JPH0627969A - In-cabin indistinct sound reducing device - Google Patents

Abstract

PURPOSE:To reduce the indistinct sound in a cabin not only in a stationary travel, but also during a transient drive without increasing the number of components. CONSTITUTION:The signals from an air suction amount sensor 5 and a crank angle sensor 7 are shaped and processed by an input signal converting circuit 9 into a signal which contains load information and engine rotation information and outputted as a primary source to an adaptive filter 10 and to an LMS(Least Mean Square) arithmetic circuit 12 through a speaker/microphone transmission characteristic estimating circuit 11. This primary source is composed by the adaptive filter 10 as a canceling signal, which is outputted as a canceling sound for a vibration noise by a speaker 15. Then the noise reduced state at a listening point is detected as an error signal by an error microphone 16 and sent to the LMS arithmetic circuit 12, which updates the filter coefficient W(N) of the adaptive filter 10 so that the error signal becomes minimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle interior muffler noise reducing apparatus for reducing the muffler noise generated in the vehicle compartment due to the vibration noise of an engine by interfering with the canceling noise.

[0002]

2. Description of the Related Art As is well known, most of the uncomfortable noises in the vehicle compartment are muffled noises caused mainly by the vibration noise of the engine. As a means for reducing this muffled sound, an additional sound source such as a speaker is arranged in the vehicle compartment, and the muffled sound is output by outputting a canceling sound of the same phase as the muffled sound at the listening position but in the opposite phase. Various techniques for reducing the amount have been proposed.

For example, in Japanese Patent Laid-Open No. 63-315346, the engine speed is calculated from the output interval of the ignition signal,
Search for the cancellation sound set for each engine speed range,
This canceling sound is output from the speaker. On the other hand, the muffled sound in the vehicle compartment is detected from the microphone arranged at the listening position, the muffled sound of this time and the previous muffled sound are compared, and when the input level of the muffled sound of this time is low (high), The input level of the muffled sound detected by the microphone is minimized by outputting the canceling sound whose phase is advanced (retarded) to a predetermined level or whose amplification degree is set low (high) to a predetermined level from the speaker. The technique of controlling is disclosed.

Since the engine rotation speed constantly changes during traveling, and especially during transient operation, the engine rotation speed changes abruptly, so even if the optimum cancellation sound is output for each engine rotation speed region, the cancellation sound is output. The waveform becomes discontinuous, and if the connection timing is incorrect, abnormal noise will occur.

Therefore, for example, in Japanese Patent Laid-Open No. 3-90448, there is provided a so-called waiting time in which the canceling noise is not output in order to smoothly connect the canceling noise used before and after the rotation fluctuation during transient operation. A technique for preventing the generation of sound is disclosed.

[0006]

However, the muffled sound reducing device disclosed in this prior art cannot positively reduce the muffled sound at the time of transition, so that it is caused by engine noise at the time of starting, for example. The muffled sound is transmitted to the passenger compartment as it is, and when the vehicle shifts to constant speed driving, the muffled sound is canceled by the canceling sound output from the speaker, and the muffled sound disappears depending on the driving condition.
The occupant will feel uncomfortable because of the occurrence.

The present invention has been made in view of the above circumstances, and is capable of reducing the muffled noise in the passenger compartment not only during steady running but also during transient operation without increasing the number of parts. An object is to provide an indoor muffled sound reducing device.

[0008]

To achieve the above object, a vehicle interior muffled noise reducing apparatus according to the present invention comprises an engine load detecting means for detecting engine load information and an engine rotation detecting means for detecting engine rotation information. An input signal converting means for converting signals from the engine load detecting means and the engine rotation detecting means into a noise vibration source signal having a frequency spectrum composed of a predetermined high order component, and the noise vibration source signal being adapted. A cancel signal synthesizing means for synthesizing as a cancel signal by a filter, a canceling sound generating means for generating the cancel signal from a sound source as a canceling sound for noise, an error signal detecting means for detecting a noise reduction state at a listening point as an error signal, A filter function of the adaptive filter based on the error signal and the noise and vibration source signal. It is obtained by a cancellation signal updating means for updating the.

