JPH04234098A - Noise reduction device for car compartment - Google Patents

Abstract

PURPOSE:To realize a noise reduction device of a car compartment without making a measurement of the compartment spatial transmission characteristics whenever the number of passengers in the compartment varies. CONSTITUTION:First, switches 16a to 16d are provided at each seat. The outputs of these switches 16a to 16d are used to find out the condition of the passengers, one of the spatial transmission characteristics between a speaker 14 and a microphone 13 which were measured in advance in accordance with various passenger conditions is selected and the inverse spatial transmission characteristic between the car body vibration system and the base of ears is identified. Therefore, no new measurement and updating of the spatial transmission characteristics are required whenever the number of passengers in the car compartment varies.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a vehicle interior noise reduction device, and more particularly to a vehicle interior noise reduction device used in a device that actively reduces low-frequency noise in a closed space inside a vehicle such as an automobile. .

0002

[Prior Art] Noise in the interior of a vehicle, etc., is caused by the resonance phenomenon that occurs in the cabin, which forms a closed space, under certain conditions, and the excitation force that causes this is the rotational vibration of the engine. It is thought that this is due to the ingredients.

Recently, attempts have been made 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 cabin inside the vehicle 1, 11 is an engine, and 12 is an engine 11.
An engine vibration sensor (a knock sensor may also be used) or an engine rotation speed sensor as a means for detecting a reference signal synchronized with the rotation of A speaker is used to generate the signal, and 15 is a seat in the vehicle interior 10.

Further, 2 is a controller that identifies the inverse transfer characteristic of the transfer characteristic of the vibration system of the vehicle body excited by engine vibration by the output of the sensor 12 and the microphone 13, and converts the analog output of the sensor 12 into a digital output. A to do/
A D converter 21, an adaptive filter 22 that inputs the digital output of the A/D converter 21, and a D/A converter 23 that converts the digital output of the adaptive filter 22 into an analog signal.
, a power amplifier 24 that amplifies this analog signal and supplies it to the speaker 14 , and an A/D converter 25 that converts the analog output of the microphone 13 into a digital signal and supplies it to the adaptive filter 22 .

FIG. 4 shows a well-known example of the adaptive filter 22 shown in FIG. 3. Examples of adaptive algorithms in this case include the well-known steepest 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)+2μe(n)
X(ni)

[0008] It is updated for each sample according to [0008]. However, i=0...n, μ is the step size described above.

By selecting the step size μ in this case, the filter coefficients can be adjusted to
By performing a convolution operation of multiplying and adding (n), the output signal y(n) to the speaker 14 is obtained.

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 based on this, LM
By updating the filter coefficients using the S algorithm, it is possible to gradually identify the inverse transfer characteristic G-1 of the transfer characteristic G of the vibration system in the vehicle interior, and the microphone output e(n) can be converged to the minimum value. I can do it.

[0011] However, in such a vehicle interior noise reduction device, operation becomes unstable when the sound is high or the distance between the speaker and the microphone is long because the transmission delay between the speaker and the microphone is not taken into account. The convergence time is delayed and the residual noise reduction effect becomes worse.

[0012] Therefore, a system as shown in FIG. 5 has already been considered, which takes into account the spatial transfer characteristic (acoustic characteristic) GD between the speaker and the microphone.

That is, by inserting a filter 26 with a pre-measured spatial transfer characteristic GD between the speaker and the microphone before the adaptive filter 22, adaptive control is performed from the beginning in consideration of the transmission delay between the speaker and the microphone. It is possible,
As shown in FIG. 6, the degree of convergence is improved and the residual noise reduction effect is also improved compared to the case where the spatial transfer characteristic GD is not provided.

The filter 26 in this case has fixed tap coefficients h1 to hn obtained by measurement as shown in FIG.
It differs from the filter of FIG. 4 only in that it has .

