JP3347147B2 - Active noise control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control device for suppressing noise in a cabin or a cabin where passengers of transportation means such as automobiles, aircraft, ships, etc. live. The present invention relates to an active noise control device that suppresses noise so that it can be heard without discomfort.

[0002]

2. Description of the Related Art When an occupant of a vehicle such as a car tries to listen to a music sound from a radio or an audio device in a cabin or a cabin while driving, the music sound is generated by the noise in the cabin. As it gets bigger, it is often masked by the noise and becomes very hard to hear. Even if the same volume is set, in particular, if the music source signal itself is small, such as pianissimo, the sound may not be heard at all.

A conventional method for solving such a problem is to automatically increase the volume of a radio or audio device by the increased noise when the noise in the vehicle interior increases. The correction is made so as to be apparent. However, in this method, even a music signal having a very low level, such as pianissimo, is intentionally made to have a high volume, so that the original musicality is neglected. In the end, it was something strange.

Conventionally, as an active noise control device, noise from a noise source is detected, and based on the detected noise signal, a cancellation signal having a transmission characteristic opposite to a noise transmission characteristic from the noise source to a person is generated. A canceling sound is generated by the canceling sound generating means according to the canceling signal, and an error between the noise from the noise source and the canceling sound from the canceling sound generating means is detected by an error sensor, and the detected error and the canceling error are detected. There has been proposed an active noise control device that controls the reverse transmission characteristic to be changed based on a transmission characteristic between a sound generation unit and the error sensor so that the error is minimized (for example, Japanese Patent Application Laid-Open No. HEI 10-130,009). -
No. 501344).

However, when noise is silenced by the conventional active noise control device, the noise is silenced at a constant ability irrespective of the sound pressure level of the music sound.
For this reason, even when the noise is loud or small, the noise is muted regardless of the level of the sound pressure level of the music sound, and the apparent music sound may become excessively loud. A sense of discomfort accompanies the sense of hearing.

[0006]

As described above, in a passenger compartment of a transportation facility such as an automobile, the occupant cannot comfortably listen to the music sound due to the noise caused by the traveling of the transportation facility. was there.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an active noise control device that enables an occupant to listen to music sound comfortably in a passenger compartment.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a means for detecting noise from a noise source, and a noise transmission characteristic from the noise source to a human based on the detected noise signal. in the active noise control system having a canceling sound generating means for silencing noise from the inverse noise source by generating a canceling sound transfer characteristics of, detecting the level of the music sound from the music source, the level of the detected music sound An active noise control device characterized by having control means for changing so as to reduce the level of the canceling sound as the noise increases .

[0009]

The control means increases the level of the canceling sound generated from the canceling sound generating means to the level of the music sound from the music source.
To decrease according to the following . By changing the level of the canceling sound so that the human sense of hearing does not cause discomfort, the human can comfortably hear the music sound.

[0010]

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

FIG. 1 is a block diagram showing an active noise control device according to one embodiment of the present invention. The illustrated device is a noise canceling device in an automobile, and has a so-called one-input one-output one-point control configuration using one noise detection sensor, one speaker as a canceling sound generating means, and one microphone as an error sensor. have.

As shown in FIG. 1, a noise detecting sensor 2 for detecting noise of an engine 1 as a noise source is mounted on a vehicle body or the like.
Is connected to the A / D converter 4 of the adaptive control circuit 3.

The adaptive control circuit 3 has an F control in which a transfer characteristic C (= H ₁ ) between the speaker 12 and the error sensor 13 is set in advance.
A process incorporating an IR filter 5, an adaptive digital filter (ADF) 6 for providing a transfer characteristic (pseudo reverse transfer characteristic) H 'opposite to the transfer characteristic H between the engine 1 and the occupant, and an arithmetic unit based on the LMS algorithm It has a unit 7 and a D / A converter 8. The output side of the adaptive digital filter 6 is
The D / A converter 8, the attenuator 9, the amplifier 10, and the adder 11 are connected to a speaker 12 as a cancellation sound generating means. A microphone 13 as an error sensor is arranged at a position facing the speaker 12, and its output side is A
/ D converter 14. The output side of the A / D converter 14 is connected to the processing unit 7 of the adaptive control circuit 3.

