JP2809135B2 - Duct silencer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer for a duct, and more particularly, to a fundamental noise and a harmonic in fan noise radiated from a duct for cooling and heating, and utilizing the same to reduce the noise. The present invention relates to a noise reduction device for ducts that achieves reduction.

[0002]

2. Description of the Related Art As shown in FIG. 4, for example, a conventional active type silencing system includes a first microphone 51 provided near a fan 50 in a duct 100.
A second microphone 52 provided in the duct 100 at a predetermined distance from the first microphone 51;
A mute speaker 53 is provided between the microphones 51 and 52. Further, a controller 54 for adjusting the level of the audio signal output from the muffling speaker 53 based on the input signals from the first and second microphones 51 and 52 is provided.

In the conventional example shown in FIG. 4, first, a sound wave propagating in the duct 100 from a fan 50 as a noise source is detected by a microphone 51 and input to a controller 54. At this time, a signal from the microphone 52 for evaluating the muffling effect is also input to the controller 54.

The second microphone 52 for evaluation is
The controller 54 detects the sound wave after the sound wave emitted from the muffling speaker 53 and the sound wave propagating from the fan 50 interfere with each other. The controller 54 processes the signal such that the signal of the second microphone 52 becomes zero by digital signal processing. And the like, and drives the above-described muffling speaker 53. Thereby, the noise at the position where the microphone 52 is provided is reduced.

In this case, the above-mentioned conventional example has an advantage that it can be installed later on the existing fan 50, and the noise on the second microphone 52 side (the side on which air is sent out from the duct) is reduced. Since it operates so as to mute the sound, it has the advantage that it is less susceptible to changes in noise characteristics and aging of the system.

[0006]

However, in the above conventional example, the operation of the controller 54 is unstable because the installation of the first microphone 51 and the muffling speaker 53 forms a closed loop in an electro-acoustic system. And always had the inconvenience of causing howling and increasing noise.

Further, in the above conventional example, the first and second microphones 51,
The installation of the controller 52 and the controller 54 invites an increase in the price of the entire system, and at the same time, has always been accompanied by inconveniences such as an increase in the size of the entire equipment.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to improve the disadvantages of the prior art, in particular to effectively reduce the noise levels of the fundamental wave having a high noise level and a plurality of harmonics, thereby achieving efficient and reliable operation. It is an object of the present invention to provide an expensive and relatively inexpensive duct silencer.

[0009]

In THE INVENTION Means for solving] first aspect of the present invention, a rotation speed sensor for detecting the rotational speed of the fan to be mounted in the duct, and the rotational speed of the fan detected by the rotational speed detection sensor fan And a frequency component generation unit that operates based on the multiplied value of the number of blades and individually generates and outputs each frequency component of a fundamental wave and one or more harmonics of the fan noise.

A plurality of output adjustment units are provided for individually adjusting the output level and phase of each frequency component of the fundamental wave and one or more harmonics output from the frequency component creation unit. if a signal output from the adjustment unit
Duct silencing speaker that emits by converting the audio signal forms
It is configured to be installed at a position distant from the fans in the unit.

According to a second aspect of the present invention, in the duct silencer according to the first aspect, a temperature sensor is provided in the duct, and each output is adjusted according to the temperature in the duct detected by the temperature sensor. The unit adjusts the phase of the signal output from the output adjustment unit.

According to a third aspect of the present invention, there is adopted a method in which each of the above-mentioned output adjusting units is constituted by an output level adjusting circuit and a phase adjusting circuit. This aims to achieve the above-mentioned object.

[0013]

According to the present invention, first, the rotation frequency of the fan is detected, and the high frequency generator generates the fundamental wave component and the harmonic frequency component based on the frequency signal. Each created frequency component is output from an independent output adjustment unit (for example,
With a gain adjuster and a phase adjuster)
An inverse waveform of each corresponding frequency component of the fan noise is created. Each of these signals is finally combined, and drives a muffling speaker to muffle fan noise by sound wave interference.

[0014]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a first embodiment. In the first embodiment shown in FIG. 1, a rotation speed detection sensor 6 for detecting the rotation speed of the fan generated by the rotation operation of the fan 4 provided in the duct 2, and a fan detected by the rotation speed detection sensor 6 And a frequency component creating unit 8 that operates based on the rotation speed information of the above and individually creates and outputs each frequency component of the fundamental wave and one or more harmonics of the fan noise.

The frequency component generator 8 includes a fundamental frequency component, a first harmonic component, a second harmonic component,..., Among the rotational speeds of the fan detected by the rotational speed detection sensor 6.
.. Has a function of forming all components such as the n-th harmonic component and outputting them at a predetermined level.

