Noise reduction device and cleaner

Abstract

To provide a noise reduction device capable of being reduced in size and effectively reducing noise.SOLUTION: A noise reduction device (1) comprises: a pipe part (2) that has a first air passage (16) for transmitting noise in a first transmission direction, and a second air passage (17) for transmitting the noise in a second transmission direction different from the first transmission direction; a reference microphone (5) into which sound in the first air passage is input; and a loudspeaker (6) that outputs sound to the second air passage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a noise reduction device and a vacuum cleaner. [Background technology]

[0002] It is known to perform ANC (Active Noise Control) that reduces noise by generating a sound that cancels the noise. For example, ANC is performed using a speaker, a reference microphone, and an error microphone to reduce noise. In addition, in ANC, an ANC feedforward method is also known that uses a feedback canceller to suppress the influence of acoustic feedback (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-190590 Summary of the Invention [Problem to be solved by the invention]

[0004] When using ANC to reduce noise transmitted through a pipe, the smaller the size of the device, the smaller the distance between the reference microphone and the speaker. This means that the time required to calculate the phase of the sound output from the speaker to cancel out the noise becomes shorter, limiting how small the device can be. In addition, the effect of acoustic feedback becomes greater, making it easier for feedback to occur.

[0005] An object of one aspect of the present invention is to provide a noise reduction device that is compact and can effectively reduce noise. [Means for solving the problem]

[0006] In order to solve the above problems, a noise reduction device according to one embodiment of the present invention includes a pipe section having a first air passage that transmits noise emitted by a noise source in a first transmission direction and a second air passage that communicates with the first air passage via a space and transmits the noise in a second transmission direction different from the first transmission direction, a reference microphone to which sound within the first air passage is input, and a speaker that outputs sound to the second air passage.

[0007] In order to solve the above problems, a noise reduction device according to one embodiment of the present invention comprises a pipe section having a first air passage that transmits noise emitted by a noise source in a first transmission direction, and a second air passage that communicates with the first air passage via a space and transmits the noise in a second transmission direction different from the first transmission direction, the pipe section having an inner pipe and an outer pipe, the inner pipe forming the first air passage inside a first inner surface of the inner pipe, and the outer pipe forming the second air passage between a second inner surface of the outer pipe and a first outer surface of the inner pipe. Effect of the Invention

[0008] According to one aspect of the present invention, it is possible to achieve miniaturization and effectively reduce noise. [Brief description of the drawings]

[0009] [Figure 1] 1 is a configuration diagram showing an example of a noise reduction device according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the noise reduction device. [Diagram 3] FIG. 11 is a configuration diagram showing another example of a noise reduction device. [Figure 4] 7 is a diagram illustrating the details and operation of a control unit of a noise reduction device according to a second embodiment. FIG. [Diagram 5] FIG. 11 is a schematic diagram showing a structure of a part of a vacuum cleaner according to a third embodiment. [Figure 6] FIG. 2 is a schematic diagram showing the overall structure of the vacuum cleaner. [Figure 7]4 is a schematic diagram showing positions of a speaker and a reference microphone of the noise reduction device in the vacuum cleaner. FIG. [Figure 8] 4 is a schematic diagram showing positions of a speaker and a reference microphone of the noise reduction device in the vacuum cleaner. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Embodiment 1] Hereinafter, one embodiment of the present invention will be described in detail.

[0011] Fig. 1 is a configuration diagram showing an example of a noise reduction device 1 according to a first embodiment. As shown in Fig. 1, the noise reduction device 1 includes a pipe section 2, a reference microphone 5, a control section 50, a speaker 6, and an error microphone 7. A noise source 9 is located at one end of the pipe section 2. The noise source 9 is a device that generates noise.

[0012] Such a noise reduction device 1 is provided in a device that generates noise, such as a vacuum cleaner or an air conditioner. In this case, the noise source 9 is, for example, a blower. The blower includes a motor that rotates a fan. The noise includes the sound of the wind and the sound of the motor.

[0013] 1, the noise source 9 may be covered with a cover 10. The cover 10 is connected to one end of the pipe section 2. The cover 10 is desirably configured to include a sound absorbing material such as urethane or felt. By covering the noise source 9, the cover 10 can confine the noise inside the pipe section 2.

[0014] The pipe section 2 transmits the noise generated by the noise source 9. The pipe section 2 is a tubular member having a cavity inside. The cavity inside the pipe section 2 functions as a transmission passage (air passage) for transmitting the noise generated by the noise source 9. In detail, the pipe section 2 has a first air passage 16 that transmits the noise generated by the noise source 9 in a first transmission direction, and a second air passage 17 that communicates with the first air passage 16 via a space 19 and transmits the noise in a second transmission direction different from the first transmission direction. The first air passage 16 includes an input part 5a where a reference microphone 5 described later acquires sound. The second air passage 17 includes an output part 6a where a speaker 6 described later outputs sound. The pipe section 2 is, for example, cylindrical or rectangular. One end of the pipe section 2 is directed toward the noise source 9. The end of the pipe section 2 on the downstream side of the transmission direction of the noise, opposite to the noise source 9, is closed. 1, in a configuration in which a cover 10 covering a noise source 9 is connected to one end, one end of the pipe section 2 is open. Hereinafter, the noise source 9 side of the pipe section 2 may be referred to as the upstream side (upstream side in the first transmission direction) and the opposite side as the downstream side (downstream side in the first transmission direction). The downstream side of the pipe section 2 has a double pipe structure.

[0015] 2 is a cross-sectional view of the noise reduction device 1. As shown in FIG.

[0016] The inner pipe 3 transmits noise and has an open downstream end 31 (first end). In this example, the inner pipe 3 also has an open upstream end 32 (third end) to which a cover 10 that covers the noise source 9 is connected.

[0017] The outer pipe 4 is inserted into the outer periphery of the inner pipe 3 on the downstream side in the transmission direction, with a distance between it and the outer periphery of the inner pipe 3. In other words, the outer pipe 4 is formed to be larger in diameter than the inner pipe 3 and shorter than the inner pipe 3. The outer pipe 4 extends downstream of the downstream end 31 of the inner pipe 3. In other words, the downstream end 41 (second end) of the outer pipe 4 is located downstream of the downstream end 31 of the inner pipe 3. The downstream end 41 of the outer pipe 4 is closed, and the upstream end 42 (fourth end) is open.

[0018] As a result, the inner pipe 3 forms a first air passage 16 (transmitting noise in a first transmission direction) inside the first inner circumferential surface 36 of the inner pipe 3. The outer pipe 4 forms a second air passage 17 (transmitting noise in a second transmission direction) between the second inner circumferential surface 46 of the outer pipe 4 and the first outer circumferential surface 37 of the inner pipe 3. That is, by inserting the outer pipe 4 into the outer periphery of the inner pipe 3 on the downstream side in the transmission direction, the downstream side of the pipe section 2 has a double pipe structure, and the first air passage 16 and the second air passage 17 are formed. The noise output from the noise source 9 is transmitted in the first transmission direction through the first air passage 16, changes direction in the space 19, transmitted in the second transmission direction through the second air passage 17, and output to the outside from the upstream end 42 of the outer pipe 4. In the example shown in FIG. 2, the second transmission direction is opposite to the first transmission direction. As a result, noise emitted from the downstream end 31 of the inner pipe 3 in the first transmission direction is redirected (ie, diffracted) to the second transmission direction and is less likely to be transmitted to the second air passage 17.

