JPH06181596A - On-vehicle speaker system - Google Patents

Abstract

PURPOSE:To correct a sound field in an automobile compartment by controlling reflected sound by an acoustic method by connecting one end of a sound tube whose length and cross-sectional area are different to one or plural speakers and connecting the other end to a horn shaped sound aperture part. CONSTITUTION:The response of reflected waves 1-b and 1-c is close to a time difference between both ears from the view point of its time order and acts as phase interference to a direct wave 1-a. Also, since the reflectivity of a dash board 6 or window glass 7 is high and energy attenuation by reflection is small, influence on the direct wave 1-a is large and the reflected waves 1-b and 1-c disturb the frequency characteristics of a listening position and hinder sound image localization. In regard to this, direct sound waves 3-b and 3-c radiated from the speaker 2 of an auxiliary sound source separated from a main sound source are generated at the listening position of a driver's seat 5 so as to respond to the reflected waves 1-b and 1-c. Thus, unrequired reflected waves 1-b and 1-c components can be cancelled and the frequency characteristics and the sound image localization can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted speaker system for improving the frequency characteristics at the listening position and the response of reflected sound that adversely affects the sound image localization during sound reproduction in the vehicle interior.

[0002]

2. Description of the Related Art At the time of sound reproduction in the vehicle compartment, the reflected wave may disturb the frequency characteristic at the listening position (exercise seat), which may be a factor to impair the localization of the sound image. In particular, since the size of the vehicle interior space is small and a reflective wall such as glass exists near the listening position, the primary or secondary reflected wave in the vehicle interior sound field greatly affects the direct wave. .

FIG. 14 shows a calculated value of an echo time pattern in a conventional vehicle-mounted speaker system. The sound source is on the passenger side, the listening position is on the driver's seat, and the frequency is 4 kHz. As can be seen from Fig. 14, 2-3 for direct waves
Reflected waves are seen concentrated after a delay of msec. Seen from the temporal order, these responses are close to the time difference between both ears, and act as phase interference of direct waves, disturb the frequency characteristics at the listening position, and hinder the localization of the sound image.

FIG. 15 is a block diagram of a conventional in-vehicle speaker system, showing a typical path of a reflected wave at a listening position in a vehicle compartment. The path difference between the direct wave 1-a from the speaker 1 (passenger side), the reflected wave 1-b by the dashboard 6 and the reflected wave 1-c by the window glass 7 is about several tens of centimeters,
The arrival time difference is 2 to 3 msec, and since the dashboard 6 and the window glass 7 are both reflective wall surfaces, the reflectance is high and the energy attenuation due to the reflection is small. Therefore, these reflected waves 1-b and 1-c are the above-mentioned listening positions.
It corresponds to the reflected wave that disturbs the frequency characteristics in (driver's seat 5) and hinders the localization of the sound image.

As a conventional sound field correction device, a graphic equalizer using an analog filter can adjust the amplitude characteristic to a flat or arbitrary characteristic, but since the phase characteristic is not considered at all, the sound localization quality is improved. It was impossible to do. Therefore, in recent years, the sound field has been corrected by a digital filter capable of controlling even the phase characteristic. By this method, it became possible to improve the frequency characteristic in the sound field where the influence of the reflected wave is large and to improve the localization feeling in the asymmetric sound field such as the sound field in the vehicle interior.

[0006]

However, since the response in the high frequency band is an extremely important factor for the localization of the sound image, even when the sound field is corrected by a digital filter, the sound field correction up to the high frequency band is required. There is a need to do. However, signal processing up to the audible frequency band requires a high sampling frequency and a high calculation speed in the filter, which increases the load on the hardware. Therefore, although it is possible in principle to control the entire audible frequency band with a digital filter, there are significant problems in terms of cost and practical use.

In view of the above points, the present invention reduces the cost by correcting the sound field in the vehicle interior by the reflected sound control by an acoustic method without using an electric method such as a digital filter. In addition, it aims to realize sound field correction up to a high frequency band, improve frequency characteristics, and realize clear sound localization.

