Additional sound generation device and additional sound generation method for improving sound quality of rotary machine

Abstract

To provide technology for improving sound quality of a rotary machine, which can improve listening comfort by generating sound which naturally sounds as mechanical sound.SOLUTION: An additional sound generation device 6 includes a sound source 7 generating additional sound and an operation control part 20 for controlling operation of the sound source 7. The operation control part 20 is configured to generate consonance consisting of operation sound and additional sound by generating additional sound which is in harmony with operation sound of a rotary machine 1 in the sound source 7. The operation control part 20 is configured to cause the sound source 7 to generate additional sound having a frequency equal to or below an allowable upper limit value calculated based on a rotation frequency of the rotor 3 of the rotary machine 1 and the number of protrusions of the rotor 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for improving the sound quality of a rotating machine such as a pump, a blower, a compressor, a turbine, or an electric motor by adding an additional sound to the operating sound generated by the rotating machine. [Background technology]

[0002] Rotating machines such as pumps, blowers, compressors, turbines, and electric motors are devices in which a rotor (e.g., an impeller, a roots rotor, or a motor rotor) rotates at high speed. Therefore, the rotating machines generate operating noise during operation. The operating noise of the rotating machines can sometimes be unpleasant to people. Thus, a technique has been proposed for improving the sound quality of the rotating machines by adding consonant sounds to the operating noise (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2006 / 095876 [Patent Document 2] JP 2013-223352 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when chords are constructed by adding consonance using the degree of consonance as an indicator, as is done in musical composition, the sound of a rotating machine may seem unnatural and may not improve the listening experience.

[0005] Therefore, the present invention provides a technology for improving the sound quality of rotating machinery, which can improve the listening comfort by generating a sound that sounds natural as a mechanical sound. [Means for solving the problem]

[0006] In one aspect, an additional sound generating device for improving the sound quality of a rotating machine is provided, the additional sound generating device comprising a sound source that generates an additional sound and an operation control unit that controls the operation of the sound source, the operation control unit being configured to cause the sound source to generate the additional sound that is consonant with the operating sound of the rotating machine, thereby creating a consonant sound consisting of the operating sound and the additional sound, and the operation control unit being configured to cause the sound source to generate the additional sound having a frequency below an allowable upper limit value calculated based on the rotational frequency of the rotor of the rotating machine and the number of protrusions of the rotor.

[0007] In one aspect, the operation control unit is configured to cause the sound source to generate the additional sound having a frequency N times (N is a natural number) the rotation frequency. In one embodiment, the operation control unit has a database including multiple candidates for the frequency of the additional sound, the multiple candidates being frequencies N times the rotation frequency (N is a natural number) and less than the allowable upper limit, and the operation control unit is configured to cause the sound source to generate the additional sound having a frequency of a candidate selected from the multiple candidates. In one embodiment, the database includes a plurality of groups corresponding to a plurality of models of rotating machines, and each group includes a plurality of candidates for the frequency of the additional sound.

[0008] In one aspect, the additional sound generating device further includes a sound measuring device that measures the operating sound of the rotating machine, and the operation control unit is configured to determine the rotation frequency by performing frequency analysis on the measured operating sound. In one aspect, the sound measuring instrument is configured to measure a sound pressure level of the operating sound of the rotating machine, and the operation control unit is configured to cause the sound source to generate the additional sound at a sound pressure level whose difference from the measured sound pressure level is within an acceptable range. In one aspect, the additional sound generating device further includes a rotational speed measuring device that measures the rotational speed of the rotor, and the operation control unit is configured to calculate the rotational frequency from the measured rotational speed. In one aspect, the motion controller is configured to calculate the rotational frequency from a rotational speed command signal for the rotor.

[0009] In one aspect, an additional sound generating method for improving the sound quality of a rotating machine is provided, which generates an additional sound that harmonizes with an operating sound of the rotating machine while rotating a rotor of the rotating machine, generating a consonant sound consisting of the operating sound of the rotating machine and the additional sound, and the frequency of the additional sound is below an allowable upper limit value calculated based on the rotational frequency of the rotor and the number of protrusions of the rotor.

