JP6222808B2 - Noise reduction device and noise reduction method - Google Patents

Description

  The present invention relates to a noise reduction device and a noise reduction method.

  In a construction site such as a muddy water shield construction, a vibration sieve device is used to separate and dehydrate solid matter such as earth and sand contained in muddy water. This vibration sieving device performs sieving of solids and the like by vibrating the sieve screen at a constant frequency, so that noise including ultra-low frequency sound (sound with a frequency of 20 Hz or less) is generated. . In the construction site described above, since a plurality of vibration sieve devices are often operated simultaneously, noise generated by each of the vibration sieve devices is superimposed to generate a beat and there is a risk that the noise will increase.

  In factories and plants, for example, equipment such as a cooling tower that cools a fluid is used. Such equipment includes, for example, a fan (cooling fan) for circulating a fluid to be cooled or a refrigerant (cooling fan). Therefore, noise including ultra-low frequency sound may be generated when the fan rotates. . Here, when a plurality of fans are provided in the equipment, the noise generated by each fan is superimposed and the beat is generated, as in the case where the plurality of vibration sieve devices are operated simultaneously. The noise may increase.

  The following Patent Documents 1 to 3 disclose techniques for reducing noise generated from a plurality of vibration devices. Specifically, in Patent Documents 1 to 3 below, a plurality of vibration devices are driven at the same frequency (frequency), and the phase difference of vibration between the plurality of vibration devices is a target phase difference (for example, 180 [degrees]). ] To cancel the noise generated by each of the vibration devices (cancellation). In Patent Document 3 below, the sound pressure level of noise generated by a plurality of vibration devices is detected at a plurality of locations, and the detected sound pressure level is determined by the above phase difference (the level of vibration between the plurality of vibration devices). It is also disclosed that an optimum phase difference is obtained such that the sound pressure level is lowered in a desired direction by relating to the phase difference).

JP 59-69548 A Japanese Patent No. 3371209 Japanese Patent No. 2925540

  Incidentally, in any of the techniques disclosed in Patent Documents 1 to 3 described above, the phase difference of vibration between a plurality of vibration devices becomes a target phase difference (for example, 180 [degrees]) manually set by an operator. Is to control. Under ideal conditions where it is not necessary to consider the influence of the surrounding environment, noise generated from a plurality of vibration devices can be effectively reduced by controlling the techniques disclosed in Patent Documents 1 to 3 described above. It is thought that it can be done.

  However, in practice, the optimum target phase difference that can effectively reduce noise is deviated from 180 [degrees] due to the distance between the plurality of vibration devices and the influence of the surrounding environment (for example, sound reflection). It can happen. In addition, when the surrounding environment changes, the optimum target phase difference may change dynamically. For this reason, even if it controls like the technique disclosed by the patent documents 1-3 mentioned above, there exists a problem that the noise which generate | occur | produces from a some vibration apparatus cannot necessarily be reduced effectively. This problem occurs not only when the noise generated from the vibration device is reduced, but also when the noise generated from a rotating device such as a fan is reduced.

  This invention is made in view of the said situation, and provides the noise reduction apparatus and noise reduction method which can reduce the noise which generate | occur | produces from several apparatuses according to the surrounding environment etc. effectively. With the goal.

