JPH0746280B2 - Vehicle interior acoustic characteristics measurement device - Google Patents

Description

The present invention relates to a device for measuring acoustic characteristics of a vehicle interior, and more particularly to a vehicle interior used for a device that actively reduces low-frequency noise in a vehicle interior closed space such as an automobile. The present invention relates to a device for measuring acoustic characteristics.

[Conventional technology]

The noise in the interior of a vehicle such as an automobile is caused by the resonance phenomenon of the interior of the closed space under certain conditions.
It is considered that the exciting force is due to the rotational order component due to the explosion of the engine.

Attempts have been made recently to adaptively reduce such vehicle interior noise, one example of which is shown in FIG.

In the figure, 1 is a vehicle such as an automobile, 10 is a vehicle interior in the vehicle 1, 11 is an engine, 12 is an engine vibration sensor (which may be a knock sensor) that directly detects engine vibration of the engine 11, or an engine based on the engine speed. An engine speed sensor for detecting the vibration frequency of the vehicle, a microphone 13 for detecting the noise level in the vehicle interior 10, a speaker 14 for producing a noise for reducing noise, and a seat 15 in the vehicle interior 10.

Further, 2 is a controller for identifying the inverse transfer function of the transfer function of the vibration system of the vehicle body excited by the vibration of the engine by the outputs of the sensor 12 and the microphone 13, and A / A for converting the analog output of the sensor 12 into a digital output. A D converter 21, an adaptive filter 22 for inputting the digital output of the A / D converter 21, a D / A converter 23 for converting the digital output of the adaptive filter 22 into an analog signal, and an amplifier for amplifying this analog signal. The power amplifier 24 to be supplied to the speaker 14 and the analog output of the microphone 13 are converted into digital signals to be supplied to the adaptive filter 22 A /
It is composed of a D converter 25.

FIG. 3 shows a well-known example of the adaptive filter 22 shown in FIG. 2, and as the adaptive algorithm in this case, the well-known steepest descent method, learning identification method, LMS method, etc. can be mentioned. Uses the LMS method.

In the figure, Z ^-1 indicates a delay element for delaying the engine vibration X (n) for each sample, and h (0) -h
( _N- 1) is a filter (tap) coefficient for multiplying the output signal of each delay element Z- ¹ and each filter coefficient is
It is updated sample by sample according to the LMS algorithm, i.e. h ( _n- 1) = h ( _n ) +2 [mu] e ( _n ) X ( _n ). However, n = 0 ... i, μ
Is the step size 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 of multiplying and adding the engine vibration X (n) of each sample by the filter coefficient.

The output e (n) = Y (n) -y (n) from the microphone 13 is generated by subtracting this spiga output y (n) from the sound pressure Y (n) actually observed at the driver's ears. Then, if the filter coefficient is updated again for each sample by the LMS algorithm, the inverse transfer function G ^-1 of the transfer function G of the space transfer system in the vehicle interior can be identified in real time, and the microphone output e ( n) can be converged to the minimum value.

However, in such a vehicle interior noise reduction device,
When the distance between the speaker and the microphone is large, the transmission delay between the speaker and the microphone is not taken into consideration, so the operation becomes unstable, the convergence time is delayed, and the effect of reducing residual noise becomes poor. It may fall out of control.

Therefore, a system as shown in Fig. 4 in consideration of the spatial transfer characteristic GD between the speaker microphones has already been considered.

That is, the spatial transfer characteristics between the speaker microphones measured in advance
By inserting the GD filter 26 in front of the adaptive filter 22, adaptive control can be performed from the beginning in consideration of the transmission delay between the speaker and the microphone. As shown in FIG. The degree of convergence is improved and the effect of reducing residual noise is also improved as compared with the case where no is prepared.

Filter 26 in this case, only that it has a tap coefficient H1～h _n fixed obtained by the measurement as shown in FIG. 6 is a third
It is different from the filter in the figure.

FIG. 7 shows a device for measuring the spatial transfer characteristic GD between the speaker and the microphone.
A white noise (random number sequence) source 27 is provided in the controller 2 without using the vibration component from 11, and 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. Then, the white noise signal is output from the speaker 14, picked up by the microphone 13 via the passenger compartment 10, converted into a digital signal by the A / D converter 25, and the adaptive filter 22 is controlled.

However, in this case, since the output itself of the filter 22 is not output to the space, it is slightly different from the adaptive filter of FIG. 3, and instead of the ear noise Y (n), the output of the microphone 13 is used. The adaptive control is performed by the LMS algorithm so that the error e (n) from the output (corresponding to y (n) in FIG. 3) is minimized.