[0008]

SUMMARY OF THE INVENTION The present invention is a vehicle-mounted speaker system comprising a main sound source and an auxiliary sound source, wherein the main sound source comprises one speaker and the auxiliary sound source comprises
One or a plurality of speakers and a plurality of acoustic tubes having different lengths and cross-sectional areas, and one end of all the acoustic tubes is connected to the one or more speakers, and the other end has a horn-shaped acoustic tube opening. It is connected to the department. Furthermore, the length and cross-sectional area of each of the plurality of acoustic tubes are set and configured so as to realize an arbitrary time axis response at the listening position in the vehicle compartment.

[0009]

According to the present invention, the frequency characteristics can be improved by controlling the reflected sound in the sound field in the vehicle interior, and the sound field can be corrected to clarify the localization feeling by an acoustic method such as an acoustic tube. Therefore, A
Time impulse response with D / D and D / A conversion
(FIR) Compared with an electrical method using a digital filter, a sound field can be easily corrected at low cost.

[0010]

1 is a block diagram of a vehicle-mounted speaker system according to a first embodiment of the present invention. 1 is a speaker of the main sound source, 2 is a speaker of the auxiliary sound source, 3 is a sound tube of the auxiliary sound source,
Reference numeral 4 denotes an opening of an acoustic tube of an auxiliary sound source, 5 a driver's seat at a listening position, 6 a dashboard, and 7 a window glass.

The operation of the vehicle-mounted speaker system configured by the above system will be described. The sound wave emitted from the speaker 1 of the main sound source and reaching the listening position of the driver's seat 5 includes many reflected waves in addition to the direct wave 1-a.
For example, the reflected wave 1-b reflected by the dashboard 6 and the reflected wave 1-c reflected by the window glass 7 are representative.

Further, the acoustic output of the speaker 2 of the auxiliary sound source is divided and guided to a plurality of acoustic tubes 3 having different lengths and cross-sectional areas, and is radiated from the opening 4 of the acoustic tube into the vehicle interior. Here, the opening portion 4 of the acoustic tube has a horn shape in order to suppress resonance in the acoustic tube 3.

FIG. 2 is a diagram showing the time-axis response characteristics of these sound waves at the listening position of the driver's seat 5, in which the direct wave 1-
arrival time difference τb, τc of reflected waves 1-b, 1-c with respect to a
Is about 2 to 3 msec because the path difference from the direct wave 1-a is several tens of cm. It will be about. Such a reflected wave 1-
The responses of b and 1-c are close to the time difference between both ears in terms of their temporal order, and act as phase interference with the direct wave 1-a. Moreover, since the dashboard 6 and the window glass 7 have high reflectance and small energy attenuation due to reflection, the influence on the direct wave 1-a is large, and the reflected waves 1-b, 1-
c disturbs the frequency characteristic at the listening position, and becomes a factor that hinders the localization of the sound image.

Therefore, the direct sound waves 3-b and 3-c emitted by the speaker 2 which is an auxiliary sound source different from the main sound source are generated at the listening position of the driver's seat 5 as shown by the broken line in FIG. This cancels unnecessary reflected wave 1-b and 1-c components, and improves frequency characteristics and sound image localization.

Next, the auxiliary sound source can achieve the purpose by controlling the amplitude and phase of the sound pressure of the sound wave by the auxiliary sound source in order to realize an arbitrary time axis response at the listening position.

FIG. 3 is a diagram showing the time-axis response characteristics of the auxiliary sound source. The time-axis responses p1 to p5 (p shown in FIG. 3 (1) are shown.
1, p3, p4 are positive responses, and p2, p5 are negative responses), in order to realize the sound pressure amplitudes a1 to a5 and delay times τ1 to τ5 in the block diagram shown in FIG. Adjust it. In the present invention, as means for controlling the amplitude and the delay time, acoustic means is used instead of electrical means such as a FIR filter.

