JPS633514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vehicle-mounted sound reproduction device for listening in the interior of a vehicle.

Conventional configuration and its problems The acoustic characteristics of a vehicle interior are different from those of a normal listening room, and in the conventional speaker mounting position shown in Figure 1 A and B, transmission is caused by specific reflected sounds and standing waves. The characteristics were greatly disturbed. In FIG. 1, reference numeral 1 indicates a speaker provided on a dash board inside the vehicle interior, 2 a speaker provided on a door, and 3 a speaker provided on a rear parcel within the vehicle interior. Figure 2 shows the transmission characteristics when a speaker is installed in the rear compartment of the vehicle interior of cars A, B, and C, which are different models, and Figure 3 shows the transmission characteristics when a speaker is installed on the dashboard board of cars D, E, and F, which are different models. The transmission characteristics are shown in the figure, and the transmission characteristics are greatly disturbed.

Therefore, in the past, electrical correction means such as a graphic equalizer was added to improve the transmission characteristics. However, since the transmission characteristics in the vehicle interior differ depending on the vehicle type, listening position, and reproduction channel, there was a drawback that the graphic equalizer had to be adjusted individually according to these factors.

Further, in the conventional example, if the graphic equalizer is adjusted so that the listening point characteristics at the driver's seat are even, the listening point characteristics at the passenger seat deteriorate.

FIG. 4 shows the listening point characteristics at the driver's seat when a speaker is attached to the front left door of the vehicle interior, and FIG. 5 shows the listening point characteristics at the passenger seat.

When the characteristic shown by the solid line in FIG. 4 is corrected using a graphic equalizer to become a flat characteristic as shown by the broken line, the listening point characteristic in the passenger seat changes from the solid line to the broken line in FIG. This has the disadvantage that the flatness of the passenger seat deteriorates.

Purpose of the Invention The present invention has been made in view of the above-mentioned drawbacks.
It is an object of the present invention to provide an in-vehicle sound reproduction device that can obtain uniform listening point characteristics and optimal sound quality regardless of the reproduction channel (passenger seat) and the reproduction channel.

Structure of the Invention The present invention divides the input signal into three bands, low, middle, and high, by two dividing frequencies _C1 and _C2 for each reproduction channel, and divides _C1 into approximately 300Hz and _C2 into approximately 3KHz. A low-frequency signal is applied to a bass speaker with a set band divider, an equalizer that corrects frequency characteristics, and a power amplifier.The bass speaker is placed in the rear parcel tray inside the vehicle, and the power amplifier is A mid-range signal is applied to a mid-range speaker through the power amplifier, the mid-range speaker is placed under the front seat of the vehicle interior or under the dart board, and a high-range signal is applied to the treble speaker via a power amplifier. This high-pitched speaker is arranged on a dart board inside the vehicle interior, and as a result, it is possible to obtain uniform listening point characteristics regardless of the vehicle type, playback channel, or listening position.

Description of examples An embodiment of the present invention will be described below.

As mentioned above, in the speaker arrangement shown in Fig. 1, as shown in Figs. 2 and 3, peaks and troughs occur in the frequency characteristics due to specific reflected sounds in the vehicle interior, and the sound quality deteriorates. do. This is because most of the walls in the upper part of the cabin sound field, excluding the ceiling, are completely reflective due to glass, etc., so speakers are placed at the top of the cabin, such as above the dart board 1 or the rear tray 3 shown in Figure 1. This is because when placed, a specific and high-level reflected sound is generated from the glass surface, and interference with direct sound causes a large peak dip in the frequency transmission characteristics. Therefore, in order to improve the sound quality in the vehicle interior, it is first necessary to place the speakers at positions where specific reflected sounds do not occur.
Locations where such specific reflected sounds do not occur include under the seat and under the dart board. The sound emitted from under the seat or the dartboard board is diffusely reflected by the seat itself or by the complex structure under the dartboard board.In particular, the mid-to-high range ( _C1 or above) is diffused and reaches the listening point. At points, peaks and valleys do not occur in a specific band. The solid line in Figure 6 shows the transmission characteristics when the speaker is installed under the seat, and the broken line shows the transmission characteristic when the speaker is installed under the dart board. It turns out that it has not occurred.

This will be explained in more detail below. First, since the listening position is off-center in the vehicle interior, even if it is located at the bottom of the vehicle interior, if the left and right speakers are installed in the door section 2 in Figure 1, the ratio of direct sound and indirect sound including reflected sound will be significantly different. Therefore, there is a large difference in the transmission characteristics between the left and right sides. That is, since speakers near the listener deviate from the directivity, the level of direct sound is lowered, and transmission is performed relatively mainly of indirect sound. On the other hand, since the directivity of distant speakers is directed toward the listener, direct sound is mainly transmitted.

