JPH0119319B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention corrects the unbalanced stereo feeling that occurs due to an unbalanced speaker arrangement for listeners in a vehicle interior, and presents a symmetrical stereo feeling even in the vehicle interior. The present invention relates to an in-vehicle sound reproduction device that can be used in a vehicle.

Generally, when speakers can only be placed in asymmetrical positions relative to the listener, such as inside a car,
That is, if the listener is off-center, there is a problem that a symmetrical sound field cannot be obtained.

Conventionally, to solve this problem, an acoustic electrical signal controlled by a correction means using an electronic circuit is emitted from both speakers located asymmetrically, so that the signal is transmitted to both ears of the listener who is located off-center. The input sound pressure is corrected so that it feels the same sound pressure as if it were produced from two speakers placed at positions other than the two speakers actually placed, and the listener is presented with a sound image in any direction. A method has been used to make people perceive.

When applying such a method, model selection is a very important point, and conventionally a model as shown in FIG. 1 has been adopted. In other words, in Figure 1, 1 is the left (L) speaker, 2 is the right (R) speaker, and 3 is the listener's left speaker.
(l) ear, 4 is the right (γ) ear, 5 is the φ speaker at the control position that should be perceived by the listener, 6 is the transfer path and transfer function from the left speaker to the left ear (H _Ll ), 7 is the left speaker 8 is the transfer path and transfer function from the right speaker to the right ear (H _Lr ), 8 is the transfer path and transfer function from the right speaker to the left ear (H _Rl ), and 9 is the transfer path and transfer function from the right speaker to the right ear (H _Rr ), 1
0 is the transfer path and transfer function (H〓 _l ) from the φ speaker to the left ear, and 11 is the transfer path and transfer function (H〓 _r ) from the φ speaker to the right ear.

Based on such a model, an acoustoelectric signal has been corrected using a correction circuit 20 surrounded by a dotted line as shown in FIG.

However, in the model shown in Figure 1, the spatial transfer function is simply understood as a binaural transfer function, so the frequency characteristics change due to the directivity of the speakers actually used, and the difference between the speakers in the sound field. Apparent changes in characteristics are completely ignored, and
Since the theoretical basis for determining the relationship between the position of the R speaker 2 and the position of the φ speaker 5, which is the control target, is unclear, a large number of transfer function systems were considered within the correction circuit 20, and a feedback system 21 was required. Therefore, the configuration of the correction circuit itself has become extremely complicated. In reality, it is extremely costly to realize such a complex circuit configuration, so omissions and simplifications are carried out based on empirical knowledge, making it impossible to obtain the desired acoustic effect. There was a problem.

SUMMARY OF THE INVENTION In order to solve such problems, it is an object of the present invention to provide a vehicle-mounted sound reproducing device that can perform sound field correction faithful to stereo acoustic theory.

Next, the configuration of the in-vehicle sound reproduction device of the present invention will be explained based on an example. FIG. 3 is a block diagram showing a first embodiment of the in-vehicle sound reproduction device according to the present invention. In the figure, denotes an acoustic signal input terminal, 31 and 32 are first and second transfer function correction circuits to be described later, and 33 is an electric signal inversion circuit. In this invention, the R channel speaker 2 is placed in front of the listener's median plane, and the control target speaker 5 is set at a position symmetrical to the left channel speaker 1 on the median plane including the listener. .

31 to 39 are spatial transfer functions according to the subscript of the capital letter H, and these spatial transfer functions include the characteristics of the speaker itself including the directivity or directionality of the speaker, and head diffraction of the listener. The transfer function is also taken into consideration. Note that among the subscripts of H, capital letters (L, R, φ) represent the speakers, and lower case letters (l, r) represent the position of the listener's ears.

Now, in order to give the listener a stereo feeling with such a speaker arrangement, it is sufficient to make the sound pressure of the φ speaker 5 and the L speaker 1 equal, so
R speaker 2 and L speaker 1 at the φ speaker position
What is necessary is to make a sound image perceived at the position of the φ speaker 5. In order to make the sound image perceived at the position of the φ speaker 5, the sound pressure from the L speaker 1 and the R speaker 2 must be equal to that when the speaker is placed at the φ speaker position and generates sound. Therefore, it is only necessary to control the signals to the L and R speakers.

Therefore, hypothetically, when the signal S is input to the φ speaker 5 and the sound is produced, the sound pressure in both ears is calculated.
When P〓 _l and P〓 _r , it can be expressed as P〓 _l = H〓 _l・S P〓 _r = H〓 _r・S ...(1).

On the other hand, in reality, these sound pressures must be generated by L speaker 1 and R speaker 2, so if the acoustic input signals to these speakers 1 and 2 are E _L・S, E _R・S, L and The transfer functions in correction books 30 _L and 30 _R connected to R speakers 1 and 2, indicated by dotted lines, are E _L
and E must be equal to _R. That is,
It is sufficient to consider each correction book 30 _L and 30 _R as a black box and find solutions for E _L and E _R. The sound pressure in both ears at this time is
Assuming P _l and P _r , P _r =E _R・H _Rr・S+E _L・H _Lr・S P _l =E _R・H _Rl・S+E _L・H _Ll・S ……(2).