[0019] The speaker 6 outputs sound under the control of the control unit 50. The speaker 6 outputs sound toward the inside of the pipe section 2. The speaker 6 outputs sound including a sound that reduces noise. Specifically, the speaker 6 outputs sound that is in the opposite phase to the noise transmitted inside the pipe section 2. The noise emitted by the noise source 9 is transmitted inside the inner pipe 3. The noise transmitted inside the inner pipe 3 is further transmitted inside the outer pipe 4. The noise transmitted inside the outer pipe 4 is canceled out by the sound output from the speaker 6. Therefore, the noise output from the downstream end of the pipe section 2 is reduced.

[0020] The speaker 6 is located in the outer pipe 4. The speaker 6 is arranged with its diaphragm facing in a direction intersecting the transmission direction. Specifically, the speaker 6 outputs sound to the space (second air passage 17) between the outer pipe 4 and the inner pipe 3, which form a double-pipe structure in the pipe section 2. An output part 6a from which the sound of the speaker 6 is output to the inside of the pipe section 2 is located on the side surface of the outer pipe 4.

[0021] As shown in the example in Fig. 2, the speaker 6 is directly connected to the pipe section 2 (specifically, the outer pipe 4). In this case, the output part 6a serves as the diaphragm of the speaker 6. The speaker 6 may be disposed inside a branch pipe branching off from the pipe section 2. In this case, the sound output by the speaker 6 is transmitted to the inside of the pipe section 2 through an opening of the branch pipe. The output part 6a serves as the opening of the branch pipe.

[0022] The reference microphone 5 acquires sound inside the inner pipe 3 (first air passage 16). An input portion 5a where the reference microphone 5 acquires sound is located on the side surface of the inner pipe 3. In the example shown in FIG. 2, the reference microphone 5 is located in the inner pipe 3. Note that the reference microphone 5, like the speaker 6, may be disposed inside a branch pipe branching off from the pipe section 2 (specifically, the inner pipe 3).

[0023] According to the above configuration, noise transmitted through the first air passage 16 enters and is transmitted through the second air passage 17, which has a different noise transmission direction from the first air passage 16. This makes it possible to shorten the actual separation distance between the reference microphone 5 and the speaker 6 while ensuring a long distance on the noise transmission path between the reference microphone 5 and the speaker 6. Therefore, the noise reduction device 1 can be made smaller while ensuring the processing time for ANC.

[0024] Furthermore, since the speaker 6 outputs sound to the second air passage 17, the sound emitted from the speaker 6 is prevented from traveling directly toward the reference microphone 5, thereby suppressing howling.

[0025] The error microphone 7 picks up sound inside the pipe section 2 at a position where the noise emitted by the noise source 9 and the sound output by the speaker 6 join together. Specifically, the error microphone 7 is located in a portion of the outer pipe 4 that extends downstream from the downstream end of the inner pipe 3. The error microphone 7 picks up sound from the overlapping portion of the outer pipe 4 where it overlaps with the inner pipe 3. By providing the error microphone 7, ANC can be performed with high accuracy even if the shape of the pipe section 2 changes or the temperature changes.

[0026] The control unit 50 controls the sound output from the speaker 6. The control unit 50 is, for example, a processor such as a CPU (Central Processing Unit) or a logic circuit (hardware) formed in an integrated circuit (IC (Integrated Circuit) chip). The control unit 50 performs ANC (Active Noise Control) to reduce noise by generating a sound that cancels the noise. For example, the control unit 50 performs ANC using the speaker 6, the reference microphone 5, and the error microphone 7 to reduce noise transmitted inside the pipe unit 2.

[0027] In the ANC, the control unit 50 controls the sound output from the speaker 6 based on the sound input to the reference microphone 5 and the error microphone 7. Specifically, for example, the control unit 50 outputs a sound that reduces noise, such as a sound in antiphase with the noise, from the speaker 6 based on the sound input to the reference microphone 5 and the error microphone 7. The control unit 50 controls the sound output from the speaker 6 so that the sound input to the error microphone 7, i.e., the reduced noise, is reduced in volume. This reduces the noise transmitted inside the pipe section 2, and the reduced noise is output from the outlet of the pipe section 2 (the upstream end 42 of the outer pipe 4).

[0028] According to the noise reduction device 1, the pipe section 2 is disposed near the noise source 9, one end of the pipe section 2 is directed toward the noise source 9, and the noise emitted by the noise source 9 can be transmitted inside the pipe section 2 by the pipe section 2. The noise transmitted inside the pipe section 2 can then be cancelled out by the speaker 6. This makes it possible to reduce the noise output from the outlet of the pipe section 2 (the upstream end 42 of the outer pipe 4). The noise reduction device according to the first embodiment further includes a cover 10 that covers the noise source 9. Covering the noise source 9 with the cover 10 enhances the effect of reducing noise.

[0029] The noise reduction device 1 further includes a wall portion 11. The wall portion 11 is provided at the downstream end portion 41 of the outer pipe 4. The wall portion 11 forms a space 19 between the downstream end portion 31 of the inner pipe 3 and the downstream end portion 41 of the outer pipe 4. Therefore, the first air passage 16 formed inside the inner pipe 3 communicates with the second air passage 17 formed between the first outer peripheral surface 37 of the inner pipe 3 and the second inner peripheral surface 46 of the outer pipe 4 through the space 19. The noise transmitted through the first air passage 16 is transmitted to the space 19. The noise transmitted to the space 19 is diffused in the space 19. The noise diffused in the space 19 can reach the second air passage 17 by diffracting toward the second air passage 17 or by being reflected by the wall portion 11. The noise that reaches the second air passage 17 is transmitted through the second air passage 17 in the opposite direction to the first air passage 16. This reduces the transmission of noise to the second air passage 17.

[0030] It is preferable that a sound absorbing material is provided on the inside of the wall portion 11. Of the noise emitted from the downstream end portion 31 of the inner pipe 3, the noise that reaches the wall portion 11 is absorbed by the sound absorbing material in the wall portion 11. Furthermore, by providing the wall portion 11 with a sound absorbing material, the noise that reaches the wall portion 11 is reflected by the wall portion 11 and is prevented from reaching the second air passage 17. This makes it possible to further reduce noise. Therefore, the sound output from the speaker 6 (sound for canceling out the noise transmitted to the second air passage) can be made smaller, and howling can be further suppressed.

[0031] The diameter of the outer pipe 4 is preferably 5 cm or less at the output part 6a where the sound of the speaker 6 is output. By making the diameter of the outer pipe 4 at the output part 6a 5 cm or less, the sound output from the speaker 6 (typically sound of 4 kHz or less) can be transmitted one-dimensionally in the sound traveling direction inside the pipe part 2 (specifically, the second air passage 17), and ANC can be performed with high accuracy.

