JPH01282996A - Detection driving system in noise eliminating device - Google Patents

Abstract

PURPOSE:To effectively eliminate an external sound without necessitating complicated calculating processing by driving a sounding body by an output obtained by adding/subtracting the output from an acoustic detector arranged in the external part of the sounding body and/from the output from the oscillation detecting means of the sounding body. CONSTITUTION:A microphone 109 is fit in a back pressure room 107 formed between an oscillating film 105 and a horn 104. Further, another microphone 108 is arranged in the external part of a speaker 102 near the speaker 102. The output of the microphone 108 is inputted through an amplifier 110 to one input edge 111-1 of an analog adder 111, and the output of the microphone 109 is inputted to the other input edge 111-2 of the analog adder 111. A driving signal is outputted from an output edge 111-3 of the analog adder 111 through an amplifier 112 to a driving coil 106 of the speaker 102.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic muffler that cancels out noise generated by a speaker.

[Conventional technology]

The above-mentioned electronic silencer can reduce noise more effectively than simple soundproofing measures such as soundproofing materials by applying sound with a waveform of the opposite phase to external noise from the speaker. It has attracted attention, and technological development regarding this has become active in recent years. And the method is
External noise is detected by a microphone, and based on the output of the microphone, an acoustic waveform is formed to cancel out the external noise to drive a speaker, and the sound from the speaker is also input to the microphone. For this reason, the microphone always detects the composite sound of the speaker sound and external noise, rather than the external noise itself, so even if this is returned, the microphone does not have a muffling effect, but rather causes the hackling phenomenon due to the self-return of the speaker sound. A problem arises.

In order to solve this problem, conventional methods have been to separate the microphone and speaker by a predetermined distance (for example, 1.5 m), perform A/D conversion on the output of the microphone, and then perform signal processing based on computer calculations using a digital filter, etc. In addition to correcting the microphone detection data, the drive waveform is synthesized by FFT calculation or the like so that the output waveform of the speaker has exactly the opposite phase to the noise waveform at that position. Furthermore, measures have been taken to prevent howling by using delay circuit means such as echo cancellers.

[Problem to be solved by the invention]

However, since the above measures require complex calculation processing and delay circuit means, the process from the generation of the detection signal in the microphone to the generation of the speaker drive signal that is synthesized based on the detection signal will inevitably take some time ( For example, the time required for
．． must be kept at least 5 m) apart.

For this reason, even if a microphone is placed at the source of the noise, the noise will often leak into the surrounding area before it can be silenced by the speaker, and except in special cases such as silencing ducts, the silencing effect is generally not significant. descend. The equipment is expensive because it requires complex calculations, and on the other hand, the upper limit of noise frequencies that can be silenced is as low as, for example, several hundred.Furthermore, the overall size of the equipment becomes too large, making it difficult to use for office automation equipment, etc. -It has the problem that it cannot be applied to numerical applications.

The present invention solves the above-mentioned problems, and has a simple configuration and a compact structure, and is capable of silencing not only low-frequency noise but also high-frequency noise. It is an object of the present invention to provide a detection drive system in a noise muffling device that can perform the detection drive system more effectively.

[Means to solve the problem]

According to the present invention, such an object includes: an electrically driven sounding body; an acoustic detector disposed outside the sounding body; a means for detecting vibrations of the sounding body; It is characterized by comprising an addition or subtraction means for inputting the output from the acoustic detector, and driving the sounding body based on the output of the addition or subtraction means to cancel the external sound.

[Effect]

According to this configuration, it is possible to extract the instantaneous value of the external noise from the above addition or subtraction means regardless of the sound generated by the speaker and drive the speaker without delay, and also to drive the speaker without delay. Since it has a function that essentially does not cause howling due to the effect that self-feedback does not apply, it is possible to place the microphone and speaker sufficiently close to each other.As a result, the above-mentioned problem is solved. , can have an extremely effective sound deadening effect.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram showing the functional configuration of an embodiment of a detection and drive system in a silencer according to the present invention. A speaker 102 placed near a noise source 101 is attached to a magnetic member 106 including a permanent magnet, a horn 104 to which the magnetic member 106 is fixed, a diaphragm 105 attached to the horn 104, and a diaphragm 105 attached to the diaphragm 105. A drive coil 106 that engages with the magnetic flux generated by the magnetic member 103 is provided, and the space between the vibrating membrane 105 and the horn 104 forms an airtight back pressure chamber 107. A second microphone 109 is installed inside the back pressure chamber 107. A first microphone 10 is located outside the speaker 102 and near it.
8 is placed. The output of the first microphone 108 is input to one input terminal 111-1 of the analog adder 111 via the first amplifier 110, and the output of the second microphone 109 is input to the other input terminal 111-1 of the analog adder 111. A drive signal is input to the input terminal 111-2, and is applied from the output terminal 111-3 of the analog adder 111 to the drive coil 106 of the speaker 102 via the second amplifier 112.

Now, if the waveform of the sound from the noise source 101 at the first microphone 108 is A, and the waveform of the sound from the speaker is B, then at the first microphone 108-, k is a coefficient determined by the first microphone 108. , k2 are coefficients determined by the structures of the second microphone 109 and the speaker 102, etc. Here, the gain of the first amplifier 110 is adjusted and one input terminal of the analog adder 111 is adjusted.

