JPH0923495A - On-vehicle acoustic reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle acoustic reproducing device for a low frequency band which produce optimum acoustic output even in the case when the level of noise in the cabin changes by the traveling of the vehicle. SOLUTION: When the vehicle stops, a voltage control amplifier 505 detects whether an engine stops or idles. At the time of idling, the amplifier 505 lifts an amplification factor and when the vehicle travels, a frequency voltage converter 501 detects the velocity of the vehicle to control the amplification factor of the voltage control amplifier 502 so as to obtain an optimum acoustic output signal corresponding to the velocity of the vehicle. Thereby, the optimum acoustic output in a cabin is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted sound reproducing device for low frequencies.

[0002]

2. Description of the Related Art At present, a speaker system for an on-vehicle sound reproducing device is mainly a four-speaker system in which full-range speakers are arranged in front, rear, left and right. For this reason, there is a limit to the reproduction capability in the low frequency range. Conventionally, it is possible to improve the reproduction capability in the low frequency range by combining this vehicle-mounted audio reproduction device with a low-frequency audio reproduction device (hereinafter simply referred to as a subwoofer). It is being appreciated.

Hereinafter, a conventional subwoofer for improving the low frequency reproduction capability will be described. FIG. 6 is a system configuration diagram in which a conventional subwoofer is combined with an in-vehicle sound reproduction device. In FIG. 6, reference numeral 101 denotes a sound source device 101a such as a compact disc player, a compact cassette player, and a tuner, an acoustic signal variable section 101b for varying the volume and sound quality of the sound source, and a power amplifier 101c for power-amplifying this acoustic signal. A sound source device with a built-in amplifier (hereinafter, simply referred to as a sound source device). 102 is a sound source device 1
It is a full-range speaker that reproduces the sound output signal of 01 in the vehicle interior. Reference numeral 103 denotes a subwoofer which obtains an acoustic output signal from the sound source device 101 and plays back a low frequency region in an auxiliary manner. FIG. 7 is a block diagram showing a configuration of a conventional subwoofer 103. In FIG. 7, 201 is a power amplifier that power-amplifies the low frequency band of the sound output signal of the sound source device 101. 202
Is a low frequency speaker that reproduces the acoustic output signal of the power amplifier 201.

The operation of the conventional subwoofer constructed as above will be described below. FIG. 8 shows the sound reproduction characteristics of the conventional device, and 3S1 shows the reproduction sound level of only the on-vehicle sound reproduction device, and 3S2 shows an example of the reproduction sound level when the sound reproduction device and the conventional subwoofer are combined. As shown in FIG. 8, although the reproduction sound level of the in-vehicle sound reproduction device is insufficient in the reproduction sound level in the low range, a conventional subwoofer is combined with these in-vehicle sound reproduction devices to improve the reproduction range in the low range. The acoustic signal of the sound source device 101 is output to the conventional subwoofer 103, and the acoustic signal connected to the conventional subwoofer 103 is input to the power amplifier 201. The power amplifier 201 extracts only the low frequency component by a low pass filter or the like and amplifies the power. The acoustic signal power-amplified by the power amplifier 201 is output to the vehicle interior as reproduced sound by the low-frequency speaker 202. As described above, by combining the conventional subwoofer 103 with the on-vehicle sound reproducing device, the reproduced sound level in the low frequency band is improved.

[0005]

However, in the vehicle interior where the vehicle traveling speed constantly changes, the vehicle interior noise level greatly changes due to road noise and the like due to the variation of the vehicle traveling speed. When the subwoofers are combined in such an environment, the SN ratio of the reproduced sound level of the subwoofer changes greatly due to the masking phenomenon. Therefore, the conventional subwoofer described above has a problem that it is difficult to set the optimum volume in the vehicle compartment.

The present invention solves the above-mentioned problems of the conventional subwoofer, and presumes the noise level inside the vehicle while the vehicle is running, and an optimum sound reproduction output can be obtained even if the noise level inside the vehicle changes. By controlling the reproduction level of the subwoofer as described above, it is possible to facilitate optimization of the volume setting of the subwoofer and perform faithful sound reproduction.

