JPH01319400A - Vehicle mounted acoustic reproducing equipment - Google Patents

Abstract

PURPOSE:T enjoy the listening of music without being disturbed by noise even under noise such as a case with an automobile during driving by increasing the compression rate of the dynamic range of an audio signal when a vehicle velocity pulse frequency is high. CONSTITUTION:A voltage in response to a peak of a monaural signal being the sum of left/right channel signals by a peak hold circuit 2 is fed to one input of an adder, while a frequency-voltage conversion circuit 5 receives a vehicle velocity pulse from a vehicle velocity sensor mounted already on a vehicle and generates a voltage in response to the velocity. Then the voltages are compared by 1st and 2nd comparators 12a, 12b, the result of comparison is added, the result is fed to other input of adder circuits 1a-1c, the adder circuit adds both the inputs to vary the amplification factor of a voltage controlled amplifier and when the frequency of the vehicle velocity pulse gets higher, the compression rate of the dynamic range of an audio signal is increased. Thus, even in the presence of noise during driving, pleasant music listening is enjoyed without sound volume adjustment.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is installed in an automobile, etc., and is designed to reproduce reproduction signals such as music so that even if there is noise that fluctuates while driving, the player can listen to it without being disturbed by the noise. The present invention relates to an in-vehicle sound reproduction device that can compress and expand the dynamic range of the vehicle.

[Conventional technology]

Conventionally, there are examples in which noise is collected with a microphone and the reproduction volume is adjusted according to the noise value, and examples in which the dynamic range of the reproduction signal is compressed by a vibration signal of the vehicle body.

Figure 5 is /lF, s Tokyo Convention °87 Proceedings (
C-3) 'p(・J-H・Kitzen, J
-1tJ ・Keo+na.

II ・F-Druyvestein, C, L, C
, M., Knibbeler.

A, T, A, M vd, νoort r No1se-
dependent 5oundreproduct
On in a Car Application o
f a Digital#audio Signal P
rocessor is a functional block diagram of a conventional in-vehicle sound reproduction device that performs dynamic range compression using a conventional vibration signal, and in the figure, 7 is a peak detection circuit, 8 is a compression ratio setting means, 9 is a V CA (Voltage Cont) whose amplification factor can be controlled by voltage.
IO is a vibration detector, and II is an amplifier.

Next, the operation will be explained. The peak value of a human-generated audio signal such as a voice is detected by the peak detection circuit 7.
It is converted into a voltage corresponding to the peak value, and the voltage is applied to the compression ratio setting means 8.
is input.

On the other hand, a vibration signal detected by a vibration detector lO attached to a part of the vehicle body and converted into a voltage is amplified by an amplifier 11 and input to the compression ratio setting means 8. Compression rate setting means 8
generates a control voltage for changing the compression ratio in a predetermined procedure from the voltage corresponding to the peak value and the vibration signal, and changes the amplification factor of the VCA 9.

It is described in the above-mentioned document that the compression ratio setting means 8 may determine the input and output level ratio depending on the magnitude of the noise, as shown in FIG. 6, for example.

It is also stated that there is a high correlation between the vibration signal detected through actual measurement and the Kl sound during driving, and that it is effective as a means for detecting noise.

[Problem to be solved by the invention]

Since conventional in-vehicle sound reproduction equipment is configured as described above, it is necessary to use vibration signals for dynamic range compression, which requires the installation of a new vibration detector 10, and In order to amplify the minute voltage generated by vibration in the
1 is required.

Furthermore, there are other problems, such as the need for electromagnetic shielding and the need for noise removal processing due to vibration noise mixed in due to the movement of passengers.

This invention was made to solve the above-mentioned problems. It effectively compresses the dynamic range without adding a new detector, and allows volume adjustment even when there is noise while driving. The purpose of the present invention is to provide an in-vehicle audio reproduction device that allows you to enjoy comfortable music listening without having to listen to music.

[Means to solve the problem]

The in-vehicle sound reproduction device according to the present invention includes a left and right channel voltage control amplifier that amplifies the left and right channel signals, a peak hold circuit that outputs a voltage according to the peak value of a monaural signal obtained by adding the left and right channel signals, and a vehicle speed. a frequency-voltage comparator that converts the pulse into a voltage proportional to the traveling speed; a first and second comparators that compare this voltage with different predetermined reference voltages; An adder is provided to control the amplification factor of the voltage control amplifier based on the sum of the output of the second comparator and the output voltage of the peak hold circuit.

[For production]

In the peak hold circuit of this invention, a voltage corresponding to the peak value of the monaural signal obtained by adding the left and right channel signals is applied to one input side of the adder. Inputs the vehicle speed pulse from the vehicle speed sensor and generates a voltage according to the vehicle speed,
This voltage is compared by the first and second comparators, and after adding the comparison results, it is added to the other input side of the adding circuit, and the adding circuit adds the input again to change the amplification factor of the voltage control amplifier. As a result, when the frequency of the vehicle speed pulse becomes high, it acts to increase the compression ratio of the dynamic range of the audio signal.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows an example of 8! In Figure 0, which is the Noji block, 1a is an adder that adds the L channel and R channel audio signals, 2 is a peak hold circuit that holds the peak of the output of this adder 1a, and 3a is composed of a resistor and a capacitor. 4L and 4R are L channel and R channel VCAs whose amplification factors can be controlled externally, respectively, 6 is an operational amplifier that inverts and amplifies the output of the time constant circuit 3a, and Ib is an inverting amplifier 6. The output of VCA4L is added to the output of adder 1c.
, 4R.

