JPS62265806A - On-vehicle acoustic reproducing device - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the sound articulation due to noise while preventing the deterioration in the sound quality by changing the frequency range of a sound signal in response to a noise level in a car body. CONSTITUTION:An output signal of sound collecting microphone 7 fitted to a prescribed position of a car body 5 is fed to a noise detector 8. The noise detector 8 consists of, e.g., a low-pass filter and an amplifier, extracts components below, e.g., 500Hz and amplifies them from the output signal of the microphone 7 and gives them as a noise signal to a control signal generator 9. The control signal generator 9 consists of an envelope detector or the like to form a DC voltage control signal CTL in response to the level of the noise signal. A frequency range control circuit 3 is controlled by the control signal CTL and the frequency range of the sound signal is changed in response to the level of the control signal CTL, that is, the nosie level in the car body 5. Thus, the frequencies of the reproduced sound and noise are separated and the deterioration in the articulation of the reproduced sound due to noise is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sound reproducing device for a vehicle such as a car radio or a car stereo.

[Conventional technology]

Most automobiles are equipped with at least one type of sound reproduction device, such as a car radio or car stereo, so that music, radio programs, etc. can be listened to inside the vehicle.

By the way, when a car is traveling at high speed or on a rough road, the effects are felt inside the vehicle, and 1! The sound level increases, making it difficult to hear music or radio programs. This is especially serious when the car windows are open. Therefore, in order to deal with this, a means for detecting the noise inside the vehicle interior and a dynamic range control means for changing the dynamic range of the audio signal according to the level of the detected noise are provided. A sound reproduction device for a vehicle has been proposed that changes the sound according to the sound so that the sound can always be heard at an appropriate level (for example, Japanese Patent Laid-Open No. 6
0-145714).

[The interlayer point that the invention attempts to solve]

By the way, the noise that occurs inside the vehicle is mainly due to

Frequencies are distributed in a relatively low frequency region, for example,
Bass sounds produced by audio signals whose frequencies are also distributed in the low frequency region, such as the male anrans on a radio program,
Even if the level of the audio signal is raised as in the above-mentioned conventional technology, the audio signal is often masked by noise and is difficult to hear.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sound reproducing device for a vehicle that can eliminate such problems and prevent a decrease in the clarity of reproduced sound due to noise.

[Means for solving problems]

In order to achieve the above object, one aspect of the present invention is to detect noise within a vehicle interior and change the frequency range of an audio signal to be reproduced in accordance with the level of the noise.

[Effect]

To reduce the area masked by the noise of an audio signal and separate the frequencies of reproduced sound and noise.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of a vehicle sound reproducing apparatus according to the present invention, in which 1 is a radio receiver, 2 is a tape deck, and 3 is a frequency range control circuit.

4 is a main up, 5 is a vehicle, 6 is a speaker, 7 is a sound collection microphone, 8 is a noise detector, and 9 is a control signal generator.

In the same figure, except for the speaker 6 and the sound collecting microphone 7, the vehicle 5
Although it is shown outside, it is of course installed on the vehicle.

Output audio signals from the radio receiver 1 and tape deck 2 are selectively input to a frequency range control circuit 3, amplified by a main amplifier 4, and then supplied to a speaker 6 located at a desired position in a vehicle 5. As a result, the sound from the radio receiver 1 or the tape deck 2 can be heard.

On the other hand, an output signal from a sound collection microphone 7 attached to a predetermined position of the vehicle 5 is supplied to a noise detector 8 . The noise detector 8 includes, for example, a low-pass filter and an amplifier, and detects, for example, 50
0I(z) and below are extracted and amplified, and supplied as a noise signal to the control signal generator 9. The control signal generator 9 is composed of, for example, an envelope detector, and detects the level of the noise signal. The frequency range control circuit 3 forms a DC voltage control signal CTL according to the control signal CTL.
The frequency range of the audio signal is changed according to the level of the control signal CTL, and thus the level of noise inside the vehicle 5.