[0032] The distance L in the first transmission direction (axial direction of the pipe section 2) between the downstream end 31 of the inner pipe 3 and the downstream end 41 of the outer pipe 4 should be equal to or less than the inner diameter of the inner pipe 3. In other words, the width of the space 19 in the first transmission direction should be equal to or less than the inner diameter of the inner pipe 3. This makes it possible to suppress pressure loss of the exhaust gas discharged from the inner pipe 3. Also, it is possible to suppress the generation of new noise due to the exhaust gas turning back.

[0033] Note that the noise reduction device 1 does not need to perform ANC (i.e., it does not need to have the reference microphone 5 and the speaker 6) so long as it has the double-tube structure of the pipe section 2 described above (the first air passage 16 and the second air passage 17). As described above, the noise reduction device 1 has at least the double-tube structure of the pipe section 2, which makes it difficult for noise transmitted through the first air passage 16 to be transmitted to the second air passage 17. In other words, noise can be effectively reduced.

[0034] Fig. 3 is a configuration diagram showing another example of a noise reduction device (referred to as noise reduction device 1A). As shown in Fig. 3, the outlet of the pipe section 2 in the noise reduction device 1A, i.e., the upstream end 42 of the outer pipe 4, has a gradually expanding diameter shape with an opening area that gradually increases. This structure of the upstream end 42 of the outer pipe 4 makes it possible to suppress the generation of new noise caused by exhaust gas generated at the exhaust outlet. Furthermore, even if there is noise that cannot be silenced by ANC, it is possible to suppress the noise from being reflected at the exhaust outlet. Therefore, it is possible to suppress the noise from becoming a cause of howling.

[0035] (Control unit of noise reduction device) Fig. 4 is a diagram illustrating the details and operation of the control unit 50 of the noise reduction device according to the second embodiment. Note that in Fig. 4, the illustration of the cover 10, the pipe portion 2, and the treble reduction portion 12 is omitted.

[0036] The control unit 50 has a signal amplification conversion unit 502, an AGC (Automatic Gain Control) unit 503, a noise filter unit 504, a low-pass filter (LPF) 505, an input filter unit 506, a feedback cancellation node 507, an adaptive filter 508, a transfer function H learning unit 509, an output filter unit 510, a DAC (Digital to Analog Converter) 511, a feedback canceller 512, an FBC gain compensation unit 513, a secondary path estimation filter 514, a secondary path correction node 515, a signal amplification conversion unit 516, an AGC unit 517, an error sound filter unit 518, a low-pass filter (LPF) 519, an input filter unit 520, a transfer function F learning unit 521, a sound signal generation unit 522, and a transfer function S learning unit 523.

[0037] Noise emitted from a noise source 9 is input to the reference microphone 5 , and the reference microphone 5 outputs a noise source signal to a signal amplification conversion unit 502 .

[0038] The signal amplification conversion unit 502 includes a programmable gain amplifier (PGA) and an analog to digital converter (ADC). The PGA amplifies the noise source signal output by the reference microphone 5. The PGA can switch the amplification factor. The PGA switches the amplification factor upon receiving an instruction from the AGC unit 503. The ADC converts the signal amplified by the PGA into a digital signal.

[0039] The AGC unit 503 controls the gain of the reference microphone 5. Specifically, the AGC unit 503 changes the amplification factor of the PGA of the signal amplification conversion unit 502. The AGC unit 503 receives a signal output by the ADC of the signal amplification conversion unit 502 and determines the amplification factor of the PGA. The AGC unit 503 determines the amplification factor of the PGA by following the signal output by the ADC. For example, the AGC unit 503 determines the amplification factor of the PGA so that the dynamic range of the PGA is maximized using AGC. For example, the AGC unit 503 performs the following process regarding AGC. The AGC unit 503 detects the output of the ADC of the signal amplification conversion unit 502 for each first period (for example, 5.21 μs), calculates the square average value for each second period (for example, 1.33 ms) from the square sum of the detected multiple (for example, 256) outputs, and calculates a moving average value from the calculated multiple square average values. The AGC unit 503 determines at regular intervals whether the calculated moving average value is greater than a preset target range and the current value of the amplification factor of the PGA of the signal amplification conversion unit 502 is not the minimum value, and if the calculated moving average value is greater than a preset target range and the current value of the amplification factor of the PGA of the signal amplification conversion unit 502 is not the minimum value, reduces the value of the amplification factor of the PGA of the signal amplification conversion unit 502 by a predetermined value. Also, the AGC unit 503 determines at regular intervals whether the calculated moving average value is less than a preset target range and the current value of the amplification factor of the PGA of the signal amplification conversion unit 502 is not the maximum value, and if the calculated moving average value is less than a preset target range and the current value of the amplification factor of the PGA of the signal amplification conversion unit 502 is not the maximum value, increases the value of the amplification factor of the PGA of the signal amplification conversion unit 502 by a predetermined value.

[0040] The noise filter unit 504 filters the signal output by the ADC to generate a filtered noise signal h(n). The noise filter unit 504 includes a low-pass filter (LPF) 505 that performs thinning, and an input filter unit 506.

[0041] The feedback cancellation node 507 generates a feedback-canceled noise signal x(n) from the filtered noise signal h(n) and an FBC (Feedback Control) gain compensation signal d(n). The feedback cancellation node 507 generates the feedback-canceled noise signal x(n) by, for example, subtracting the FBC gain compensation signal d(n) from the filtered noise signal h(n).

[0042] The adaptive filter 508 generates an anti-noise signal y(n) from the feedback-canceled noise signal x(n). The anti-noise signal y(n) includes information for reducing the noise generated by the noise source 9. The adaptive filter 508 is, for example, a digital filter that operates dynamically. The adaptive filter 508 has a transfer function H that generates the anti-noise signal y(n) from the feedback-canceled noise signal x(n). The transfer function H is learned from the filtered error signal k(n) of the error microphone 7 and the secondary path estimation filtered signal r(n) of the feedback-canceled noise signal x(n). The transfer function H is learned by the transfer function H learning unit 509. A specific example will be described. The filtered noise signal h(n) that has passed through the noise filter unit 504 is processed by the adaptive filter 508 to obtain the anti-noise signal y(n). The anti-noise signal y(n) passes through the output filter unit 510 and the DAC 511 and is input to the speaker 6, which then emits a control sound. The control sound emitted by the speaker 6 interacts with the noise that has passed through the primary path. The sound resulting from the interaction of the noise that has passed through the primary path and the control sound emitted by the speaker 6 is input to the error microphone 7. The transfer function H is trained so as to reduce the sound input to the error microphone 7. Here, it is preferable to train the transfer function H based on the secondary path estimation filtered signal r(n) output from the secondary path estimation filter 514 that imitates the characteristics of the auxiliary path including the output filter unit 510, the secondary path, and the error sound filter unit 518. This is because a transfer function H that can remove the influence of the auxiliary path including the output filter unit 510, the secondary path, and the error sound filter unit 518 and accurately cancel out the noise that has passed through the primary path can be obtained.

[0043] The output filter unit 510 filters the anti-noise signal y(n) and includes a low-pass filter that performs interpolation.