FIG. 4 is an external view of an auxiliary sound source of the present invention which realizes the time base response shown in FIG. 3 by acoustic means. The sound waves radiated from the openings 4 of the five acoustic tubes 3 in the driver's seat 5 at the listening position have time-axis responses p1 to p5 shown in FIG. 3 (1).
So that the amplitude a1 of the sound pressure is determined by the cross-sectional area of the acoustic tube 3.
.About.a5, the delay times .tau.1 to .tau.5 are controlled by the length of the acoustic tube.

The time-axis response to be realized may be a response in which the reflected wave components 1-a and 1-b of the speaker 1 of the main sound source are canceled at the listening position, or the reflected wave components of the speaker 1 of the main sound source are canceled and further arbitrary. It may be a response that realizes the impulse response of the sound field.

FIG. 5 is a sectional view showing the structure of the speaker 2 of the auxiliary sound source. Regarding the phase of the amplitude at the listening position, the positive outputs p1 and p are determined by the acoustic output on the front surface of the diaphragm 8.
Negative responses p2 and p5 can be realized by acoustic output of the back surface of the diaphragm 8 with respect to 3 and p4.

By using the speaker 2 having the above structure as an auxiliary sound source, the sound waves 3-b and 3-c shown in FIG. 1 are controlled in amplitude and arrival time of the sound pressure at the listening position. Reflected waves 1-b and 1- from the speaker 1 of the sound source
It is possible to cancel c at the listening position.

FIG. 6 is a block diagram of a vehicle-mounted speaker system according to the second embodiment of the present invention. In this embodiment, the main sound source and the auxiliary sound source are driven by the same speaker 10. That is, the acoustic output of the speaker 10 is divided by the acoustic tube 9 of the main sound source and the acoustic tube 3 of the auxiliary sound source. The length and cross-sectional area of each of the auxiliary sound source acoustic tubes 3 that control the responses 3-b ′ and 3-c ′ of the auxiliary sound source are
Direct wave 1-a 'and reflected wave 1-
It is set according to the response at the listening position of b ', 1-c'.

The structure in which the main sound source and the auxiliary sound source are the same speaker can reduce the space in the passenger compartment used for mounting the speaker system.

FIG. 7 is a block diagram of a vehicle-mounted speaker system according to the third embodiment of the present invention. In this embodiment, the influence of the reflected wave of the auxiliary sound source itself is taken into consideration. That is, the speaker 2, the acoustic tube 3, and the opening 4 of the acoustic tube 3 of the auxiliary sound source are the driver's seat 5 and the headrest of the driver's seat 5.
It is installed by being embedded in 11. According to this configuration, the energy component of the direct sound is dominant in the response from the speaker 2 of the auxiliary sound source at the listening position (driver's seat 5). That is,
The influence of the reflected wave of the auxiliary sound source itself is reduced, and the accuracy of controlling the reflected wave from the speaker 1 of the main sound source installed on the dashboard 6 is improved.

FIG. 8 is a diagram showing calculated values of the echo time pattern when a sharp directional characteristic is given to the sound source under the same calculation conditions as in FIG. Compared to FIG. 14, the temporal pattern of the response does not change because the geometric shape of the space is the same, but the energy level in the direction away from the directional axis of the sound source is small due to the sharp directional characteristics, and the listening position It can be seen that the level of the unnecessary reflected wave at is lowered. Therefore, the influence of the reflected wave can be reduced by making the directional characteristics of the sound source sufficiently sharp.

FIG. 9 is a block diagram of a vehicle-mounted speaker system according to the fourth embodiment of the present invention, in which the main sound source is composed of the speaker 1 and directivity control means capable of limiting the area for emitting acoustic power. In this embodiment, the directivity control means is an acoustic lens 12 capable of converging the acoustic output radiated from the speaker 1 of the main sound source to the listening position of the driver's seat 5.

FIG. 10 is a schematic diagram showing the principle of the acoustic lens 12. The acoustic lens has a plurality of sound paths with different paths.
It utilizes a phenomenon in which sound waves are refracted due to equivalent sound velocity differences.