Among them, for example, the fundamental frequency component can be calculated by “the number of rotations of the fan × the number of blades”, and the first harmonic component, the second harmonic component,. It is created effectively based on the calculated fundamental wave and is output at a predetermined level.

The fundamental frequency component, the first harmonic component, the second harmonic component,
,..., Each of the n-th harmonic components is an output adjustment unit 10 ₀ , 10 ₁ , 10 ₂ , 10 ₃ ,.
The output level and phase are individually adjusted by _n and output.

[0019] Each output adjusting unit 10 _0, 10 _1, 1
0 ₂ , 10 ₃ ,..., 10 _n are gain adjusters 1 respectively.
_{1 0, 11 1, 11 2} , 11 3, ...... 11 n and the phase adjuster 12 _0, 12 _1, 12 _2, 12 _3, provided with a ...... 12 _n, by which each frequency component of fan noise So that the fundamental frequency component and the first
Each of the second harmonic component, the second harmonic component,..., And the nth harmonic component is adjusted and output.

Therefore, each of the fundamental frequency component, the first harmonic component, the second harmonic component,..., And the n-th harmonic component output from the frequency component creating unit 8 is individually Moreover, the output level and the phase are freely set so as to have the same amplitude and the opposite phase to each frequency component of the fan noise with high accuracy.

Reference numeral 15 denotes each of the output adjustment units 1 described above.
A muffling speaker for synthesizing signals output from 0 ₀ , 10 ₁ to 10 _n , converting the signals to a predetermined position in the duct 2 as described above, and outputting the converted signals is shown. This audio speaker 15
Is installed at a position away from the fan 4 as shown in FIG.
Have been.

Next, the operation of the above embodiment will be described. When the fan 4 starts rotating, the rotational speed is detected by the rotational speed detection sensor 6. In the harmonic component creator 8, the primary, secondary, and
... Generate an n-th harmonic and output a signal having a magnitude proportional to the number of rotations. Each frequency signal is supplied to an independent gain adjuster 11 ₀ , 11 _{1 to} 11 _n and a phase adjuster 12.
₀ , 12 _{1 to} 12 _n are adjusted so as to have the same amplitude and opposite phase as each frequency component of the fan noise. These signals are finally combined to drive the muffling speaker 15.

As a result, it is possible to always create an appropriate reverse waveform with respect to the rotation of the fan 4 and to achieve noise reduction.

FIG. 2 shows the measurement results of noise reduction according to the above embodiment. FIG. 2A shows a noise waveform in the duct 2. FIG. 2B shows the result when the present embodiment is operated.

In the case of fan noise, the number of rotations of the fan
The fundamental frequency component of "number of wings" and its harmonic components show peaks. The same applies to the case of this example, as shown in FIG. 2A, where the fundamental frequency component and the first harmonic frequency component are 49 [d
B], and the first and second harmonic frequency components follow this.

On the other hand, when this embodiment is operated,
As shown in FIG. 2B , a remarkable peak is about 20 [dB].
The result of reduction was obtained.

As a result, the waveforms of the opposite phases created by the harmonic generator 8 and the output adjusters 10 ₀ , 10 ₁ to 10 _n become ideal sound wave interferences when the sound wave propagation speed is constant. At the same time, since a closed loop is not formed in the electro-acoustic system as in the above-described conventional example, the operation of the control system can be stabilized, and howling can be reliably eliminated. There is an advantage that can be.

Next, a second embodiment will be described with reference to FIG. Here, the same reference numerals are used for the same components as those in the first embodiment.

The second embodiment shown in FIG. 3 is based on the premise that the temperature in the duct is constant in the first embodiment described above, whereas the temperature in the duct 2 varies. It is based on the case.

That is, in the second embodiment shown in FIG. 3, a rotation speed detection sensor 6 for detecting the rotation speed of the fan 4 mounted on the A frequency component creation unit 8 that operates based on the rotation speed of the fan 4 detected by the rotation speed detection sensor 6 and individually creates and outputs each frequency component of a fundamental wave and one or more harmonics of the fan noise; It has.

A plurality of output adjusters 20 ₀ , 20 ₁ for individually adjusting the output level and phase of each frequency component of the fundamental wave and one or more harmonics output from the frequency component generator 8. , 20 ₂ , 20 ₃ ,..., 20 _n .