In order to solve the above-described problems, a noise reduction device according to the present invention includes sensors (11a, 11b) that detect operation states of a plurality of target devices (B1, B2) that perform periodic operations, and detection of the sensors. In a noise reduction device (1) comprising a control unit (20) for controlling the operating frequency of the target device and the phase difference between the target devices based on the result, a synthesized sound of noise emitted from the target device is measured. The microphone (12) and a search range for changing the phase difference controlled by the control unit are set, and the synthesis is performed based on the measurement result of the microphone obtained while changing the phase difference within the search range. And an estimation unit (30) for estimating an optimum phase difference that minimizes sound.
In the noise reduction device of the present invention, the estimation unit obtains a plurality of phase differences that minimize the measurement result of the microphone, performs a predetermined calculation using the plurality of phase differences, and performs the calculation by the calculation. A value obtained is estimated as the optimum phase difference.
Moreover, the noise reduction apparatus of the present invention is characterized in that the estimation unit performs a calculation for obtaining a median value, an average value, or an intermediate value of the plurality of phase differences.
In the noise reduction apparatus according to the present invention, the estimation unit sequentially obtains the measurement results of the microphone while changing the phase difference by a certain amount within the search range.
In the noise reduction apparatus of the present invention, the estimation unit sets all or part of a phase difference range from 0 [degrees] to 360 [degrees] as the search range.
In the noise reduction device according to the present invention, when the estimation unit sets a part (R11, R21) of the phase difference range as the search range, a plurality of measurement results of the microphone are minimized. When the phase difference cannot be obtained, all or a part (R12, R22, 23) of the remaining part of the phase difference range is reset as the search range.
In the noise reduction device of the present invention, the microphone is an omnidirectional microphone.
Further, the noise reduction device of the present invention is characterized in that the target device performs a vibration operation or a rotation operation as the periodic operation.
The noise reduction method of the present invention is a noise reduction method for reducing noise emitted from a plurality of target devices (B1, B2) that perform periodic operations, and includes a search range for changing a phase difference between the target devices. A first step (S11) to be set, and a second to measure a synthesized sound of noise emitted from the target device with a microphone (12) while changing the phase difference within the search range set in the first step. Based on the measurement results of steps (S13 to S16), the second step, a third step (S19) for estimating the optimum phase difference that minimizes the synthesized sound, and the phase difference is estimated in the third step. And a fourth step of controlling the phase difference so that the optimum phase difference is obtained.
In the noise reduction method of the present invention, when a part of a phase difference range from 0 [degree] to 360 [degree] is set as the search range in the first step, the noise is reduced in the third step. When the optimum phase difference that minimizes the synthesized sound cannot be obtained, the method has a fifth step of resetting all or part of the remaining portion of the phase difference range as the search range.

  According to the present invention, a search range for changing the phase difference controlled by the control unit is set, and a microphone measurement result obtained while changing the phase difference within the search range (a synthesized sound of noise emitted from the target device). The optimum phase difference that minimizes the synthesized sound is estimated on the basis of the measurement results), and the phase difference that can minimize the synthesized sound is automatically obtained. There is an effect that it can be effectively reduced according to the above.

It is a block diagram which shows the principal part structure of the noise reduction apparatus by one Embodiment of this invention. It is a figure which shows the relationship between the phase difference between vibration apparatuses in one Embodiment of this invention, and the amplitude of the synthetic sound measured with a microphone. It is a flowchart which shows the calculation method of the optimal phase difference performed in one Embodiment of this invention. It is a figure which shows an example of the measurement result of the synthetic sound recorded in one Embodiment of this invention. It is a figure which shows the other example of a setting of the search range in one Embodiment of this invention.

  Hereinafter, a noise reduction device and a noise reduction method according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of a noise reduction apparatus according to an embodiment of the present invention. As shown in FIG. 1, the noise reduction device 1 of the present embodiment includes proximity sensors 11a and 11b (sensors), a microphone 12, a controller 13, and an inverter 14, and is generated by vibration devices B1 and B2 (target devices). Reduce noise.

  Here, the vibration devices B1 and B2 are vibration sieve devices used for separating and dewatering solid materials such as earth and sand contained in the muddy water in a construction site such as a muddy water shielding work. This vibration sieving device includes, for example, a motor, an eccentric shaft, and a sieve mesh (all of which are not shown), and rotates the eccentric shaft by the motor to vibrate the sieve mesh, thereby sieving solid matter and the like. .

  The vibration device B1 is driven by a drive pulse D1 output from a drive device (not shown), and the vibration device B2 is driven by a drive pulse D2 output from the inverter 14. The drive pulse D1 is a pulse having a constant frequency (for example, a power supply frequency), and the drive pulse D2 is a pulse having a frequency defined by the control of the controller 13. Accordingly, the vibration device B1 vibrates at a constant frequency (cycle), and the vibration device B2 vibrates at a frequency (cycle) corresponding to the frequency of the drive pulse D2. However, the vibration frequency of the vibration devices B1 and B2 may slightly vary depending on the weight of the solid material to be screened.