As shown in FIG. 10, if the sound path 13 at the center of the acoustic lens is lengthened and a path difference is given to the sound path so that it becomes shortest at both ends, the sound waves passing through the longer sound path are The sound velocity is equivalently slowed down, and the sound wave that has passed through the acoustic lens is refracted inward, and a convergent acoustic lens 12 that focuses at a certain point on the central axis can be realized.

Therefore, as shown in FIG. 9, the acoustic lens 12
Is connected to the speaker 1 of the main sound source, the acoustic power is reduced by the acoustic lens 12 for the reflected wave 1-c ″ radiated in the direction away from the directional axis of the main sound source and reaching the listening position. The influence on the wave 1-a ″ can be greatly reduced. Further, by using such an acoustic lens 12, the reflected wave to be controlled by the speaker 2 of the auxiliary sound source is radiated in the direction close to the directional axis of the main sound source as 1-b ″ and reaches the listening position. Since it is limited to the reflected wave, the number of the acoustic tubes 3 of the auxiliary sound source is small, and the structure of the speaker system constituting the auxiliary sound source can be simplified.

FIG. 11 is a structural diagram showing a second embodiment of the directivity control means capable of limiting the area for emitting the acoustic power shown in FIG. Two sets of horns 14 each having an elongated rectangular opening having a long side and a short side are connected to the speaker 1 of the main sound source. The number written on the dimension line indicates the length in mm. Further, the wall forming the horn 14 is formed of a sound absorbing material 15 in order to reduce the influence of the standing wave generated inside the horn 14. If such a horn is used as the directivity control means, the directional characteristics in the long side direction of the horn 14 become sharp,
The same effect as that of the acoustic lens 12 described above can be obtained.

FIG. 12 is a structural diagram showing a third embodiment of the directivity control means capable of limiting the area for emitting the acoustic power shown in FIG. Reference numeral 16 is an opening portion of an acoustic tube linearly arranged at equal intervals, and 17 is an acoustic tube. The acoustic output of the speaker 1 of the main sound source is divided and guided to a plurality of acoustic tubes 17, and the opening of the acoustic tube is divided.
Radiates from 16 into the passenger compartment. Here, the respective lengths of the plurality of acoustic tubes 17 are set so that the phases of the sound waves from the openings 16 of the respective acoustic tubes match at the listening position. If a plurality of such acoustic tubes are used as the directivity control means, the directional characteristics in the direction in which the openings 16 of the acoustic tubes are arranged become sharp, and the same effect as the acoustic lens 12 described above can be obtained.

FIG. 13 is a block diagram of the fifth embodiment of the vehicle-mounted speaker system of the present invention.

When reproducing a stereo signal, a so-called crosstalk component of the L channel signal reaching the right ear and the R channel signal reaching the left ear becomes a factor for impairing the stereo sound field of the listener.

In FIG. 13, the speaker system 18, which constitutes the main sound source, radiates an L-channel signal into the passenger compartment, and generates a direct wave 1-a and reflected waves 1-b to 1-e. The speaker system 19 constituting the first auxiliary sound source,
Response 3 that cancels the reflected waves 1-b and 1-c from the speaker system 18 that constitutes the main sound source in the left ear of the listener
-b, 3-c, which is a speaker system, and which constitutes the second auxiliary sound source, the speaker system 20 comprises a crosstalk component 1-d from the speaker system 18 which constitutes the main sound source in the right ear of the listener. Response 3 that cancels 1-e
It is a speaker system that realizes -d and 3-e.

In this embodiment, a speaker system 18 which constitutes a main sound source, a speaker system 19 which constitutes a first auxiliary sound source, and a speaker system 20 which constitutes a second auxiliary sound source.
The structure and the mounting position can be similarly applied to the speaker systems in the first to fourth embodiments shown in FIGS. 1 to 7 and 9.