[0007]

To achieve this object, an in-vehicle sound reproducing apparatus of the present invention is provided with a frequency voltage conversion circuit having an input terminal for a vehicle speed pulse, and an input signal based on an output signal of the frequency voltage conversion circuit. A first voltage control amplifier for controlling an acoustic signal to be input, a second voltage control amplifier for controlling an acoustic signal input based on a control signal according to an operating state of the engine, and an output of the first voltage control amplifier Power amplifying means for amplifying the low-frequency signal of the sound output signal from the second voltage controlled amplifier to which is input or the output of the second voltage controlled amplifier from the first voltage controlled amplifier, and this power It is characterized in that a low-frequency speaker for reproducing the acoustic output signal of the amplifying means is provided.

[0008]

According to the present invention, the vehicle speed is detected by the frequency voltage converter, and the acoustic signal is controlled by adding the control signal proportional to the vehicle speed to the first voltage control amplifier. The subwoofer volume can be obtained, and the subwoofer volume similar to that when the vehicle is stopped can be obtained even when the vehicle is traveling. Further, since the acoustic signal is controlled by adding the control signal according to the operating state of the engine to the second voltage control amplifier, the optimum subwoofer volume is obtained by detecting whether the engine is stopped or idling even when the vehicle is stopped. be able to.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vehicle-mounted sound reproducing device for low frequencies (hereinafter, simply referred to as a subwoofer) of the present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram in which an on-vehicle sound reproducing device and a subwoofer according to the embodiment of the present invention are combined, and FIG. 2 is a block diagram showing the subwoofer according to the embodiment of the present invention. In FIGS. 1 and 2, 401 is a sound source device 401a such as a compact disc player, a compact cassette player, a tuner, a variable section 401b for varying the volume and sound quality of a sound source, and a power amplifier 401c for power-amplifying the sound output signal. It is a sound source device. Four
Reference numeral 02 denotes a full-range speaker that reproduces the sound output signal of the sound source device 401 in the vehicle interior. 403 is a sound source device 401
3 is a subwoofer of the present embodiment to which an acoustic output signal from is connected.

The subwoofer 403 of this embodiment is constructed as shown in FIG. In FIG. 2, reference numeral 501 is a frequency voltage converter for converting the frequency of the vehicle speed pulse on the vehicle side into a DC voltage proportional to the vehicle speed. Reference numeral 502 is a voltage control amplifier that outputs an acoustic signal proportional to the control voltage from the acoustic input signal by the control voltage of the frequency voltage converter 501. Reference numeral 503 is an integration circuit that prevents the output signal of the voltage controlled amplifier 502 from frequently changing due to the control voltage of the frequency voltage converter 501. Reference numeral 504 is a signal limiting circuit that suppresses an excessive sound output signal when the volume of the subwoofer of this embodiment is sufficiently large and is not affected by the noise in the vehicle interior. Reference numeral 505 is a voltage control amplifier that controls the acoustic signal by the output voltage when the engine switch is turned on so that an optimum volume can be obtained even when the engine is idling when the vehicle is stopped. Reference numeral 506 denotes a pulse width modulation type power amplifier that power-amplifies only the low frequency range of the output signal of the voltage control amplifier 502. Reference numeral 507 is a passive radiator type Kelton type speaker system for reproducing the acoustic output signal of the power amplifier 506.

Reference numeral 508 denotes a feedback circuit which detects an acoustic signal radiated from the speaker system 507 by the microphone 509 and controls the acoustic signal based on the output signal from the microphone 509, and the signal limiting circuit 504.
And the power amplifier 506. here,
The signal limiting circuit 504, the feedback circuit 508, and the power amplifier 506 constitute power amplifying means for power-amplifying only the low frequency signal of the sound output signal from the voltage control amplifier 502 and inputting it to the speaker system.

As shown in FIG. 3, the feedback circuit 508 receives the output signal of the microphone 509 and the subtractor 2 in which the input terminal 1 to which the output of the signal limiting circuit 504 is added is connected to the inverting input terminal. Microphone amplifier 6 and an adder / subtractor 7 for adding / subtracting the output of the microphone amplifier 6 and the acoustic signal input to the power amplifier 506. The output of the adder / subtractor 7 is non-inverted by the subtractor 2. Connected to the input terminal.