[0010] In one embodiment, the frequency of the additional sound is N times (N is a natural number) the rotation frequency. In one embodiment, the method for generating additional sound further includes selecting at least one candidate from a plurality of candidates for the frequency of the additional sound contained in a database, the additional sound having a frequency of the selected candidate, the plurality of candidates being a frequency that is N times (N is a natural number) the rotation frequency and is equal to or lower than the allowable upper limit value. In one embodiment, the database includes a plurality of groups corresponding to a plurality of models of rotating machines, and each group includes a plurality of candidates for the frequency of the additional sound.

[0011] In one aspect, the additional sound generating method further includes measuring the operating sound of the rotating machine with a sound measuring device and performing a frequency analysis on the measured operating sound to determine the rotational frequency of the rotor. In one aspect, the additional sound has a sound pressure level whose difference from the sound pressure level of the measured operating sound is within an acceptable range. In one aspect, the method of generating additional sound further includes measuring a rotation speed of the rotor with a rotation speed measuring device, and calculating the rotation frequency from the measured rotation speed. In one aspect, the method of generating additional sound further includes calculating the rotational frequency from a rotational speed command signal for the rotor. Effect of the Invention

[0012] The additional sound generating device generates an additional sound having a frequency equal to or lower than an allowable upper limit calculated based on the rotation frequency of the rotor and the number of protruding portions of the rotor. The operation sound of the rotating machine and the additional sound constitute a consonant sound. This consonant sound is a sound having a frequency equal to or lower than an allowable upper limit and does not sound unnatural as an operation sound of the rotating machine. As a result, the pleasantness of the operation sound of the rotating machine can be improved. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a mechanical system including a rotating machine and an additive sound generating device. [Diagram 2] FIG. 1 is a schematic diagram showing an embodiment of an additional sound generating device equipped with a sound measuring device. [Diagram 3] FIG. 1 is a schematic diagram showing an embodiment of an additional sound generating device equipped with a rotation speed measuring device. [Figure 4] 1 is a graph showing an example of a frequency analysis result of an operating sound of a turbo pump, which is an example of a rotating machine. [Diagram 5] 4 is a graph showing an example of an operating sound and an additional sound. [Figure 6] 13 is a graph showing another example of the operation sound and the additional sound. [Figure 7] 11 is a schematic diagram showing another embodiment of the additional sound generating device. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of an additional sound generating device and an additional sound generating method for improving the sound quality of a rotating machine will be described with reference to the drawings. Fig. 1 is a schematic diagram showing an embodiment of a mechanical system including a rotating machine and an additional sound generating device. As shown in Fig. 1, the mechanical system has a rotating machine 1 and an additional sound generating device 6. The additional sound generating device 6 is installed adjacent to the rotating machine 1, or away from the rotating machine 1, or in contact with the rotating machine 1.

[0015] The rotating machine 1 includes a rotor 3 which is a rotating body, a bearing 5 which rotatably supports the rotor 3, and a base 10 on which the bearing 5 is mounted. The base 10 has a bearing holder 12 which holds the bearing 5. The rotor 3 is connected to a drive source (not shown) such as an electric motor, and is rotated by the drive source. Examples of the rotating machine 1 include a pump, a blower, a compressor, a turbine, and an electric motor. Specific examples of the rotor 3 include an impeller, a Roots rotor of a Roots-type pump, and a motor rotor of an electric motor.

[0016] The additional sound generating device 6 includes a sound source 7 configured to generate an additional sound that is in harmony with the operating sound of the rotating machine 1, and an operation control unit 20 that controls the operation of the sound source 7. In the embodiment shown in FIG. 1, the sound source 7 is an electric sound source that electrically generates the additional sound. In one example, the sound source 7 includes a sound wave generator 15 that generates a sound signal of a variable frequency, an amplifier 16 that amplifies the sound signal, and a speaker 17 that emits the amplified sound signal as the additional sound. However, as long as the additional sound can be generated, the specific configuration of the sound source 7 is not limited to the embodiment shown in FIG. 1. The additional sound generating device 6 further includes an input device 21 for inputting data and command values. The input device 21 is electrically connected to the operation control unit 20. Specific examples of the input device 21 include a keyboard, a mouse, and a numeric keypad.