Therefore, place the speaker 1 in the position shown in Figure 1.
2 is not preferable from the viewpoint of flatness of frequency transmission characteristics and uniformity of left and right transmission characteristics for two-channel stereo reproduction.

As a specific example of this, FIGS. 20 and 21 show impulse responses (right and left) at the driver's seat caused by speakers installed in the rear parcel tray 3. Furthermore, FIGS. 22 and 23 show impulse responses from a speaker installed in the door section 2. From these figures, it can be seen that there is a large difference between the left and right impulse responses.

Figures 24 and 25 show the right and left impulse responses when the speakers 7 and 8 are installed under the seats facing the forward direction of the vehicle as shown in Figure 9 for these conventional speaker installation positions. .

From this figure, it is clear that the difference between the left and right impulse responses is smaller when the speakers 7 and 8 are installed under the seat than when the rear tray 3 and door section 2 are installed. This means that the sound from the left and right speakers under the seat is not directly transmitted to both.
This is because the indirect sound is transmitted to the listening position as diffused by the concave curved surface under the dart board.

In other words, as a typical feature of the installation position of the speaker under the seat, it is first placed at the bottom of the passenger compartment in order to prevent interference between direct sound and specific loud reflected sound from a wall that is close to a completely reflective flat surface such as glass. In addition, there is no direct sound path with a large difference between the left and right transmission paths, or in other words, the speaker cannot be seen by the listener.

Another position that satisfies these conditions is the 9th position.
There are 9, 10, etc. at the bottom of the dash board shown in the figure.

In addition, as another effect of the indirect sound-based transmission in which the speaker is placed under the seat of the present invention, the fact that there is little difference depending on the vehicle type will be explained.

Conventional speaker mounting methods differ greatly in design between car models in the upper half of the vehicle interior, such as the glass surface, the dart board, the angle and curvature of the top panel of the rear tray, the presence or absence of a sunroof window in the ceiling, and the rear half of the vehicle interior. For example, the transmission characteristics of wagons, hatchbacks, and vans vary greatly depending on the vehicle type, but the shape of the lower half of the vehicle interior, especially under the dash board, has a statistical effect on the space required for the range of motion of the legs. It is designed based on ergonomics, and there are few differences between car models.

Therefore, it can be said that according to the speaker mounting method of the present application, there is not only a small difference in the left and right transmission characteristics in the same vehicle model, but also a small difference in the transmission characteristics between vehicle models for the reasons stated above.

Next, the effect of flattening the transmission frequency characteristics according to the method of attaching a speaker that mainly uses indirect sound will be explained in more detail.

Figures 26, 27, 28, and 29 model the transmission characteristics in the sound field.
FIGS. 26 and 27 show the transmission characteristics mainly of the direct sound A ₁ including the specific reflected sound A ₇ , and show the characteristics in the time domain and frequency domain, respectively. In other words, it can be seen that in this case, one reflected sound A ₇ interferes with the direct sound A ₁ in the sound field, resulting in the large peak dip shown in FIG. 27.

On the other hand, FIGS. 28 and 29 show the transmission characteristics when the energy of the specific reflected sound A ₇ described above is dispersed or diffused from A ₂ to A ₆ . Similarly, the time domain and frequency domain are shown respectively.

In this way, it can be said that a large number of small reflected sounds that are dispersed or diffused in direction and distance have a smaller level difference in peak dip and a flatter transmission frequency characteristic than a specific large reflected sound. A suitable location for installing a speaker is under the seat or under the dash board, but depending on the car model, the space is small and it may be difficult to install a large-diameter speaker or speaker box for bass reproduction. Additionally, when a person sits in the seat, the sound pressure may be attenuated by 3 to 5 dB in the high range ( _C2 or higher). In FIG. 7, the solid line shows the frequency characteristic of the listening point when no one is present, and the broken line shows the frequency characteristic of the listening point when a person is sitting on the seat.

As is clear from Figure 7, the frequency characteristics of the listening point change depending on whether a person is seated or not in the band above about 3KHz.In order to eliminate the change in characteristics due to seating, the frequency characteristics of the listening point change depending on whether the person is seated or not. This can be resolved by reproducing the frequency band (approximately 3KHz or less) that is not used.

