JP5992169B2 - Method for reducing low-frequency sound generated from mechanical equipment - Google Patents

Description

  The present invention attenuates low-frequency sound generated by two mechanical equipments having a vibration source by canceling each other with a phase difference, thereby reducing sound pressure of low-frequency sound at a place away from the mechanical equipment. Concerning the method.

When mechanical equipment with a vibration source used in the factory is a source of low-frequency sound (especially very low-frequency sound), there is a problem of vibrating the fixtures (secondary vibration) in the houses around the factory There is.
As a method for reducing low-frequency sound, there is a method in which a soundproof wall or a silencer is installed and attenuated. However, in order to obtain a sufficient damping effect by these methods, a large equipment cost is required.
On the other hand, Patent Document 1 proposes a method for reducing low-frequency sound by giving a phase difference to low-frequency sound generated by a plurality of mechanical equipment having a vibration source and canceling waves to each other.

Japanese Patent No. 2925540

  In the method of Patent Document 1, theoretically, if two waves are in opposite phases (180 degree phase difference), they will cancel each other most efficiently. However, in actual facilities, this is not always the case, and due to the influence of surrounding buildings and weather conditions, it is effective in reducing low frequency sound depending on the direction and time from the mechanical facility that is the source of low frequency sound. It has been found that the optimum phase difference is different.

  Accordingly, an object of the present invention is to reduce the sound pressure of low frequency sound in any direction from the mechanical equipment when the low frequency sound emitted by the two mechanical equipment having the vibration source is attenuated by canceling each other by the phase difference. It is to provide a method that can be effectively attenuated.

The gist of the present invention for solving the above problems is as follows.
[1] A method of attenuating low frequency sound generated by two mechanical facilities (1a) and (1b) having a vibration source by canceling each other with a phase difference,
By performing the operation [X] consisting of the following (a) to (c) at least once a day for a plurality of days, the optimum phase difference ΔP at which the sound pressure of the low frequency sound becomes the lowest in the direction in which the low frequency sound is desired to be reduced. Seeking
(A) Measure the sound pressure of the low-frequency sound emitted by the mechanical equipment (1a) and (1b) in the direction where you want to reduce the low-frequency sound and away from the mechanical equipment (1a) and (1b). While
(B) By controlling the drive conditions of the mechanical equipment (1a) and (1b), the phase difference of the low-frequency sound emitted by both mechanical equipment (1a) and (1b) is changed,
(C) Obtain an optimum phase difference ΔP at which the sound pressure of the low frequency sound to be measured is lowest.
After each operation [X], the mechanical equipment (1a), (1b) is operated under the driving condition with the optimum phase difference ΔP. A method for reducing low-frequency sound generated from the mechanical equipment.

[2] In the method of [1 ] above, the operation [X] is performed during the stationary operation stop of the mechanical equipment (1a), (1b), and the method for reducing low-frequency sound generated from the mechanical equipment .
[3] In the method of [1] , the operation [X] is performed during steady operation of the mechanical equipment (1a) and (1b), and a method for reducing low-frequency sound generated from the mechanical equipment.

  According to the method of the present invention, when the low frequency sound generated by the two mechanical equipment having the vibration source is attenuated by canceling each other by the phase difference, the sound pressure of the low frequency sound in any direction from the mechanical equipment is reduced. It can be effectively attenuated. For this reason, the influence on the surrounding area of the low frequency sound which generate | occur | produces in a factory facility can be reduced stably.

Explanatory drawing which shows the implementation condition of the equipment configuration used for implementation of the method of the present invention and the mute test conducted using this equipment The sound of low-frequency sound measured at each measurement position in the east, west, north, and south directions when changing the phase difference of low-frequency sound emitted by two mechanical equipments in the range of 0 to 360 degrees in the mute test Graph showing pressure In the mute test, when the phase difference between the low frequency sound emitted by the two mechanical equipment is 160 degrees, the daily change in the sound pressure of the low frequency sound measured at each measurement position in the east, west, north and south directions from the mechanical equipment Graph showing

FIG. 1 is an explanatory diagram showing an equipment configuration used for carrying out the method of the present invention and an implementation status of a mute test conducted using this equipment. In the figure, reference numerals 1a and 1b denote two mechanical facilities having a vibration source that emits low frequency sound. Examples of the mechanical facilities 1a and 1b include a vibration sieve and a reciprocating compressor, but are not limited thereto. Each machine equipment 1a, 1b includes drive motors 10a, 10b and speed reducers 11a, 11b, respectively.
Note that the low frequency sound to be reduced in the method of the present invention is generally a wave having a frequency of 100 Hz or less, and the range of the low frequency sound to be processed from this frequency region (for example, a frequency of 100 Hz or less, a frequency of 80 Hz or less, etc. ) Is selected, but it is necessary to include an extremely low frequency sound of 20 Hz or less.