A device for measuring the spatial transfer characteristic GD between the speaker and the microphone is shown in FIG. 8. This device is constructed by switching the control system shown in FIG. White noise (random number sequence) provided in controller 2 instead of using vibration components
The white noise from the source 27 is applied to the adaptive filter 22 and is passed through the D/A converter 23 without passing through the adaptive filter 22.
The white noise signal is converted into an analog signal by the amplifier 24 and output from the speaker 14, and this white noise signal is picked up by the microphone 13 via the passenger compartment 10, converted into a digital signal by the A/D converter 25, and then sent to the adaptive filter 22. It controls the

However, in this case, the output of the filter 22 itself is not output into space, so it is slightly different from the adaptive filter shown in FIG. 4, and the output of the microphone 13 is used instead of the ear noise Y(n), Output of the filter itself (Figure 4
Adaptive control is performed by the LMS algorithm so that the error e(n) with respect to y(n) of y(n) is minimized.

FIG. 9 shows an equivalent circuit when using the filter 26 with GD' having the transfer characteristic actually measured in this way, and this spatial transfer characteristic GD' is shown in FIG.
By being copied to the spatial transfer characteristic GD of
Since the transfer characteristic GD of these was measured as described above, only the remaining transfer characteristic GC is identified by the adaptive filter 22.

It should be noted that the vehicle interior space transfer characteristic GD is determined by measurement.
The reason for determining ' is that the amplifier that generates the speaker output may change over time or due to changes in the atmospheric pressure, temperature, humidity, etc. of each vehicle environment regarding the spatial transfer characteristics between the speaker and the microphone.
This is because the characteristics of the incorporated electronic circuit will change and the value will be different from the previously measured transfer characteristic, and the filter with the transfer characteristic GD' measured in this way will be
For example, it will be updated at the time of periodic inspection of the vehicle.

[0019]

[Problem to be Solved by the Invention] In such conventional vehicle interior noise reduction devices, the vehicle interior transfer characteristics from the speaker to the microphone are first identified using white noise, and based on this, adaptive control is performed using the LMS algorithm. It is carried out.

[0020] Therefore, depending on the number of people riding in the car, the transmission characteristics inside the vehicle change during measurement, and each time it is necessary to switch to the measurement system shown in Figure 8 and re-measure the transmission characteristics from the speaker to the microphone using white noise. However, there were problems in that it was troublesome and caused discomfort to the occupants.

Therefore, an object of the present invention is to realize a device that can reduce vehicle interior noise without having to measure the spatial transmission characteristics inside the vehicle each time the number of passengers in the vehicle changes. do.

[0022]

[Means for Solving the Problems] A vehicle interior noise reduction device according to the present invention includes means for detecting a reference signal synchronized with engine rotation, a speaker provided in the vehicle interior, and a microphone for detecting vehicle interior noise. an adaptive controller that identifies the reverse transfer characteristic of the transfer characteristic from the reference signal to the ear of the vibration system of the vehicle body and controls the speaker so that the input of the microphone is minimized; and a switch provided on each seat. The controller determines the riding state based on the output of the switch, selects one of the spatial transfer characteristics between the speaker and the microphone measured in advance for each riding state, and determines the reverse transfer characteristic. It is characterized by identifying.

[0023]

[Operation] In the vehicle interior noise reduction device according to the present invention, the spatial transmission characteristics between the speaker and the microphone are measured in advance in each riding state corresponding to the number of vehicle occupants. Then, the controller that receives the output signal from the switch installed on each seat determines the current riding condition, selects the space transfer characteristic corresponding to this riding condition, and uses the conventional method based on this space transfer characteristic. By identifying the inverse transfer function,
Control the speaker output so that the microphone input is minimized.

[0024] In this way, even if the number of vehicle occupants changes, the noise inside the vehicle can be optimally reduced without measuring the spatial transmission characteristics one by one.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of a vehicle interior noise reduction device according to the present invention.The difference between the present invention and the conventional device shown in FIG. , 15b, and seat switches 16a and 16b are provided at the bottom of the rear seats 15c and 15d.
6c and 16d are provided.