Then, by finding the conditions for making equations (1) and (2) equal, it can be expressed by the following determinant.

Therefore, solving for E _R and E _L , we get That is, becomes.

Here, in this invention, as mentioned above, R
Since the channel speaker 2 is placed on the median plane that includes the listener, H _Rr = H _Rl (6), and the position of the φ speaker 5 is symmetrical to the L speaker 1 with respect to the median plane. Since _the control _{target is set} at

Substituting these conditions shown in equations (6) and (7) into equation (5), we get becomes.

Therefore, the block _30R is configured with a first transfer function correction circuit H _Ll /H _Rl and a second transfer function correction circuit H _Lr /H _Ll , and the block ₃₀
It has become clear that the circuit can be constructed using an electrical signal inversion circuit. That is, when an input signal S is applied to the input terminal I, the listener's right ear 4 receives H _Ll・S,
Or, the sound pressure signal H _Lr ·S is sent to the left ear 3, that is, the same sound pressure is generated in both ears as when the main path 34 and cross path 35 are completely reversed when the L speaker 1 is used alone. is given to
The listener can perceive a clear sound image at a position symmetrical to the actual L speaker 1. That is, if the input terminal I is used as the R channel input terminal, the R channel speaker 2 can be corrected to the position of the control target speaker 5.

Next, the specific configuration for realizing the functions of each block _30R , _30L will be explained in the fourth section.
This will be explained based on the diagram. In the figure, I _R and I _L are input terminals of the R and L channels, 41 is a frequency characteristic correction equalizer, and 42 is an electrical signal delay circuit. Further, 43 is a frequency characteristic correction equalizer, and 44 is an electric signal delay circuit, and these 43 and 44 form a second transfer function correction circuit. These frequency characteristic correction equalizers 41 and 43 are for adjusting the frequency characteristics of the gain section of each transfer function correction circuit.

Of these frequency characteristic correction equalizers,
It is also possible to omit the frequency characteristic correction equalizer 41 and configure the frequency characteristic correction equalizer 43 by a low-pass filter. The electrical signal delay circuits 42 and 44 may also be constructed from phase shift circuits.

Further, 45 is an adder circuit, 46 is an electric signal inversion circuit, and 47 is an adder circuit.

In such a configuration, when adjusting the frequency characteristic correction equalizers 41 and 43, the reference signal is input to the input terminal of the speaker actually used, and the output from the microphones attached to both ears of the dummy head is measured. , it is possible to easily adjust the frequency characteristics of the gain part of the transfer function (H _Rr , H _Rl , H _Lr ·H _Ll ) including the directivity of the speaker, head diffraction, etc.

On the other hand, regarding the delay times τ ₁ and τ ₂ of each electric signal delay circuit 42 and 44, the distances L _Rr , L _Rl , L _Ll , and L _Lr corresponding to each spatial transfer function are measured, and the sound speed is determined by C
(340m/s), All you have to do is adjust the relationship accordingly.

That is, the frequency characteristic equalizer in the first transfer function correction circuit is adjusted to the frequency characteristic of the gain section of the ratio of the transfer function between the L speaker 1, the R speaker 2, and both ear holes, and the electric signal delay circuit It is adjusted to delay the electrical signal by a time equal to the value obtained by dividing the difference in distance between the speakers 1 and 2 by the speed of sound C, and the frequency characteristic correction equalizer in the second transfer function correction circuit is configured to The electrical signal delay circuit is adjusted to the frequency characteristic of the gain section of the ratio of the transfer function between the is adjusted to be equal to the value obtained by dividing by the speed of sound.

By adjusting each circuit using these steps, it is possible to correct a real speaker placed off-center so that it produces the same stereo effect as if it were placed symmetrically. .

Next, a specific example will be described in which a vehicle-mounted sound reproduction device having such a correction circuit is installed in a vehicle interior. In the vehicle interior, the position of each speaker must be asymmetrical with respect to the listener.
Now, assume that the listening seat is the driver's seat or the passenger's seat, and that the speakers can be placed on the ceiling, near the dart board, or on the rear parcel tray. In FIGS. 5 and 6, reference numeral 51 denotes an R speaker, which is placed below the dashboard in the median plane that includes the listener's head. 52 is R speaker 5
The L speaker 51 is paired with the R speaker 51, and is arranged under the dart board so as to be symmetrical with the R speaker 51 with respect to the center line of the vehicle, taking into consideration the case where the listener is a passenger in the passenger seat. In addition, when placing the speakers on the rear parcel tray, each speaker has an R speaker 53 and an L speaker 54 on an axis that is mirror symmetrical to the R speaker 51 and L speaker 52 placed under the dart board. By arranging them, a transmission path as shown by each dotted line can be realized. Note that if the listening position is not considered other than the driver's seat, there is no restriction on the position of the L speaker.