[0044] A digital to analog converter (DAC) 511 converts the signal filtered by the output filter unit 510 into an analog signal, and outputs it to the speaker 6 .

[0045] The speaker 6 receives the analog signal from the DAC 511 and emits a control sound. The speaker 6 emits a sound that cancels the noise that has passed through the primary path at the control point. Then, the noise that has been controlled at the control point, i.e., the reduced noise, is output from the pipe section 2 and reaches the user.

[0046] The feedback canceller 512 generates a feedback suppression signal i(n) from the anti-noise signal y(n). The feedback suppression signal i(n) includes information regarding the input of the sound output by the speaker 6 to the reference microphone 5. A part of the sound output by the speaker 6 is input to the reference microphone 5 through a feedback path. The feedback canceller 512 is, for example, a dynamically operating digital filter. The feedback canceller 512 has a transfer function F that generates the feedback suppression signal i(n) from the anti-noise signal y(n). The transfer function F estimates the input of the sound output by the speaker 6 to the reference microphone 5 to generate a signal. The transfer function F is learned during the path estimation operation and stored in the feedback canceller 512.

[0047] The FBC gain compensation unit 513 generates an FBC gain compensation signal d(n) from the feedback suppression signal i(n). The FBC gain compensation signal d(n) includes information on the input of the sound output by the speaker 6 to the reference microphone 5. The FBC gain compensation unit 513 generates the FBC gain compensation signal d(n) from the feedback suppression signal i(n) and a correction coefficient Z. For example, the correction coefficient Z is generated from the amplification factor WMEAS of the PGA of the signal amplification conversion unit 502 acquired at the time of path estimation and the current amplification factor WAN C of the PGA of the signal amplification conversion unit 502. The amplification factor WMEAS is a fixed value, and the amplification factor WAN C is a variable value. For example, the correction coefficient Z is obtained by dividing the amplification factor WAN C of the PGA of the signal amplification conversion unit 502 at the time of path estimation by the amplification factor WMEAS of the PGA of the signal amplification conversion unit 502 acquired at the time of path estimation. For example, the FBC gain compensation signal d(n) is obtained by multiplying the feedback suppression signal i(n) by the correction coefficient Z. The gain factor WMEAS is an example of the setting value of the gain of the reference microphone 5 acquired at the time of path estimation. The gain factor WAN C is the current setting value of the gain of the reference microphone 5.

[0048] The secondary path estimation filter 514 generates a secondary path estimation filtered signal r(n) from the feedback cancellation noise signal x(n). The secondary path estimation filter 514 is, for example, a digital filter that operates dynamically. The secondary path estimation filter 514 has a transfer function S that generates the secondary path estimation filtered signal r(n) from the feedback cancellation noise signal x(n). The transfer function S generates a signal by estimating the input of the sound output by the speaker 6 to the error microphone 7. The transfer function S is learned during the path estimation operation and stored in the secondary path estimation filter 514.

[0049] The secondary path correction node 515 generates a secondary path correction signal e(n) from the secondary path estimated filtered signal r(n) and the filtered error signal k(n). For example, the secondary path correction node 515 obtains the secondary path correction signal e(n) by subtracting the filtered error signal k(n) from the secondary path estimated filtered signal r(n).

[0050] Noise (error sound) after being controlled by the control point is input to error microphone 7 , and error microphone 7 outputs the error sound signal to signal amplification conversion unit 516 .

[0051] The signal amplification conversion unit 516 includes a PGA and an ADC. The PGA amplifies the error sound signal output by the error microphone 7. The PGA can switch the amplification factor. The PGA switches the amplification factor upon receiving an instruction from the AGC unit 517. The ADC converts the signal amplified by the PGA into a digital signal.

[0052] The AGC unit 517 controls the gain of the error microphone 7. Specifically, the AGC unit 517 changes the amplification factor of the PGA of the signal amplification conversion unit 516. The AGC unit 517 receives the signal output by the ADC of the signal amplification conversion unit 516 and determines the amplification factor of the PGA of the signal amplification conversion unit 516. The AGC unit 517 determines the amplification factor of the PGA of the signal amplification conversion unit 516 in accordance with the signal output by the ADC of the signal amplification conversion unit 516. The AGC unit 517 determines the amplification factor of the PGA of the signal amplification conversion unit 516, for example, so that the dynamic range of the PGA of the signal amplification conversion unit 516 is maximized.

[0053] The error sound filter unit 518 filters the signal output by the ADC of the signal amplification conversion unit 516 to generate a filtered noise signal k(n). The error sound filter unit 518 includes, for example, a low-pass filter (LPF) 519 that performs thinning, and an input filter unit 520.

[0054] The transfer function F learning unit 521 learns the transfer function F from the post-feedback cancellation noise signal x(n) and the output a(n) of the sound signal generating unit 522. The transfer function F learning unit 521 implements least mean squares (LMS), recursive least mean squares (RLMS), normalized least mean squares (NLMS), or any other suitable algorithm.

[0055] The transfer function S learning unit 523 learns the transfer function S from the filtered error signal k(n) and the output a(n) of the sound signal generating unit. The transfer function S learning unit 523 implements least mean squares (LMS), recursive least mean squares (RLMS), normalized least mean squares (NLMS), or any other suitable algorithm.

[0056] The transfer function H learning unit 509 learns the transfer function H from the filtered error signal k(n) and the secondary path estimated filtered signal r(n). The transfer function H learning unit 509 implements least mean squares (LMS), recursive least mean squares (RLMS), normalized least mean squares (NLMS), or any other suitable algorithm.

[0057] (Route Estimation) Here, a description will be given of path estimation in ANC, learning of transfer function F, and learning of transfer function S. Path estimation is to estimate the path of sound propagating inside pipe 401. The path of sound propagating inside pipe 401 includes a feedback path and a secondary path.

[0058] The route estimation is performed, for example, before the shipment of a product equipped with the noise reduction device 1. Note that the route estimation may be performed based on an instruction from a user after the shipment of the product.

[0059] During path estimation, the amplification factor of the PGA of each of the signal amplification and conversion unit 502 and the signal amplification and conversion unit 516 is fixed.

[0060] The sound signal generating unit 522 outputs, for example, a uniform random number signal. The sound signal generating unit 522 outputs a random number signal using, for example, a random number signal having a specific frequency distribution. The speaker 6 generates a sound based on the random number signal generated by the sound signal generating unit 522. The sound generated by the speaker 6 is transmitted to the feedback path and the secondary path.

[0061] (Learning the transfer function F) The sound output from the speaker 6 and transmitted to the feedback path is input to the reference microphone 5. The signal output from the reference microphone 5 is processed by the signal amplification conversion unit 502 and the noise filter unit 504, and a filtered noise signal h(n) is output to the feedback cancellation node 507. Meanwhile, the feedback canceller 512 receives the output a(n), which is a random number signal having a specific frequency distribution, and outputs a feedback suppression signal i(n) based on the currently stored transfer function F. The FBC gain compensation unit 513 generates an FBC gain compensation signal d(n) from the feedback suppression signal i(n). The feedback cancellation node 507 calculates the difference between the filtered noise signal h(n) and the FBC gain compensation signal d(n) to generate a feedback canceled noise signal x(n).

