JPH05121983A - On-vehicle audio equipment - Google Patents

Abstract

PURPOSE:To detect noise well corresponding to a listening sense by using a microphone so as to detect noise and estimating the quantity of noise based on the drive speed of a concerned vehicle when the detection of noise is difficult. CONSTITUTION:A microphone 2 converts an acoustic signal in a cabin into an electric signal, a noise level detector 3 converts the signal into a level signal corresponding to the quantity of noise, and the converted signal is given to a controller 9. On the other hand, a sound signal level detector 7 converts a sound signal being the output of a sound volume sound quality control means 4 into a level signal representing an amplitude and gives the converted signal into the controller 9. The controller 9 compares a microphone input voltage level with an in-cabin reproduction sound pressure level assumed from the sound signal level and adopts the former to represent the in-cabin noise only when the former is sufficiently larger. When the condition is not satisfied, the control is implemented by estimating the in-cabin noise quantity from a vehicle velocity based on a vehicle velocity detection means. Thus, the sound volume is adjusted automatically and properly independently of the drive state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise detecting method for an on-vehicle acoustic device having a function of automatically adjusting reproduction volume and sound quality according to the amount of noise in a vehicle compartment.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional vehicle-mounted acoustic device disclosed in, for example, Japanese Patent Laid-Open No. 62-89830, in which 1 is an audio signal source, 10 is a noise detection pickup, and 3 is a noise detection pickup. Is a noise detector, 11 is a VCA
(Voltage Controlled Ampli
5) is an amplifier and 6 is a speaker.

Next, the operation will be described. In an on-vehicle audio system, the noise level in the vehicle compartment is different when the vehicle is stopped and when the vehicle is running. Therefore, even if the device is adjusted to a sufficient volume when the vehicle is stopped, the noise level increases when the vehicle starts running The volume part is masked and I feel the lack of volume.

This on-vehicle audio system is provided with noise pickup means 2 such as a microphone / vibration sensor, and the noise level detection circuit 3 causes the pickup means 10 to pick up noise.
The noise level in the passenger compartment is detected from the detection signal from the
A11 is controlled to change the amplification degree with respect to the signal from the audio signal source 1 according to the noise level in the vehicle interior. When the noise level in the vehicle interior increases, the playback volume is automatically adjusted accordingly. Therefore, when stopped
This is to give an appropriate volume regardless of whether the vehicle is running.

[0005]

In the conventional vehicle-mounted acoustic device, a vibration sensor or a microphone is used for noise detection. Therefore, when using a vibration sensor,
Depending on the mounting position and mounting method, even if the noise level in the passenger compartment is the same, the output will differ greatly, and in addition to the problem that many components that are not related to the annoyance of actual noise will be detected, traveling in a tunnel Since the noise coming from outside the vehicle cannot be detected when the vehicle is running or when running in parallel with another large vehicle, there is a problem in that the volume of the result of the automatic adjustment is not always proper in hearing.

Further, when a microphone is used, the reproduced sound from the vehicle-mounted acoustic device is also detected as noise,
There is a problem that it is difficult to constantly detect only the target noise.

The present invention has been made to solve the above-mentioned problems. As a main means for noise detection, a microphone is used to detect noise over the entire voice band and the influence of reproduced sound is great. When noise detection is difficult, it is possible to detect noise that is audible and compatible by estimating the amount of noise using the vehicle's running speed (vehicle speed) as a clue, and equipped with an audio volume control function that is appropriate for hearing. The purpose is to obtain a sound device.

[0008]

An on-vehicle audio system according to the present invention comprises a microphone, a sound quality volume control means, a control device connected to the sound quality volume control means, and a microphone input sound pressure level connected to the control device. A noise level detector for detecting, a voice signal level detector connected to the control device, and a vehicle speed detection means connected to the control device, wherein the control device detects the microphone input sound pressure level and the voice signal level. A comparison is made with an assumed vehicle interior reproduced sound pressure level, and only when the microphone input sound pressure level is sufficiently high, the microphone input sound pressure level represents vehicle interior noise, and when this condition is not satisfied, It has means for estimating the noise amount in the vehicle compartment from the vehicle speed and controlling the sound quality and volume.

Further, the control device compares the sound pressure level input to the microphone with the sound pressure level reproduced in the vehicle interior that is assumed from the sound signal level, and only when the sound pressure level input to the microphone is sufficiently large, the microphone input is performed. If the sound pressure level represents vehicle interior noise, and this condition is not satisfied, the noise amount obtained from the change in vehicle speed from the time when the noise amount was detected, with respect to the noise amount detected from the microphone sound pressure at the end. It has a means for correcting the variation and estimating the noise amount in the vehicle compartment.