At this time, the other input terminal 111- of the analog adder 111
2 is the second microphone as described above, and the output terminal 111-3 of the analog adder 111 outputs a signal of 2 to A/ as the sum of the input signals. By adjusting the gain of the second amplifier 112, the speaker 102 is driven through the amplifier 112, and the waveform B of the sound from the speaker 102 at the first microphone 10 becomes B=-A. In this way, it has a characteristic opposite to that of noise and cancels it.

The first and second amplifiers 110, 112 and analog adder 111 can be constructed from operational amplifiers and operate with extremely fast response. Speaker 1 for speaker 102
Since the generated sound B of 02 is not returned, howling does not occur, and the speaker 102 and the first microphone 108 can be brought sufficiently close to each other.

FIG. 2 is a block diagram showing the functional configuration of another embodiment of the present invention. In addition to the drive coil 106, the vibration membrane 105 of the speaker 102 is equipped with a detection coil 206 that engages with the magnetic flux generated by the magnetic member 106, and the output B/2 of the detection coil 206 is an analog subtracter 2110 input terminal. 211-2 and functions similarly to the embodiment of FIG. In this case, the space 2 between the vibrating membrane 105 and the horn 104
07 does not need to be airtight.

FIG. 3 is a block diagram showing the functional configuration of another embodiment of the present invention. A strain detection element 607 such as a piezoelectric element is attached to the vibrating membrane 105, detecting vibration changes of the vibrating membrane 105, and adding 2 to the output B/ to the input terminal 211-2 of the analog subtracter 211, as shown in FIG. The same effect as in the embodiment is performed.

FIG. 4 is a block diagram showing the functional configuration of another embodiment of the present invention. The output of the first drive coil 106 of the speaker 102 is input to the input end 211-2 of the analog subtracter 2110 as a B/2 signal via the third amplifier 516, and the same effect as in the embodiment of FIG. 1 is obtained. do.

FIG. 5(a) and tb+ are a plan view and a side view showing the mechanical configuration of an embodiment of an impact printer using a silencer having a detection drive system according to the present invention. In FIG. 5, a carriage 401 is guided by a guide member 402 and slides along a platen 406. Platen 4
The paper (not shown) is fed by its rotation, and the paper is sandwiched between it and the print head 404 mounted on the carriage 401, and the impact of the actuator of the print head 404 causes the paper to pass through the ink ribbon 405. Perform printing.

A sound deadening container 406 is mounted on the carriage 401 and surrounds a portion of the print head 404 and platen 406, and the wall of the sound deadening container 406 has a second back pressure chamber as shown in the embodiment of FIG. A speaker 102 with a microphone 109 is mounted, and a first microphone 108 is arranged inside the container.

In FIG. 5, most of the noise generated by the above-mentioned printing operation is taken into the silencing container 406, and the first and second microphones 108, 109, the speaker 102, etc. The effect shown in the actual case in the figure effectively silences the noise, and the noise of the printer is greatly attenuated.

〔Effect of the invention〕

As described above, according to the present invention, an electronic silencer can eliminate not only low frequency noise but also high frequency noise more effectively than before, and has a simple configuration and a compact structure. It is summarized as follows, and its benefits are great.

[Brief explanation of the drawing]

FIGS. 1, 2, 3, and 4 are block diagrams showing the functional configuration of an embodiment of the detection drive system in the silencing device according to the present invention, and FIGS. 5(a) and 4(b) are BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view and a side view showing the mechanical configuration of an embodiment of an impact printer using a silencer having a detection and drive system according to the present invention. 101... Noise source, 102...
Speaker, 103...Magnetic member, 104
...Horn, 105...Vibration membrane,
106..., drive coil, 107...
・Back pressure chamber, 108...First microphone, 109...
...Second microphone, 111...Analog adder, 206...Detection coil, 211...Analog subtracter, 307...Distortion detection element , 401... Carriage, 402... Guide member, 406...
...Platen, 404...Print head, 4
06... Sound deadening container. Figure ``i'' ball (A-?B) Figure 2 Figure 3 Figure 4 Figure 7 (A0B)

Claims (5)

[Claims] (1) An electrically driven sounding body, an acoustic detector disposed outside the sounding body, a vibration detection means provided on the sounding body for detecting vibrations of the sounding body, and the vibration detection means and an addition or subtraction means that inputs the output from the acoustic detector, and drives the sounding body based on the output of the addition or subtraction means to cancel external sound. . (2) A speaker having a back pressure chamber, a first microphone arranged outside the speaker, a second microphone arranged inside the back pressure chamber of the speaker, and a plurality of the first and second microphones. 1. A detection drive system for a noise muffling device, comprising: means for adding or subtracting a signal based on the output, and driving the speaker based on the output of the adding or subtracting means to cancel external sound. (3) A speaker equipped with a drive coil and a detection coil, a microphone disposed outside the speaker, and means for adding or subtracting signals based on the outputs of the microphone and the detection coil, the adding or subtracting means 1. A detection drive system for a noise muffling device, characterized in that the speaker is driven based on the output of the noise reduction device to cancel external sound. (4) comprising a speaker with a distortion detection element attached to a diaphragm or a diaphragm, a microphone disposed outside the speaker, and means for adding or subtracting signals based on the outputs of the microphone and the distortion detection element, A detection drive system for a noise muffling device, characterized in that the speaker is driven based on the output of the addition or subtraction means to cancel external sounds. (5) A speaker, a microphone disposed outside the speaker, and means for adding or subtracting a signal based on the output of the microphone and the drive coil of the speaker, the speaker according to the output of the adding or subtracting means. A detection drive system in a silencer, characterized in that it drives and cancels external sound.