Reference numerals 2a and 2b denote sensors (vibration detection means) for detecting vibrations (vibration frequency / amplitude) of the mechanical equipments 1a and 1b. For example, distance sensors, laser displacement meters, accelerometers, overcurrent meters, ultrasonic sensors Etc.
Reference numeral 3 denotes a controller, which obtains a phase difference between low-frequency sounds generated by the two mechanical equipments 1a and 1b based on outputs from the sensors 2a and 2b. Further, the rotational speeds of the drive motors 10a and 10b of the respective mechanical equipments 1a and 1b are controlled through the inverters 4a and 4b, respectively, thereby controlling the phase difference between the low frequency sounds generated by the two mechanical equipments 1a and 1b. it can. Specifically, among the inverters 4a and 4b, for example, the operation rotational speed of the drive motor 10a controlled by the inverter 4a is fixed, and the operation rotational speed of the drive motor 10b controlled by the inverter 4b is adjusted, thereby changing the position. Control the phase difference to the target value.

In a factory where the mechanical facilities 1a and 1b are vibrating sieves (the interval between the two vibrating sieves is 3 m), the following noise reduction test was performed. The power source frequency of the drive motor of the vibration sieve is 60 Hz, and the frequency of the very low frequency sound generated from the vibration sieve is 11.6 Hz.
As shown in FIG. 1, the measurement position of the sound pressure of the low frequency sound is a point about 40 m east from the east end of the mechanical equipment 1a, 1b, a point about 10 m north from the north end of the mechanical equipment 1b, It was set as a point about 20 m away from the west end of the machine equipment 1a, 1b and a point about 10 m south from the south end of the machine equipment 1a. The controller 3 controls the rotational speeds of the drive motors 10a and 10b of the mechanical equipments 1a and 1b through the inverters 4a and 4b, respectively, so that the phase difference of the low frequency sound generated by the mechanical equipments 1a and 1b (vibrating sieve) is reduced to 0 to 0. The sound pressure of low-frequency sound (100 Hz or less) was measured with a low-frequency sound pressure level meter at each of the above measurement positions. Note that distance sensors were used as the sensors 2a and 2b for detecting vibration (displacement) of the vibrating screen.

  The measurement result of the low frequency sound is shown in FIG. 2, and it can be seen that the optimum phase difference at which the sound pressure of the low frequency sound is lowest is different for each measurement position in the east, west, south, and north directions. That is, the optimum phase difference at which the sound pressure of the low frequency sound is lowest is 160 degrees on the east side, 70 degrees on the west and south sides, and 240 degrees on the north side. FIG. 3 shows daily changes in the sound pressure of the low frequency sound in each direction when the phase difference of the low frequency sound emitted from the mechanical equipment 1a, 1b is 160 degrees (display the measurement date in the figure). Even if the phase difference is the same, it can be seen that the sound pressure of the low-frequency sound that is measured changes daily. In this way, the optimum phase difference where the sound pressure of the low frequency sound is the lowest differs depending on the direction from the mechanical equipment 1a, 1b. This is considered to be because of different directions. Moreover, it is considered that the sound pressure of the low-frequency sound varies from day to day even with the same phase difference due to the influence of changes in weather conditions, changes in the surrounding conditions, changes in the operating posture of the mechanical equipment 1a, 1b, and the like.

  As described above, when the low frequency sound generated by the two mechanical equipments 1a and 1b having the vibration source is attenuated by canceling each other by the phase difference, the direction from the mechanical equipment 1a and 1b and the daily It was found that the optimum phase difference at which the sound pressure of the low frequency sound is lowest differs depending on the situation. Therefore, in the present invention, the sound pressure of the low frequency sound is reduced in a direction (for example, the east direction) in which the low frequency sound is desired to be reduced at regular time intervals or irregular time intervals (for example, every day or every several hours). The optimum phase difference ΔP that is the lowest is obtained, and thereafter, the mechanical equipment 1a, 1b is operated under a driving condition that provides the optimum phase difference ΔP.