Furthermore, the control device compares the sound pressure level of the microphone input with the sound pressure level reproduced in the vehicle cabin that is assumed from the sound signal level, and only when the sound pressure level of the microphone input is sufficiently high. It is assumed that the input sound pressure level represents the vehicle interior noise, and if this condition is not satisfied, the estimated value of the vehicle interior noise amount is calculated from the noise amount detected from the microphone sound pressure at the end to the noise amount obtained from the vehicle speed. It has means for processing so as to be asymptotic.

[0011]

In the control device of the present invention, it is appropriate that the signal detected by the microphone is regarded as noise by estimating the vehicle interior noise amount from the vehicle speed and calculating and comparing the microphone input sound pressure level and the voice signal level. It is determined whether or not the estimated value from the vehicle speed and the microphone input sound pressure are selected as appropriate noise data, and volume / sound quality control is performed based on this.

[0012]

Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is an audio signal source,
Reference numeral 2 is a microphone, 3 is a noise level detector, 4 is sound quality volume control means, 5 is an amplifier, 6 is a speaker, 7 is a voice signal level detector, 8 is vehicle speed detection means, and 9 is a control device.

In this on-vehicle audio system, the microphone 2 converts an acoustic signal in the vehicle interior into an electric signal, and this signal is noise by the noise level detector 3 with an appropriate time response characteristic matching the auditory response characteristic to noise. After being converted into a level signal corresponding to the quantity, it is given to the control device 9. on the other hand,
The voice signal level detector 7 converts the voice signal, which is the output of the sound quality / volume control means 4, into a level signal substantially representing its amplitude, with the same characteristics as the noise level detector 3.

Here, the sound quality and volume control device 4 uses the V of the conventional example.
CA may be used, and in this case, only the volume is controlled, but it is well known that a digital signal processing device can be used in place of the VCA to realize an equivalent function. Accordingly, it becomes possible to give an appropriate sound quality change together with the change of the volume.

As described above, the signal detected by the microphone contains the component of the acoustic signal reproduced from the on-vehicle acoustic device itself, and if it is detected as noise, it increases as the reproduced sound increases. Furthermore, a vicious cycle (positive feedback operation) of increasing the reproduction volume is caused, and finally the volume is increased to the maximum of the control range.

In order to eliminate this inconvenience, the control device 9 refers to the output of the audio signal level detector 7 and determines whether or not the output of the noise level detector 3 is determined to be due to noise. This point will be described in detail below.

First, the signal detected from the microphone 2 is generated by the acoustic signal reproduced by the vehicle-mounted audio device if the noise in the vehicle interior is sufficiently low and there is an audio signal level to some extent, and passes through the vehicle-mounted audio device. It can be considered that it has a high correlation with the electrical signal.

Specifically, in this embodiment, the output of the sound quality / volume control means 4 is detected by the audio signal level detector 7, but the output of the sound quality / volume control means 4 is simultaneously amplified by the amplifier 5 and the speaker 6 is used. Will be played back in and will enter the microphone 2 through the vehicle interior space. Accordingly, if the fidelity of the amplifier 5 is sufficiently high and the electroacoustic conversion of the speaker 6 and the acoustoelectric conversion of the microphone 2 are ideally performed and the influence of reflection in the vehicle interior space can be ignored, the microphone is used. The detected signal is obtained by simply multiplying the input signal of the amplifier 5 by the amplification factor of the amplifier 5 and the conversion efficiency of the speaker 6 and the microphone 2 to give a delay equivalent to the passenger compartment space.

Therefore, the signal obtained from the microphone 2 in this ideal case is basically due to the sound pressure in which the reproduced voice and other noise are combined. That is, in this ideal case, comparing the signal obtained from the microphone 2 with the signal obtained by multiplying the output signal of the sound quality volume control means 4 by an appropriate coefficient to give a delay, when the vehicle interior is quiet, both signals are compared. Are substantially the same, and if there is noise in the vehicle compartment, it is considered that the detection signal from the microphone 2 is correspondingly increased.

As described above, in the ideal case, the level of the microphone detection signal is compared with the level of the electrical signal in the vehicle-mounted audio device with an appropriate coefficient and a slight delay to compare the level of the noise in the vehicle interior. It is clear that the presence or absence of the noise can be detected and the noise level can be estimated when the audio reproduction sound is smaller than the vehicle interior noise.

In an actual vehicle-mounted acoustic device, it is difficult to obtain a speaker having a flat frequency characteristic in the entire audio band, and the transmission characteristic of the vehicle interior space greatly changes in the frequency characteristic due to reflection of glass windows, wall surfaces, etc. It has a peak dip), and because a normal on-vehicle audio system uses multiple speakers, there are variations in frequency characteristics due to interference between the speakers at the microphone position. A difficult difference comes out.