  Proximity sensors 11a and 11b detect rotation states (operation states) of motors provided in vibration devices B1 and B2, respectively. Specifically, the proximity sensor 11a is attached in the vicinity of the motor provided in the vibration device B1, and the level is determined according to the proximity state of a specific part of the motor (for example, a metal piece attached to the rotating shaft). The pulse signal S1 in which changes is output. Similarly, the proximity sensor 11b is attached in the vicinity of the motor provided in the vibration device B2, and outputs a pulse signal S2 whose level changes according to the proximity state of a specific part of the motor. These pulse signals S1 and S2 are at “H (high)” level when the specific part of the motor is closest to the proximity sensors 11a and 11b, and at “L (low)” level in other states. .

  The microphone 12 measures the synthesized sound of the noises emitted from the vibration devices B1 and B2, and outputs a measurement signal S10 indicating the measurement result. The microphone 12 is, for example, omnidirectional (omnidirectional) capable of measuring sound from all directions, and is installed in a place where noise reduction is desired (a place where noise should be reduced). Here, as the microphone 12, a microphone 12 having an arbitrary frequency characteristic can be used as long as it can measure at least noise to be reduced. In addition, when reducing the very low frequency sound (sound whose frequency is 20 Hz or less) included in the noise emitted from the vibration devices B1 and B2, it is desirable to use the one having high sensitivity to the very low frequency sound.

  The controller 13 includes a vibration control unit 20 (control unit) and an optimum phase difference estimation unit 30 (estimation unit), and uses the pulse signals S1 and S2 from the proximity sensors 11a and 11b and the measurement signal S10 from the microphone 12. The command signal C1 is generated to control the vibration of the vibration device B2. Specifically, the controller 13 generates a speed command signal for the motor provided in the vibration device B2 as the command signal C1 and outputs it to the inverter 14, and the vibration frequency (operation frequency) of the vibration device B2 and the vibration device The phase difference (phase difference) of vibration between B1 and B2 is controlled.

  The vibration control unit 20 includes a frequency phase difference detection unit 21, a calculation unit 22, a calculation unit 23, a phase difference control unit 24, a calculation unit 25, and a frequency control unit 26. A command signal C1 is generated based on a signal indicating the target phase difference (Φ) output from the phase difference estimation unit 30. The frequency phase difference detector 21 detects the vibration frequencies (f1, f2) of the vibration devices B1, B2 from the pulse signals S1, S2, respectively, and detects the phase difference (θ) between the vibration devices B1, B2. The calculation unit 22 calculates the difference between the vibration frequency (f1) of the vibration device B1 detected by the frequency phase difference detection unit 21 and the vibration frequency (f2) of the vibration device B2.

  The calculation unit 23 calculates the difference between the target phase difference (Φ) from the optimum phase difference estimation unit 30 and the phase difference (θ) between the vibration devices B1 and B2 detected by the frequency phase difference detection unit 21. The phase difference control unit 24 uses the calculation result (f1-f2) of the calculation unit 22 and the calculation result (Φ-θ) of the calculation unit 23 to set a command value for controlling the phase difference between the vibration devices B1 and B2. Generate. The calculation unit 25 performs a calculation of adding the calculation result (f1−f2) of the calculation unit 22 and the command value output from the phase difference control unit 24. The frequency control unit 26 generates a command signal C1 for controlling the vibration frequency of the vibration device B2 based on the calculation result of the calculation unit 25.

  The optimum phase difference estimation unit 30 sets a search range for changing the target phase difference (Φ), and based on the measurement signal S10 from the microphone 12 obtained while changing the target phase difference (Φ) within the set search range. Thus, the phase difference (optimal phase difference) that minimizes the measurement signal S10 (the synthesized sound measured by the microphone 12) is estimated. Note that the sound pressure of the synthesized sound measured by the microphone 12 may be obtained from the measurement signal S10, and the phase difference that minimizes the sound pressure may be estimated as the optimum phase difference. In addition, a filter for extracting a specific frequency component (for example, a frequency component of very low frequency sound) included in the measurement signal S10 is provided in the optimal phase difference estimation unit 30, and the phase difference that minimizes the specific frequency component is optimized. It may be estimated as a phase difference.