The operation of the subwoofer of the present embodiment constructed as described above will be described below. The sound signal input from the sound source device 401 is the voltage controlled amplifier 50.
5 is input. The amplification degree of the voltage control amplifier 505 rises to a certain level when the voltage output when the vehicle engine switch is turned on is detected. Frequency voltage converter 5
A vehicle speed pulse on the vehicle side is input to 01, and a control voltage proportional to the vehicle speed is output to the voltage control amplifier 502 via the integrating circuit 503. In addition, the voltage control amplifier 50
The acoustic signal output from 5 is input to the voltage controlled amplifier 502. The amplification degree of the voltage control amplifier 502 is controlled in direct proportion to the control voltage of the frequency voltage converter 501, that is, the vehicle speed. The acoustic output of the voltage controlled amplifier 502 is input to the signal limiting circuit 504. Signal limiting circuit 50
No. 4 is when the volume of the subwoofer of this embodiment is sufficiently large and is not affected by vehicle interior noise such as road noise,
It works to suppress excessive volume when the vehicle speed increases.
The acoustic output signal from the signal limiting circuit 504 is fed back to the feedback circuit 50.
8 is input. The feedback circuit 508 detects the acoustic output of the passive radiator type Kelton type speaker system 507 by the microphone 509, forms a feedback loop through the microphone amplifier 6, the subtractor 2 and the adder / subtractor 7 to improve the sound quality of the subwoofer. The acoustic output of the feedback circuit 508 is input to the pulse width modulation type power amplifier 506. The pulse width modulation type power amplifier 506 has a low-pass filter circuit and the like built therein, and power is amplified only in the low frequency band. The passive radiator type Kelton type speaker system 507 is connected to the acoustic output signal of the pulse width modulation type power amplifier 506 and outputs a reproduced sound to the vehicle interior.

With the above configuration, the vehicle interior noise level increases in the order of vehicle stop, engine idling, vehicle low speed traveling, medium speed traveling, and high speed traveling, but the volume of the subwoofer 403 of this embodiment is increased. Also increases in proportion to the noise level in the vehicle compartment, so that the S / N ratio of the reproduced sound level of the subwoofer of the present embodiment is improved to be kept constant, and optimum sound reproduction can be performed. Further, when the volume of the subwoofer of this embodiment is large and is not affected by the noise in the vehicle compartment, the volume of the subwoofer 403 of this embodiment does not rise more than necessary even when the vehicle is traveling at high speed by the signal limiting circuit 504.
Further, even if the vehicle speed changes frequently by the integrating circuit 503, the volume of the subwoofer of this embodiment does not change frequently.

FIG. 4 shows an example of the noise level in the passenger compartment. N
0A is the vehicle interior noise level when the engine is idling with the vehicle stopped, N06 is the vehicle interior noise level when the vehicle is traveling at 60km / h, and N10 is the vehicle interior noise level when the vehicle is traveling at 100km / h. Indicates the level.

FIG. 5 shows an example of the reproduced sound level when the sound reproducing device and the subwoofer of this embodiment are combined. In S00, the combined reproduction sound level of the sound reproduction device and the subwoofer of this embodiment when the vehicle is stopped and the engine is stopped is
The sound reproduction level of the combination of the sound reproduction device and the subwoofer of the present embodiment at the time of engine idling with the vehicle stopped at 0 A,
In S06, the combined reproduction sound level of the sound reproduction device when the vehicle is traveling at 60 km / h and the subwoofer of the present embodiment, and in S10 the sound reproduction device when the vehicle is traveling at 100 km / h and this embodiment Indicates the combined playback sound level of the subwoofer. As shown in FIGS. 4 and 5, by combining the sound reproduction device with the subwoofer of this embodiment, the volume of the subwoofer is optimized even when the vehicle is stopped and the vehicle is traveling at high speed, and the S / of the low-range reproduction level is reduced. The N ratio is greatly improved.

Although the output of the voltage control amplifier 505 is input to the voltage control amplifier 502 in the embodiment, the output of the voltage control amplifier 502 may be input to the voltage control amplifier 505.