Therefore, when the output of the noise level detector 3 and the output of the voice signal level detector 7 are compared in the control device 9, when the microphone detection level is simply higher than the average level expected from the voice signal level. If this is taken as the noise level, the positive feedback operation will still occur in the frequency band where the frequency characteristic peaks.
For this reason, in order to determine that the microphone detection signal level is due to vehicle interior noise, the condition that the output of the noise level detector 3 is larger than that due to the reproduced audio signal assumed from the audio signal level with an appropriate margin. Need to impose.

If this margin is increased, the risk of falling into the positive feedback operation is reduced, but it becomes difficult to detect noise. Therefore, it is important for this noise detection method to properly determine this margin, but empirically this is about 6 to 12 dB. As described above, in this method, the noise can be detected only in a state in which the noise is considerably larger than the reproduced voice, but in the vehicle-mounted acoustic device, the volume sound quality control is actually required.
Since it is recognized that the noise level is high enough to mask the reproduced audio signal, there is little practical problem.

However, in the case of reproducing music having a high level on average, noise cannot be detected when the reproduced sound level is high only by the above-described method, so that there is a problem that the detected noise data is scattered in time. is there. If the volume control is applied as it is based on this scattered data, even if the previous value is held for a period during which noise cannot be detected, if the noise amount changes significantly at the next noise detection, a considerably large amount at that time Will be applied, which will cause the listener to feel uncomfortable as a sudden change in volume. Therefore, even when noise cannot be detected by the above method, it is desirable to continue estimating the noise level by some auxiliary method.

The present invention uses vehicle speed for this purpose. FIG. J. W. The article "Noise-Dependent Sound Re by Kitzen et al.
production in a Car: Appl
ication of a Digital Audio
o Signal Processor "(J. Aud
io Eng. Soc. , Vol. 36, No. 1 /
2, 1988), which shows that the amount of noise is approximately proportional to the vehicle speed if the traveling road surface conditions are the same. Therefore, when the noise detection by the noise level detector 3 becomes impossible, the previous value is simply held by paying attention to the change in the vehicle speed and correcting the estimated value of the vehicle interior noise by an amount corresponding to this change. Accurate estimation is possible compared to.

Specifically, noise is detected at substantially equal time intervals, and the noise level detector 3 can detect noise up to a certain point of time, and the estimated noise level at that time is Nn-.
1. If the vehicle speed is Vn-1, and the noise level detector 3 cannot detect noise at the next time point, the estimated noise value Nn at that time is Nn = Nn-1 + (Vn-Vn-1). This is equivalent to obtaining as A ... (1). However, Vn is the vehicle speed at the time of calculation, and A is the slope of the vehicle speed versus noise curve under the average road surface condition of FIG.

FIG. 2 shows the control device 9 relating to the above noise detection.
3 is a flowchart showing the operation of FIG. This will be described below. However, FIG. 2 shows only a part relating to the noise detection operation which is the main point of the present invention. The other parts are the same as those in the conventional vehicle-mounted acoustic device equipped with a control device such as a microcomputer. This processing is regularly performed at appropriate time intervals, and the processing is to be periodically moved to the start 20.

Next, in step 21, the vehicle speed detecting means 11 detects the vehicle speed Vn at this time. The vehicle speed detecting means 11 is, for example, a wheel speed sensor, which is usually attached to the axle of a vehicle and its teeth are magnetized. It consists of a gear wheel and a reed relay mounted opposite to the gear wheel. The vehicle speed is
The reed relay on / off cycle based on the change in the distance between the magnetized portion of the gear and the reed relay according to the rotation of the axle is given by the shorter the axle rotation speed (the higher the vehicle speed). Therefore, the vehicle speed is obtained by detecting this pulse width and multiplying it by a coefficient determined by the number of teeth of the wheel speed sensor and the diameter of the wheel. Regarding the detection of the pulse period, when a microcomputer is used as the control device 9,
Some have a function of inputting a pulse signal and detecting the cycle thereof.

Next, in process 22, the output of the audio signal level detector 7 is read and converted into a decibel value (this value is set as Sn here). Here, the output of the audio signal level detector 7 is usually given as an analog voltage level, which must be converted into a digital value for reading by a microcomputer as a control device. This kind of AD converter is well known. .. Further, a microcomputer in which this function is incorporated has been put into practical use and need not be described in particular. Next, in process 23, the output of the noise level detector 3 is read and converted into a decibel value (this value is Mn here).

Next, in the judgment processing 24, the values of Mn and Sn + 10 are compared. At this time, the numerical value 10 is the margin of the detection judgment described above. Here, the output of the noise level detector 3 and the sound signal level detection are performed. It is assumed that the output of the device 7 is arranged to be approximately equal when there is no noise in the passenger compartment and there is a suitable audio signal level. This determination process 24
If Mn is larger than Sn + 10, Mn is set as the estimated noise value Nn (process 25). If Mn is smaller than Sn + 10 and the noise cannot be detected from the noise level detector 3, the calculation of the above-mentioned formula (1) is performed in process 26, and
This is the estimated noise value Nn. At this time, Nn in the calculation formula of the process 26 is the estimated noise value obtained in the process one time before, and indicates that the calculation result using this is newly substituted for Nn. Finally, in process 27, the vehicle speed Vn detected in process 21 is substituted for Vn-1 to prepare for the next process, and then the process ends (process 28).

