JP2868631B2 - Vehicle radio - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio for a vehicle, and more particularly to an improvement in a radio having means for reducing noise mixed in an input signal.

[0002]

2. Description of the Related Art Conventionally, as this kind of vehicular radio, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-279718, the nth and n + 1st harmonics of a switching pulse are tuned to a radio receiving station. There is known an apparatus in which a switching frequency of an oscillator is controlled so as not to be in a frequency band, thereby preventing generation of a beat sound from a radio apparatus.

[0003] Conventionally, as a means for reducing noise of a vehicle radio, for example, noise of a high-frequency component that is unpleasant to humans is generated by R.
A high-frequency cut control that attenuates by a C integration circuit (low-pass filter) to improve the S / N ratio in the sense of hearing. It reduces stereo noise by reducing the degree of sound separation between the left and right speakers of the stereo. No noise is left in the ear by performing stereo noise control to reduce the output and improve the S / N ratio, or by lowering the output signal value from the speaker including the audio signal to reduce the output sound. There is one that performs soft muting control to make it so.

[0004]

However, in the high-frequency cut control, the high-frequency range is attenuated, so that the FM broadcast has a sound that is similar to an AM broadcast, so that the high-fidelity is reduced. In the stereo noise control, when the electric field strength of the received signal changes during traveling of the vehicle, the localization of the music instrument at the right position or the left position in stereo moves to the center of the vehicle. Gives discomfort to the person. Further, in the soft muting control, since the audio signal is also reduced, the output sound becomes fluffy with the change in the electric field strength of the received signal.

The present invention has been made in view of the above points, and has as its object to reduce the Hi-Fi performance of FM broadcasts due to the operation of noise reduction means, to shift the localization of music instruments, and to realize the fluffiness of output sounds. It is an object of the present invention to effectively suppress a decrease in sound quality of an output sound, such as generation, and to effectively reduce a sense of noise while securing relatively good sound quality.

[0006]

In order to achieve the above object, the present invention focuses on the ambient sound around the vehicle radio and the volume of the radio, and appropriately adjusts the degree of operation of the noise reduction means in accordance with these. It will be changed. That is, in a situation where the ambient sound is loud, the noise of the output sound is low and the noise does not need to be reduced so much. In a situation where the volume of the radio is low, the noise is small and the noise does not need to be reduced so much. I do.

That is, a specific solution of the invention according to claim 1 is based on the premise that a vehicle radio provided with a noise reduction means for reducing noise mixed into an input signal is used to reduce ambient sounds around the vehicle radio. A sound collecting means for collecting sound and a suppressing means for suppressing the operation of the noise reducing means as the surrounding sound collected by the sound collecting means is louder are provided.

A specific solution of the invention according to claim 2 is a sound volume detection means for detecting the volume of a vehicle radio, instead of the sound collection means and suppression means of the invention according to claim 2; And a suppression unit that suppresses the operation of the noise reduction unit as the volume detected by the volume detection unit decreases.

Further, a concrete solution of the invention described in claim 3 is a combination of the invention described in claim 1 and the invention described in claim 2.

[0010]

According to the above-mentioned structure, according to the first aspect of the present invention,
In a situation where the ambient sound around the vehicular radio is low, the occupant of the vehicle feels a relatively large amount of noise included in the output sound of the radio. In this situation, the suppression means is stopped and the noise reduction means operates as usual, so that the noise of the output sound is effectively reduced, and the passenger can listen to a good voice with little noise.

On the other hand, in a situation where the ambient sound around the vehicle radio is loud, the occupant does not feel much annoying even if the noise of the output sound is loud. Therefore, in this situation, even if the soft muting control is suppressed, for example, the passenger can comfortably listen to the output sound with little noise and the soft muting control is suppressed. Since the fluffiness of the sound accompanying the change is reduced and the sound quality is improved, the passenger can more comfortably listen to the sound of the radio.

According to the second aspect of the present invention, when the volume of the vehicle radio is large, the noise of the output sound is also large, but the suppression means is stopped and the noise reduction means is provided. Works normally, so that noise is effectively reduced and the occupant can hear the sound well. On the other hand, in a situation where the volume is low, the noise included in the output sound is also small.For example, even if the high-frequency cut control is suppressed in this situation, the noise increases little and the occupant perceives a sound with little noise. While listening well, the attenuation of the high frequency component is suppressed, so that the high fidelity of the FM broadcast is enhanced and the sound quality is improved.

[0013] In addition, according to the third aspect of the invention, both the operation of the first aspect of the invention and the operation of the second aspect of the invention are obtained.