  The optimum phase difference estimator 30 has a minimum measurement signal S10 when the power is turned on and immediately after the operation of the noise reduction apparatus 1 is started or when there is an instruction from the outside (for example, an instruction from a worker). The process which estimates the phase difference which becomes becomes. This is because an optimum target phase difference is obtained according to the structure around the place where the vibration devices B1 and B2 are installed, or a change in the vibration state of the vibration devices B1 and B2 (for example, an increase in mass of the movable part). Etc.) and changes in the surrounding structure (new construction, demolition, collapse, etc.) so that the optimum target phase difference can be obtained.

  Specifically, the optimal phase difference estimation unit 30 sequentially obtains the measurement signal S10 of the microphone 12 while changing the phase difference by a certain amount within the set search range, and obtains a plurality of phase differences that minimize the measurement signal S10. Then, a value obtained by performing a predetermined calculation using this phase difference is estimated as the optimum phase difference. For example, when the entire range (phase difference range) of 0 to 360 [degrees] is set as the search range, the measurement signal S10 of the microphone 12 is changed while being changed by several [degrees] (for example, 5 [degrees]). Get sequentially. Then, a plurality of phase differences that minimize the measurement signal S10 are obtained, and the median value, average value, or intermediate value of these phase differences is estimated as the optimum phase difference.

  Here, the optimal phase difference estimation unit 30 sets all of the range of 0 to 360 [degrees] as the search range as described above, or sets a part of the range of 0 to 360 [degrees] as the search range. Set as. When a part of the range of 0 to 360 [degrees] is set as the search range, for example, the range of 0 to 180 [degrees], the range of 90 to 270 [degrees], or the range of 180 to 360 [degrees]. Set the range as the search range. Thus, the reason why a part of the range of 0 to 360 [degrees] is set as the search range is to reduce the time required to obtain the optimum phase difference.

  When a part of the range of 0 to 360 [degrees] is set as the search range and the plurality of phase differences that minimize the measurement signal S10 are not obtained, the optimum phase difference estimation unit 30 selects 0 to 360 [degrees]. ] All or part of the remaining part of the range is reset as the search range. For example, when the range of 0 to 180 [degrees] is set as the search range, the remaining range of 180 to 360 [degrees] is reset as the search range. This is for obtaining a phase difference that minimizes the measurement signal S10 within the reset search range.

  FIG. 2 is a diagram showing the relationship between the phase difference between the vibration devices and the amplitude of the synthesized sound measured by the microphone in one embodiment of the present invention. In FIG. 2, the horizontal axis represents the phase difference between the vibration devices B1 and B2, and the vertical axis represents the amplitude of the synthesized sound measured by the microphone 12. The phase difference α in FIG. 2 is an optimum phase difference at which the amplitude of the synthesized sound measured by the microphone 12 is minimized, and is 180 [degrees] under ideal conditions where it is not necessary to consider the influence of the surrounding environment. It is.

  In the example shown in FIG. 2, when the phase difference between the vibration devices B1 and B2 is in the range of 0 to α [degrees], the amplitude of the synthesized sound measured by the microphone 12 monotonously decreases as the phase difference increases. On the other hand, when the phase difference between the vibration devices B1 and B2 is in the range of α to 360 [degrees], the amplitude of the synthesized sound measured by the microphone 12 monotonously increases as the phase difference increases. However, when the phase difference between the vibration devices B1 and B2 is close to the optimum phase difference α, the amplitude of the synthesized sound measured by the microphone 12 becomes small, and background noise (noise emitted from the target vibration devices B1 and B2). The noise of the synthesized sound becomes a constant value.

  As described above, the relationship between the phase difference between the vibration devices B1 and B2 and the amplitude of the synthesized sound measured by the microphone 12 is basically that the amplitude of the synthesized sound is substantially monotonically decreased or monotonous according to the change in the phase difference. There is a relationship in which the amplitude of the synthesized sound becomes substantially constant at a value close to the optimum phase difference α. Therefore, the optimum phase difference estimation unit 30 sequentially obtains the measurement signal S10 of the microphone 12 while changing the phase difference by a certain amount within the search range, and obtains a plurality of phase differences that minimize the measurement signal S10. Thus, the optimum phase difference is estimated reliably and efficiently.