[0009]

[Operation] In the above configuration, first, the engine load detection means detects the engine load information, and the engine rotation detection means detects the engine rotation information. Next, the input signal converting means converts the signals from the engine load detecting means and the engine rotation detecting means into a noise vibration source signal having a frequency spectrum composed of predetermined high order components.
Then, the cancel signal synthesizing means synthesizes the noise and vibration source signal as a cancel signal by an adaptive filter,
This cancel signal is generated from the sound source as a canceling sound for noise by the canceling sound generating means. Then, the noise reduction state at the listening point is detected as an error signal by the error signal detection means and input to the cancellation signal update means, and the filter coefficient of the adaptive filter is updated based on this error signal and the noise vibration source signal. .

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a system schematic diagram of a vehicle interior muffled noise reducing device, FIG. 2 is an explanatory diagram of an input signal conversion circuit, and FIG. 3 is a correlation between a primary source and vibration noise. In the illustration, (a) is a molded and processed primary source, (b) is engine-related vibration noise, (c)
Is a primary source viewed from the frequency domain, and (d) is engine-related vibration noise viewed from the frequency domain.

In the figure, reference numeral 1 indicates a four-cycle engine, an air cleaner 4 is disposed upstream of an intake manifold 2 via an intake pipe 3, and immediately below the air cleaner 4, engine load detection is performed. An intake air amount sensor 5 as a means is provided. A crank angle detecting rotor 6 is mounted on the crankshaft 1a of the engine 1. The crank angle detecting rotor 6 is mounted on the crankshaft 1a.
A crank angle sensor 7 as an engine rotation detecting means, such as an electromagnetic pickup for detecting a protrusion that is a detected object, is provided opposite to the outer periphery of the crank angle sensor 7.

Further, in the figure, reference numeral 8 indicates a canceling sound generating device, and an input signal converting circuit 9 as an input signal converting means of the canceling sound generating device 8 is provided with the intake air amount sensor 5 and the crank angle sensor 7. The signal of is input.

In the input signal conversion circuit 9, as shown in FIG. 2, the input signal from the crank angle sensor 7 is synchronized with the engine rotation to generate one pulse for two engine revolutions. 0.5 × n (integer)
In addition to shaping and processing into a signal having a frequency spectrum of the next component, the input signal from the intake air amount sensor 5 is reflected as load information in the signal having a frequency spectrum of the 0.5 × nth component (for example, , The value in the amplitude direction is changed according to the load), and as the noise vibration source signal (primary source), the adaptive filter 10 as the cancel signal synthesizing means and the speaker / microphone transfer characteristic estimation circuit (CMN0 circuit) 11 are provided. Output.

This is because the vibration noise related to the 4-cycle engine (FIG. 3 (b)) is caused by the engine 1 rotating twice (720 ° C.).
In order to complete the four strokes of intake / compression / explosion / exhaust in A), there is vibration noise that makes the engine 2 revolutions in one cycle. In the frequency range, the 0.5th order component of the engine revolution (the engine 2 revolutions) A frequency spectrum (0.5 × n (integer) order component) whose main component is a higher order component (FIG. 3 (d)) is a sine wave component that becomes one cycle at It is because it is configured). Therefore, by shaping and processing the signals from the intake air amount sensor 5 and the crank angle sensor 7 as described above, the load information is reflected, the transient response of the engine is excellent, and the vibration noise desired to be silenced is generated. An extremely highly correlated primary source can be obtained (Fig. 3 (a),
(C)).

The adaptive filter 10 to which the primary source from the input signal conversion circuit 9 is input is an L filter which will be described later.
FIR (Finit) having a filter coefficient W (n) that can be updated by an MS (Least Mean Square) arithmetic circuit 12
e Impulse Response) filter having a tap number of 256 in this embodiment. Note that the number of taps is not limited to 256, and a filter with a larger number of taps may be used if sufficient calculation speed and cost performance can be obtained, and if sufficient accuracy is obtained, more taps can be used. A filter with a small number may be used. The primary source input to the adaptive filter 10 is convolution product-added with the filter coefficient W (n) and is output as a cancellation signal to the D / A converter 13 and the speaker 1 which is an additional sound source via the amplifier 14.
It is designed to be generated as a canceling sound from 5.