An equivalent circuit is shown in Fig. 8 in the case of using the filter 26 in which the transfer characteristic actually measured in this way is GD ', and the transfer characteristic from the engine mount to the microphone 13 is shown.
GP is the true spatial transfer characteristic from speaker 14 to microphone 13.
Transfer characteristics GC from GD and engine mount to speaker 14
Since the transfer characteristic GD among these is measured as described above, only the remaining transfer characteristic GC is identified by the adaptive filter 22.

The reason why the vehicle interior acoustic characteristic GD ′ is obtained by measurement is as follows.
Regarding the spatial acoustic characteristics between the speaker and microphone, the amplifier that generates the speaker output changes the characteristics of the built-in electronic circuit due to changes over time and changes in the atmospheric temperature and humidity of each vehicle environment, and the previously measured acoustic This is because the value will be different from the characteristic, and the filter having the acoustic characteristic GD ′ thus measured will be replaced, for example, at the time of regular inspection of the vehicle.

[Problems to be Solved by the Invention]

In such a conventional device for measuring the acoustic characteristics of the vehicle interior,
When the measurement is performed with the door open, there is a problem that the acoustic characteristics of the vehicle interior space are significantly changed, resulting in an incorrect measurement result.

Therefore, it is an object of the present invention to realize an apparatus capable of confirming that a door is not opened and measuring the acoustic characteristics of a vehicle compartment.

[Means for Solving the Problems]

In the vehicle interior acoustic characteristic measuring device according to the present invention, a speaker provided in the vehicle interior, a microphone provided at a position near the ear of the seat in the vehicle interior, a door switch, and a white noise source, the switch closing the door. A controller that outputs the white noise from the speaker only when the state is indicated and performs adaptive control from the white noise source and the output of the microphone to measure the in-vehicle acoustic characteristic from the speaker to the microphone. By providing, the above-mentioned subject is solved.

[Action]

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 in the open state, the controller which receives the switch measures the acoustic characteristic. It does so and eliminates false measurements of the acoustic properties of the passenger compartment.

〔Example〕

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

In this case, the door switch 16 may be provided only in the door of the driver's seat, but in addition, it is also provided in the doors of the passenger seat and the rear seat, and the operation of the controller 2 is performed only when both door switches are turned off. Is preferably performed.

Further, it is preferable that the measurement of the acoustic characteristic is performed in a state where the engine is stopped. Therefore, in order to perform the measurement with the engine stopped and the door closed, the door switch 16 is turned off during the period when the power is retained as the normal self-retention period after the key switch (not shown) of the engine is turned off. If so, it is possible to measure.

Further, when the operation of the controller 2 is stopped, the adaptive filter 22
Since it is not preferable to reset the tap coefficient of No. 2, it is preferable to use the switch 28 that is closed when the output of the door switch 16 is off, as shown by the dotted line in FIG.

〔The invention's effect〕

As described above, in the vehicle interior acoustic characteristic measuring device according to the present invention, the white noise is output from the speaker only when the door switch indicates the closed state of the door, and the white noise source and the output of the microphone are applied. Since it is configured to control the acoustic characteristics of the vehicle interior from the speaker to the microphone, it is possible to avoid measurement in the open door state where the acoustic characteristics of the vehicle interior space change significantly, and to maintain accurate The measurement result is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a vehicle interior acoustic characteristic measuring device according to the present invention, and FIG. 2 is a block diagram showing an example of a conventional vehicle interior noise reducing device. 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 which is an improvement of the conventional example of FIG. 2, and FIG. 2 is a graph for comparing the conventional examples of FIG. 2 and FIG. 4 in the degree of convergence, FIG. 6 is a block diagram showing a filter having the vehicle interior acoustic characteristics obtained by measurement, and FIG. FIG. 8 is a block diagram showing a conventional vehicle interior acoustic characteristic measuring device, and FIG. 8 is a block diagram showing an equivalent circuit of the vehicle interior noise reducing device of FIG. In the figure, 1 is a vehicle, 2 is a controller, 10 is a passenger compartment,
11 is an engine, 13 is a microphone, 14 is a speaker, 16 is a door switch, and 22 is an adaptive filter. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A speaker provided in a vehicle compartment, a microphone provided at a position near an ear of a seat in the vehicle compartment, a door switch, and a white noise source, and only when the switch indicates a closed state of the door. A vehicle including: a controller that outputs white noise from the speaker, performs adaptive control based on the white noise source and the output of the microphone, and measures a vehicle interior acoustic characteristic from the speaker to the microphone. Measuring device for room acoustic characteristics.