  Note that it is conceivable that a portion where the amplitude of the synthesized sound is minimized due to a phase difference other than the optimum phase difference α due to the influence of the surrounding environment (for example, reflection of sound). If such a portion occurs, depending on how the search range is set, the phase difference of that portion may be erroneously estimated as the optimal phase difference α, but it is within the range of 0 to 360 [degrees]. If all of these are used as the search range, the correct optimum phase difference α can be finally obtained.

  The inverter 14 is provided for the vibration device B2, generates a drive pulse D2 corresponding to the command signal C1 output from the vibration control unit 20 of the controller 13, and outputs the drive pulse D2 to the vibration device B2. That is, under the control of the controller 13, the inverter 14 generates a drive signal used for controlling the vibration frequency of the vibration device B2 and the phase of the vibration device B2 (phase difference between the vibration devices B1 and B2).

  Next, the operation of the noise reduction device 1 having the above configuration will be described. When the vibration devices B1 and B2 and the noise reduction device 1 are powered on, a drive pulse D1 from a drive device (not shown) is input to the vibration device B1 and a command signal C1 (initial value) output from the controller 13 ), The drive pulse D2 from the inverter 14 is input to the vibration device B2. Then, the motors provided in the vibration devices B1 and B2 start to rotate, whereby the vibrations of the vibration devices B1 and B2 are started.

  When the vibrations of the vibration devices B1 and B2 are started, the rotation states of the motors provided in the vibration devices B1 and B2 are detected by the proximity sensors 11a and 11b, respectively, and a pulse signal is sent from the proximity sensors 11a and 11b to the controller 13. S1 and S2 are output. When the pulse signals S11 and S12 from the proximity sensors 11a and 11b are input to the controller 13, the frequency phase difference detector 21 in the controller 13 causes the vibration frequency (f1) of the vibration device B1 and the vibration frequency ( f2) is detected, and the phase difference (θ) between the vibration devices B1 and B2 is detected.

  The vibration frequency (f1) of the vibration device B1 and the vibration frequency (f2) of the vibration device B2 detected by the frequency phase difference detection unit 21 are output to the calculation unit 22, and the difference (f1-f2) is calculated in the calculation unit 22. Calculated. The phase difference (θ) between the vibration devices B1 and B2 detected by the frequency phase difference detector 21 is output to the calculator 23, and the target phase difference (θ) output from the optimum phase difference estimator 30 in the calculator 23 is output. The difference between the initial value of Φ) and the phase difference (θ) between the vibration devices B1 and B2 is calculated.

  The calculation result (f1-f2) of the calculation unit 22 and the calculation result (Φ−θ) of the calculation unit 23 are input to the phase difference control unit 24, and the phase difference control unit 24 uses these calculation results as command values ( A command value for controlling the phase difference between the vibration devices B1 and B2 is generated. The command value generated by the phase difference control unit 24 is output to the calculation unit 25, and the calculation unit 25 adds the calculation result (f1-f2) of the calculation unit 22 and the command value generated by the phase difference control unit 24. An operation is performed. The calculation result of the calculation unit 25 is output to the frequency control unit 26, and the frequency control unit 26 generates the command signal C1 based on the calculation result of the calculation unit 25. The command signal C1 generated by the frequency control unit 26 is output to the inverter 14.

  The inverter 14 generates a drive pulse D2 corresponding to the command signal C1 and outputs it to the vibration device B2. Here, the command signal C1 input to the inverter 14 is a speed command signal for the motor provided in the vibration device B2. For this reason, when the drive signal B2 generated by the inverter 14 is input to the vibration device B2, the rotational speed of the motor provided in the vibration device B2 changes.

  The phase difference control unit 24 provided in the controller 13 controls the phase so that the calculation result (Φ−θ) of the calculation unit 23 becomes zero, and the frequency control unit 26 calculates the calculation result (f1-f2) of the calculation unit 22. ) Is controlled to be zero. For this reason, the above operations are repeated, and the phase control by the phase difference control unit 24 and the frequency control by the frequency control unit 26 are continued, so that the vibration devices B1 and B2 vibrate at the same vibration frequency. The phase difference between the vibration devices B1 and B2 is set to a target phase difference (Φ).

