JPH06259084A - Silencer - Google Patents

Abstract

PURPOSE:To improve a silencing effect by exactly detecting the noise with a microphone, the silencer in which the microphone and speaker are disposed in a duct for guiding the blast delivered from a fan and which is so formed to silence the noise generated from this fan by the sound waves outputted from this speaker. CONSTITUTION:An air passage 1A of the duct 1, to a discharge port 2 of which the blast from the fan 5 is supplied, is internally provided with a cylindrical member 7 of length L made from an acoustical absorbent. The microphone 3 is embedded at a prescribed point of this cylindrical member 7 and a circular or polygonal hollow part 8 is formed in the cylindrical member 7. The cylindrical member is so formed that the level of the noise M1 is uniform over the entire part of the hollow part 8. The microphone 3 is embedded at the prescribed point of the cylindrical member 7 to exactly detect the noise M1, the accuracy of the output signal Sb of the filter part 6 by a detection signal Sa is enhanced and the adequate sound wave M2 to silence the noise is outputted from the speaker 4. The silencing effect is thus improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a microphone and a speaker arranged in a duct that guides the air blown from a blower, and the noise generated from the blower is silenced by a sound wave output from the speaker. The present invention relates to a muffling device formed as described above.

[0002] In an electronic device, a blower is generally provided to cool the heat generated by an internal electronic device, and the heat generated by the electronic device is cooled by ventilation of the blower.

On the other hand, when driving such a blower, noise is generated. Therefore, particularly when the electronic device is installed in a general office, noise causes a problem of environmental degradation. Therefore, it is desired to minimize noise generated from such a blower.

[0004]

2. Description of the Related Art Conventionally, the structure is shown in FIG. Figure 3 (a) is the block diagram and (b) is the BB of (a).
FIG.

Conventionally, as shown in FIG. 3A, a frame 10A is used.
The duct 1 is provided at a predetermined location of the shelves 10 formed by housing the printed circuit board 10B in the housing, the blower 5 is locked at one end of the duct 1, and the blower 5 is driven to drive the outside air to the shelves 10 as shown by arrow F1. Take in the duct 1 ventilation path 1A
The heat generation of the printed circuit board 10B has been performed by blowing air as indicated by the arrow F2 and exhausting air through the exhaust port 2 formed at the other end of the duct 1 as indicated by the arrow F3.

A sound absorbing material 1B is fixed to the inner wall of the duct 1, the ventilation passage 1A is covered with the sound absorbing material 1B, and noise M1 generated by driving the blower 5 is absorbed by the sound absorbing material 1B. , Microphone 3, 9 in the air passage 1A
And a speaker 4 are provided, the detection signals Sa and Sc detected by the microphones 3 and 9 are sent to the filter unit 6, and the output signal Sb from the filter unit 6 causes the speaker 4 to generate a sound wave M2 having a phase opposite to the noise M1. The sound M1 is output and the noise M1 is silenced by the sound absorption by the sound absorbing material 1B and the output of the sound wave M2.

The filter unit 6 receives the detection signal Sa of the noise M1 detected by the microphone 3 and receives the digital signal S1.
A / D converter 6A for converting to 1 and DS for receiving the digital signal S11 and calculating the waveform data S13 having the opposite phase to the noise M1
The analog signal S1 is received by receiving the P calculation unit 6C and the waveform data S13.
A D / A converter 6D for converting to 4 and an amplifier 6E for outputting an output signal Sb for receiving the analog signal S14 and outputting a sound wave M2 to the speaker 4, and a detection signal Sc for the noise M1 detected by the microphone 9 are received. Is provided with an A / D converter 6B for converting into a digital signal S12 to output a sound wave M2 having a phase opposite to the noise M1 from the speaker 4, while the microphone 9
The detection signal Sc by is sent to the DSP operation unit via the A / D converter 6B.
The waveform data S13 sent to the 6C and calculated by the DSP calculation unit 6C is checked, and the sound wave M2 is corrected.

[0008]

However, by causing the speaker 4 to output the sound wave M2 having a phase opposite to that of the noise M1 by the detection signal Sa from the microphone 3, the actual noise M1 can be reduced by the duct 1 Is formed by a rectangular cross section, the level of the noise M1 decreases at the corners as shown in FIG.
The area of is circular and it becomes difficult to detect the actual noise M1 depending on the position where the microphone 3 is arranged.

Therefore, the noise M1 from the microphone 3
Noise that cannot mute the noise M1 because it cannot be accurately detected
There is a problem that it becomes difficult to output the sound wave M2 from the speaker 4 having a phase opposite to that of M1, and the muffling effect decreases.

Therefore, it is an object of the present invention to accurately detect noise with a microphone and to improve the silencing effect.

[0011]

1A and 1B are explanatory views of the principle of the present invention. FIG. 1A is a configuration diagram, and FIG. 1B is a sectional view taken along line AA of FIG.

As shown in FIG. 1 (a), a duct 1 having a ventilation passage 1A having a rectangular cross section and an exhaust port 2 formed at the other end of the duct 1 are engaged with each other. The blower 5 that blows air, the microphone 3 that is disposed in the ventilation passage 1A near the position where the blower 5 is locked, detects the noise M1 generated from the blower 5, and the ventilation that is near the exhaust port 2 Road 1A
Speaker 4 which outputs a predetermined sound wave M2 and a detection signal Sa of the microphone 3 and outputs an output signal Sb so that the sound wave M2 having a phase opposite to that of the noise M1 is output from the speaker 4. A sound deadening device comprising a filter section 6 for sending out the sound wave M2, and silencing the noise M1 sent out from the exhaust port 2 by outputting the sound wave M2 to the ventilating path 1A.
Inside 1A, install a cylindrical member 7 made of sound absorbing material and having a predetermined length L.
The microphone 3 is embedded in the tubular member 7 so that the noise M1 passing through the hollow portion 8 of the tubular member 7 is detected by the microphone 3, and as shown in FIG. 1 (b). The hollow portion 8 of the tubular member 7 is formed so that its cross section is circular or polygonal.