That is, in the present invention, first, by performing the operation [X] consisting of the following (a) to (c) at regular or irregular time intervals (for example, every day or every several hours), An optimum phase difference ΔP is obtained at which the sound pressure of the low frequency sound is lowest in the direction in which the wave sound is desired to be reduced (for example, the east direction).
(A) While measuring the sound pressure of the low frequency sound emitted by the mechanical equipment 1a, 1b at a position away from the mechanical equipment 1a, 1b in a direction where the low frequency sound is desired to be reduced,
(B) By controlling the driving conditions of the mechanical equipment 1a, 1b, the phase difference of the low frequency sound generated by both the mechanical equipment 1a, 1b is changed.
(C) Obtain an optimum phase difference ΔP at which the sound pressure of the low frequency sound to be measured is lowest.

  For example, when the direction in which the low frequency sound is to be reduced is the east direction, the controller 3 measures the sound pressure of the low frequency sound generated by the mechanical equipment 1a, 1b at the east direction measurement position in FIG. The rotational frequency of the drive motors 10a and 10b of the mechanical equipment 1a and 1b is controlled through 4a and 4b, and the phase difference of the low frequency sound generated by both the mechanical equipment 1a and 1b is in the range of 0 to 360 degrees as shown in FIG. Change with. Thus, the optimum phase difference ΔP at which the sound pressure of the low frequency sound to be measured is the lowest is obtained (the operation [X]).

Here, when measuring the sound pressure of the low frequency sound while changing the phase difference of the low frequency sound in the range of 0 to 360 degrees, the low frequency sound is usually low for each phase difference of 10 degrees or less in the range of 0 to 360 degrees. It is preferable to measure the sound pressure of the frequency sound.
Then, after the operation [X] is performed and the optimum phase difference ΔP at that time is obtained, the mechanical equipment 1a, 1b is moved to the drive condition (for example, rotation of the drive motors 10a, 10b) that has the optimum phase difference ΔP. Number).
As a means for obtaining the optimum phase difference ΔP at which the sound pressure of the low frequency sound to be measured is lowest and outputting this to the controller 3, a personal computer is usually used.

The operation [X] can be performed at any regular or irregular time interval, but since the optimum phase difference ΔP at which the sound pressure of the low-frequency sound to be measured becomes the lowest changes every day, it is at least 1 per day. Preferably, it is performed twice, more preferably twice or more.
The operation [X] may be performed during the steady operation of the mechanical equipment 1a, 1b, or may be performed during the steady operation of the mechanical equipment 1a, 1b. In the former case, it is preferable to carry out each time the machine equipment 1a, 1b is started / stopped. Even in the latter case, there is no particular problem because the phase difference can be changed by slightly changing the operating conditions such as the motor speed.

The position for measuring the sound pressure of low-frequency sound need only be some distance from the mechanical equipment 1a, 1b, but if it is too close to the main body of the mechanical equipment, the ultra-low frequency synthesis by the mechanical equipment 1a, 1b may become unstable. Therefore, in general, a position 10 m or more away from the mechanical facilities 1a and 1b is preferable.
According to the present invention, it is possible to reduce the sound pressure of low-frequency sound in a desired direction by about 1 to 5 dB, compared to the case of continuous operation with a fixed phase difference.
In the present invention, the two mechanical facilities 1a and 1b need to have the same specifications as the mechanical facility (therefore, the same output at an extremely low frequency).

1a, 1b Mechanical equipment 2a, 2b Sensor 3 Controller 4a, 4b Inverter 10a, 10b Drive motor 11a, 11b Reducer

Claims (3)

A method of attenuating low frequency sound generated by two mechanical facilities (1a) and (1b) having a vibration source by canceling each other with a phase difference,
By performing the operation [X] consisting of the following (a) to (c) at least once a day for a plurality of days, the optimum phase difference ΔP at which the sound pressure of the low frequency sound becomes the lowest in the direction in which the low frequency sound is desired to be reduced. Seeking
(A) Measure the sound pressure of the low-frequency sound emitted by the mechanical equipment (1a) and (1b) in the direction where you want to reduce the low-frequency sound and away from the mechanical equipment (1a) and (1b). While
(B) By controlling the drive conditions of the mechanical equipment (1a) and (1b), the phase difference of the low-frequency sound emitted by both mechanical equipment (1a) and (1b) is changed,
(C) Obtain an optimum phase difference ΔP at which the sound pressure of the low frequency sound to be measured is lowest.
After each operation [X], the mechanical equipment (1a), (1b) is operated under the driving condition with the optimum phase difference ΔP. A method for reducing low-frequency sound generated from the mechanical equipment. 2. The method for reducing low-frequency sound generated from mechanical equipment according to claim 1, wherein the operation [X] is performed during the stationary operation suspension of the mechanical equipment (1a), (1b). The operation [X] is performed during steady operation of the mechanical equipment (1a), (1b), and the method for reducing low-frequency sound generated from the mechanical equipment according to claim 1 .

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