JPH0453995A - Measuring instrument for acoustic characteristic in car room - Google Patents

Abstract

PURPOSE:To prevent the sense of discomfort from being given to a person in a car room by stopping the measurement of an acoustic characteristic by a controller, when it is displayed that a person is not seated by an output of a seat switch provided on a seat of a vehicle. CONSTITUTION:A seat switch 16 is provided on the lower part of a seat 15 in a car room 10, and when this seat switch 16 is, for instance, turned off and it is shown that a person is not in the car room 10, an operation of a controller 2 is stopped. In such a way, only when the seat switch 16 shows a state that a driver is absent, a whie noise is outputted from a loudspeaker 14, and by executing adaptively the control from outputs of its white noise source and microphone 13, an acoustic characteristic in the car room extending from the loudspeaker 14 to the microphone 13 is measured. In such a way, the acoustic characteristic can be measured without giving a sense of discomfort to a person.

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 compartment inside the vehicle 1, 11 is an engine, and 12 is an engine vibration sensor (a knock sensor may be used) that directly detects the engine vibration of the engine 11, 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 paranormal, descent 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(i+1)=h(i)
+2, l/e(n)X(ni) updated every sample. However, i-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 is obtained by performing a convolution operation in which the filter coefficient is multiplied by and added to the engine vibration X (nl) of each sample.

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) −
y (n) is generated and the filter coefficients are updated again using the LMS algorithm based on this, it is possible to gradually identify the inverse transfer function G-' of the transfer function G of the vibration system in the vehicle interior. The microphone output e (n) can be converged to the minimum value.

However, with such a vehicle interior noise reduction device,
When the sound is high or the distance between the speaker microphones is large, the operation becomes unstable, the convergence time is delayed, and the residual noise reduction effect deteriorates unless consideration is given to the transmission delay between the speaker microphones.

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 CD 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 GD is not provided.

The filter 26 in this case differs from the filter shown in FIG. 3 only in that it has fixed tap coefficients h1 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 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 GD'
An equivalent circuit when using the filter 26 shown in FIG. 8 is shown in FIG. GC to the speaker 14, of which the transfer characteristic CD was measured as described above, so only the remaining transfer characteristic GC is identified by the adaptive filter 22.

The reason why the vehicle interior acoustic characteristics CD' 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.

[Problem to be solved by the invention]

In conventional equipment for measuring vehicle interior acoustic characteristics,
Since white noise is output from the speaker as sound,
There is a problem in that if this is done while there are people inside the vehicle, it will cause discomfort.

Accordingly, an object of the present invention is to realize an apparatus that can measure the acoustic characteristics of a vehicle interior while confirming that no person is present in the vehicle interior.

[Means to solve the problem]

The measuring device for the acoustic characteristics of a vehicle interior according to the present invention includes a speaker provided in the vehicle interior, a microphone provided near the ear of a sort in the vehicle interior, a seat switch, and a white noise source, and the switch is in a state where the driver is not present. a controller that outputs the white noise source from the speaker and performs adaptive control based on the white noise and the output of the microphone to measure the acoustic characteristics of the vehicle interior from the speaker to the microphone. This solves the above problems.

[For production]

In the vehicle interior acoustic characteristic measuring device according to the present invention, a switch is provided on the seat of the vehicle, and when the output of the seat switch indicates that no person is sitting on the seat, the controller that receives this output measures the acoustic characteristics. Measurements are stopped so as not to cause discomfort to people inside the vehicle.

〔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. A seat switch 16 is provided at the bottom, and the operation of the controller 2 is stopped when the seat switch 16 is turned off, indicating that there is no person in the vehicle interior 10.

In this case, the seat switch 16 may be provided only on the driver's seat, but it may also be provided on the passenger seat or rear seat.
Preferably, the operation of the controller 2 is stopped only when any seat switch is turned off.

Additionally, it is preferable to measure this acoustic characteristic with the engine stopped. Therefore, in order to measure with the engine stopped and no one in the vehicle, it is necessary to switch the engine key switch (not shown). ) during the period in which the power is maintained as a normal self-holding period after turning off the seat switch 1.
6 is turned off.

Furthermore, when the controller 2 stops operating, the adaptive filter 2
Since it is undesirable to reset the tap coefficient of 2, it is preferable to use a switch 28 that opens when the output of the sheet switch 16 is off, as shown by the dotted line in FIG.

〔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 seat switch indicates the driver's absence state, and the white noise is adaptively adjusted from the white noise source and the output of the microphone. Since the vehicle interior acoustic characteristics from the speaker to the microphone are measured by controlling the vehicle interior, the acoustic characteristics can be measured without a person being present in the vehicle interior, that is, without causing discomfort to the person.

[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
Figure 6 is a block diagram showing a filter having the measured vehicle interior acoustic characteristics. 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, l is a vehicle, 2 is a controller, 10 is a passenger compartment, 11 is an engine, 13 is a microphone, 14 is a speaker, 1
Reference numeral 6 indicates a sheet switch, and reference numeral 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 seat switch, and a white noise source, and the white noise is emitted from the speaker only when the switch indicates that the driver is not present. A controller for measuring vehicle interior acoustic characteristics from the speaker to the microphone by performing adaptive control based on the output of the white noise source and the microphone. .