FIG. 2 is a characteristic diagram showing a specific example of how the frequency range of the audio signal changes with respect to the noise level by the frequency range control circuit 3. Here, it is assumed that the frequency range is changed in five steps.

In the figure, when there is almost no noise and the control signal CTL is below the first reference level, the frequency characteristic of the audio signal is represented by the widest characteristic curve α, and sound can be reproduced down to the lowest frequency.

When the noise inside the vehicle increases to, for example, 60 dB or more and the level of the control signal CTL exceeds the first reference level, the frequency characteristic of the audio signal becomes as shown in the characteristic curve with a cutoff frequency of 1257. The following low frequency components are cut. Then, the noise level inside the vehicle becomes even higher, and the control signal CTL changes to the second level. When the third reference level is exceeded, the frequency characteristics of the audio signal have a cut-off frequency of 250Hz,
The characteristic curves c and d are 500Hz, and the noise level is 10
When the control signal CTL exceeds the maximum reference level by 0 dB or more, the frequency characteristics of the audio signal have a cut-off frequency of 1k.
The characteristic curve e of llz is obtained.

In general, noise inside a vehicle interior is mainly low-frequency, but as the level increases, the frequency range expands, as is clear from, for example, the case where the running speed of the vehicle is gradually increased. Therefore, as described above, by increasing the cutoff frequency on the lower side of the audio signal as the noise level increases, the frequency ranges of reproduced sound and noise are separated.

The part where the sound is masked by noise is reduced and the clarity of the sound is maintained well, and by lowering the cutoff frequency when the influence of the noise level is small, the deterioration of the sound quality of the sound is prevented as much as possible. Then.

FIG. 3 is a block diagram showing a specific example of the frequency range control circuit in FIG. 1, in which 10.11 is an input terminal, 12
is the power supply terminal, and 13 is the first stage amplifier.

14 is a frequency range switching circuit, and 15 is a rear stage amplifier.

16 is the output terminal, SW engineering ~ SW4 are analog switches,
C□ to C5 are capacitors, and R1 to R7 are resistors.

In the figure, radio reception m1. Tape deck 2 (1st
The audio signal from either of the above is supplied from the input terminal 10 to the first stage amplifier 13 and amplified, passes through the frequency range switching circuit 14 and capacitor C6, is amplified by the second stage amplifier 15, and is sent from the output terminal 16 to the main stage amplifier 13. Amplifier (1st
Figure).

The frequency range switching circuit 14 is an analog switch SW□~
It consists of SW4 and capacitors C~C4, and is a series circuit of analog switch SW and capacitor C□.
. . . A series circuit of an analog switch SW4 and a capacitor C4 is connected in parallel to an open transmission line between the first stage amplifier 13 and a capacitor C6, and a resistor R. One end of this resistor R6 to which these series circuits are connected is connected to the transmission path between the capacitor C3 and the subsequent stage amplifier 15, while the other end is grounded.

On the other hand, a resistor R,
, R□+R,, R3, R41R5 are connected in series in this order, and input terminal 1 is connected to the connection point P of resistors R7 and R□.
1 is connected. Although not shown in the figure, this input terminal is connected to means for changing the resistance value in response to a control signal CTL from the control signal generator 9 (FIG. 1), for example. A voltage V5 obtained by dividing the 10B voltage is obtained at the connection point P.

For this reason, the voltage at point P v2. changes depending on the level of the control signal CTL, but here, the control signal CTL
When the level of v1. shall rise.

Analog switch S in frequency range switching circuit 14
W□ is controlled on and off by the voltage ■ at the connection point P of resistors R□ and R2, and analog switches sw, , sw3 . sw are the resistances R,,R,
, R, , R, each connection point P2゜p3. ffi pressure at pJ, -V2. V3. V, Niyotte on, off controlled.

Here, V□>V2>V, >V, each analog switch SW~SW4 is turned on when the voltage V~SW4 that controls these is below a predetermined level, and exceeds this predetermined level. shall be turned off. In addition, the control signal CTL
the first reference pressure.