  When the power of the noise reduction apparatus 1 is turned on, in addition to the operation described above, the optimum phase difference estimation unit 30 starts processing for obtaining the optimum phase difference. FIG. 3 is a flowchart showing an optimal phase difference calculation method performed in an embodiment of the present invention. When the process is started, a process for setting a search range for changing the target phase difference (Φ) is first performed in the optimum phase difference estimation unit 30 (step S11: first step). Here, to simplify the description, it is assumed that the entire range of 0 to 360 [degrees] is set as the search range.

  Next, processing for setting initial values of the target phase difference (Φ) and the amount of change in phase difference (Δθ) is performed by the optimum phase difference estimation unit 30 (step S12). As the initial value of the target phase difference (Φ), for example, the minimum phase difference (0 [degree]) in the search range set in step S11 is set, and the initial value of the change amount (Δθ) of the phase difference is set. For example, 5 degrees is set. As the initial value of the target phase difference (Φ), the maximum phase difference (360 [degrees]) in the search range set in step S11 is set, and the initial value of the phase difference change amount (Δθ) is set. It is also possible to set a negative value (for example, −5 [degrees]).

  When the setting of the initial value is completed, the synthesized sound of the noises emitted from the vibration devices B1 and B2 is measured by the microphone 12, and the process of recording the measurement result (value indicated by the measurement signal S10 from the microphone 12) is optimal. This is performed by the phase difference estimation unit 30 (step S13: second step). Here, it is desirable to record the measurement result in association with the target phase difference (Φ) when the synthesized sound is measured by the microphone 12.

  Next, the optimum phase difference estimator 30 performs a process of adding the amount of change in phase difference (Δθ) to the current target phase difference (Φ) and changing the value of the target phase difference (Φ) by Δθ (step S30). S14: Second step). When the current target phase difference (Φ) is 0 [degree], the target phase difference (Φ) becomes Δθ (for example, 5 [degree]) by performing this process. Subsequently, it is determined whether or not the search has been completed for all the search ranges set in step S11 (step S15: second step).

  When it is determined that the search has not been completed for all the search ranges (when the determination result is “NO”), the target phase difference changed in step S14 is constant so as to be reflected in the control of the vibration device B2. Processing for waiting for a time is performed by the optimum phase difference estimation unit 30 (step S16: second step). Here, the standby time of the optimum phase difference estimation unit 30 is a phase difference change period (for example, about several tens of seconds to several minutes) defined in advance.

  When the process of step S16 is completed, the synthesized sound of the noises emitted from the vibration devices B1 and B2 is measured again by the microphone 12, and the measurement result (value indicated by the measurement signal S10 from the microphone 12) is recorded optimally. This is performed by the phase difference estimation unit 30 (step S13: second step). Thereafter, until it is determined in step S15 that the search is completed (until the determination result is “YES”), the processing of steps S13 to S16 is repeated, and the measurement result of the synthesized sound is sequentially transmitted to the optimum phase difference estimation unit 30. To be recorded.

  Here, in step S15, when it is determined that the search has been completed for all of the search range set in step S11 (when the determination result is “YES”), a plurality of positions at which the measurement result is minimized are determined. A process for obtaining (extracting) the phase difference is performed by the optimum phase difference estimation unit 30 (step S17). Specifically, the optimum phase difference estimator 30 includes the measurement result having the smallest value among the plurality of measurement results recorded in the processes of steps S13 to S16, and the measurement result having a value close to the measurement result (the difference between the values). Measurement results that fall within a predetermined threshold value) are obtained, and a phase difference (target phase difference (Φ)) when these measurement results are obtained is obtained.

  FIG. 4 is a diagram showing an example of the measurement result of the synthesized sound recorded in one embodiment of the present invention. In FIG. 4, the measurement results recorded in the optimum phase difference estimation unit 30 are indicated by black circles. As described with reference to FIG. 2, the relationship between the phase difference between the vibration devices B1 and B2 and the amplitude of the synthesized sound measured by the microphone 12 is basically the amplitude of the synthesized sound according to the change in the phase difference. There is a relationship that is almost monotonously decreasing or monotonically increasing, and there is a relationship that the amplitude of the synthesized sound becomes substantially constant at a value close to the optimum phase difference. Therefore, as shown in FIG. 4, even if the change amount of the phase difference is the same (Δθ), the measurement results (A1, A2) obtained with the phase difference close to the optimal phase difference hardly change. For other phase differences (phase differences other than the phase difference close to the optimum phase difference), the value of the measurement result changes greatly.