[0062] Furthermore, the output a(n) of the sound signal generating unit 522 is input to the transfer function F learning unit 521. The transfer function F learning unit 521 learns the transfer function F from the feedback-canceled noise signal x(n) and the output a(n) of the sound signal generating unit 522. At this time, for example, a wideband random number signal uncorrelated with the noise source signal is input to the feedback canceller 512, and the output is compared with a signal passed through the feedback path and the noise filter unit 504 and a signal passed through the feedback canceller 512 and the FBC gain compensation unit 513, and the filter coefficient of the feedback canceller 512, i.e., the transfer function F, is learned in a direction that reduces the difference, that is, the feedback-canceled noise signal x(n). The transfer function F learning unit 521 can make the filter coefficient of the feedback canceller 512 closer to the characteristics of the path including the feedback path and the noise filter unit 504 by using the various algorithms described above. The learned transfer function F is stored in the feedback canceller 512.

[0063] (Learning the transfer function S) The sound output from the speaker 6 and transmitted through the secondary path is input to the error microphone 7. The signal output from the error microphone 7 is processed by the signal amplification conversion unit 516 and the error sound filter unit 518, and the filtered error signal k(n) output from the error sound filter unit 518 is output to the secondary path correction node 515. On the other hand, the secondary path estimation filter 514 takes as input the output a(n) which is a random number signal having a specific frequency distribution, and generates a signal r(n) after the secondary path estimation filter based on the transfer function S currently stored. The secondary path correction node 515 calculates the difference between the signal r(n) after the secondary path estimation filter and the filtered error signal k(n), and generates a secondary path correction signal e(n). The secondary path correction signal e(n) is input to the transfer function S learning unit 523. The transfer function S learning unit 523 performs learning of the transfer function S from the secondary path correction signal e(n) and the output a(n) of the sound signal generation unit 522. At this time, for example, a broadband random number signal uncorrelated with the noise source signal is input to the secondary path estimation filter 514, and the output thereof is compared with the signal passing through the secondary path and the error sound filter unit 518 and the signal passing through the secondary path estimation filter 514, and the filter coefficients of the secondary path estimation filter 514, that is, the transfer function S, are learned in the direction of reducing the secondary path correction signal e(n) which is the difference. The transfer function S learning unit 523 can approximate the filter coefficients of the secondary path estimation filter 514 to the characteristics of the path including the secondary path and the error sound filter unit 518 by using the above various algorithms. The learned transfer function S is stored in the secondary path estimation filter 514.

[0064] <ANC operation> Next, the processing during the operation of ANC will be described.

[0065] During ANC operation, AGC is performed on the reference microphone 5 and the error microphone 7, and the amplification factor of the PGA of each of the signal amplification conversion unit 502 and the signal amplification conversion unit 516 becomes variable. That is, the AGC unit 503 controls the gain of the reference microphone 5. Specifically, the AGC unit 503 changes the amplification factor of the PGA of the signal amplification conversion unit 502. In addition, the AGC unit 517 controls the gain of the error microphone 7. Specifically, the AGC unit 517 changes the amplification factor of the PGA of the signal amplification conversion unit 516.

[0066] The sound input to the reference microphone 5 is processed by the signal amplification and conversion unit 502, the noise filter unit 504, and the feedback cancellation node 507, and the post-feedback cancellation noise signal x(n) output from the feedback cancellation node 507 is input to the adaptive filter 508.

[0067] The anti-noise signal y(n) generated by the adaptive filter 508 is input to the output filter unit 510, which filters the anti-noise signal y(n), and the DAC 511 converts the signal filtered by the output filter unit 510 into an analog signal and outputs it to the speaker 6. The speaker 6 receives the analog signal from the DAC 511 and emits a control sound, thereby reducing the noise emitted by the noise source 9.

[0068] The anti-noise signal y(n) generated by the adaptive filter 508 is input to the feedback canceller 512, which generates a feedback suppression signal i(n) from the anti-noise signal y(n) and outputs it to the FBC gain compensation unit 513. The FBC gain compensation unit 513 generates an FBC gain compensation signal d(n) from the feedback suppression signal i(n) and a correction coefficient Z and outputs it to the feedback cancellation node 507. For example, the correction coefficient Z is obtained by dividing the current amplification factor WAN C of the PGA of the signal amplification conversion unit 502 by the amplification factor WMEAS of the PGA of the signal amplification conversion unit 502 acquired at the time of path estimation. Also, for example, the FBC gain compensation signal d(n) is obtained by multiplying the feedback suppression signal i(n) by the correction coefficient Z.

[0069] The sound input to the error microphone 7 is processed by a signal amplification conversion unit 516 and an error sound filter unit 518 , and the filtered error signal k(n) output from the error sound filter unit 518 is input to a transfer function H learning unit 509 .

[0070] The sound input to the reference microphone 5 is processed by the signal amplification and conversion unit 502, the noise filter unit 504, the feedback cancellation node 507, and the secondary path estimation filter 514, and the secondary path estimation filtered signal r(n) output from the secondary path estimation filter 514 is input to the transfer function H learning unit 509.

[0071] A transfer function H learning unit 509 learns a transfer function H from the filtered error signal k(n) and the secondary path estimation filtered signal r(n).

[0072] In noise reduction device 1 of the second embodiment, the amplification factor (volume) of the PGA of each of signal amplification conversion units 502 and 516 is fixed during path estimation, and the amplification factor of each of the PGA of signal amplification conversion units 502 and 516 is made variable during ANC operation, and the FBC gain compensation signal d(n) is compensated by multiplying the feedback inhibition signal i(n) by a gain that offsets the varied gain amount.

[0073] According to the noise reduction device of the second embodiment, the volumes of the reference microphone and the error microphone can be fixed during path estimation, and AGC operation can be performed during ANC operation. This makes it possible to make the most of the dynamic range of the reference microphone and the error microphone, and maximize the sensitivity of the reference microphone and the error microphone, thereby maximizing the effect of the ANC. In particular, by maximizing the sensitivity of the error microphone, it is possible to minimize the noise after reduction by the sound output from the speaker as a result of the ANC.

[0074] (Treble reduction section) 5 is a schematic diagram showing the structure of part (motor 202 and noise reduction device 1) of vacuum cleaner 110 according to the third embodiment. As shown in FIG. 5, noise reduction device 1 may further include a treble reduction section 12.

[0075] The treble reduction section 12 is located between the noise reduction device 1 and the noise source 9. The treble reduction section 12 reduces high-frequency sounds (2 KHz or higher) contained in the noise emitted by the noise source. The treble reduction section 12 is provided, for example, inside the inner pipe 3 upstream of the reference microphone 5, and is an absorbing material capable of absorbing high-frequency sounds.

[0076] The noise that passes through the treble reduction section 12 and is transmitted to the downstream end of the pipe section 2 becomes a low-frequency sound with high-frequency sounds reduced by the treble reduction section 12. The sound of the speaker 6 that is output to cancel out such noise also becomes a low-frequency sound. Here, low-frequency sounds are less likely to be diffracted than high-frequency sounds. Therefore, the noise emitted from the downstream end 31 of the inner pipe 3 is diffracted and is less likely to be transmitted to the second air passage 17. In addition, the sound of the speaker 6 is also less likely to be transmitted to the reference microphone 5 on the upstream side of the inner pipe 3. Therefore, by providing the treble reduction section 12 in the noise reduction device 1, it is possible to further suppress howling.