[0017] The operation control unit 20 includes a storage device 20a in which a program is stored, and a calculation device 20b that executes calculations according to instructions included in the program. The operation control unit 20 is composed of at least one computer. The storage device 20a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the calculation device 20b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the operation control unit 20 is not limited to these examples.

[0018] The additional sound generating device 6 may be installed at a location remote from the rotating machine 1. In another example, the additional sound generating device 6 may be installed on the rotating machine 1. In yet another example, the additional sound generating device 6 may be installed at a sound receiving point where the user can hear the operation sound of the rotating machine 1, or may be set at a sound receiving point where the user cannot hear the operation sound of the rotating machine 1. In yet another example, the additional sound generating device 6 may be a portable device that the user can carry with him / her.

[0019] The operation sound of the rotating machine 1 is basically generated due to the rotation of the rotor 3. Therefore, the operation sound of the rotating machine 1 has a frequency that depends on the rotation speed (rotation frequency) of the rotor 3. The additional sound generated by the additional sound generating device 6 is a sound that is consonant with the operation sound of the rotating machine 1. In other words, the additional sound is a sound in which the composite sound of the operation sound of the rotating machine 1 and the additional sound becomes a consonant sound. A consonant sound is a sound in which two or more sounds are in harmony, and is a sound that is pleasant to hear when heard by a person. Examples of consonant sounds include chords that are composed only of a perfect first, a perfect octave, a perfect fifth, a perfect fourth, a major and minor third, or a major and minor sixth.

[0020] In one embodiment, the operation control unit 20 is configured to give a command to the sound source 7 to generate an additional sound having a frequency N times (N is a natural number) the rotational frequency of the rotor 3 in the sound source 7. The rotational frequency of the rotor 3 is input to the operation control unit 20 via the input device 21. In another example, the operation control unit 20 is configured to calculate the rotational frequency of the rotor 3 from a rotational speed command signal of the rotor 3. More specifically, the operation control unit 20 is configured to receive a rotational speed command signal of the rotor 3 from a drive control unit (not shown) for controlling a drive source such as an electric motor connected to the rotor 3, and to calculate the rotational frequency of the rotor 3 from the rotational speed command signal.

[0021] In another embodiment, as shown in FIG. 2, the additional sound generating device 6 includes a sound measuring device 25 that measures the operation sound of the rotating machine 1. The sound measuring device 25 is, for example, a microphone. The sound measuring device 25 is electrically connected to the operation control unit 20. The operation control unit 20 is configured to determine the rotation frequency of the rotor 3 by performing a frequency analysis on the measured operation sound. More specifically, the operation control unit 20 determines the frequency of the operation sound by performing a frequency transformation (for example, a fast Fourier transform) on the measured operation sound, and determines the rotation frequency of the rotor 3, which is the frequency of the operation sound.

[0022] In yet another embodiment, as shown in Fig. 3, the additional sound generating device 6 includes a rotation speed measuring device 26 that measures the rotation speed of the rotor 3. The rotation speed measuring device 26 may be a non-contact type rotation speed measuring device or a contact type rotation speed measuring device. The rotation speed measuring device 26 is electrically connected to the operation control unit 20. The operation control unit 20 is configured to calculate the rotation frequency of the rotor 3 from the measured rotation speed.

[0023] The rotation speed of the rotor 3 may be constant or variable. According to the embodiment shown in Figures 2 and 3, even if the rotation frequency of the rotor 3 changes due to a change in the load applied to the rotor 3, the operation control unit 20 can determine an appropriate frequency that can form a consonant sound and issue a command to the sound source 7 to cause the sound source 7 to generate an additional sound having the determined frequency.