The speaker 15 is arranged in a vehicle compartment (not shown), and an error microphone serving as an error signal detecting means, which is a sound pressure sensor, is provided at a listening point (for example, a position close to the driver's ear) in the vehicle compartment. 16 are provided. The error microphone 16 detects the result of the interference between the vibration noise and the canceling sound, and inputs the result to the LMS arithmetic circuit 12 as an error signal.

Further, in the speaker / microphone transfer characteristic estimation circuit (CMN0 circuit) 11, the speaker / microphone transfer characteristic CMN is previously obtained and set, and the primary source from the input signal conversion circuit 9 is The signal is input to the LMS arithmetic circuit 12 after being corrected by being multiplied by the speaker / microphone transfer characteristic CMN.

In the LMS arithmetic circuit 12, the filter correction amount is obtained from the error signal from the error microphone 16 and the signal from the CMNO circuit 11 so that the error signal from the error microphone 16 is minimized. The filter coefficient W (n) of the adaptive filter 10 is updated. In the present embodiment, the sampling time of the error signal by the error microphone 16 is set to 3 kHz (that is, the filter coefficient W (n) of the adaptive filter 10 is updated 3000 times per second). The sampling time is not limited to 3kHz.

Further, reference character C in FIG. 1 is a transfer characteristic of the vehicle body with respect to vibration noise of the engine 1, and CMN is a transfer characteristic between the speaker 15 and the microphone 16.

Next, the operation of the embodiment having the above structure will be described. First, engine vibration noise is
From the inside to the inside of the vehicle through a mount or the like (not shown), and the sounds of intake and exhaust also propagate inside the vehicle. As shown in FIG. 3, each of these engine-related vibration noises is composed of a frequency spectrum of a 0.5 × n (integer) order component in the frequency domain, and is multiplied by the vehicle body transfer characteristic C to obtain a listening point. Reach

On the other hand, the signals from the intake air amount sensor 5 and the crank angle sensor 7 of the engine 1 are input to the input signal conversion circuit 9 of the canceling noise generator 8. Then, in the input signal conversion circuit 9, the signal from the crank angle sensor 7 is synchronized with the engine rotation in one pulse for two engine revolutions, and in the frequency domain, a 0.5 × n (integer) order component of the engine revolution. The signal from the intake air amount sensor 5 is reflected as load information on the signal having the frequency spectrum of the 0.5 × n-order component (for example, the value in the amplitude direction). Is changed according to the load) and output as a noise vibration source signal (primary source) to the adaptive filter 10 and the speaker / microphone transfer characteristic estimation circuit (CMNO circuit) 11.

Next, the primary source from the input signal conversion circuit 9 input to the adaptive filter 10 is a canceling sound signal for canceling vibration noise by the convolution product sum with the filter coefficient W (n). The cancellation signal is output to a speaker 15 (not shown) in the vehicle compartment through the D / A converter 13 and the amplifier 14, and is output from the speaker 15 as a canceling sound against the vibration noise at the listening point (for example, the position close to the driver's ear). To be done. At this time, the canceling sound output from the speaker 15 is multiplied by the speaker / microphone transfer characteristic CMN and reaches the listening point.

Therefore, at the listening point, the engine-related vibration noise interferes with the canceling noise to reduce the vibration noise, and at the same time, the error microphone 16 arranged near the listening point causes The result of the interference between the vibration noise and the canceling noise is detected and sent to the LMS arithmetic circuit 12 as an error signal.

The primary source output to the speaker / microphone transfer characteristic estimation circuit (CMN0 circuit) 11 is multiplied by the speaker / microphone transfer characteristic CMN obtained in advance and sent to the LMS operation circuit 12. . Then, in this LMS arithmetic circuit 12, a filter correction amount is obtained from the error signal from the error microphone 16 and the corrected primary source, and the above-mentioned adaptation is performed so that the error signal from the error microphone 16 is minimized. An algorithm for updating the filter coefficient W (n) of the filter 10 is performed.