[0035]

As described above, the in-vehicle speaker system of the present invention improves the frequency characteristics by controlling the reflected sound in the sound field in the passenger compartment and corrects the sound field for clarifying the localization by using an acoustic tube or the like. It is realized by an acoustic method, and as a result,
The sound field can be easily corrected at a low cost as compared with an electrical method using an FIR digital filter that involves A / D and D / A conversion.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a vehicle-mounted speaker system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a time axis response characteristic in the first embodiment of the present invention.

FIG. 3 is a diagram showing a time axis response characteristic of an auxiliary sound source in the first embodiment of the present invention.

FIG. 4 is an external view of an auxiliary sound source according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the structure of the speaker of the auxiliary sound source in the first embodiment of the present invention.

FIG. 6 is a configuration diagram of an in-vehicle speaker system according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of an in-vehicle speaker system according to a third embodiment of the present invention.

FIG. 8 is a diagram showing calculated values of an echo time pattern in the in-vehicle speaker system of the present invention.

FIG. 9 is a configuration diagram of an in-vehicle speaker system according to a fourth embodiment of the present invention.

10 is a principle configuration diagram of the acoustic lens shown in FIG.

11 is a structural diagram showing a second embodiment of the directivity control means shown in FIG.

FIG. 12 is a structural diagram showing a third embodiment of the directivity control means shown in FIG.

FIG. 13 is a configuration diagram of an in-vehicle speaker system according to a fifth embodiment of the present invention.

FIG. 14 is a diagram showing calculated values of an echo time pattern in a conventional vehicle-mounted speaker system.

FIG. 15 is a configuration diagram of a conventional vehicle-mounted speaker system.

[Explanation of symbols]

1 ... speaker of main sound source, 2 ... speaker of auxiliary sound source,
3 ... Acoustic tube of auxiliary sound source, 4 ... Opening of acoustic tube of auxiliary sound source, 5 ... Driver's seat, 6 ... Dashboard, 7 ... Window glass, 8 ... Vibration plate, 9 ... Acoustic tube of main sound source, 10 ... Speaker , 11… Headrest, 12… Acoustic lens, 13
… Central sound path, 14… Horn, 15… Sound absorbing material, 16…
Acoustic tube opening, 17 ... Acoustic tube, 18 ... Main sound source speaker system, 19 ... First auxiliary sound source speaker system,
20 ... Second auxiliary sound source speaker system.

Claims (18)

