JPH031555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic muffling system, and particularly to a multi-point electronic muffling system suitable for controlling a plurality of electronic mufflers.

[Conventional technology]

Electronic silencing systems utilize the principle of emitting additional sound with the same sound pressure and opposite phase to the noise propagating from the sound source, and forcibly producing a silencing effect through sound wave interference.

Regarding this electronic silencing system, the present applicant has already filed Japanese Patent Application No. 60-139293, Japanese Patent Application No. 60-139294,
System configurations for practical use have been disclosed in Japanese Patent Application No. 1983-7115 and elsewhere.

These systems are mainly for muffling noise that propagates through pipe systems such as ducts and piping, and include a first sensor that detects noise within the pipe;
An additional sound generating means is provided downstream of the first sensor to generate a sound wave having the same sound pressure and an opposite phase to the noise, and an additional sound generating means is provided further downstream of the additional sound generating means. a second sensor for detecting noise in the conduit, and a control means for calculating a comprehensive sound wave transfer function of a system constituted by the conduit, the first sensor, the additional sound generating means, and the second sensor. and a drive signal creation means for creating a drive signal to be applied to the additional sound generation means so that the output signal of the second sensor approaches zero based on the transfer function specified by the control means.

A microphone is mainly used as the first sensor and the second sensor, a speaker is used as the additional sound generating means, and a digital filter is mainly used as the drive signal generating means.

In an electronic silencer equipped with each of the above configurations,
The heart of the system is the control means.

That is, in this control means, based on the output signals of the first and second sensors, the transmission coefficient indicating the propagation characteristics of sound waves in the conduit, and the sound pressure-voltage between each electroacoustic transducer such as a microphone and a speaker are determined. To obtain a transfer function indicating a conversion characteristic or a voltage-sound pressure conversion characteristic, and based on these transfer functions, determine a transfer function for causing the output signal of the second sensor to approach zero, and generate additional sound. This transfer function is given to the drive signal generating means.

When the electronic silencer is applied to, for example, an air conditioning duct system, it is rarely used alone;
As shown in the figure, a plurality of electronic silencers 14 are used as a whole, arranged at key points in a plurality of ducts 12 leading to a room 10. By the way, as mentioned above, the control means in the electronic silencer has a complicated arithmetic circuit that determines the transfer function based on various input signals, and as a result, there is a problem that the price accounts for a large proportion of the entire electronic silencer.
Furthermore, the three-dimensional space occupied by the control means could not be ignored.

Therefore, when a plurality of electronic mufflers are required as described above, it is disadvantageous both economically and in terms of occupied space to provide one set of control means for each muffler.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a multi-point electronic silencer system in which a plurality of electronic silencers are installed, in which the cost and area occupied by the control means can be minimized.

[Means for Solving the Problems] The present invention focuses on the unique function of the control means in the electronic silencer, and in a multi-point electronic silencer system in which a plurality of electronic silencers are installed, only the control means is connected to each electronic silencer. The feature is that it can be shared with a silencer.

[Effect]

In cases such as air conditioning ducts, where the change in noise over time in a conduit is relatively small, the overall transfer function of sound waves over time is determined by the equipment configuration including the conduit of each electronic silencer and the propagated sound. Changes are also small. Therefore, in one electronic silencer,
Based on the transfer function as a fixed amount at a certain time determined by the control means, an appropriate drive signal can be given to the additional sound generation means for a certain period of time. Therefore, the control means can be used for other electronic silencers during the certain period of time.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

In FIG. 1, a plurality of air conditioning ducts 20, 3
0 and 40 have arrows 21, 31, and 41, respectively.
Noise is propagated from this direction. Each air conditioning duct includes a first microphone 22, 32, 42 for detecting noise, a speaker 23, 33, 43 as an additional sound generating means provided downstream from the first microphone, and a speaker 23, 33, 43 for generating additional sound. A second microphone 24 provided further downstream of the speaker,
34 and 44. 25, 35, 45 are adder circuits, and the first microphones 22, 32, 42
For the output of the second microphone 24, 3
The outputs of 4 and 44 are added with opposite phases. Also 2
6, 36, 46 are input/output interfaces, and an A/D converter 26 converts the analog signals from the adder circuits 25, 35, 45 into digital signals.
a, 36a, 46a, D/A converter 26b, 36b, 46b that converts a digital signal from a digital filter (to be described later) into an analog signal, and A that converts an analog signal of the second microphone 24, 34, 44 into a digital signal. /D converter 26c, 3
It consists of 6c and 46c. A/D converter 26a, 3
Digital signals from 6a and 46a are input to digital filters 27, 37, and 47, and can also be input to a shared control section 50. Furthermore, digital signals from the A/D conversion units 26c, 36c, and 46c can also be input to the shared control unit 50. First, the output of the adder circuit 25 related to the electronic silencer in the air conditioning duct 20 is input to the shared control unit 50 as a digital signal via the A/D conversion unit 26a, and similarly
4 is input as a digital signal via the A/D converter 26c. Based on these signals, the control unit 50 performs predetermined arithmetic processing to determine a transfer function for causing the output signal of the second microphone 24 to approach zero, and outputs this transfer function to the digital filter 27. . The digital filter 27 drives a speaker having predetermined amplitude characteristics and phase characteristics based on the output signal of the addition circuit 25 inputted via the A/D conversion section 26a and the transfer function given from the control section 50. Create a signal. This drive signal is transmitted to the D/A converter 26
b to the speaker 23, and the speaker 2
3 radiates additional sound into the air conditioning duct 20. Therefore, the noise propagating to the air conditioning duct 20 is canceled by the sound wave interference, and a silencing effect is forcibly produced. Regarding the meaning of the adder circuit, the calculation process of the transfer function in the control section, etc., please refer to the aforementioned Japanese Patent Application No. 1983-
The details are described in issue 7115, so they will be omitted here.

