JPH0227680Y2 - - Google Patents

Description

[Detailed explanation of the idea]

INDUSTRIAL APPLICATION FIELD The present invention relates to correction of a sound transmission system in a vehicle-mounted sound reproduction device. Conventional configuration and its problems This type of sound transmission system consists of the characteristics of the speaker and the characteristics of the sound field affected by reflected sound in the vehicle interior. This is done as shown in Figure 1. 1 is a vehicle interior, 2 is a listener, 3 is a speaker, and 4 is a sound source, such as a tape deck, radio, tuner, etc. 5 is an equalizer for correcting the sound transmission system, and 6 is a power amplifier. The equalizer 5 is a tone control or graphic equalizer with secondary resonance characteristics, and correction is performed on the frequency axis. However, with this method, it is not possible to correct disturbances in characteristics due to complex reflected sounds within the vehicle interior 1. Furthermore,
As shown in FIG. 2, which is a plan view of FIG. , 3-2 shows that not only direct sound but also reflected sound is transmitted to listener 2 separately for the left and right sides. Figures 5a and 5b show speaker 3-1,
3-2 shows response waveforms from each speaker at the position of the listener 2 when an impulse is applied to the speaker 3-2. FIG. 7 is an enlarged view of the time axis. In the case of such a sound field, it is difficult to correct and match the phase characteristics of both the left and right channels, including the time axis, using a method that flattens the frequency sound pressure characteristics, as typified by conventional graphic equalizers. Therefore, the sound image localization of sound sources that should be localized in the center, such as a singer's voice, and monaural sound sources becomes blurred as shown by diagonal lines in FIG. 2, making it difficult to provide the listener with clear sound localization. <Purpose of the invention> The present invention provides an in-vehicle sound reproducing device that can improve reproduction sound quality and sound image localization in a vehicle interior by correcting disturbances in characteristics due to reflected sound in the vehicle interior and disturbances in characteristics due to interference between two speakers. The purpose is to <Configuration of the invention> The in-vehicle sound reproducing device of the invention includes a convolution integrator circuit in series with a signal transmission system to two speakers disposed at arbitrary positions in front of or behind a listener in a vehicle interior. The present invention is characterized in that a convolution equalizer is provided, and the tap coefficients of the convolution equalizer are set so that the ideal impulse positions match in the two acoustic transmission systems. <Description of Embodiment> An embodiment of the present invention will be described below with reference to FIGS. 3 to 8. FIG. 3 shows the configuration of the convolution integrator. 7,
8 is the signal input terminal for the right channel and the left channel, 9 and 10 are the signal output terminals for the right channel and the left channel, 11-1 to 11-m, 12-1 to 1
2-m are delay elements, which are connected in series to form m-stage delay elements for the left and right channels.
13-1 to 13-m and 14-1 to 14-m are coefficient units, respectively, and delay elements 11-1 to 11-m, 1
One end is connected to the connection point of each stage 2-1 to 12-m, and acts as a tap coefficient unit as a weighting element for the left and right channels. 15 and 16 are adders. Here, each of the measurement points of the impulse response in the vehicle interior 1 is represented by n sample values, and these are expressed as vectors h ₁ and h ₂ , and their expansion matrices are expressed as H ₁ and H ₂ . That is, h ₁ = [h ₁₁ , h ₁₂ , ... h _1o ] h ₂ = [h ₂₁ , h ₂₂ , ... h _2o ]

