sound field with disturbed transfer characteristics into a desired sound field.

[Example] FIG. 2 is a schematic diagram of a vehicle interior sound field and a dummy head microphone. In the figure, the transfer function HR@HRO for the output of the right speaker 3 inside the vehicle gives an impulse signal to the input signal SA, and the built-in microphone 5.
It can be obtained by performing FFT calculation on the response of No. 6. Similarly, the transfer function H for the output of the left speaker 4,
,,HL. can be obtained by applying an impulse signal to the input signal SL and performing FFT calculation on the exclusive responses of the built-in microphones 5 and 6 of the dummy head 7. Further, the transfer function H, Ho in the target sound field shown in FIG. 2 can also be obtained using the same procedure. E shows the response of the built-in microphones 5.6 in both ears of the dummy head 7 when the left and right speakers are disturbed simultaneously.
*, EL (target sound field) is next.

If the response of the binaural built-in microphone 5.6 is E,, EL (inside the vehicle), then the response of each ear is equal in the rain sound field (EL=E-, E
Jl=E 11) Matrix elements, that is, filters 9 to 12 of the sound field conversion network 8 shown in FIG.
Letting the transfer function of T, , T, ,cL,c, the above (
From equations 1) and (2).

However, Δ: HL B HR@-HL OHRt3.

The numerator and denominator of the matrix elements of the conversion network can be determined as more accurate time responses than actual measurement results by linear convolution calculation.

Therefore, a digital filter that outputs the time response of the numerator and inputs the time response of the denominator can be designed using the method of least squares or the like. As a result, a sound field conversion network can be realized, and a desired reproduction sound field can be obtained.

Furthermore, by storing multiple types of digital filter coefficients designed using the above method in memory, recalling them according to the music source and preference, and rewriting the digital filter coefficients, it is possible to reproduce another desired sound field. .

Hereinafter, specific embodiments of the present invention will be described based on FIG. In the figure, tuner 15. Cassette deck 16,
The output (audio signal) of audio equipment such as the CD player 17 and DAT 18 is output from the input/output switching circuit 19 of the sound field conversion device 26.
selected by

The analog signal selected here is the A/D converter 20.
．． 21 into a digital signal, and the digital signal is input as is to the sound field conversion network 18. The input digital signal is passed through digital filters 9 to 12.
The signal is supplied to the sound field conversion network 8 composed of adders 13 and 14, where it is processed based on the above equation (3), and then converted into an analog signal by the D/A converter 22 at the next stage. This analog signal is acoustically output into the vehicle interior from a speaker 3.4 via a power amplifier.

The coefficients of the digital filters constituting the sound field conversion matrix elements 9 to 2 are stored in the memory 25 in accordance with the characteristics of several types of target sound fields, and central processing is performed depending on the type of music source or preference. The device 24 can read out the data from the memory 25 and reset the coefficients of the digital filter.

[Effects of the Invention] According to the present invention, an asymmetrical sound field or a sound field with disturbed transmission characteristics can be converted into a desired sound field, so it can be used in the interior of an automobile, which is subject to various restrictions as an acoustic space. It can also reproduce a good sound field.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a schematic diagram showing the relationship between the vehicle interior sound field and the dummy head microphone, and Fig. 3 is a schematic diagram showing the relationship between the ideal sound field and the dummy head microphone. FIG. 4 is a schematic diagram showing the relationship between the sound field conversion network, the vehicle interior sound field, and the dummy head microphone. 8: Sound field conversion network 9: Matrix elements T, 1Lc of sound field conversion network
Rch signal filter 10 for h output: Matrix element of sound field conversion network R for CaLch output
Channel signal crosstalk component filter 11: matrix element CLLc of sound field conversion network
Filter 12 for the crosstalk component of the Rch signal for the h output: Matrix component of the sound field conversion network Filter for the Lch signal for the Lch output 13.14: Adder 24: Central processing unit for filter coefficient control 26: Sound field conversion device

Claims (1)

[Claims] 1. An audio device, a speaker, and an output signal of the audio device that is converted to be equal to a binaural response in a desired sound field aimed at a binaural response of a listener in a vehicle interior. An in-vehicle audio device characterized by being provided with a sound field converting means. 2. The vehicle-mounted audio device according to claim 1, wherein the sound field converting means is constituted by a digital filter. 3. The sound field converting means constituted by the digital filter is provided with a memory and a controller, and the coefficients of the digital filter are configured to be rewritten to the coefficients recorded in the memory. In-vehicle audio equipment listed.