JPH0453996A - Measuring instrument for acoustic characteristic in car room - Google Patents

Abstract

PURPOSE:To avoid the erroneous measurement of an acoustic characteristic of a space in a car room by stopping the measurement of the acoustic characteristic by a controller, when it is shown that a door is not in an open state by the output of a door switch provided on the door of a vehicle. CONSTITUTION:A door switch 16 is provided on a door of a vehicle 1, and when this door switch 16 is, for instance, turned off and it is shown that the door is closed, an operation of a controller 2 is stopped. In such a way, only when the door switch 16 shows state that the door is opened, a white noise is outputted from a loudspeaker 14, and by executing adaptively the control from outputs of its white noise source and a microphone 13, and acoustic characteristic in a car room extending from the loudspeaker 14 to the microphone 13 is measured. In such a way, the measurement in a door open state that the acoustic characteristic of a space in the car room is greatly varied can be avoided.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for measuring the acoustic characteristics of a vehicle interior, and particularly to a device for actively reducing low-frequency noise in a closed space inside a vehicle such as a vehicle. The present invention relates to an acoustic characteristic measuring device.

[Conventional technology]

Noise inside a vehicle such as a car is caused by the resonance phenomenon that occurs in the cabin, which forms a closed space, under certain conditions.
The vibrational force that is the cause of this is thought to be due to the rotational vibration component of the engine.

Recently, attempts have been made to adaptively reduce such vehicle interior noise, an example of which is shown in FIG.

In the figure, 1 is a vehicle such as a car, 10 is a passenger compartment in vehicle 1, 11 is an engine, and 12 is an engine vibration sensor (a knock sensor may also be used) that directly detects the engine vibration of engine 1, or an engine based on the engine rotation speed. 13 is a microphone that detects the noise level in the vehicle interior 10, 14 is a speaker that generates a sound to reduce the noise, and 15 is a seat in the vehicle interior 10.

Further, 2 is a controller that identifies the inverse transfer function of the transfer function of the vibration system of the vehicle body excited by the vibration of the engine using the outputs of the sensor 12 and the microphone 13, and the controller 2 that converts the analog output of the sensor 12 into a digital output. D converter 21
, an adaptive filter 22 that inputs the digital output of the A/D converter 21, a D/A converter 23 that converts the digital output of the adaptive filter 22 into an analog signal, and amplifies this analog signal and provides it to the speaker 14. power amplifier 2
4, and an A/D converter 25 that converts the analog output of the microphone 13 into a digital signal and provides it to the adaptive filter 22.

FIG. 3 shows a well-known example of the adaptive filter 22 shown in FIG. 2, and examples of adaptive algorithms in this case include the well-known acute subrenal method, learning identification method, LMS method, etc. , here the LMS method is used.

In the figure, Z-1 indicates a delay element for delaying engine vibration X (n) for each sample, and h (0) to h(
n-1) is a filter (tap) coefficient for multiplying the output signal of each delay element z-1, and each filter coefficient is determined by the LMS algorithm, that is, h (++1)-h
(i) + 2 u e (n)X (ni) updated sample by sample. However, 1-0...n and μ are the step sizes described above.

By selecting the step size μ in this case, the output signal y (n) to the speaker 14 can be obtained by multiplying the filter coefficient by the engine vibration X (nl) of each sample and performing convolution by multiplying it by the previous page. .

By subtracting this speaker output y (n) from the sound pressure Y (n) actually observed near the driver's ear, the output from the microphone 13 e (n) = Y (n)
3' (n) is generated, and based on this, LMS
By updating the filter coefficients using an algorithm, it is possible to gradually identify the inverse transfer function G -1 of the transfer function G of the vibration system in the vehicle interior, and it is possible to converge the microphone output e (n) to the minimum value. can.

However, in such a low fIi device for vehicle interior noise, when the sound is high or the distance between the speaker microphones is large, the transmission delay between the speaker microphones is not taken into account, so the operation becomes unstable and the convergence time is delayed. The residual noise reduction effect deteriorates.

Therefore, a system as shown in FIG. 4, which takes into consideration the spatial transfer characteristic GD between speaker microphones, has already been considered.

That is, by inserting the filter 26 with the spatial transfer characteristic GD between the speaker microphones measured in advance before the adaptive filter 22, adaptive control can be performed from the beginning in consideration of the transmission delay between the speaker microphones. As shown in FIG. 5, the degree of convergence is improved and the effect of reducing residual noise is also improved compared to the case where the spatial transfer characteristic CD is not prepared.

The filter 26 in this case is different from the filter shown in FIG. 3 only in that it has fixed tap coefficients hl to hn obtained by measurement as shown in FIG.

Such a device for measuring the spatial transfer characteristic CD between speaker microphones is shown in FIG. The white noise is converted into an analog signal by the D/A converter 23 and the amplifier 24 without passing through the adaptive filter 22, and is output to the speaker 1.
4, this white noise signal is picked up by the microphone 13 via the passenger compartment 10, and converted into a digital signal by the A/D converter 25 to control the adaptive filter 22.