Further, in this embodiment, the controller 2 has not only one spatial transfer characteristic GD but also the above four spatial transfer characteristics GD.
A filter 30 in which eight spatial transfer characteristics GD1 to GD8 are measured and stored in advance according to the four sheet switches 16a to 16d, and a spatial transfer characteristic GD1 in this filter 30.
This differs from the conventional device shown in FIG. 5 in that a selector 31 is provided for selecting one of the sheet switches 16a to 16d based on the output signals of the sheet switches 16a to 16d. still,
The reason why eight space transfer characteristics GD1 to GD8 are required for the four seat switches 16a to 16d is based on the assumption that the driver is always seated, as shown in FIG.
Eight states exist depending on whether the remaining three seat switches are on or off.

In the operation of this embodiment, first, the measurement system of FIG. 8 described above is used to measure the distance between the speaker and the microphone in each of the riding conditions shown in FIGS. 2 (1) to (8) corresponding to the number of vehicle occupants. Measure the spatial transfer characteristics.

Then, the selector 31 in the controller 2 receives the output signals from the switches 16a to 16d provided on each of the seats 15a to 15d, and determines the current riding condition, and this riding condition is shown in FIG. 2(1), for example. If it is, the selector 31 selects the spatial transfer characteristic GD1 corresponding to FIG. 2(1) from the filter 30 and applies it to the adaptive filter 22.

As a result, the controller 2 identifies the transfer characteristic GC equivalently shown in FIG. 9 using the conventional LMS algorithm shown in FIG. 5 based on the spatial transfer characteristic GD1. The output of the speaker 14 is controlled so that the input of the speaker 13 is minimized.

[0030] In the above embodiment, an example was explained in which eight riding conditions were determined by four seat switches.
By measuring not only this but various spatial transfer characteristics in advance, adaptive control suitable for many riding conditions can be realized.

[0031]

[Effects of the Invention] As described above, in the vehicle interior noise reduction device according to the present invention, each seat is provided with a switch, the riding condition is determined based on the output of the switch, and measurements are made in advance for each riding condition. The configuration is such that one of the spatial transfer characteristics between the speaker and the microphone is selected and the reciprocal spatial transfer characteristic of the transfer characteristic of the vibration system of the car body up to the ears is identified. If it is measured and read, there is no need to identify it after that, and it is possible to eliminate the trouble of having to update the spatial transfer characteristics with white noise every time a passenger gets in or out of the vehicle.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a vehicle interior noise reduction device according to the present invention.

FIG. 2 is a block diagram showing examples of various riding states in a vehicle.

FIG. 3 is a block diagram showing an example of a conventional vehicle interior noise reduction device.

FIG. 4 is a block diagram showing a general configuration of an adaptive filter.

FIG. 5 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. 3;

FIG. 6 is a graph diagram for comparing the conventional examples shown in FIG. 3 and FIG. 5 in terms of convergence.

FIG. 7 is a block diagram showing a filter having measured spatial transfer characteristics.

FIG. 8 is a block diagram illustrating an apparatus for measuring spatial transfer characteristics.

9 is a block diagram showing an equivalent circuit of the vehicle interior noise reduction device shown in FIG. 5; FIG.

[Explanation of symbols]

1 Vehicle 2 Controller 10 Vehicle interior 11 Engine 13 Microphone 14 Speakers 15a to 15d
Seats 16a to 16d Seat switch 22
Adaptive filter 30 Filter 31 In the selector diagram,
The same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] Claim 1: Means for detecting a reference signal synchronized with engine rotation, a speaker provided in a vehicle interior, a microphone for detecting vehicle interior noise, and transmission characteristics from the reference signal to the ear of a vibration system of the vehicle body. an adaptive controller that identifies the reverse transfer characteristic of the speaker and controls the speaker so that the input of the microphone is minimized; and a switch provided on each seat, and the controller determines the riding state based on the output of the switch. A vehicle interior noise reduction device characterized in that the inverse transfer characteristic is identified by selecting one of spatial transfer characteristics between a speaker and a microphone measured in advance for each riding condition.