Example 2. In the above embodiment, when the noise level detector 3 cannot detect the noise, the estimated noise value is obtained according to the change in the vehicle speed.
The influence of the noise level immediately before the noise level detector 3 cannot detect noise remains until the noise level detector 3 can detect noise next time. However, under actual driving conditions, the noise in the passenger compartment constantly changes depending on road surface conditions, tunnels, the presence or absence of parallel running vehicles, etc. Therefore, when noise cannot be detected by the noise level detector 3, such a variation range is large. Rather than leaving the effect of the noise level detector 3 output, it is considered appropriate to bring the estimated value from the vehicle speed that corresponds better to a more average noise level.

In this embodiment, when the noise level detector 3 cannot detect the noise, the estimated noise value is made asymptotic to the estimated value from the vehicle speed. Specifically, this can be performed by setting the calculation of the process 26 in the flowchart of FIG. 3 as Nn ← K · Nn + (1-K) · (Vn · A + B) (2). Where K is 0 <K <
It is a constant of 1 and is a coefficient that determines the speed of convergence to the noise value obtained from the vehicle speed. Further, B is a noise level corresponding to a vehicle speed of 0 when the vehicle speed-noise characteristic is linearly approximated. The fact that the desired asymptote can be achieved by this calculation means that this calculation is repeated unless the noise level detector 3 can detect the noise, and the influence of Nn in the first term of the calculation formula is calculated every time the calculation is repeated. It is clear from the fact that it becomes smaller at a rate of several K smaller than 1.

[0033]

As described above, according to the present invention, the noise level in the vehicle compartment can be detected with high accuracy in response to the audible feeling by a relatively simple method in which the microphone detection signal and the vehicle speed information are used in combination. There is an effect that an in-vehicle acoustic device that automatically adjusts the volume appropriately regardless of the situation can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of a device of the present invention.

FIG. 2 is an operation flowchart of the control device according to the first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram in the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional device.

[Explanation of symbols]

 1 Audio signal source 2 Microphone 3 Noise level detector 4 Sound quality volume control means 5 Amplifier 6 Speaker 7 Voice signal level detector 8 Vehicle speed detection means 9 Control device

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

This on-vehicle audio system is provided with a noise pickup means 10 such as a microphone / vibration sensor.
The noise level in the passenger compartment is detected from the detection signal from 0, V
The CA 11 is controlled to change the amplification degree for the signal from the audio signal source 1 according to the noise level in the vehicle interior. When the noise level in the vehicle interior increases, the playback volume is automatically adjusted accordingly. Therefore, it gives an appropriate volume regardless of whether it is stopped or running.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

Claims (3)

[Claims] 1. A microphone and sound quality volume control means,
A control device connected to the sound quality volume control means, a noise level detector connected to the control device for detecting a microphone input sound pressure level, an audio signal level detector connected to the control device, and a control device connected to the control device. And a vehicle speed detecting means, the control device compares the microphone input sound pressure level with the sound pressure level reproduced in the vehicle cabin that is assumed from the audio signal level, and only when the microphone input sound pressure level is sufficiently high. An in-vehicle acoustic device comprising means for performing sound quality volume control by estimating a vehicle interior noise amount from a vehicle speed when the microphone input sound pressure level represents vehicle interior noise, and when this condition is not satisfied. 2. The control device compares a microphone input sound pressure level with a sound pressure level reproduced in a vehicle cabin that is assumed from a sound signal level, and only when the microphone input sound pressure level is sufficiently high, the microphone input is performed. If the sound pressure level represents vehicle interior noise, and this condition is not satisfied, the noise amount obtained from the change in vehicle speed from the time when the noise amount was detected, with respect to the noise amount detected from the microphone sound pressure at the end. The vehicle-mounted acoustic apparatus according to claim 1, further comprising means for correcting a change amount and estimating a vehicle interior noise amount. 3. The control device compares the sound pressure level of the microphone input with the sound pressure level reproduced in the vehicle cabin that is assumed from the sound signal level, and only when the sound pressure level of the microphone input is sufficiently large, the microphone input is performed. If the sound pressure level represents the vehicle interior noise, and if this condition is not satisfied, the estimated value of the vehicle interior noise amount is asymptotic to the noise amount obtained from the vehicle speed from the noise amount detected from the microphone sound pressure at the end. The vehicle-mounted acoustic device according to claim 1, further comprising a processing unit for performing the processing.