[0077] 5, the reference microphone 5 may be provided on the outer circumferential surface of the outer pipe 4. The reference microphone 5 acquires sound at an input part 5a located on a side surface of the inner pipe 3 via a branch pipe 3a branching off from the inner pipe 3. The branch pipe 3a is located in the second air passage, and connects the outside of the outer pipe 4 with the inside of the inner pipe 3.

[0078] 5, the outer pipe 4 may extend upstream so that the upstream end 42 of the outer pipe 4 is located upstream of the cover 10. The upstream end 42 of the outer pipe 4 is opened and functions as a blowing section 403, which will be described later.

[0079] Fig. 6 is a schematic diagram showing the overall structure of vacuum cleaner 110. As shown in Fig. 6, vacuum cleaner 110 includes suction unit 121, extension tube 141, filter unit 131, motor 202, cover 10, noise reduction device 1, blowing unit 403, handle 122, display unit 601, and operation unit 701.

[0080] Suction unit 121 sucks in a fluid. Suction unit 121 includes an extension tube 141 extending from filter unit 131 and a nozzle provided at the tip of extension tube 141. Suction unit 121 sucks in dust together with air from the nozzle, and the sucked air and dust are introduced into filter unit 131 through the inside of the extension tube. Air is an example of a fluid.

[0081] The filter unit 131 removes dust from the fluid sucked by the suction unit 121. Specifically, for example, the filter unit 131 separates the sucked dust from the air by a cyclone method.

[0082] The motor 202 includes a blower that generates a suction force, and drives the blower to cause a flow of a fluid. Specifically, for example, the motor 202 drives the blower to suck dust together with air from the suction portion 121 into the filter portion 131.

[0083] The cover 301 covers the motor 202. The cover 301 has an opening 302, and the opening 302 is connected to the upstream end of the pipe section 2 of the noise reduction device 1.

[0084] The motor sound generated by the motor 202 is transmitted to the pipe section 2 as noise. That is, the motor 202 is an example of the noise source 9 described in the first embodiment. The cover 301 covering the motor 202 is the cover 10 described in the first embodiment. The motor 202 and the pipe section 2 communicate with each other to form an exhaust path. The fluid sucked into the suction section 121 and the noise of the motor 202 are output to the exhaust path.

[0085] The noise reduction device 1 is located between the motor 202 (noise source 9) and the blowing section 403, and reduces the noise of the motor 202 transmitted through the exhaust path.

[0086] The blowing section 403 blows out the fluid flowing out from the filter section 131 and the noise of the motor 202. The blowing section 403 is the upstream end 42 of the outer pipe 4. The blowing section 403 opens toward the suction section 121. That is, the blowing section 403 opens toward the side opposite to the user side when the vacuum cleaner 110 is in use. As a result, the fluid passing through the exhaust path is discharged from the blowing section 403 toward the side opposite to the user side. Therefore, the user does not feel uncomfortable when the vacuum cleaner 110 is in use. Even if noise is output from the blowing section 403, the noise is directed toward the side opposite to the user side, so that the volume of the noise heard by the user can be reduced.

[0087] The control unit 50 of the noise reduction device 1 is provided inside the cover 301, and controls the vacuum cleaner 110. The control unit 50 performs ANC to reduce noise by generating a sound that cancels the noise. For example, the control unit 50 performs ANC using the speaker 6, the reference microphone 5, and the error microphone 7, and reduces noise transmitted inside the pipe unit 2. The processing of the control unit 50 is similar to that of the second embodiment, so a description thereof will be omitted.

[0088] When noise is reduced by ANC, if the noise becomes louder, the control unit 50 increases the amount of noise reduction by increasing the sound output from the speaker 6. As a result, the loudness of the noise heard by the user may not change, or may change only slightly. In this way, even if the power of the vacuum cleaner 110 is increased to strengthen the suction force, the loudness of the noise heard by the user may not change, and the user may have difficulty in understanding the operating state of the vacuum cleaner 110. Therefore, the control unit 50 may control the sound output from the speaker 6 so that the amount of noise reduction is not increased from a predetermined value even if the power of the vacuum cleaner 110 increases and the noise becomes louder. The control unit 50 detects the magnitude of the power of the vacuum cleaner 110, for example, from the number of rotations of the motor 202 or the control amount of the motor 202. The control unit 50 also detects the loudness of the noise, for example, from the loudness of the sound input to the reference microphone 5.

[0089] The display unit 601 displays a screen including the status (eg, dust clogging status) of the vacuum cleaner 110. The operation unit 701 accepts user operations.

[0090] 7 is a schematic diagram showing the positions of speaker 6 and reference microphone 5 of noise reduction device 1 in vacuum cleaner 110. Vacuum cleaner 110 is formed by rod-shaped body 111, suction part 121 provided at the bottom of rod-shaped body 111, and handle 122 provided at the top of rod-shaped body 111. The extension tube 141, filter part 131, motor 202, and noise reduction device 1 described above are located on rod-shaped body 111.

[0091] Rod-shaped body 111 is rotatably connected to suction portion 121. Rod-shaped body 111 is inclined with respect to the vertical direction toward the side where the user who operates vacuum cleaner 110 is located when suction portion 121 is in contact with the floor surface. The user operates vacuum cleaner 110 by gripping handle 122 provided on the upper part of rod-shaped body 111 with suction portion 121 in contact with the floor surface. In the example shown in FIG. 7, handle 122 is further inclined toward the floor side with respect to rod-shaped body 111 so that the user can easily grip it when suction portion 121 is in contact with the floor surface. Hereinafter, the surface of rod-shaped body 111 and handle 122 that faces the floor side when in use is referred to as the bottom surface, and the surface opposite the bottom surface is referred to as the top surface.

[0092] The display unit 601 is provided on the upper surface of the rod-shaped body 111 (the noise reduction device 1 in the example shown in FIG. 7) so that the user who is using the vacuum cleaner 110 can easily see it. Similarly, the operation unit 701 is provided on the upper surface of the handle 122 so that the user who is using the vacuum cleaner 110 can easily operate it. Meanwhile, the speaker 6 and the reference microphone 5 are provided on the lower surface of the rod-shaped body 111 (specifically, the noise reduction device 1) that faces the floor when in use. In other words, the speaker 6 and the reference microphone 5 are provided on the opposite side (back side) of the rod-shaped body 111 from the side where the display unit 601 or the operation unit 701 is located. In further other words, the speaker 6 and the reference microphone 5 are provided on the surface of the rod-shaped body 111 where the handle 122 is bent (inclined) with respect to the rod-shaped body 111.