The audio device 15 includes an amplifier 16
Are connected to the attenuator 9 as a control means and the adder 11 via the. As shown in FIG. 2, the attenuator 9 has an attenuation characteristic such that the output signal level decreases as the input signal level increases. The attenuator 9 reduces the noise silencing ability of the adaptive control circuit 3 as the input signal level of the music signal from the audio device 15 increases.

A music signal from the audio device 15 is amplified by an amplifier 16, one of which is input to an attenuator 9, and the other is input to an adder 11 to drive a speaker 12. Generated. On the other hand, the output of the sensor 2 for detecting the vibration sound of the engine 1 is converted into a digital signal by the A / D converter 4 of the adaptive control circuit 3 and then supplied to the adaptive digital filter 6 and the FIR filter 5 as a reference signal x. You. The adaptive digital filter 6 generates a cancellation signal having the pseudo inverse transfer characteristic H ′ based on the reference signal x, and supplies the cancellation signal to the D / A converter 8. D
The analog signal from the A / A converter 8 is attenuated by the attenuator 9 in accordance with the signal level of the music signal input to the attenuator 9 via the amplifier 16, amplified by the amplifier 10, and added via the adder 11. The speaker 12 is driven to generate a canceling sound from the speaker 12 together with the music sound. The microphone 13 detects the canceling sound, and its output is converted into a digital signal by the A / D converter 14 and supplied to the processing unit 7 as an error signal ε. Processing unit 7
Changes the transfer characteristic H 'of the adaptive digital filter 6 according to the following equation so as to minimize the error signal ε according to the error signal ε and the transfer characteristic C from the FIR filter 5.

Ε = Hx + CH′x For example, while driving a car, as shown in FIG. 3, among the noises of the sound pressure level Lno, the music sound whose sound pressure level is from low level Lm1 to high level Lm2 like pianissimo. In the case of trying to listen to music, the muffling ability is changed by changing the level of the canceling signal according to the level of the music signal, so that the normal muffling ability is exhibited for the music sound of the low level Lm1. The noise signal level Lno is reduced to the level Ln1, and for the high level Lm2, the noise reduction capability is reduced to lower the noise signal level Lno to the level Ln2.

Thus, the occupant can listen to music without discomfort while the vehicle is running. In addition, an audio speaker generally has a low output sound pressure level (efficiency). However, according to the present invention, when the output of the music sound is at a high level, the output of the noise canceling sound can be at a low level. In addition, control that does not exceed the maximum capacity of the speaker can be performed.

In the above embodiment, the apparatus of the present invention is applied to a so-called one-input, one-output, one-point control structure using one noise detection sensor, one canceling sound generating means, and one error sensor. Although an example has been described, the present invention is not limited to this, and the method of the present invention can be applied to a configuration using a plurality of the above-described components, and an adaptive control circuit having a plurality of control blocks.

[0019]

As described above, according to the present invention,
The level of the canceling sound generated from the canceling sound generating means is reduced as the level of the music sound from the music source increases.
Because Uni change, it is possible to provide an active noise control device occupant can hear the auditory sensory comfort music sound cabin.

[Brief description of the drawings]

FIG. 1 is a block diagram of an active noise control device according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram of the attenuator shown in FIG.

FIG. 3 is a diagram showing an output example of the speaker shown in FIG. 1;

[Explanation of symbols]

 Reference Signs List 6 adaptive digital filter 9 attenuator (control means) 11 adder 12 speaker (cancellation sound generating means) 13 microphone 15 audio device (music source)

Continuation of the front page (56) References JP-A-57-114738 (JP, A) JP-A-3-178845 (JP, A) JP-A-5-11772 (JP, A) JP-A-2-161896 (JP) , A) Japanese Utility Model 63-12454 (JP, U) Japanese Utility Model 2-12947 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G10K 11/178 B60R 11/02 F01N 1/00 F01N 1/06

Claims (1)

(57) [Claims] 1. A means for detecting noise from a noise source, and generating a canceling sound having a transmission characteristic opposite to a noise transmission characteristic from the noise source to a human on the basis of the detected noise signal, thereby generating a noise from the noise source. In the active noise control device having the canceling sound generating means for silencing the sound, the level of the music sound from the music source is detected, and the level of the canceling sound is decreased as the level of the detected music sound increases. An active noise control device comprising control means.