[0019]

As described above, the in-vehicle sound reproducing device for low frequencies according to the present invention controls the frequency-voltage converter and the voltage-controlled amplifier that can obtain the optimum volume for the vehicle speed, and also controls them according to the operating state of the engine. With the voltage control amplifier, the volume of the subwoofer can be maintained at the same level as when the vehicle is stopped, and the volume of the subwoofer can be controlled in consideration of the idling noise of the engine. The value is enormous. Further, by providing the signal limiting circuit, when the volume of the vehicle-mounted sound reproduction device is large and the vehicle interior noise is not affected even when the vehicle is running, the volume of the subwoofer is suppressed from increasing more than necessary. Also, by providing an integrating circuit, even if the vehicle speed changes frequently,
The volume of the subwoofer does not fluctuate more than necessary, so its practical value is great.

[Brief description of drawings]

FIG. 1 is a system configuration diagram in which an in-vehicle sound reproducing device according to an embodiment of the present invention is combined with an in-vehicle sound reproducing device.

FIG. 2 is a block diagram of an in-vehicle sound reproduction device for low frequencies according to an embodiment of the present invention.

FIG. 3 is a circuit diagram showing a feedback circuit used in the in-vehicle sound reproduction device for low frequencies.

FIG. 4 is a characteristic diagram showing a noise level in a vehicle interior.

FIG. 5 is a sound reproduction characteristic diagram in which the on-vehicle sound reproducing apparatus is combined with the low-frequency car on-vehicle reproducing apparatus according to the embodiment of the present invention.

FIG. 6 is a system configuration diagram in which an in-vehicle sound reproduction device is combined with a conventional in-vehicle sound reproduction device for low frequencies.

FIG. 7 is a block diagram of a conventional in-vehicle sound reproduction device for low frequencies.

FIG. 8 is a sound reproduction characteristic diagram in which a conventional low-frequency on-vehicle sound reproducing device is combined with the on-vehicle sound reproducing device.

[Explanation of symbols]

Reference Signs List 101 sound source device 102 full range speaker 103 conventional subwoofer 201 power amplifier 202 low frequency speaker 401 sound source device 402 full range speaker 403 subwoofer 501 frequency voltage converter 502 voltage control amplifier 503 integrating circuit 504 signal limiting circuit 505 voltage in the embodiment of the present invention Control amplifier 506 Pulse width modulation type power amplifier 507 Passive radiator type Kelton type speaker system 508 Feedback circuit 509 Microphone

Claims (7)

[Claims] 1. A frequency-voltage conversion circuit having a vehicle speed pulse input terminal, a first voltage-controlled amplifier for controlling an acoustic signal input based on an output signal of the frequency-voltage conversion circuit, and a first voltage-controlled amplifier depending on an operating state of an engine. Of the second voltage control amplifier for controlling the input acoustic signal based on the control signal and the output of the first voltage control amplifier for inputting the second voltage control amplifier or the second voltage control amplifier. In-vehicle sound reproduction provided with power amplification means for amplifying a low frequency signal of the sound output signal from the first voltage controlled amplifier to which the output is input, and a low frequency speaker for reproducing the sound output signal of the power amplification means. apparatus. 2. The in-vehicle sound reproduction device according to claim 1, wherein the output voltage from the frequency-voltage conversion circuit is applied to the first voltage-controlled amplifier via an integration circuit. 3. The on-vehicle sound reproducing device according to claim 1, wherein the voltage amplifying means has a signal limiting circuit for limiting an output signal of the first or second voltage control amplifier before the power amplifier. 4. The second voltage control amplifier according to claim 1, wherein the second voltage control amplifier is configured to detect the voltage supplied when the engine switch of the vehicle is on and increase the amplification factor. The in-vehicle sound reproduction device described. 5. The power amplifying means comprises a subtractor provided in a stage preceding the power amplifier, a microphone amplifier for amplifying an acoustic output signal detected by a microphone for detecting an acoustic output signal emitted from a low frequency speaker, and 2. A feedback circuit comprising an adder / subtractor for adding or subtracting an output signal of a microphone amplifier and an input signal of the power amplifier, and including a feedback circuit configured to add the output signal of the adder / subtractor to the subtractor. The in-vehicle sound reproduction device according to any one of 3 and 4. 6. The on-vehicle sound reproducing device according to claim 1, wherein the power amplifier is a pulse width modulation amplifier. 7. A low-frequency speaker using a passive radiator-type Kelton-type speaker system.
The in-vehicle sound reproduction device according to any one of 2, 3, 4, 5, and 6.