[0093] As a result, the speaker 6 and the reference microphone 5 are positioned between the vacuum cleaner 110 and the user when the vacuum cleaner 110 is in use. This reduces the possibility that the speaker 6 and the reference microphone 5, which are precision machines, will hit something. Even if the vacuum cleaner 110 is laid down on the floor so that the lower surface of the rod-shaped body 111 faces the floor, the speaker 6 and the reference microphone 5 are located in the space formed by the rod-shaped body 111 and the handle 122, and therefore can avoid contact with the floor. Even if the vacuum cleaner 110 is laid down on the floor so that the side surface of the rod-shaped body 111 contacts the floor, the diameter of the rod-shaped body 111 is larger than the width of the speaker 6 and the reference microphone 5, and therefore can avoid contact with the floor.

[0094] In other words, the speaker 6 and the reference microphone 5 may be provided on a surface facing a straight line L1 connecting an end 122a opposite to the base end of the handle 122 (the connection portion between the noise reduction device 1 and the handle 122) and the connection portion 161 between the suction portion 121 and the rod-shaped body 111 (see FIG. 7). In detail, the speaker 6 and the reference microphone 5 are preferably located closer to the main body of the vacuum cleaner 110 than the straight line L1. This further reduces the possibility that the speaker 6 and the reference microphone 5, which are precision machines, will collide with an object or the floor.

[0095] FIG. 8 is a schematic diagram showing the positions of the speaker 6 and the reference microphone 5 of the noise reduction device 1A in the vacuum cleaner 110 (when the vacuum cleaner 110 is equipped with the noise reduction device 1A described above). In the noise reduction device 1A, the upstream end 42 of the outer pipe 4 (i.e., the blowing section 403) has a gradually expanding diameter shape with an opening area. In this case, the speaker 6 and the reference microphone 5 may be provided on a surface facing a straight line L2 connecting the end 122a on the opposite side to the base end of the handle 122 and the upstream end 42 of the outer pipe 4 on the lower surface of the rod-shaped body 111. In detail, the speaker 6 and the reference microphone 5 are preferably located closer to the main body of the vacuum cleaner 110 than the straight line L2. This further reduces the possibility that the speaker 6 and the reference microphone 5, which are precision machines, hit an object or the floor.

[0096] 〔summary〕 A noise reduction device according to a first aspect of the present invention includes a pipe section having a first air passage that transmits noise emitted by a noise source in a first transmission direction, and a second air passage that communicates with the first air passage via a space and transmits the noise in a second transmission direction different from the first transmission direction, a reference microphone to which sound within the first air passage is input, and a speaker that outputs sound to the second air passage.

[0097] According to the above configuration, the noise transmitted through the first air passage enters the second air passage, which has a different noise transmission direction from the first air passage, and is transmitted therethrough. This makes it possible to shorten the actual distance between the reference microphone and the speaker while ensuring a long distance on the noise transmission path between the reference microphone and the speaker. This makes it possible to miniaturize the noise reduction device while ensuring the processing time for ANC.

[0098] In addition, since the speaker outputs sound to the second air passage, it is possible to prevent the sound from the speaker from traveling directly toward the reference microphone, thereby suppressing feedback, thereby effectively reducing noise.

[0099] In a noise reduction device according to aspect 2 of the present invention, in the above-mentioned aspect 1, the pipe section may have an inner pipe and an outer pipe, the inner pipe may form the first air passage inside a first inner circumferential surface of the inner pipe, and the outer pipe may form the second air passage between a second inner circumferential surface of the outer pipe and a first outer circumferential surface of the inner pipe.

[0100] According to the above configuration, the first air passage and the second air passage can be formed by inserting the outer pipe into the outer circumference of the downstream side of the inner pipe. In this case, typically, the second transmission direction is opposite to the first transmission direction. Therefore, noise that comes out of the downstream end of the inner pipe toward the first transmission direction is redirected (i.e., diffracted) toward the second transmission direction and is less likely to be transmitted to the second air passage. Therefore, noise can be reduced before ANC is performed.

[0101] In a noise reduction device according to aspect 3 of the present invention, in aspect 2 above, a second end, which is the end of the outer pipe on the downstream side in the first transmission direction, is located downstream of a first end, which is the end of the inner pipe on the downstream side, and a wall portion is further provided at the second end to prevent transmission of the noise downstream in the first transmission direction, thereby forming the space between the first end and the second end.

[0102] According to the above configuration, the first air passage formed inside the inner pipe communicates with the second air passage formed between the first outer peripheral surface of the inner pipe and the second inner peripheral surface of the outer pipe via a space. Noise transmitted through the first air passage is transmitted to the space. The noise transmitted to the space is diffused in the space. Of the noise diffused in the space, only diffracted noise is transmitted through the second air passage in the opposite direction to the first air passage. This makes it possible to reduce noise transmission to the second air passage.

[0103] A noise reduction device according to a fourth aspect of the present invention is similar to the noise reduction device according to the third aspect, in which a sound absorbing material may be provided on the inside of the wall portion.

[0104] According to the above configuration, noise emitted from the downstream end of the inner pipe that reaches the wall is absorbed by the sound absorbing material at the wall. Furthermore, by providing the wall with sound absorbing material, the noise that reaches the wall is reflected by the wall and prevented from reaching the second air passage. This further reduces noise. Therefore, the sound output from the speaker can be reduced, and feedback can be further suppressed.

[0105] In a noise reduction device according to a fifth aspect of the present invention, in any of the second to fourth aspects described above, the outer pipe may have a diameter of 5 cm or less at an output portion where sound from the speaker is output into the second air passage.

[0106] According to the above configuration, by making the diameter of the outer pipe at the output point 5 cm or less, the sound output from the speaker can be transmitted one-dimensionally in the sound propagation direction inside the pipe section 2 (specifically, the second air passage 17), allowing ANC to be performed with high precision.

[0107] A noise reduction device according to a sixth aspect of the present invention is in accordance with the fourth aspect above, wherein a distance between the first end and the second end in the first transmission direction may be equal to or less than an inner diameter of the inner pipe.

[0108] According to the above-mentioned configuration, it is possible to suppress pressure loss of the exhaust gas discharged from the inner pipe and also to suppress the generation of new noise caused by the exhaust gas being turned back.

[0109] In a noise reduction device according to a seventh aspect of the present invention, in any of the second to sixth aspects described above, a fourth end portion, which is the end portion of the outer pipe downstream in the second transmission direction, may have an expanding diameter shape in which the opening area gradually increases.

[0110] According to the above configuration, it is possible to suppress new noise caused by exhaust gas generated at the exhaust outlet. Also, even if there is noise that cannot be silenced by ANC, the noise can be prevented from being reflected at the exhaust outlet. Therefore, it is possible to prevent the noise from causing howling.

[0111] A noise reduction device according to an eighth aspect of the present invention comprises a pipe section having a first air passage that transmits noise emitted by a noise source in a first transmission direction, and a second air passage that communicates with the first air passage via a space and transmits the noise in a second transmission direction different from the first transmission direction, the pipe section having an inner pipe and an outer pipe, the inner pipe forming the first air passage inside a first inner surface of the inner pipe, and the outer pipe forming the second air passage between a second inner surface of the outer pipe and a first outer surface of the inner pipe.

[0112] According to the above configuration, noise transmitted through the first air passage along the first transmission direction is unlikely to change direction and be transmitted to the second air passage in the second transmission direction. By confining the noise in the space between the first air passage and the second air passage, the noise output to the outside can be reduced.