[0014]

As described above, according to the vehicular radio according to the first, second and third aspects of the present invention, as the ambient sound around the radio becomes larger and the volume of the radio becomes lower, By suppressing the effect of the noise reduction means, the noise contained in the output sound of the radio is suppressed to the extent that the occupants of the vehicle do not feel discomfort, and the sound quality of the output sound is reduced as much as possible conventionally. Since it is suppressed, the sound quality can be improved accordingly, and the effect of being able to comfortably listen to the output sound of the radio is achieved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic electric circuit diagram of a vehicle radio. In the figure, 1 is a receiving antenna, 2 is a high frequency amplifier for amplifying a high frequency component of a signal of a desired broadcasting station received by the receiving antenna 1, and 3 is a signal after the signal from the high frequency amplifier 2 is converted into an intermediate frequency. , A demodulator for demodulating the signal from the intermediate frequency amplifier 3, a demodulator for FM stereo constituted by a multiplex receiving the signal from the detector 4, 6 According to the operation of the volume knob 7, the FM stereo demodulator 5
8 is a low-frequency amplifier that amplifies the low-frequency component of the signal at the subsequent stage of the volume control mechanism 6, and 9 receives the audio signal of the low-frequency amplifier 8 and outputs sound into the passenger compartment. A radiating speaker.

The FM stereo demodulator 5 has a stereo noise control to reduce stereo noise by lowering a voice separation between the left and right speakers 9 and 9 and an aural sensation by attenuating a high frequency component of a signal. It has an additional function of performing three controls: a high-frequency cut control for improving the S / N ratio and a soft muting control for lowering the output signal value of the entire speaker 9 including the audio signal. The above three controls of the FM stereo demodulator 5 constitute a noise reduction means 10 for reducing noise mixed into the input signal.

Reference numeral 15 denotes a control circuit for operating stereo noise control, high frequency cut control, or soft muting control in the demodulator 5 for FM stereo. The control circuit 15 has a transistor Tr and a control signal output circuit 16. When the signal meter voltage of the intermediate frequency amplifier 3 (positive DC voltage proportional to the electric field strength of the input signal) acts on the base of the transistor Tr, and the signal meter voltage is lower than the set value, the signal field voltage becomes lower. The transistor Tr turns on. The control signal output circuit 16 receives the collector current of the transistor Tr and inputs a control signal having a value corresponding to the collector current value of the transistor Tr, that is, a signal meter voltage value during the input, to the FM stereo demodulator 5. Is output to On the other hand, the FM stereo demodulator 5 divides the electric field intensity of the received signal into three regions as shown in FIG. 2, and performs stereo noise control, high frequency cut control, and soft muting control in this order as the electric field intensity becomes weaker. While receiving the control signal from the control signal output circuit 16, the left and right speakers 9, 9
It has a function to smoothly change the degree of sound separation between 9 or the amount of high frequency attenuation.

Reference numeral 19 denotes a microphone arranged in the passenger compartment,
Reference numeral 20 denotes a subtractor. The signal from the microphone 19 is input to a + terminal of the subtracter, and the audio signal of the low-frequency amplifier 8 is delayed by a delay circuit 21 for a set time τ to a-terminal thereof. The signal whose signal level has been adjusted at is input. The set time τ of the delay circuit 21 is
This is a value equal to the propagation time of the sound wave from to the microphone 19. Therefore, with the above configuration, the microphone 19
Does not collect both the ambient sound around the radio device and the output sound of the speaker 9, but removes the output sound of the speaker 9 by the subtracter 20 and collects only the ambient sound around the radio device. The sound collecting means 23 is configured to output the ambient sound signal.

In addition, a low-pass filter 25 detects the ambient sound signal from the subtractor 20 and converts its intensity level into a DC voltage. The low-pass filter 25 includes an integrating circuit of a resistor R and a capacitor C. The low-pass filter 25 also receives, via a wiring 28, a volume inversely proportional signal that becomes smaller as the volume of the radio adjusted by the volume adjustment mechanism 7 becomes larger. By taking out the volume inversely proportional signal, a volume detection means 29 for detecting the volume of the vehicular radio is constituted.

Reference numeral 26 denotes a first field-effect transistor having a gate to which the ambient sound signal and the volume inverse proportional signal converted into a DC voltage by the low-pass filter are input, and 27 denotes a gate input of the drain of the first field-effect transistor 26. The source is connected to the base of the transistor Tr of the control circuit 15. Therefore, the low-pass filter 25 is connected to the two field-effect transistors 26 and 27 by the wiring connection.
The larger the ambient sound signal from the receiver or the larger the volume inversely proportional signal (ie, the lower the volume), the lower the signal meter voltage of the intermediate frequency amplifier 3 becomes, even if the signal meter voltage is lower than the ambient sound signal. The value of the control signal output from the control signal output circuit 16 is reduced by multiplying the signal or the volume inversely proportional signal to increase the value, and
The first suppression means 31 and the second suppression means 32 are configured to suppress the action of zero.

Next, the operation of the above embodiment will be described. FIG.
As shown by the solid line, when performing the stereo noise control, the high frequency cut control, and the soft muting control, as compared with the case where each control indicated by the broken line in the same figure is not performed,
Since the noise can be greatly reduced, the S / N ratio can be improved as the electric field strength (antenna input) of the input signal decreases.