【formula】

[Formula] At this time, set the target waveform to the J-th sample ideal impulse, Expressed as. The m tap coefficients to be found at this time are x ₁ and x ₂ , respectively, and the squared error is the evaluation value p.
Then, p ₁ = (H ₁・x ₁ −d ^T ) ^T (H ₁・x ₁ −d _T ) p ₂ = (H ₂・x ₂ −d ^T ) ^T (H ₂・x ₂ −d ^T ) x ₁ and x ₂ that minimize _{p 1 and} p _{2 ,} respectively, are _{x 1 =} (H ^T ₁・H ₁ ) ^-1・H ^T ₁・d ^T x ₂ = (H ^T ₂・H ₂ ) ⁻¹・H ^T ₂・d ^T is obtained. In other words, the coefficient units 13-1 to 13 in FIG.
By setting x ₁ to -m and x ₂ to 14-1 to 14-m, the ideal impulse can be approximated to the J-th sample position with errors p ₁ and p ₂ . FIG. 4 shows a configuration diagram of one channel of the in-vehicle sound reproduction device. 17 is a measurement microphone;
18 is a microphone amplifier, 19 is an A/D converter, 20 is a storage circuit, 21 is an arithmetic circuit, 22 is a convolution equalizer having the configuration shown in FIG. 3, and 23
2 is an impulse generator, and 24 is a switch for switching between measurement and reproduction. Other components having the same functions as those in FIG. 1 are given the same reference numerals. First, the switch 24 is connected to the impulse generator 23 side to measure the impulse response of the acoustic transmission system from the speaker 3 to the microphone 17 at the listening position, and this measurement result is input into the storage circuit 20. Next, the arithmetic circuit 21 calculates a tap coefficient according to the algorithm and inputs it to the convolution equalizer 22. Next, the switch 24 is connected to the convolution equalizer 22 to reproduce the signal from the sound source 4 through the convolution equalizer 22. The convolution equalizer of the other channel is also set in the same way. Figure 6a shows the impulse response after correction using the convolution equalizer with tap coefficients set to minimize the squared error from the ideal impulse by correction using the above-mentioned in-vehicle sound reproduction device. , b and their time axis enlarged diagrams As shown in Fig. 8a and b, by removing the influence of reflected sound in the vehicle interior and making the impulse concentration positions of both channels equal, the result is as shown in Fig. 9. The distance between both speakers 3-1, 3-2 and listener 2 is l.
You can get the same effect as setting it equal to . Due to this physical effect, the sound source that should be localized to the center of the singer's voice, etc. perceived by the listener, and the sound image localization of the monaural sound source are shifted to the speaker 3 - shown by diagonal lines in Figure 9.
It is clearly localized to the position of the virtual sound source 3-3 in the center of 1 and 3-2. 5a and 5b are the impulse responses from the speakers 3-1 and 3-2 in the passenger compartment 1 to the listener 2 before correction, respectively, and FIGS. 6a and 6b are the impulse responses from the convolution equalizers 22-1 and 22-2, respectively. 2 is an impulse response from the speakers 3-1 and 3-2 to the listener 2 after correction according to 2. The squared errors are 33% and 39%, respectively. In this way, not only the influence of reflected sound inside the vehicle compartment 1 is reduced, but also the
Fig. 8, a, b, and the enlarged time axis diagram of Fig. 6 a, b.
As can be seen by comparing Figures a and b, the concentration time positions of the impulse responses of both channels match, and for the listener, the phase shift due to the difference in distance from the speakers of both channels is corrected. This has the effect of improving sound image localization, in that the singer's voice recorded in phase is accurately localized to the center of both speakers. <Effects of the Invention> As explained above, according to the in-vehicle sound reproducing device of the present invention, the signal transmission system to two speakers placed at arbitrary positions in front of or behind the listener in the vehicle interior can be transmitted in series. A convolution equalizer composed of a convolution integration circuit was installed for each, and the tap coefficients of the convolution equalizer were set so that the ideal impulse positions matched in the two acoustic transmission systems, so the sound of the two acoustic transmission systems Since the arrival times of the two systems coincide, there is less interference when the two systems are reproduced simultaneously, and the same effect can be achieved when listening from the center of the two speakers.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a conventional in-vehicle sound reproducing device, FIG. 3 is a configuration diagram of a convolution integrator, and FIG. 4 is an illustration of one embodiment of the in-vehicle sound reproducing device according to the present invention. A channel configuration diagram, FIGS. 5 and 7 are impulse response waveform diagrams from the speakers 3-1 and 3-2 in the vehicle interior, and FIGS. 6 and 8 are impulse response waveform diagrams after correction according to this embodiment. FIG. 9 is a diagram showing an equivalent sound field resulting from the effects of this embodiment. 1... Vehicle interior, 2... Listener, 3, 3-1, 3-
2...Speaker, 4...Sound source, 6, 6-1, 6-
2...Power amplifier, 11-1 to 11-m, 12
-1 to 12-m...Delay element, 13-1 to 13-
m, 14-1 to 14-m... Coefficient unit, 15, 16
... Adder, 21 ... Arithmetic circuit, 22 ... Convolution equalizer.

Claims (1)

[Claims for Utility Model Registration] 1. A convolution system consisting of convolution and integration circuits connected in series to a signal transmission system to two speakers placed at arbitrary positions in front of or behind a listener in a vehicle interior. An in-vehicle sound reproduction device includes an equalizer, and tap coefficients of the convolution equalizer are set so that ideal impulse positions match in two sound transmission systems. 2. The vehicle-mounted sound reproducing device according to claim 1, wherein the tap coefficient of the convolution equalizer is set so that the impulse response of the sound transmission system approximates the ideal impulse response.