As shown in Figure 2, when speakers are installed in the rear parcel, it can be seen that there is almost no difference between vehicle models in the band below approximately 300Hz. Therefore, the speaker installed in the rear parcel has a frequency of approximately 300Hz.
It is sufficient to play the following, and use a speaker installed under the seat or under the dart board to play approximately 300Hz to approximately 3KHz. In other words, as the frequency decreases, the relationship between direct sound and indirect sound becomes more ambiguous due to factors such as diffraction, wavelength, and interior dimensions of the vehicle, and differences in transmission characteristics depending on speaker mounting position (including left and right) and vehicle model. is decreasing. This is the second
As shown in the figure, in the rear tray, despite the differences in car models A, B, and C, there is no difference in transmission characteristics below about 300 Hz. Similarly, on the dash board, there is no difference in transmission characteristics between car models below approximately 100Hz. The wavelength of 300Hz is just over 1 meter, and when the length becomes equal to or longer than the interior dimensions of the vehicle, there are no differences in characteristics due to small differences (within 1 meter) between vehicle models.

In other words, when performing band-divided sound reproduction in the vehicle interior, it can be said that there are no limiting conditions regarding the speaker installation position in the above-mentioned low range. Therefore, even if the band below about 300 Hz mentioned earlier is played back on the rear tray, where a relatively large-diameter speaker can be installed, the difference in transmission characteristics between the left and right sides and the difference depending on the car model can be minimized. Since it is only necessary to reproduce frequencies above 300Hz, the speaker box can be made smaller.

Next, since the effect of the feet of a passenger on the under-seat speaker appears above about 3KHz, this band can be compensated for by using another high-frequency speaker.

Therefore, the speaker under the seat is approximately 300Hz to approximately 3KHz.
This means that a playback band of

However, as mentioned above, if the speaker is installed under the seat or under the dart board, high frequency ( _C2 or higher)
Since the characteristics change depending on whether a person is seated or not, high frequencies (above _C2 ) can be reproduced by a tweeter installed on the dart board.
FIG. 8 shows the listening point characteristics when the tweeter is installed on the dart board. The solid line is when no one is present, and the broken line is when a person is seated. There is almost no change in the characteristics depending on whether or not a person is sitting.

As mentioned above, in Figures 7 and 8, flat characteristics can be obtained when no one is present by reproducing the low range from the rear parcel speaker and placing the mid range under the seat or under the dart board. By playing through speakers, it is possible to flatten the low-mid range. On the other hand, when reproducing high frequencies, if a tweeter is installed under the dart board, the high frequencies will change depending on the presence or absence of people, but if a tweeter is installed above the dart board, the characteristics will not change depending on the presence or absence of people. . Furthermore, when a tweeter is provided on the dart board to reproduce high frequencies, the characteristics of the high frequencies do not change depending on the presence or absence of people, and the presence or absence of people does not make it difficult to flatten the characteristics of the high frequencies.

However, when a tweeter is provided on the dart board, the direct sound is dominantly transmitted, and therefore it is not possible to evenly transmit the sound to unbalanced listening positions in the vehicle interior.

However, if the directivity of the tweeter is used, the signal can be transmitted equally to the driver's seat and passenger seat.

In other words, if the tweeter on the driver's seat side of the two tweeters installed on the dart board is directed toward the passenger's seat, and the tweeter on the passenger's seat is directed toward the driver's seat, the tweeter axis will be Since the directivity is in about 30 directions upward, the sound pressure level in the seat near the tweeter decreases, and the sound pressure from the tweeter at the listening points in the driver's seat and passenger seat becomes equal.

The device of the present invention has been made in consideration of the above matters, and the speaker arrangement is shown in FIGS. 9A and 9B.

In FIGS. 9A and 9B, 4 and 5 are tweeters installed on the right and left sides of the dash board 6, and the tweeter 4 is directed toward the driver's seat. Therefore, it has a directivity of approximately 30° in the direction of the passenger seat. Furthermore, the tweeter 5 is directed toward the passenger seat, and therefore has a directivity of approximately 30° toward the driver's seat.

In other words, the angle between the direction in which the head of the seat on the opposite side is viewed from the edge of the dart board and the direction in which the head of the seat on the nearer side is viewed in the vehicle interior is approximately 30 degrees regardless of the vehicle type, but it is important to place the tweeter at this position. (The positional relationship between the seat and the dart board is ergonomically designed to be almost constant), so the approximately 30 degree directivity of the tweeter is attenuated by the difference in distance to both seats compared to the on-axis direction. If the directivity is designed so that it is attenuated by (dashed line in FIG. 10), the sound pressure frequency characteristics at both seats can be flattened.