[Claims] 1. A main sound source composed of one speaker and an auxiliary sound source composed of a plurality of acoustic tubes having different cross-sectional lengths from one or a plurality of speakers, and one end of each acoustic tube is It is connected to one or a plurality of speakers and the other end is connected to a horn-shaped acoustic tube opening, and the length and cross-sectional area of each of the plurality of acoustic tubes are arbitrary time-axis responses at the listening position in the vehicle interior. An in-vehicle speaker system, which is set so as to realize the following. 2. The in-vehicle speaker system according to claim 1, wherein the time-axis response is a response for canceling a reflected sound component of a main sound source at a listening position in a vehicle compartment. 3. The time axis response is a response that cancels a reflected sound component of a main sound source at a listening position in a vehicle interior and realizes an impulse response of an arbitrary sound field. In-vehicle speaker system. 4. The in-vehicle device according to claim 1, wherein the main sound source and the auxiliary sound source are driven by the same speaker, and the sound output is separated into a sound tube of the main sound source and a sound tube of the auxiliary sound source. Speaker system. 5. The main sound source and the auxiliary sound source are driven by different speakers, and the auxiliary sound source is provided at a position where the energy component of the direct sound is dominant in the response from the auxiliary sound source at the listening position in the vehicle compartment. The in-vehicle speaker system according to claim 1, which is characterized in that. 6. The main sound source is composed of a speaker and a directivity control means capable of limiting a region for radiating acoustic power, and the directivity axis of the directivity control means is set toward a listening position in a vehicle interior, and The auxiliary sound source includes one or a plurality of speakers and a plurality of acoustic tubes having different lengths and cross-sectional areas. One end of each of the acoustic tubes is connected to the one or a plurality of speakers, and the other end is a horn shape. And a length and a cross-sectional area of each of the plurality of acoustic tubes are set so as to realize an arbitrary time axis response at a listening position in the vehicle interior. Speaker system. 7. The in-vehicle speaker system according to claim 6, wherein the directivity control means is a horn having an elongated shape in a direction for controlling directivity. 8. The acoustic directivity control means is an acoustic lens set so that acoustic power radiated from a speaker of the main sound source can be converged to a listening position in a vehicle compartment. In-vehicle speaker system. 9. The directivity control means divides the acoustic power radiated from the speaker of the main sound source to form a plurality of sound sources, and the phases of the sound waves from the respective sound sources match at the listening position in the vehicle interior. 7. The vehicle-mounted speaker system according to claim 6, wherein the plurality of sound sources are set to 10. A main sound source, a first auxiliary sound source, and a second auxiliary sound source, wherein the main sound source comprises one speaker,
The first and second auxiliary sound sources each include one or a plurality of speakers and a plurality of acoustic tubes having different lengths and cross-sectional areas. One end of all the acoustic tubes is connected to the one or the plurality of speakers. , The other end is connected to an acoustic tube opening having a horn shape, and the length and cross-sectional area of each of the plurality of acoustic tubes of the first auxiliary sound source are the positions of the listener's ears close to the main sound source. Is set so as to realize an arbitrary time-axis response, and the length and the cross-sectional area of each of the plurality of acoustic tubes of the second auxiliary sound source are different from the main sound source at a position of a listener's ear far from the main sound source. An in-vehicle speaker system, which is set so as to realize an impulse response that cancels the crosstalk of the above. 11. The time axis response realized by the first auxiliary sound source is a response for canceling a reflected sound component of the main sound source at a position of a listener's ear close to the main sound source. 10. The in-vehicle speaker system described in 10. 12. The time-axis response realized by the first auxiliary sound source cancels a reflected sound component of the main sound source at a position of a listener's ear close to the main sound source, and an impulse response of an arbitrary sound field. 11. The in-vehicle speaker system according to claim 10, which is a response that realizes 13. The main sound source and the first auxiliary sound source are driven by the same speaker, and the sound output is divided into a sound tube of the main sound source and a sound tube of the auxiliary sound source. The in-vehicle speaker system described. 14. The main sound source and the first auxiliary sound source are driven by different speakers, and the first and second auxiliary sound sources are from the first and second auxiliary sound sources at respective listening positions in the vehicle compartment. 11. The in-vehicle speaker system according to claim 10, wherein the first and second auxiliary sound sources are provided in a position where the energy component of the direct sound is dominant in the response of. 15. The main sound source is composed of a speaker and directivity control means capable of limiting a region for radiating sound power,
The directivity axis of the directivity control means is set toward the listening position in the vehicle compartment, and the first and second auxiliary sound sources each have one or more speakers and a plurality of acoustic tubes having different lengths and cross-sectional areas. And connecting one end of each of the acoustic tubes to the one or more speakers and the other end to an acoustic tube opening having a horn shape, and the plurality of acoustic sounds of the first auxiliary sound source. The length and cross-sectional area of each of the tubes is
The listener is set so as to realize an arbitrary time axis response at the position of the listener's ear close to the main sound source, and the length and cross-sectional area of each of the plurality of acoustic tubes of the second auxiliary sound source are far from the main sound source. An in-vehicle speaker system that is set to realize an impulse response that cancels out crosstalk from the main sound source at the position of the ear. 16. The in-vehicle speaker system according to claim 15, wherein the directivity control means is a horn having an elongated shape in a direction for controlling directivity. 17. The acoustic directivity control means is an acoustic lens set so that acoustic power radiated from a speaker of the main sound source can be converged to a listening position in a vehicle compartment. In-vehicle speaker system. 18. The directivity control means divides the acoustic power emitted from the speaker of the main sound source to form a plurality of sound sources, and the phases of the sound waves from the respective sound sources match at the listening position in the vehicle compartment. 16. The vehicle-mounted speaker system according to claim 15, wherein the plurality of sound sources are set to