However, in this case, the output of the filter 22 itself is not output to space, so it is slightly different from the adaptive filter shown in FIG.
Instead of the ear noise Y (n), use the output of the microphone 13,
This microphone output and the output of the filter itself (y in Figure 3 (
L so that the error e (n) with respect to
Adaptive control is performed by the MS algorithm.

The transfer characteristic actually measured in this way is CD'
An equivalent circuit when using the filter 26 shown in FIG. 8 is shown in FIG. Since the transfer characteristics C and D of these are measured as described above, only the remaining transfer characteristics GC will be identified by the adaptive filter 22.

The reason why the vehicle interior acoustic characteristics GD' is determined by measurement is that the amplifier that generates the speaker output with respect to the spatial acoustic characteristics between the speaker microphones changes over time and due to changes in the atmospheric pressure, temperature, humidity, etc. of each vehicle environment. This is because the characteristics of the built-in electronic circuit will change, resulting in a value different from the previously measured acoustic characteristic.A filter with the acoustic characteristic GD" measured in this way may be used, for example, during periodic vehicle inspections. It will be replaced from time to time.

[Intelligence to be solved by the invention] In such a conventional device for measuring vehicle interior acoustic characteristics,
If measurements were taken with the doors open, the acoustic characteristics of the interior space of the vehicle would have changed significantly, resulting in incorrect measurement results.

Therefore, an object of the present invention is to realize a device that can confirm that the door is not open when measuring the acoustic characteristics of a vehicle interior.

[Means to solve the problem]

The vehicle interior acoustic characteristic measuring device according to the present invention includes a speaker provided in the vehicle interior, a microphone provided near the ear of a seat in the vehicle interior, a door switch, and a white noise source. a controller that outputs the white noise from the speaker only when a state is indicated, performs adaptive control based on the output of the white noise source and the microphone, and measures the acoustic characteristics of the vehicle interior from the speaker to the microphone; By preparing for this, the above issues are solved.

[For production]

In the vehicle interior acoustic characteristic measuring device according to the present invention, a switch is provided on the door of the vehicle, and when the output of the door switch indicates that the door is not open, the controller receives the output and starts measuring the acoustic characteristic. This eliminates false measurements of the acoustic characteristics of the vehicle interior.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the vehicle interior acoustic characteristic measuring device according to the present invention.The difference between the present invention and the conventional measuring device shown in FIG. is provided, and the operation of the controller 2 is stopped when the door switch 16 is turned off, indicating that the door is closed, for example.

In this case, the door switch 16 may be provided only on the driver's seat door, but it may also be provided on the passenger seat and rear seat doors, and the controller 2 will operate only when either door switch is turned off. It is preferable to stop.

Also, it is preferable to measure this acoustic characteristic with the engine stopped. Therefore, to measure with the engine stopped and the door closed, turn off the engine key switch (not shown). If the door switch 16 is turned off during a period in which the power is maintained as a normal self-holding period after the power is turned off, measurement can be performed.

Furthermore, when the controller 2 stops operating, the adaptive filter 2
Since it is not desirable to reset the tap coefficient of door switch 1, as shown by the dotted line in Figure 1,
It is preferable to use a switch 28 that closes when the output of 6 is off.

〔Effect of the invention〕

As described above, in the vehicle interior acoustic characteristic measuring device according to the present invention, white noise is output from the speaker only when the door switch indicates the closed state of the door, and the white noise is adapted from the white noise source and the output of the microphone. Since the configuration is configured to measure the acoustic characteristics of the vehicle interior from the speaker to the microphone, it is possible to avoid measurements with the doors open, where the acoustic characteristics of the vehicle interior space vary greatly, and to ensure accurate measurements at all times. Measurement results are obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a vehicle interior acoustic characteristic measuring device according to the present invention. FIG. 2 is a block diagram showing an example of a conventional vehicle interior noise reduction device. 4 is a block diagram showing a general configuration of an adaptive filter, FIG. 4 is a block diagram showing an example of a conventional vehicle interior noise reduction device that is an improvement on the conventional example shown in FIG. 2, and FIG. Second
A graph for comparing the degree of convergence between Fig. 4 and the conventional example shown in Fig. 4. Fig. 6 is a block diagram showing a filter having the measured vehicle interior acoustic characteristics. Fig. 7 is a conventional example. FIG. 8 is a block diagram showing an apparatus for measuring vehicle interior acoustic characteristics. FIG. 8 is a block diagram showing an equivalent circuit of the vehicle interior noise reduction device shown in FIG. 4. In the figure, 1 is a vehicle, 2 is a controller, IO is a passenger compartment, 11 is an engine, 13 is a microphone, 14 is a speaker, 1
6 indicates a door switch, and 22 indicates an adaptive filter. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] It includes a speaker installed in the vehicle interior, a microphone installed near the ear of the seat in the vehicle interior, a door switch, and a white noise source, and the white noise is transmitted to the speaker only when the switch indicates the closed state of the door. and a controller that performs adaptive control based on the output of the white noise source and the microphone to measure the acoustic characteristics of the vehicle interior from the speaker to the microphone. Device.