JPH07168579A - Electronic noise canceler - Google Patents

Abstract

PURPOSE:To prevent degradation of ambient environment (especially, influence to a human being) caused by a noise which cannot be canceled by ANC. CONSTITUTION:This device consists of cases 10, 13 incorporating electronic parts 11, 28 to be cooled, ducts 12, 14 sending air for cooling to the electronic parts 11, 28, connecting sections 4, 29 in which the ducts 12, 14 are connected in a freely turnable state for the cases 10, 13, while fans 5, 6 are stored in them, microphones 1, 22 for detecting an error provided near intake openings 121, 27 of the ducts 12, 14, microphones 3, 20 for detecting a noise provided near the fans 5, 16 of the ducts 12, 14, and loudspeakers 2, 21 for controlling provided between the both microphones 1, 22, 3, 20 of the ducts 12, 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel of an AV device including a part which generates a high heat such as a liquid crystal projector, or an OA which needs to be kept at a low temperature such as a personal computer.
The present invention relates to an electronic silencer that reduces noise of a small fan for cooling a circuit board of a device.

[0002]

2. Description of the Related Art Generally, fan noise has no direction and is radiated in all directions. Conventionally, this noise is guided to one place using a duct, and ANC (Active Noise Cancellation)
I used technology to mute electronically.

In such a conventional technique, the duct is fixed to the device, and the open ends of the duct are always oriented in the same direction.

[0004]

By the way, since the fan noise is radiated in all directions as described above, there is no duct A.
The application of NC is very difficult, and there is a problem that the sound cannot be silenced well to an acceptable level.

As one method of successfully applying ANC, it is considered that fan noise is collected at two places of intake and exhaust ports of the duct by using a duct to reduce the noise by ANC. However, even with this method,
There is a problem that noise is increased near the exhaust port as compared with the case where no duct is provided, and even if a large noise reduction effect is obtained by ANC, the noise remains.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to alleviate the deterioration of the surrounding environment (particularly the effect on humans) due to noise that cannot be erased by ANC. is there.

[0007]

According to the present invention, there is provided a box body containing an electronic component to be cooled, a duct for sending cooling air to the electronic component, and the duct for rotating the duct with respect to the box body. A connection part that is movably connected and houses a fan therein, an error detection microphone provided near the intake port of the duct, a noise detection microphone provided near the fan of the duct, and The control speaker is provided between the two microphones of the duct.

[0008]

[Function] By eliminating the fan noise that has disappeared by ANC in the direction where there is no person, it becomes difficult for noise to enter the human ear,
A comfortable environment around the device can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments in which the electronic silencer of the present invention is applied to a personal computer and a liquid crystal projector device will be described in detail below with reference to the drawings. [Embodiment 1] First, FIG. 1 is a diagram showing a schematic configuration when the electronic silencer of the present invention is used in a personal computer, in which 10 is a personal computer main body, and 11 is a circuit board built in the main body 10.

A duct 12 is externally attached to the main body 10 via a rotary shaft 4 serving as a connecting portion. The rotating shaft 4 is rotatable so that the intake port 12A of the duct 12 can be directed in all directions as shown by arrows A1 and A2 in the drawing, and the intake port 12A of the duct 12 is provided therein. A small OA (Office Aut) that takes in cooling air from the main body 10 and sends the cooling air flow to the circuit board 11 in the main body 10.
omation) Fan 5 is buried. An error detection microphone 1 is installed near the intake port 12A of the duct 12, a noise detection microphone 3 is installed near the OA fan 5, and a control speaker 2 is installed between the microphones 1 and 3. ing.

Since the rotating shaft 4 and the duct 12 rotate integrally, the positional relationship among the fan 5, the noise detecting microphone 3, the control speaker 2 and the error detecting microphone 1 does not change due to these rotations. Therefore, it is not necessary to adjust various settings for ANC every rotation. [Embodiment 2] Next, FIG. 2 is a diagram showing a schematic configuration in the case where the electronic silencer of the present invention is used in a liquid crystal projector device. A cooling substrate is provided in the projector body 13 and an intake air is provided on one side outside the body. The exhaust duct 14 is attached to the other side, and the exhaust duct 15 is attached to the other side. And the intake duct 14
An intake port 27 is provided in the exhaust duct 15, and an exhaust port 26 is provided in the exhaust duct 15. A lens 17 for projection is attached to the front part of the main body 13.

