JPH0830958B2 - Noise canceller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise canceller using active noise control in a noisy environment.

2. Description of the Related Art In recent years, an active noise control method has been proposed in which a control sound is output from a speaker by using a digital signal processing technique to suppress environmental noise and the sound is muted at a listening position.

Conventionally, this type of noise canceller has generally been constructed as shown in Japanese Patent Publication No. 62-56995. The configuration will be described below with reference to FIG.

As shown in FIG. 4, the detection signal obtained by detecting the noise emitted from the noise source 17 by the noise detecting means 1 is passed through the amplifier 2 and is convolved by the convolution integration circuit 41. Of the small speakers 9 and 10 built in the headrest 44 of the listener's chair through the power amplifier 7 and the phase inverting means 43.
Will be pronounced by the listener and will be muted by both ears 19, 20 of the listener.

However, in the configuration of the conventional example as described above, when the position of the listener changes, the transfer function stored in the memory is fixed, so that the muffling is not accurately performed. The first problem is that the common control sound output is given to both ears of the listener, and therefore the second problem that different noises cannot be accurately silenced for both ears, and the headrest. There is a third problem in that the small speaker built in does not perform accurate silencing due to difficulty in linear operation, such as increased distortion for low-frequency noise with large energy.

The present invention is to solve the above problems, it is possible to accurately mute even a change in listening position, different noise for both ears, and low-frequency noise with large energy,
It is an object of the present invention to provide a noise canceller that can be easily set up for a plurality of listeners.

Means for Solving the Problems The present invention, in order to achieve the above object, a noise detector installed in the vicinity of a noise source, an adaptive filter receiving the output thereof, a power amplifier cascade-connected to the adaptive filter, and The first and second speakers installed near the ears of the listener driven by the output, the first and second error detectors, and the adder for combining the outputs of both detectors The adaptive filter is adjusted so that the output of the above becomes small.

With the above-described structure, the present invention directly detects the nature of the noise source by the detector in the vicinity of the noise source, creates a control signal with an adaptive filter, and provides an error detector provided near each of the two ears of the listener. Since the adaptive filter is adjusted by the combined output of the outputs,
It is possible to muffle noise coming from a noise source propagating in a three-dimensional space. In addition, one end of the opening is near the listener's ear and the other end is equipped with a sound tube with a large-diameter speaker installed.
Since a sufficiently large sound pressure can be applied to the listener's ears, it is possible to accurately mute low-frequency noise with large energy.

EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1, 2, and 3.
This will be described with reference to the drawings. The purpose of this embodiment is to eliminate the low-frequency, high-energy noise that propagates through the three-dimensional space and arrives even when the position of the listener changes.

As shown in FIG. 1, the detection signal of the noise detector 1 installed near the noise source 17 passes through the amplifier 2 and is then input to the adaptive filter 5, where the power amplifier 7 causes the ears 19 of the listener 18 to listen to it. , 2
The first and second speakers 9 and 10 installed near 0 are driven. Further, the detection signals from the first and second error detectors 13 and 14 installed in the same manner are combined by the adder 21 via the amplifiers 15 and 16. The adaptive filter is controlled so that this combined signal becomes small.

To explain the operation in the above-mentioned configuration, the noise generated from the noise source 17 is generated by the adaptive filter 5 from the signal detected by the noise detector 1 to generate a signal of opposite phase, and the noise from the noise source 17 is heard by the listener's both ears. Cancel. That is, the sign inversion characteristic of the transfer function from the noise source 17 to both ears 19 and 20 is calculated as follows.
It is realized by the transfer function from 7 to both ears 19 and 20 via the adaptive filter. Here, the error detectors 13 and 14 always detect the error signal of the muffling in both ears of the listener, and control the adaptive filter so that the combined signal becomes small. This algorithm can use, for example, a learning identification method (see “Application of Digital Signal Processing” p219 Corona Publishing Co., Ltd.).
The Institute of Electrical Communication).

Further, in this embodiment, as shown in FIGS. 6 and 7, one end 30 and 31 of the opening is near the ears 19 and 20 of the listener, and the other end is the acoustic tube in which the speakers 9 and 10 are installed. 11 and 12 are integrated with the seat from the back to the bottom of the seat. As a result, the speakers 9 and 10 can be installed at a sufficient distance from the vicinity of the listener, and by utilizing the internal volume of the chair, a large control sound of low-frequency energy can be generated without distortion, and the acoustic tube The control sound is guided to both ears of the listener by 11 and 12.

As described above, according to this embodiment, even if the position of the listener moves together with the chair, the change can be accommodated, and the noise with a large low frequency energy that propagates three-dimensionally from the noise source can be silenced.

EFFECTS OF THE INVENTION As is clear from the above examples, according to the present invention,
By installing a noise detector near the noise source to detect the nature of the noise source itself, and by installing an error detector near the listener's ear, the noise propagating three-dimensionally from the noise source can be silenced. , One end of the opening is close to the listener's ear, and the other end has a large-diameter speaker attached to the acoustic tube using the internal volume of the chair, so that a sufficiently large sound pressure can be applied to the listener's ear. It is possible to provide a noise canceling device that can accurately muffle low-frequency noise with large energy.

[Brief description of drawings]

FIG. 1 is a signal processing block diagram of an embodiment of the present invention equipped with an error detector and an adaptive filter, FIG. 2 is a perspective view of a chair incorporating the acoustic tube of the embodiment, and FIG. 3 is an internal structure of the acoustic tube. 4 and 5 are block diagrams of a conventional noise canceller. 1 ... noise detector, 3 ... transmitting means, 4 ... receiving means,
5,6 ... Adaptive filter, 7,8 ... Power amplifier, 9,10 ... Speaker, 11,12 ... Acoustic tube, 13,14 ... Error detector, 18 ...
… Listener, 21 …… Adder.

Front page continued (72) Hiroyuki Hashimoto, Inventor, 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. References Japanese Unexamined Patent Publication No. 64-58200 (JP, A) Actually developed 63-70785 (JP, U)

Claims (1)

[Claims] 1. A noise detector installed near a noise source,
An adaptive filter for inputting the output of the noise detector, a power amplifier cascade-connected to the adaptive filter, first and second speakers driven by the output of the power amplifier, and the first and second A speaker is attached to one end of the opening and the other end of the opening is located near the first and second acoustic tubes installed near the ears of the listener, and near the openings of the first and second acoustic tubes. A chair in which the installed first and second error detectors and an adder that combines the outputs of the first and second error detectors, and in which the first and second acoustic tubes are seated by a listener A noise canceller, which is incorporated into a device for adjusting the adaptive filter so that the output of the adder becomes small.