Regarding the specific reflected sound mentioned earlier, in this tweeter's band, the specific reflected sound from the glass window is 90
The problem described in the conventional example does not occur because it can be suppressed by using a directivity of more than 100 degrees. FIG. 10 shows the sound pressure frequency characteristics of the tweeters 4 and 5.
The solid line shows the sound pressure frequency characteristics on the tweeter axis, and the broken line shows the sound pressure frequency characteristics in the 30° direction with respect to the tweeter axis. At _C2 (approximately 3 KHz) or higher, the sound pressure in the 30° direction is on the axis. The sound pressure is lower than that of .

In Fig. 9, 7 and 8 are mid-range speakers installed under the seat, 9 and 10 are mid-range speakers installed under the dart board 6, and 11 and 12 are bass speakers installed in the rear parcel 13. It is.

FIG. 11 shows the device of the invention including the circuitry. In FIG. 11, 14 is a band divider, and one channel signal is transmitted through the band divider 14.
It is divided into a high range H, a middle range M, and a low range L.
15 is a panpot for dividing the high frequency signal into two and changing the level ratio between both outputs; 16
are the mid-range signal M and the high-range signal H from panpot 15.
17 is an equalizer, 18,
19 and 20 are power amplifiers, and the output of the amplifier 18 is applied to the tweeter 4, and the power amplifier 19
The output of the power amplifier 20 is applied to the speaker 7 or 9, and the output of the power amplifier 20 is applied to the speaker 11. Similarly, other channels are connected to tweeter 5, speaker 8 or 10, and speaker 1 through the same circuit.
2.

The equalizer 17 is for correcting the transmission characteristics unique to the speakers installed in the rear parcel 13 and the low-frequency falling sound pressure characteristics of the woofers 11 and 12, and the correction characteristics are independent of the reproduction channel, vehicle type, and listening position. constant.

Figure 12 shows A, which has different car models, similar to Figure 2.
It shows the transmission characteristics of rear parcels B and C.
When a speaker having an anechoic chamber on-axis sound pressure characteristic shown in FIG. 13 is arranged in this rear parcel, the listening point characteristic becomes the frequency characteristic shown in FIG. 14. As mentioned above, in this embodiment, frequencies of approximately 300 Hz or higher are not reproduced by the rear parcel woofer, so the 14th
This is the characteristic shown by the solid line in the figure, and it is possible to eliminate the influence of the part where the characteristic changes due to differences in vehicle models above about 300 Hz. Therefore, by applying the correction shown in FIG. 15, as shown in FIG.
This makes it possible to flatten the 300Hz low-frequency response regardless of the car model, listening position, or playback channel. Furthermore, as mentioned above, in this example,
Even in the mid-range range of approximately 300Hz to 3KHz, the car model,
Regardless of the listening position or playback channel, the characteristics can be made even. The same holds true for frequencies above about 3KHz.

Therefore, the pan pot 15 in FIG.
first to the tweeter side, that is, to the high frequency signal H.
is applied only to the tweeters 11 and 12, and by adjusting the gain of the power amplifier to make the sound pressure level constant in each playback band at the listening point, the sound pressure level can be adjusted over the entire playback band depending on the vehicle type, listening position,
Flat listening point characteristics can be obtained regardless of the playback channel and whether or not the user is seated. Furthermore, by adjusting the panpot 17, the ratio of the direct sound and the diffusely reflected sound of the high frequency signal H at the listening point can be arbitrarily set. At this time, if the influence of sitting is taken into account, as shown in FIG.
6, by applying equivalent processing similar to the above, the ratio of high-frequency direct sound to indirect sound at the listening point can be set arbitrarily, while keeping the listening point characteristics flat even when seated. It can be adjusted according to the source being played or the listener's preferences.

FIG. 18 shows another embodiment of the present invention,
One power amplifier per channel is omitted from the embodiment shown in FIG. 11, and the direct sound/diffuse reflection sound control function is omitted. FIG. 19 shows an embodiment in which the tweeter is further omitted.

In Fig. 18, 22 is a band divider with _C1 , MH is a mid-high range output, L is a low range output, 23 is an equalizer, 24 and 25 are power amplifiers, and 26 is a
A network with _C2 , H is high frequency output, M is mid frequency output, and L is low frequency output. In FIG. 19, MH is the mid-high range output, and L is the low range output.