FIG. 3 shows changes in operating characteristics when the volume control knob 7 is at each of the high, middle, and low positions of the volume. The figure shows two field effect transistors 2
6 and 27 are specified, and when the sound level of the noise included in the input signal is smaller than the sound level L1 of the surrounding sound at that time by a value L1-ΔL smaller than the sound level L1 by a minute value ΔL, the control circuit 15
Is designed to turn on the transistor Tr. In the figure, when the sound volume of the radio is low, the ambient sound signal from the subtracter 20 is greatly added to the sound volume inversely proportional signal.
The signal meter voltage of the intermediate frequency amplifier 3 at the time when is turned on becomes low. Therefore, as shown in the figure, the lower the volume of the radio, that is, the smaller the noise included in the radio sound and the less the noise is, the more the antenna input (volume of the volume) when the noise reduction unit 10 starts to operate. E1 at the small position, E2 at the middle position, and E3 at the large position) have small values (E1 <E2 <E3), and the noise reduction means 1
The effect of 0 is suppressed. As a result, since the operation of the noise reduction means 10, for example, the high frequency cut control is suppressed, the high fidelity of the FM broadcast is ensured and the sound quality is improved, so that the passenger of the vehicle can comfortably hear the sound from the radio. You can listen.

FIG. 4 shows a change in output characteristics with respect to ambient sound at a predetermined antenna input, for example, an antenna input value indicated by a symbol A in FIG. In the figure, the sound level of the noise included in the input signal is slightly lower than the sound level of the surrounding sound at that time at each of the large, medium and small positions of the volume control knob 7 (in the figure, the middle position of the sound volume). Ambient sound P at the time
At 1, the large position P2), the suppression of the operation of the noise reduction unit 10 is started as described with reference to FIG. Thereafter, as the ambient sound increases, the transistor T
Since the collector current of r increases and the control signal value of the control signal output circuit 16 increases, the degree of suppression of the operation of the noise reduction unit 10 gradually increases, and the noise gradually increases. The S / N ratio in this case decreases as the ambient sound increases, as shown in FIG. 5. However, since the ambient sound is large, even if the noise increases, the occupant does not care much and the S / N ratio in the sense of hearing increases. The N ratio is well ensured. Moreover, in this state, the effect of the noise reduction means 10 is suppressed. For example, in stereo noise control, the localization of the music instrument between the left and right speakers 9, 9 is suppressed from wandering, and the sound quality is improved. So
Therefore, the passenger can listen to the radio sound comfortably.

FIG. 6 shows a modification of the sound collecting means. In the above-mentioned embodiment, instead of using the microphone 19 and the subtracter 20, the wind noise of the vehicle and the running sound from the wheels, which form the ambient sound, are used for wheel rotation. The sound collecting means is configured to be detected by a number sensor and an engine speed sensor.

That is, in FIG. 6, reference numeral 35 denotes a wheel speed sensor, and 36 denotes an engine speed sensor. The wheel speed pulse and the engine speed pulse are input to the low-pass filter 25. Other configurations are the same as those of FIG. 1 described above, and thus the same portions are denoted by the same reference characters and description thereof will be omitted.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a vehicle radio.

FIG. 2 is an explanatory diagram of a noise reduction effect by a noise reduction unit.

FIG. 3 is an operation explanatory view.

FIG. 4 is an explanatory diagram of how output characteristics change with respect to ambient sound.

FIG. 5 is an explanatory diagram of how the S / N ratio changes.

FIG. 6 is an electric circuit diagram of a vehicular radio showing a modification of the sound collecting means.

[Explanation of symbols]

 Reference Signs List 3 Intermediate frequency amplifier 5 FM stereo demodulator 7 Volume control knob 9 Speaker 10 Noise reduction means 15 Control circuit Tr transistor 16 Control signal output circuit 19 Microphone 20 Subtractor 23 Sound collecting means 25 Low pass filter 26, 27 Field effect transistor 29 Volume detection means 31 First suppression means 32 Second suppression means 35 Wheel speed sensor 36 Engine speed sensor

Claims (3)

(57) [Claims] 1. A vehicular radio comprising a noise reduction unit for reducing noise mixed into an input signal, wherein said vehicular radio collects ambient sounds around said vehicular radio, and said vehicular radio comprises a noise collection unit. A vehicle radio comprising: a suppression unit that suppresses the function of the noise reduction unit as the ambient sound is louder. 2. A vehicle radio comprising noise reduction means for reducing noise mixed in an input signal, wherein the volume detection means detects the volume of the vehicle radio, and the volume detected by the volume detection means. A vehicle radio comprising: a suppression unit that suppresses the operation of the noise reduction unit as the size of the radio signal decreases. 3. A vehicle radio provided with noise reduction means for reducing noise mixed in an input signal, wherein said sound collection means collects ambient sounds around said vehicle radio, and said sound collection means collects said sound. First suppression means for suppressing the operation of the noise reduction means as the ambient sound is loud, volume detection means for detecting the volume of the vehicle radio, and noise reduction as the volume detected by the volume detection means decreases Second to suppress the action of the means
A vehicular radio comprising a suppression means.