As described above, in the present embodiment, since the existing engine load detection means and engine rotation detection means can obtain the primary source having a very high correlation with the vibration noise to be silenced, a new vibration sensor or the like is required. Instead, it becomes possible to provide an inexpensive and highly reliable vehicle interior muffler noise reduction device.

Further, since the engine load is reflected in the primary source, the followability during transient operation is improved.

Further, since the engine-related vibration noise has factors such as intake and exhaust noises in addition to engine vibration transmission noise, rather than detecting a partial vibration of the engine with a vibration sensor or the like and using it as a primary source, More effective noise reduction can be realized.

Further, since a primary source having a very high correlation with engine-related vibration noise can be obtained without using a new sensor such as a vibration sensor, it can be applied to a vehicle not equipped with a muffler noise reduction device in the passenger compartment. It can be installed easily.

In this embodiment, an example of the noise reduction device using the LMS algorithm of 1 channel (1 error microphone, 1 speaker) has been described, but the MEFX (Multipl) in which the LMS algorithm is expanded to multiple channels is described.
It can also be applied to a vehicle interior muffler noise reduction device (for example, a device with four error microphones, four speakers, etc.) that uses the e Error Filtered X) algorithm, and obtains a primary source from engine load information and rotation information. Thus, it is possible to realize a vehicle interior muffler noise reduction device that has a very high correlation with engine-related vibration noise and has good followability during transient operation.

Further, in the present embodiment, the engine load information is obtained from the intake air amount sensor, but from the engine load detecting means other than the intake air amount, for example, the throttle opening, the engine intake pipe negative pressure, etc. You may get it.

In the present embodiment, the engine rotation information is obtained from the crank angle sensor. However, signals from engine rotation detecting means other than the crank angle, for example, a cam angle sensor, a fuel injection pulse, an ignition pulse signal. It may be obtained from the etc.

[0033]

As described above, according to the present invention,
Since the engine load is reflected in the primary source, it is possible to reduce the muffled noise in the passenger compartment not only during steady running but also during transient running without increasing the number of parts. It

[Brief description of drawings]

FIG. 1 is a system schematic view of a vehicle interior muffled noise reducing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an input signal conversion circuit according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a correlation between a primary source and vibration noise according to an embodiment of the present invention.

[Explanation of symbols]

 1 engine 5 intake air amount sensor (engine load detection means) 7 crank angle sensor (engine rotation detection means) 9 input signal conversion circuit (input signal conversion means) 10 adaptive filter (cancellation signal synthesis means) 11 speaker / microphone transfer characteristics Estimating circuit 12 LMS arithmetic circuit (cancellation signal updating means) 15 Speaker (cancellation sound generating means) 16 Error microphone (error signal detecting means) W (n) filter coefficient

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Iidaka 1-7-2 Nishishinjuku, Shinjuku-ku, Tokyo Fuji Heavy Industries Ltd. (72) Inventor Kazuyuki Kondo 1-7-2 Nishishinjuku, Shinjuku-ku, Tokyo Within Fuji Heavy Industries Ltd.

Claims (1)

[Claims] 1. An engine load detecting means for detecting engine load information, an engine rotation detecting means for detecting engine rotation information, and a signal from the engine load detecting means and the engine rotation detecting means. Input signal converting means for converting as a noise vibration source signal of a frequency spectrum composed of higher-order components, a cancel signal combining means for combining the noise vibration source signal as a cancel signal by an adaptive filter, and a canceling sound for canceling the cancel signal against noise. As a canceling sound generating means generated from a sound source, an error signal detecting means for detecting a noise reduction state at a listening point as an error signal, and a filter coefficient of the adaptive filter is updated based on the error signal and the noise vibration source signal. A cabin interior fog characterized by comprising a cancellation signal updating means. Sound reduction device.