The above-mentioned problems can be solved by such a configuration.

[0014]

[Function] That is, the air passage 1A of the duct 1 through which the air blown from the air blower 5 is discharged to the exhaust port 2 is internally provided with the tubular member 7 of length L made of a sound absorbing material, and the microphone 3 is provided at a predetermined position of the tubular member 7. Embedded in the cylindrical member 7 and the hollow 8
Are formed so that the level of the noise M1 is uniform in the entire hollow portion 8.

Therefore, the noise M1 can be accurately detected by embedding the microphone 3 in a predetermined position of the tubular member 7.
The accuracy of the output signal Sb of the filter unit 6 based on the detection signal Sa can be improved, and the sound wave M2 that is suitable for silencing can be output from the speaker 4, and the silencing effect can be improved.

[0016]

The present invention will be described in detail below with reference to FIG.
2A and 2B are explanatory views of an embodiment according to the present invention. FIG. 2A is a perspective view, FIG. 2B is a perspective view of a tubular member, and FIGS. 2C1 and 2C2 are sectional views taken along the line AA of FIG. Throughout the drawings, the same reference numerals denote the same objects.

The present invention, as shown in FIG. 2 (a), is a ventilation path of the duct 1 to which the noise M1 generated from the blower 5 is sent.
When a cylindrical member 7 made of a sound absorbing material having a hollow portion 8 is installed inside 1A, a microphone 3 for detecting noise M1 is embedded in the cylindrical member 7, and when the noise M1 passes through the hollow portion 8, the microphone
The noise M1 is detected by 3 and the other configurations are the same as described above.

As shown in FIG. 2 (b), the tubular member 7 is formed to have a length L, and a hollow portion 8 of size D is formed in the central portion. In this case, if the length L of the tubular member 7 is made extremely small, it becomes difficult to detect the level of the noise M1 stably due to the turbulent flow generated in the air flow passing through the hollow portion 8.

Therefore, the length L of the tubular member 7 is 1 of the size D.
If it is formed more than twice, the air flow flowing through the hollow portion 8 becomes uniform at the location of L / 2 in the hollow portion 8, and the level of the noise M1 that is uniform over the entire cross section of the hollow portion 8 in the lateral direction. By arranging the microphone 3 at the position of L / 2, the actual noise M1 can be accurately detected by the microphone 3.

Further, in this case, the size D of the hollow portion 8 is, as shown in (c1) (c2) of FIG.
Alternatively, if it is formed so as to correspond to the diagonal length D2 formed in a polygonal shape, the same effect can be obtained even if the hollow portion 8 is formed in a circular shape or a polygonal shape.

Therefore, the noise M1 can be accurately detected by burying the microphone 3 in a predetermined position of the tubular member 7 provided in the ventilation passage 1A of the duct 1, and the detection signal Sa
The output signal Sb output from the filter unit 6 due to the above becomes an appropriate value, and the silencing effect by the sound wave M2 output from the speaker 4 can be improved.

[0022]

As described above, according to the present invention,
Accurate noise can be detected by internally arranging a cylindrical member made of a sound absorbing material having a circular or polygonal hollow portion in the flow passage of the duct, and burying a microphone for detecting noise in the cylindrical member. .

Therefore, since the conventional noise detection accuracy is low, it is possible to prevent the sound wave that does not match the noise from being output from the speaker, improve the silencing effect, and have a large practical effect.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is an explanatory diagram of an embodiment according to the present invention.

FIG. 3 is a conventional explanatory diagram.

[Explanation of symbols]

 1 Duct 2 Exhaust port 3 Microphone 4 Speaker 5 Blower 6 Filter part 7 Cylindrical member 8 Hollow part 1A Ventilation path

Claims (2)

[Claims] 1. A duct (1) having an air passage (1A) having a rectangular cross section, and locked to one end of the duct (1),
A blower that blows air to the exhaust port (2) formed at the other end
(5), a microphone (3) arranged in the ventilation passage (1A) near the blower (5) to be locked, for detecting noise (M1) generated from the blower (5), and the exhaust gas The ventilation passage near the mouth (2)
Speaker installed in (1A) and outputting a predetermined sound wave (M2)
(4) and the detection signal (Sa) of the microphone (3), the output signal (Sb) so that the sound wave (M2) having a phase opposite to that of the noise (M1) is output from the speaker (4) Filter part that sends out
(6), the sound wave (M2) is output to the ventilation passage (1A) by the sounding device for muffling the noise (M1) sent from the exhaust port (2), The air passage (1A) is provided with a tubular member (7) of a predetermined length (L) made of a sound absorbing material, and the noise (M1) passing through the hollow portion (8) of the tubular member (7) is A silencer characterized in that the microphone (3) is embedded in the tubular member (7) so as to be detected by the microphone (3). 2. The silencer according to claim 1, wherein the hollow portion (8) of the tubular member (7) has a circular cross section or a polygonal cross section.