FIG. 7 is a main part diagram showing a second embodiment of the present invention. From equation (8) mentioned above, Since the following relationship also holds true, a first transfer function correction circuit having the same transfer function H _Ll /H _Rl as the first transfer function correction circuit 31 described above and a first transfer function correction circuit having the same transfer function H Ll /H Rl and a transfer function of H _Lr /H Rl
It can be configured with a third transfer function correction circuit H _Rl . These first and third transfer function correction circuits can be formed by a frequency characteristic correction equalizer and an electrical signal delay circuit in the same manner as in the first embodiment described above, and can be adjusted using the same procedure. Can be done.

That is, this first transfer function correction circuit has the frequency characteristics and delay time adjusted in the same way as the first transfer function correction circuit 31 in the first embodiment described above, and the third transfer function correction circuit The frequency characteristic correction equalizer is adjusted to the frequency characteristic of the gain part of the ratio of the transfer function in the relationship between the left speaker and the right ear, and the right speaker and the left ear, and the electric signal delay circuit adjusts the distance difference in the above relationship to the speed of sound. It is adjusted to be equal to the value divided by .

Since the in-vehicle sound reproduction device of the present invention is configured as described above, it is possible to highly accurately correct the sound pressure of the speaker placed at a position asymmetrical to the listener with a simple configuration. , an in-vehicle sound reproduction device with high acoustic effects can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining a model for sound image control adopted in a correction circuit in a conventional in-vehicle sound reproduction device, and FIG. 2 is a diagram illustrating a correction circuit in a conventional in-vehicle sound reproduction device. Block diagram, 3rd
The figure is a block diagram showing the first embodiment of the correction circuit for sound image control used in the in-vehicle sound reproduction device according to the present invention, and FIG. 4 is the correction circuit shown in FIG. FIGS. 5 and 6 are block diagrams showing a specific configuration for realizing the circuit; FIGS. FIG. 7 is a block diagram showing the second embodiment. 1...Left channel speaker, 2...Right channel speaker, 3...Left ear, 4...Right ear, 5...
Control target speaker, 6 to 11... Transfer path (transfer function), 20... Correction circuit, 21... Feedback system,... Signal input terminal, 31 to 39... Transfer function, 30 _R , 30 _L ... Correction Book, I _R ...Right channel input terminal, I _L ...Left channel input terminal, 41...Frequency characteristic correction equalizer, 42...
...Electric signal delay circuit, 43... Frequency characteristic correction equalizer, 44... Electric signal delay circuit, 45... Addition circuit, 46... Electric signal inversion circuit, 47... Addition circuit, 51-54... Speaker.

Claims (1)

[Scope of Claims] 1. In a vehicle interior, one of the two speakers constituting the right channel side and the left channel side is arranged in the median plane including the listener, and an electric signal is provided. The first and second circuits are configured by cascading a delay circuit and a frequency characteristic correction equalizer.
It has a transfer function correction circuit, an electric signal inversion circuit, and two adder circuits, and the input signal to the channel of the speaker placed on the median plane is input to the first transfer function correction circuit, and the output from this is input to the first transfer function correction circuit. After adding the outputs from the first and second transfer function correction circuits in an adder circuit, the power is amplified as necessary and input to a speaker placed on the median plane. In addition, after the input signal is inverted by an electric signal inverting circuit and the input signal of the channel of the speaker other than the median plane is added by an adder circuit, the power is amplified as necessary to send the signal to the speaker other than the median plane. At the same time, the delay time of the first transfer function correction circuit is set as the quotient of the difference in sound speed between the distances to both speakers, with the ear canal of the listener on the side of the speaker other than the median plane as the reference, and the frequency characteristic correction equalizer is The delay time of the second transfer function correction circuit is adjusted to the frequency characteristic of the gain part of the ratio of the transfer function between the two speakers and the ear canal, and the delay time of the second transfer function correction circuit is adjusted to the distance between the listener's ears with respect to the speaker other than the median plane. A vehicle-mounted sound reproducing device characterized in that the quotient of the difference in sound speed is adjusted, and the frequency characteristic correction equalizer is adjusted to the frequency characteristic of the gain section of the ratio of the transfer function between both ears of a listener and both speakers. 2. The in-vehicle sound reproducing device according to claim 1, wherein the speaker is disposed in the vicinity of the dart board, in the rear parcel tray, or on the ceiling in the vehicle interior. 3. Claim 1, characterized in that the frequency characteristic correction equalizer of the first transfer function correction circuit is omitted, and the frequency characteristic correction equalizer of the second transfer function correction circuit is constituted by a low-pass filter. The described in-vehicle sound reproduction device. 4. The in-vehicle sound reproducing device according to claim 1, wherein the electric signal delay circuits of the first and second transfer function correction circuits are constructed with phase shift circuits. 5 Input the input signal of the channel of the speaker placed on the median plane to the first and third transfer function correction circuits, add the outputs from these in the adder circuit, and calculate the delay time of the third transfer function correction circuit. is the quotient of the sound speed of the difference in distance between a pair of left and right speakers and the ear canal, and
The vehicle-mounted sound reproducing device according to claim 1, wherein the frequency equalizer is adjusted to the frequency characteristics of the gain section of the ratio of the transfer functions in these relationships.