..., the fourth (maximum) group 1! ! The voltages are set to E1. E,
,E.

Assuming E4, the values of the resistors R7゜R1 to Rs are set so that each analog switch SW to SW is controlled on and off as follows according to the level E of the control signal CTL. ing.

EmuE work...SW work~SW4 is on E, <E≦E2...SWl is off, S2~SW is off E, <E≦E4...SW□~SW3 is off, SW
, is on E, <E ... SW□ to SW4 are off Therefore, if the control signal CTL is below the first reference level E and all analog switches SW□ to SW4 are on, the audio signal at this time The cut-off frequency is the lowest, and a frequency characteristic extending to the lowest region, as shown by the characteristic curve α in FIG. 2, is obtained.

When the control signal CTL exceeds the first reference level E□ and is below the second reference level E2, and the analog switch SW is off and the analog switches SW2 to SW are on, the audio signal at this time Therefore, the cutoff frequency is higher than the +C type. Assuming that the frequency characteristic of the audio signal at this time is represented by the characteristic curve shown in FIG. 2, this cutoff frequency +02 is 1257. Similarly, as the level of the control signal CTL rises, the cutoff frequency becomes the following margin 9c,=2πR,C.

If the frequency characteristics of the audio signals are characteristic curves c, d, and e in Fig. 2, then the cutoff frequency) c3 r
"f c41 jc5 are each 250) (z, 500H
z.

1 becomes 7.

As described above, the frequency range of the audio signal can be changed depending on the noise level.

In the above embodiment, the nine frequency ranges are changed by changing the region to be cut on the low frequency side of the audio signal depending on the noise level. 2 to 4k) Iz region) may be emphasized. This further improves the clarity of the sound. For this purpose, for example, in FIG.
3 and the rear-stage amplifier 15, a plurality of circuits for emphasizing different high frequencies and an analog switch for switching these circuits according to the level of the control signal CTL may be provided.

Moreover, each of the above numerical values is shown as an example for convenience of explanation, and the present invention is not limited to these numerical values.

Furthermore, in FIG. 3, when the level of the control signal CTL is zero, the voltage V at one point P, 9, is the minimum, but in this case, the voltage V at one point P may be the maximum. At this time,
Each analog switch SW~SW4 is turned on when the voltage V~v4 at points P~P4 is above a predetermined level, and turned off when it is below this predetermined level, and the control signal CT
As the level of L increases, analog switch sw4
．． sw3゜sw2. What is necessary is to change from on to off in the order of sw□.

〔Effect of the invention〕

As explained above, according to the present invention, since the frequency range of the audio signal can be changed according to the noise level inside the vehicle, the noise and the reproduced sound can be separated in terms of frequency. It is possible to prevent the deterioration of the sound quality due to noise as much as possible, and to prevent the deterioration of the clarity of the sound due to noise, and it is possible to solve the problems of the above-mentioned conventional technology and provide a sound reproducing device for a vehicle with excellent functions. .

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a vehicle sound reproducing device according to the present invention, and FIG. 2 is a characteristic diagram showing an example of a frequency range change of an audio signal with respect to a noise level caused by the frequency and range control circuit in FIG. 1. , FIG. 3 is a block diagram showing a specific example of the frequency range control circuit in FIG. 1. 3... Frequency range control circuit, 6... Speaker. 7...Sound collection microphone, 8...Noise detector, 9.
...Control signal generator.

Claims (1)

[Claims] 1. In a vehicle sound reproducing device installed in a vehicle interior, which supplies an audio signal from an audio signal generation source to a voice generating means, and which enables desired sounds to be heard in the vehicle interior, the sound inside the vehicle interior is collected. a noise detector that detects an output signal of the microphone as a noise signal; a control signal generator that generates a control signal according to the output level of the noise detector; 1. A sound reproducing device for a vehicle, comprising: a frequency range control circuit for changing the frequency range; and an audio signal from the audio signal generation source is supplied to the generation means via the frequency range control circuit.