  Using the above properties, the optimum phase difference estimation unit 30 has the measurement value (A1) having the smallest value among the plurality of measurement results recorded in the processes of steps S13 to S16 and the measurement result having a value close to this. (A2) is obtained, and the phase differences (Φ1, Φ2) when these measurement results (A1, A2) are obtained are respectively obtained, thereby obtaining a plurality of phase differences that minimize the measurement results. ing. In this process, since it is necessary to obtain the phase differences (Φ1, Φ2) from the measurement results (A1, A2), respectively, in order to simplify the processing, the measurement results are preliminarily processed in the process of step S13. It is desirable to record in association with the phase difference (target phase difference (Φ)).

  When the above process ends, the optimum phase difference estimation unit 30 performs a process of calculating the median value of the phase differences obtained (extracted) in the process of step S17 (step S18). In the example shown in FIG. 4, only two phase differences (Φ1, Φ2) are obtained for the sake of simplicity, and thus the calculated median value is the same as the average value.

  When the above processing ends, the median value calculated in step S18 is estimated as the optimum phase difference, and the optimum phase difference estimator 30 performs processing for setting the optimum phase difference to the target phase difference (Φ) (step S1). S19: Third step). Thus, the phase difference control unit 24 provided in the controller 13 performs phase control so that the calculation result (Φ−θ) of the calculation unit 23 becomes zero, and finally the phase difference between the vibration devices B1 and B2. Control is performed so that (θ) becomes the optimum phase difference estimated in step S19 (fourth step).

  In addition, in the above, in order to simplify description, the case where the whole range of 0 to 360 [degrees] was set as the search range in step S11 in FIG. 3 was described as an example. However, as shown in FIG. 5, in order to shorten the time required for the search, a part of the range of 0 to 360 [degrees] may be set as the search range. FIG. 5 is a diagram illustrating another setting example of the search range according to the embodiment of the present invention.

  In the example shown in FIG. 5A, a range R11 of 0 to 180 [degrees] of the range of 0 to 360 [degrees] is set as the search range. As shown in FIG. 5A, when the optimum phase difference α exists in the range R11, the optimum phase difference can be obtained only by searching only the range R11. If the optimum phase difference α does not exist within the range R11, the same search may be performed by resetting the remaining range R12 of 180 to 360 [degrees] as the search range (fifth step).

  In the example shown in FIG. 5B, the range R21 of 90 to 270 [degrees] of the range of 0 to 360 [degrees] is set as the search range. As shown in FIG. 5B, when the optimum phase difference α exists in the range R21, the optimum phase difference can be obtained by searching only the range R21. If the optimum phase difference α does not exist within the range R21, the remaining range 0 to 90 degrees] R22 and the range 270 to 360 [degrees] R23 are reset to the search range and the same A search may be performed (fifth step).

  Further, the second search range may be dynamically set based on the first search result. For example, in the first search, for example, all of the range of 0 to 360 [degrees] is set as the search range, and the phase difference change amount (Δθ) is set to a large value (for example, 10 to several tens [degrees]). ) To search roughly. In the second search, only the range where the first measurement result is equal to or smaller than a certain threshold is set as the search range, and the change amount (Δθ) of the phase difference is set to a small value (for example, several [degrees]). And so on.

  As described above, in the present embodiment, a search range for changing the phase difference between the vibration devices B1 and B2 is set, and the measurement result (from the vibration devices B1 and B2) obtained while changing the phase difference within the search range. The optimum phase difference that minimizes the synthesized sound is estimated based on the measurement result of the synthesized sound of the generated noise. As a result, the optimum phase difference that can minimize the synthesized sound is automatically obtained, so that the noise generated from the vibration devices B1 and B2 can be effectively reduced according to the surrounding environment and the like. In addition, since an optimum phase difference can be obtained by an instruction from an operator or the like, it is possible to cope with environmental changes.

  The noise reduction device and the noise reduction method according to the embodiment of the present invention have been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. For example, in the above-described embodiment, an example in which only the vibration device B2 of the two vibration devices B1 and B2 is controlled has been described, but both the vibration devices B1 and B2 may be controlled.