[0113] A vacuum cleaner according to aspect 9 of the present invention has a suction section that sucks in a fluid, a filter section that removes dust from the fluid sucked in by the suction section, and a blowing section that blows out the fluid that flows out from the filter section, and is further equipped with a noise source having a motor that causes a flow of the fluid, and a noise reduction device described in aspects 1 to 7 above, wherein the noise reduction device is positioned between the noise source and the blowing section.

[0114] According to the above configuration, it is possible to provide a vacuum cleaner equipped with a noise reduction device that can reduce noise from a noise source that is transmitted through the pipe together with the fluid that has flowed out of the filter portion.

[0115] A vacuum cleaner according to a tenth aspect of the present invention may be configured in such a way that, in the above-mentioned ninth aspect, a treble reduction section is provided between the noise reduction device and the noise source, which reduces sounds of 2 KHz or higher contained in the noise emitted by the noise source.

[0116] According to the above configuration, the noise transmitted through the treble reduction section to the downstream end of the pipe section becomes a low-frequency sound with high-frequency sounds reduced by the treble reduction section. The sound of the speaker output to cancel such noise also becomes a low-frequency sound. Here, low-frequency sounds are less likely to be diffracted than high-frequency sounds. Therefore, the sound of the speaker is less likely to be diffracted and return to the reference microphone. Therefore, by providing a treble reduction section in the noise reduction device, howling can be further suppressed.

[0117] A vacuum cleaner according to aspect 11 of the present invention, in aspect 9 or 10 above, may comprise a rod-shaped body in which the filter section and the noise source are located, which is rotatably connected to the suction section, and which is inclined with respect to the vertical direction when the suction section is in contact with a floor surface for use, and the noise reduction device may be located on the rod-shaped body, and the speaker and the reference microphone may be provided on a surface of the rod-shaped body that faces the floor when in use.

[0118] According to the above configuration, the speaker and the reference microphone are positioned between the vacuum cleaner and the user when the vacuum cleaner is in use, which reduces the possibility that the speaker and the reference microphone, which are precision machines, will collide with an object or the floor.

[0119] A vacuum cleaner according to aspect 12 of the present invention, in accordance with aspect 9 or 10 above, comprises a rod-shaped body in which the filter section and the noise source are located and which is rotatably connected to the suction section, and which is inclined with respect to the vertical direction when the suction section is in contact with a floor surface for use, and a handle provided on an upper part of the rod-shaped body, wherein the noise reduction device is located on the rod-shaped body, and the speaker and the reference microphone may be provided on a surface of the rod-shaped body facing a straight line connecting the end of the rod-shaped body opposite the base end of the handle and the connection between the suction section and the connection section of the rod-shaped body.

[0120] According to the above configuration, the possibility that the speaker and the reference microphone, which are precision machines, will collide with an object or the floor can be further reduced.

[0121] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Furthermore, new technical features can be formed by combining the technical means disclosed in the respective embodiments. [Explanation of symbols]

[0122] 1. 1A Noise reduction device 2 Pipe section 3 Inner pipe 4 Outer pipe 5 Reference Mic 5a Input site 6 Speakers 6a Output part 7 Error Microphone 9. Noise Sources 11 Wall 12 Treble reduction section 16 First air passage 17 Second air passage 19 Space 31 Downstream end (first end) of inner pipe 41 Downstream end (second end) of outer pipe 42 upstream end of outer pipe (fourth end) 36 First inner surface 37 First outer surface 46 Second inner surface 50 Control section 110 Vacuum cleaner 111 Rod-shaped body 122 Handle 122a End of handle 161 Connection 202 Motor

Claims

1. a pipe section including a first air passage that transmits noise generated by a noise source in a first transmission direction, and a second air passage that communicates with the first air passage via a space and transmits the noise in a second transmission direction different from the first transmission direction; a reference microphone to which sound from within the first air passage is input; a speaker that outputs sound to the second air passage; A noise reduction device comprising:

2. The pipe portion includes an inner pipe and an outer pipe, The inner pipe defines the first air passage inside a first inner circumferential surface of the inner pipe, The noise reduction device according to claim 1 , wherein the outer pipe defines the second air passage between a second inner circumferential surface of the outer pipe and a first outer circumferential surface of the inner pipe.

3. 3. The noise reduction device according to claim 2, wherein a second end, which is an end on a downstream side in the first transmission direction of the outer pipe, is located downstream of a first end, which is an end on the downstream side of the inner pipe, and a wall portion is provided at the second end to prevent transmission of the noise downstream in the first transmission direction, thereby forming the space between the first end and the second end.

4. The noise reduction device according to claim 3, wherein a sound absorbing material is provided on the inside of the wall portion.

5. 3. The noise reduction device according to claim 2, wherein the outer pipe has a diameter of 5 cm or less at an output portion where the sound from the speaker is output into the second air passage.

6. 5. The noise reduction device according to claim 4, wherein a distance between the first end and the second end in the first transmission direction is equal to or less than an inner diameter of the inner pipe.

7. 6. The noise reduction device according to claim 5, wherein a fourth end portion of the outer pipe, which is an end portion on a downstream side in the second transmission direction, has a diameter-increasing shape in which an opening area gradually increases.

8. a pipe section having a first air passage that transmits noise generated by a noise source in a first transmission direction, and a second air passage that communicates with the first air passage via a space and transmits the noise in a second transmission direction different from the first transmission direction, The pipe portion includes an inner pipe and an outer pipe, The inner pipe defines the first air passage inside a first inner circumferential surface of the inner pipe, The outer pipe defines the second air passage between a second inner circumferential surface of the outer pipe and a first outer circumferential surface of the inner pipe.

9. A vacuum cleaner having a suction section that sucks in a fluid, a filter section that removes dust from the fluid sucked in by the suction section, and a blow-out section that blows out the fluid that flows out from the filter section, a noise source having a motor that induces the flow of the fluid; The noise reduction device according to claim 1, The noise reduction device is located between the noise source and the blowing section.

10. The vacuum cleaner according to claim 9, further comprising a treble reduction section between the noise reduction device and the noise source, the treble reduction section reducing sounds of 2 KHz or more contained in the noise emitted by the noise source.

11. a rod-shaped body in which the filter section and the noise source are located, which is rotatably connected to the suction section, and which is inclined with respect to a vertical direction when the suction section is in contact with a floor surface for use; The noise reduction device is located on the rod-shaped body, The vacuum cleaner according to claim 9 , wherein the speaker and the reference microphone are provided on a surface of the rod-shaped body that faces a floor when in use.

12. a rod-shaped body in which the filter section and the noise source are located, which is rotatably connected to the suction section, and which is inclined with respect to a vertical direction when the suction section is in contact with a floor surface for use; A handle is provided on an upper portion of the rod-shaped body, The noise reduction device is located on the rod-shaped body, The vacuum cleaner of claim 9, wherein the speaker and the reference microphone are provided on a surface of the rod-shaped body opposite a straight line connecting the end opposite the base end of the handle and the suction portion and the connection portion of the rod-shaped body.

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