Effects of the Invention The present invention has the above configuration, and according to the present invention, even listening point characteristics can be obtained and optimum sound quality can be obtained regardless of the vehicle type, reproduction channel, or listening position.

[Brief explanation of the drawing]

Figures 1A and B are diagrams showing the speaker arrangement in the vehicle interior of a conventional in-vehicle sound reproduction device, Figure 2 is a transmission characteristic diagram of the same equipment from the rear parcel to the listening point, and Figure 3
The figure is a transmission characteristic diagram from the top of the dart board to the listening point of the same device, and Figures 4 and 5 are listening point characteristic diagrams of the driver's seat and passenger seat, respectively, from the speaker installed in the front left door of the vehicle compartment of the same device. Figure 6 shows the transmission characteristics from under the seats and the dart board in the passenger compartment to the listening point, and Figure 7 shows the change in transmission characteristics depending on whether or not a person is seated when the speaker is placed under the seat or the dart board in the passenger compartment. Figure 8 is a diagram showing the transmission characteristics with and without the seated person when only high-frequency signals are reproduced by a tweeter placed on the dashboard board in the vehicle interior, and Figures 9A and B are diagrams showing the transmission characteristics of a vehicle installed in an embodiment of the present invention. A diagram showing the speaker arrangement of the sound reproduction device, FIG. 10 is a sound pressure frequency characteristic diagram of the tweeter of the same device,
Fig. 11 is a block diagram of the device, Fig. 12 is a transmission characteristic diagram from the rear parcel to the listening point in different types of cars, Fig. 13 is a speaker axial sound pressure frequency characteristic diagram, and Fig. 14 is a diagram of the axial sound pressure frequency characteristic of the speaker. Figure 15 is a listening point characteristic diagram when a speaker with the characteristics shown in the figure is installed in the rear parcel, Figure 15 is a correction characteristic diagram of the equalizer used in the device of the present invention, and Figure 16 is a diagram showing the characteristics shown in Figure 14. A diagram showing characteristics corrected by a characteristic equalizer, and FIGS. 17 to 19 are block diagrams of main parts of other embodiments of the present invention, and FIGS.
Figure 1 is a characteristic diagram showing the impulse response in the driver's seat due to the speaker installed in the rear parcel tray, Figures 22 and 23 are characteristic diagrams showing the impulse response due to the speaker installed in the door, and Figure 24
Figure 25 is a characteristic diagram showing the impulse response when the speaker is installed under the seat facing the forward direction of the vehicle, Figures 26, 27, 28, and 29 are modeled transmission diagrams. It is a characteristic diagram. 4, 5...Speaker for high tone, 6...Dasshu board, 7,8,9,10...Speaker for medium tone, 11,
12...Bass speaker, 13...Rear parcel, 1
4...band divider, 15...panpot, 16...mixer, 17...equalizer, 18, 19, 20, 2
4, 25...power amplifier, 21...amplifier, 22...
Band splitter, 23...Equalizer, 26...Network.

Claims (1)

[Claims] 1. For each playback channel, the input signal is divided into three bands, low, middle, and high, by two dividing frequencies _C1 and _C2 , with _C1 set to about 300 Hz and _C2 set to about 3 KHz. A low-frequency signal is applied to a bass speaker using a set band divider, an equalizer that corrects frequency characteristics, and a power amplifier.The bass speaker is placed in the rear parcel tray inside the vehicle, and the power amplifier is A mid-range signal is applied to a mid-range speaker through a power amplifier, and this mid-range speaker is placed under the front seat of the vehicle interior or under the dash board, and a high-range signal is applied to a treble speaker through a power amplifier. , an in-vehicle sound reproducing device in which this high-pitched speaker is placed on a dashboard board in the vehicle interior. 2. The in-vehicle sound reproducing device according to claim 1, wherein the directivity axis of the high-pitched speaker is directed toward the farthest of the driver's seat and the passenger's seat. 3 The dividing frequency of the band splitter is only _C1 , and there is a separate network with _C2 , and the mid-high range output of the band splitter above _C1 is connected to the power amplifier and the network, and the high range output of the network is An in-vehicle sound reproducing device according to claim 1, wherein the in-vehicle sound reproduction device is configured to apply a mid-range output to a high-pitched speaker and a mid-range output to a mid-range speaker. 4. Claim 1, in which the divided frequency of the band divider is set to _C1 only, the output of the band divider is connected to a power amplifier and a speaker for medium and high frequencies, and the speaker is placed under the seat or under the dash board. The in-vehicle sound reproduction device described in Section 1.