The intake duct 14 is connected to the main body 13 via a rotary shaft 9 in which a small fan 16 for intake is installed. The rotary shaft 29 causes the duct 14 to move in four directions relative to the main body 13. It is rotatable in eight directions, and therefore, the intake port 27 can be freely directed to a place where there is no person by the rotation.

In the intake duct 14, an error detection microphone 22 and the rotary shaft 2 are provided near the intake port 27.
A noise detection microphone 20 is provided in the vicinity of the fan 16 in the device 9, and a control speaker 21 is provided between the error detection microphone 22 and the noise detection microphone 20 to drive the control speaker 21 based on the noise detected by the noise detection microphone 20. The control speaker 21 is configured to generate a sound for muffling so that the noise detected by the error detection microphone 22 becomes substantially zero.

The fan 16, the noise detection microphone 20, the control speaker 21, and the error detection microphone 2 are provided.
Since the positional relationship of 2 does not change due to the rotation of the intake duct 14, various conditions for driving the control speaker 21 do not need to be changed due to the rotation. [Verification] FIG. 3 is a diagram showing a sound deadening effect in the case of an example of a liquid crystal projector. As shown in FIGS. 4A and 4B, the intake duct 14 and the exhaust duct 15 in the first embodiment.
Each of the fans 16, 116, noise detection microphone 2
0 and 120, error detection microphones 22 and 122, control speakers 21 and 121 are provided, and the intake port 27 and the exhaust port 2 are provided.
The sound deadening effect was measured in a state where 6 was directed to the front of the main body 13.

In this measurement, as shown in FIGS. 4A and 4B, the detection signal of the noise detecting microphone 20 of the intake duct 14 is filtered by the transfer function H2 from the control speaker 21 to the error detecting microphone 22, and the LMS
(Least Mean Square) An appropriate filter tap coefficient is set in the adaptive filter 2 so that the detection signal of the error detection microphone 22 is input to the LMS control unit LMS, and the adaptive speaker 2 drives the control speaker 21 optimally. To be done.

The output of the adaptive filter 2 is fed back to the detection signal of the noise detection microphone 20 via the feedback correction filter 2.
The above-mentioned configuration is the same in the exhaust duct 15.

When the electronic silencing was operated in this way (the sampling frequency was 8 kHz and the cut-off frequency was 3 kHz), the silencing effect was measured. As shown in FIG. 3, the silencing effect was obtained 1 m in front of the intake port 27 and the exhaust port 26. The effect is the smallest at 2.0 dBA, 1m dBA at 1 m on the intake duct 14 side of the main body 13, exhaust duct 1
It is 11.0dBA at 1m on the 5th side and 7.3dBA at 1m behind the main body 13, which is not uniform depending on the observation position.
Therefore, if the intake duct 14 (and / or the exhaust duct 15) is rotated to change the direction of the intake port 27 (and / or the exhaust port 26) to the direction where there is no person, a sufficient noise reduction effect can be expected in the place where the person is. .

The exhaust duct 15 is replaced by the intake duct 1
As in the case of 4, the direction of the exhaust port 26 can be freely changed by making it rotatable with respect to the main body 13, so that it is possible to further reduce the noise toward the person.

[0019]

As described above, according to the present invention, even if the ANC is used, the direction of the intake port (and / or the exhaust port) where the sound deadening efficiency is poor can be freely changed in all directions. It is expected that an electronic silencer that can efficiently reduce the ANC effect and obtain the maximum effect can be obtained.

[Brief description of drawings]

FIG. 1 is an outline diagram showing an example in which an electronic silencer of the present invention is applied to an OA device.

FIG. 2 is a schematic view showing an example in which the electronic silencer of the present invention is applied to a liquid crystal projector.

FIG. 3 is a top view illustrating the silencing effect of the example of FIG.

4 (a) and 4 (b) are plan views illustrating a configuration for measuring the sound deadening effect of FIG.

[Explanation of symbols]

 1, 22 Error detection microphone 2, 16 Control speaker 3, 20 Noise detection microphone 4, 29 Rotating shaft 5, 16 Fan 10, 13 Main body 11, 28 Substrate 12, 14 Intake duct 15 Exhaust duct

Claims (1)

[Claims] 1. A box body containing an electronic component to be cooled,
A duct for sending cooling air to the electronic component,
A connecting portion that rotatably connects the duct to the box and houses a fan therein, an error detection microphone provided near the intake port of the duct, and a connection portion near the fan of the duct. Electronic silencer comprising the noise detecting microphone and a control speaker provided between the both microphones of the duct.