  Moreover, in the said embodiment, although the rotation state of the motor provided in vibration apparatus B1, B2 was each detected by proximity sensor 11a, 11b, respectively, it uses vibration encoders B1, B2 using an encoder (for example, rotary encoder). You may make it detect the rotation state of the provided motor. Specifically, encoders that output a number of pulses corresponding to the amount of rotation are respectively attached to the rotation shafts of the motors provided in the vibration devices B1 and B2, and vibration is generated depending on the number of pulses output per unit time from these encoders. The rotation state of the motor provided in the devices B1 and B2 is detected.

  In the above embodiment, the vibration state (operating state) of the vibration devices B1 and B2 is detected by detecting the rotation state of the motors provided in the vibration devices B1 and B2. Or by detecting sounds emitted from the vibration devices B1 and B2. The vibration of the sieve mesh can be detected using a proximity sensor, for example, as in the case of detecting the rotation of the motor, or can be detected by providing a displacement sensor on the sieve mesh. The sound emitted from the vibration devices B1 and B2 can be detected, for example, by attaching a microphone for measuring operation sound to each of the vibration devices B1 and B2.

  In the above-described embodiment, the noise reduction device 1 that reduces noise emitted from the plurality of vibration devices B1 and B2 (devices that perform vibration operation) has been described. However, the present invention provides a plurality of rotation devices (rotations of fans and the like). It is also possible to apply the present invention to a noise reduction device that reduces noise generated from an operation device). That is, the present invention can be applied to a noise reduction device that reduces noise emitted from a plurality of target devices that perform periodic operations.

DESCRIPTION OF SYMBOLS 1 ... Noise reduction apparatus, 11a, 11b ... Proximity sensor, 12 ... Microphone, 20 ... Vibration control part, 30 ... Optimum phase difference estimation part, B1, B2 ... Vibration apparatus

Claims (8)

A sensor that detects the operating states of a plurality of target devices that perform periodic operations, and a control unit that controls the operating frequency of the target devices and the phase difference between the target devices based on detection results of the sensors. In noise reduction equipment,
A microphone for measuring a synthesized sound of noise emitted from the target device;
The search range for changing the phase difference controlled by the control unit is set, and based on the measurement result of the microphone obtained while changing the phase difference within the search range, the optimal synthesized sound is minimized. An estimation unit for estimating a phase difference , and
The estimation unit obtains a plurality of phase differences that minimize the measurement result of the microphone, performs a predetermined calculation using the plurality of phase differences, and estimates a value obtained by the calculation as the optimum phase difference Do
A noise reduction device characterized by that . The noise reduction apparatus according to claim 1 , wherein the estimation unit performs a calculation to obtain a median value, an average value, or an intermediate value of the plurality of phase differences. The noise reduction device according to claim 1 , wherein the estimation unit sequentially obtains the measurement results of the microphones while changing the phase difference by a certain amount within the search range. The estimating unit, 0 [degrees] from the 360 [degrees] to any one of claims 1 to 3, all or part of the phase difference range and sets as said search range The noise reduction device described in 1. The estimation unit, when a part of the phase difference range is set as the search range, and when a plurality of phase differences that minimize the measurement result of the microphone cannot be obtained, The noise reduction apparatus according to claim 4 , wherein all or part of the part is reset as the search range. The noise reduction device according to claim 1, wherein the microphone is an omnidirectional microphone. The noise reduction device according to any one of claims 1 to 6 , wherein the target device performs a vibration operation or a rotation operation as the periodic operation. A noise reduction method for reducing noise emitted from a plurality of target devices that perform periodic operations,
A first step of setting a search range for changing a phase difference between the target devices;
A second step of measuring with a microphone a synthetic sound of noise emitted from the target device while changing the phase difference within the search range set in the first step;
A third step of estimating an optimum phase difference that minimizes the synthesized sound based on the measurement result of the second step;
A fourth step of controlling the phase difference so that the phase difference becomes the optimum phase difference estimated in the third step ;
When a part of the phase difference range from 0 [degree] to 360 [degree] is set as the search range in the first step, the optimum phase difference that minimizes the synthesized sound is set in the third step. And a fifth step of resetting all or part of the remaining part of the phase difference range as the search range when the phase difference range cannot be obtained .

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