[0032] In addition, the each output adjustment section 20 _0, 20 ₁ ~
The sound output speaker 15 that synthesizes the signal output from the second _n and converts it into a sound signal at a predetermined location in the duct 2 and emits the sound signal.
It has.

Further, a temperature sensor 26 is provided in the duct 2 described above. The temperature sensor 26 is provided on the upstream side of the muffling speaker 15 in the above-described duct 2 and close to the muffling speaker 15.

[0034] Each output adjusting unit 20 _0, 20 ₁ ~20 _n is
As in the case of the first embodiment, the gain adjusters 21 ₀ , 21 ₁ , 21 ₂ , 21 ₃ ,... 21 _n and the phase adjusters 22 ₀ , 22 ₁ , 22 ₂ , 22 ₃ ,. 2
2 _n , so that the fundamental frequency component, the first harmonic component, the second harmonic component,.
Each of the higher harmonic components is adjusted and output.

Of these, each of the phase adjusters 22 ₀ , 22 ₁ , 2
2 ₂ through 22 _n is provided with a temperature compensation function receives the temperature information is in accordance with the duct temperature correcting the phase of the signal corresponding to each frequency component of fan noise (adjustment) from the temperature sensor 26 described above I have. Other configurations are the same as those described in the first embodiment.
This is the same as the embodiment.

[0036] Thus, in the second embodiment, the temperature change of the medium to propagate the sound waves as described above is detected by the temperature sensor 26, the shift of the sound wave corresponding to the propagation velocity changes, each phase adjuster 22 ₀ This is characterized in that it is corrected by .about.22 _n and is operated so as to always have an inverted waveform.

Thus, it is possible to obtain a noise reduction system which is not affected by the rotation speed of the fan 4, the temperature change of the propagating medium (air or the like), or the like.

Here, in each of the above-described embodiments, the case where the information on the fan noise in the duct is detected by the rotation speed detection sensor 6 is exemplified.
The frequency level of the fan noise is measured by a noise frequency measurement sensor capable of simultaneously measuring from the fundamental wave to a plurality of harmonics, and the fundamental wave component and the plurality of harmonic components obtained by the measurement are distributed to each output adjusting unit 20. ₀ , 20 ₁ ~
20 _n may be input.

[0039]

Since the present invention is constructed and functions as described above, according to the present invention, there is no danger of noise increase due to howling between the microphone and the speaker which has occurred in the conventional example, and the simple structure as described above is achieved. The element can effectively and reliably reduce the high-level fundamental component and multiple harmonic components of the noise in the duct by the fan, and thus is efficient, reliable and relatively inexpensive for a duct fan. A silencer can be provided.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing experimental results of the embodiment shown in FIG. 1, wherein FIG. 2A shows a state before operation and FIG. 2B shows a state after operation.

FIG. 3 is an overall configuration diagram showing a second embodiment.

FIG. 4 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

2 the duct 4 Fan 6 rotational speed detecting sensor 8 harmonics generator _{10 0, 10 1, 10 2} , 10 3, ... 10 n output adjusting unit _{11 0, 11 1, 11 2} , 11 3, ... 11 n gain adjustment vessel _{12 0, 12 1, 12 2} , 12 3, ... 12 n phase adjuster 15 muffling speaker _{20 0, 20 1, 20 2} , 20 3, ... 20 n output adjusting unit 21 _0, 21 _1, 21 _2, 21 ₃ ,... 21 _n gain adjusters 22 ₀ , 22 ₁ , 22 ₂ , 22 ₃ ,... 22 _n phase adjusters 26 Temperature sensors

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G10K 11/178

Claims (3)

(57) [Claims] A rotation speed detection sensor for detecting a rotation speed of a fan mounted on a duct, and a multiplication value of a rotation speed of the fan detected by the rotation speed detection sensor and the number of blades of the fan. A frequency component creating section that operates based on the frequency of the fundamental wave of the fan noise and one or two or more harmonics, and outputs the individual components. Alternatively, a plurality of output adjustment units for individually adjusting the output level and phase of each frequency component of two or more harmonics are provided, and the signals output from each of the output adjustment units are synthesized and converted into an audio signal. The sound emission speaker that emits
A muffler for ducts, which is provided at a position distant from the fan . 2. The duct silencer according to claim 1, further comprising: a temperature sensor provided in the duct, wherein each of the output adjustment units adjusts the output temperature in accordance with a temperature in the duct detected by the temperature sensor. A silencer for a duct, which adjusts the phase of a signal output from a duct. 3. The muffler for a duct according to claim 1, wherein each of the plurality of output adjustment units includes an output level adjustment circuit and a phase adjustment circuit.