On the other hand, 5 is a frequency that inputs a vehicle speed pulse that is conventionally output from a vehicle speed sensor installed in a car and is used for calculating running speed, mileage, and other purposes, and converts the frequency of this vehicle speed pulse into a voltage. - Voltage converter 3b is an R, C time constant circuit made up of a resistor and a capacitor, which inputs the output of the frequency-voltage converter 5 and outputs a voltage signal that changes with a predetermined time constant. .

12a and 12b are comparators, respectively, and the time constant circuit 3
The output of b is compared with a reference voltage, and the output is supplied to the adder IC.

Further, the comparator 12b compares the output of the time constant circuit 3b with a reference voltage and supplies the output to the adder IC.

The reference voltage of the comparator 12a is supplied from the connection point between the resistors R1 and R2, and the reference voltage of the comparator 12b is supplied from the connection point between the voltage 11Va and the resistor R1. In addition, the resistors R1 and R
2 is connected between the power source Va and the ground.

Next, the operation will be explained. The input audio signals of the L channel and the R channel, and R, are added by the adder 1a to become a monaural signal, which is then converted to a voltage value according to the peak value by the peak hold circuit 2, and the time constant determined by the time constant circuit 3a. becomes a voltage signal that changes at
Enter b.

On the other hand, a vehicle speed pulse generated by a conventional vehicle speed sensor is converted into a voltage proportional to the traveling speed by a frequency-voltage conversion circuit 5, and a voltage signal that changes with a time constant different from that of the time constant circuit 3a by a time constant circuit 3b. converted, comparator 12
a and 12b, the voltage value divided by the resistors R1 and R2 and the voltage value of the power source Va are compared with respective reference voltages, and the results of both comparisons become voltage values and enter the adder 1c.

The adder 1c adds the voltage values of the two comparators 12a and 12b, and the added voltage value is input to the adder 1b. The adder 1b adds the output of the inverting amplifier 6 and the output of the adder 1c, and controls the amplification factors of the VCAs 4L and 4R using the added voltage value.

With this configuration, the output voltage of the comparators 12a and 12B is 0 when stopped or when driving at low speed, so that the VC
The control voltage Vc of A4L and 4R becomes negative, and VCA4L,
The amplification factor of 4R is constant and no dynamic range compression is performed.

Next, during high-speed running, the output voltages of the comparators 12a and 12b are added by the accelerator 1c, and the amplification factors of the VCAs 4L and 4R are controlled by the positive control voltage Vc.

Therefore, for small amplitude audio signals, the control voltage Vc becomes large, and the amplification factors of VCA4L and 4R are large, and when the amplitude is large, the control voltage Vc becomes small, so the amplification factor becomes small and dynamic range compression is performed. . Low-speed driving according to this embodiment (low frequency of vehicle speed pulse)
FIG. 2 shows an example of the input-to-output level ratio corresponding to each of , medium-speed running (medium frequency of vehicle speed pulse), and high-speed running (high frequency of vehicle speed pulse).

The relationship between the frequency of the vehicle speed pulse and running noise differs depending on the vehicle type, but once the vehicle type is determined, the frequency and noise value can be measured in advance by actual measuring means, and the amplification factor of the control inverting amplifier 6 can be adjusted to match the vehicle type. By doing so, an appropriate compression ratio can be obtained.

Furthermore, in the prior art document shown in FIG. 5, actual measurement data shows that there is a high correlation between traveling speed and noise level on expressways from 70 km/h to 130 km/h, and compression is performed using vehicle speed pulses. is valid.

Furthermore, the peak hold circuit 2 and the frequency-voltage conversion circuit 5 use several circuit examples using operational amplifiers, etc., and the circuit examples with known circuit examples are shown in FIGS. 3 and 4 respectively.
As shown in the figure.

Further, the VCAs 4L and 4R can be constructed by combining an operational amplifier with a diode, a transistor, a CDS opto-isolator, etc. whose resistance value changes depending on the voltage, and these days, integrated circuits are easily available.

〔Effect of the invention〕

As described above, according to the present invention, as the frequency of the vehicle speed pulse increases, the compression ratio of the dynamic range of the audio signal is increased. This has the effect of allowing you to enjoy listening to music without having to listen to music.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram of an in-vehicle sound reproduction device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the input-to-output level ratio of the above embodiment, and Fig. 3 is a peak hold circuit in the above embodiment. 4 is a circuit diagram showing an example of the frequency-voltage conversion circuit in the same embodiment as above, FIG. 5 is a functional block diagram of a conventional in-vehicle audio equipment, and FIG. 6 is a conventional in-vehicle audio equipment. FIG. 3 is an explanatory diagram showing an input-to-output level ratio of an audio device. 13-1c...Adder, 2...Peak hold circuit, 3a, 3b--Time constant circuit, 4L, 4R/VCA. 5... Frequency-voltage conversion circuit, 7... Peak detection circuit, 12a, 12b... Comparator. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A voltage control amplifier for the left channel and right channel that amplifies the left channel signal and right channel signal by changing the signal amplification factor, and outputs a voltage according to the peak value of the monaural signal added from the left channel and right channel. a peak hold circuit, a frequency-voltage conversion circuit that converts the vehicle speed pulse into a voltage proportional to the distance traveled by the vehicle, and first and second comparators that compare the voltage with a different reference voltage;
By adding the sum of the outputs of the first and second comparators and the output voltage of the peak hold circuit, the left channel is set such that as the frequency of the vehicle speed pulse increases, the compression ratio of the dynamic range of the audio signal increases. and an adder for controlling the amplification factor of the voltage-controlled amplifier of the right channel.