The feature of this embodiment is that, regarding the electronic muffler in the air conditioning duct 20, the transfer function obtained at a certain time by the control unit 50 is given to the digital filter 27 as a fixed value for a certain period of time. That is, the digital filter 27 creates a drive signal for the speaker 23 based on the transfer function given as a fixed value for a certain period of time and the output signal from the adder circuit 25 that is inputted every moment from the A/D converter 26a. . In cases where the change in noise over time in a conduit is relatively small, such as in an air conditioning duct, the change over time in the sound wave transfer function of an electronic silencer as an independent system is also extremely small. The drive signal provides a sufficient sound deadening effect. Therefore,
During the certain period of time, the input/output at the control unit 50 is controlled by the electronic silencer related to the air conditioning duct 30, and then by the air conditioning duct 4.
By sequentially switching to the electronic silencer according to No. 0, the control unit 50 can be shared by a plurality of electronic silencers. It is preferable to automatically perform these changes using a timer.

The reliable duration of the transfer function that a given electronic silencer uses as a fixed value varies depending on the situation of the noise source.
minute (300 seconds), and if the calculation processing time for determining the transfer coefficient in the control section is 10 seconds, one control section can be shared by 30 electronic silencers. , the economic and footprint benefits of this sharing are significant.

In addition, the noise sources are common, such as air conditioning ducts, and the pipes, microphones, and
When applying the present invention to multiple electronic silencers with the same or similar specifications such as speakers and digital filters, the control information of each electronic silencer is compatible, so this information can be shared. This also makes it possible to further reduce the calculation time in the control section.

The microphone and speaker that make up each electronic silencer are installed directly in the pipe, but the other components, such as the addition circuit, digital filter, and shared control section, are located in a control room where a good environment is maintained, for example. It is desirable to install them in concentrated locations. Through such centralized management, it is possible to simplify the adaptive control of each electronic silencer, realize efficient operation by allocating the number of units in operation, and maintain the operating environment with respect to the temperature and humidity of the electronic circuit.

Note that in the above embodiment, the adder circuit 25,
35, 45 has been described, the electronic silencer according to the present invention is not limited to this, and the adding circuit is omitted and the output signal from the first microphone is directly transmitted to the digital filter or the like. The device configuration may be such that the input signal is input to the control section, and the output signal from the second microphone is directly input to the control section.

[Effect of idea]

In the present invention, in a multi-point electronic silencer system in which a plurality of electronic silencers are installed, only the control means for determining the transfer function of sound waves in each electronic silencer is shared, so that the control means for the entire system is occupied. The price and footprint can be kept to a minimum, contributing to significant cost reductions for multi-point electronic silencing systems.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the overall arrangement of a multi-point electronic silencing system, which is the premise of the present invention. 20, 30, 40... Air conditioning duct, 22, 3
2, 42...first microphone, 23, 33,
43... Speaker, 24, 34, 44... Second microphone, 25, 35, 45... Addition circuit,
26, 36, 46... input/output interface,
27, 37, 47...Digital filter, 50
...control section.

Claims (1)

[Scope of Claims] 1. A first sensor for detecting noise in a pipe, and an addition provided downstream of the first sensor to generate a sound wave with the same sound pressure and opposite phase relative to the noise. a sound generating means, a second sensor that is provided further downstream of the additional sound generating means and detects noise in the pipe at this position, and an output of the first sensor or the first and second sensors. and a digital filter that creates a drive signal to be applied to the additional sound generating means so that the output signal of the second sensor approaches zero based on the output of the second sensor and the specified transfer function. one control means is provided for the plurality of electronic silencers, and the control means controls each conduit and the first sensor based on the output of the first sensor and the second sensor of each electronic silencer. The overall sound wave transfer function of the system constituted by the first sensor, the additional sound generating means, and the second sensor is repeatedly calculated for each electronic silencer, and the corresponding electronic silencer is 1. A multi-point electronic silencing system characterized in that a transfer function of a digital filter is specified, and the transfer function of the digital filter is updated at a predetermined period.