[0024] The operation control unit 20 determines the frequency of the additional sound by multiplying the rotation frequency of the rotor 3 obtained as described above by N (N is a natural number). The sound source 7 generates an additional sound having the determined frequency, and generates a consonant sound in which the operation sound of the rotating machine 1 and the additional sound are in harmony. As long as the additional sound has a frequency N times the rotation frequency of the rotor 3, the additional sound generating device 6 may generate multiple additional sounds with different frequencies. In this case, the operation sound of the rotating machine 1 and the multiple additional sounds form a consonant sound.

[0025] In the embodiment shown in FIG. 2, the sound measuring device 25 is configured to measure the sound pressure level [dB] of the operation sound of the rotating machine 1. The operation control unit 20 is configured to give a command to the sound source 7 based on the measured sound pressure level of the operation sound, so as to cause the sound source 7 to generate an additional sound of a sound pressure level whose difference from the measured sound pressure level is within an allowable range. If the sound pressure level of the additional sound is too high or too low compared to the sound pressure level of the operation sound, the operation sound and the additional sound may not form a consonant sound that is pleasant to hear. The sound source 7 can generate a consonant sound in which the operation sound and the additional sound are in harmony with each other by generating an additional sound of a sound pressure level based on the actual sound pressure level of the operation sound.

[0026] If the sound pressure level of the operating sound of the rotating machine 1 itself is too low, the additional sound generating device 6 may generate an additional sound (N=1) having the rotational frequency of the rotor 3, and may also generate an additional sound (N≠1) having a frequency different from the rotational frequency of the rotor 3.

[0027] The dominant frequency of the operating sound of the rotating machine 1 is basically N times the rotation frequency fn of the rotor 3 (Nfn). The symbol N is a natural number. If the number of blades of the impeller of a pump, which is an example of the rotating machine 1, is z, the range of N corresponding to the main frequencies contained in the operating sound is approximately 1≦N≦3z to 5z for turbo pumps such as feedwater pumps and drainage pumps. In a Roots-type pump, if the number of leaves of the Roots rotor is z, then it is approximately 1≦N≦10×2z. In this specification, functional protrusions of the rotor 3, such as the blades of the impeller and the lobes of the Roots rotor, are collectively referred to as protrusions of the rotor 3.

[0028] Fig. 4 is a graph showing an example of the frequency analysis results of the operation sound of a turbo pump, which is an example of a rotating machine 1. In Fig. 4, the horizontal axis represents the frequency of the operation sound, and the vertical axis represents the intensity of the frequency components contained in the operation sound. When an impeller, which is an example of a rotor 3, has five blades (z=5), the range of N as the operation sound is 25 or less (N≦25). The symbol fn represents the rotational frequency of the rotor 3. As shown in Fig. 4, in the high frequency band, the intensity of the frequency components decreases as the frequency increases.

[0029] The operation control unit 20 stores in the storage device 20a an allowable upper limit value determined based on the rotation frequency fn of the rotor 3 and the number of protrusions (e.g., the number of blades) z of the rotor 3. The operation control unit 20 is configured to give a command to the sound source 7 to cause the sound source 7 to generate an additional sound having a frequency equal to or lower than the allowable upper limit value. This is for the purpose of adding a sound of a frequency that may actually be generated from the rotating machine 1, from among a plurality of musically harmonious frequencies.

[0030] 4, for example, it is highly likely that a high-frequency sound having a frequency 40fn, which is 40 times the rotational frequency fn of the rotor 3, will not actually be generated from the rotating machine 1. For this reason, if a sound with a frequency of 40fn is added as an additional sound to the operating sound of the rotating machine 1, it will sound unnatural as the sound of the rotating machine 1.

[0031] Therefore, the additional sound generating device 6 is configured to generate additional sound having a frequency equal to or lower than an allowable upper limit determined based on the rotation frequency fn of the rotor 3 and the number of protrusions (e.g., the number of blades) z of the rotor 3. As a result, a consonant sound characteristic of the rotating machine 1 is obtained, improving the listening comfort.

[0032] Example 1 (Figure 5) When the rotation frequency is fn (Hz) and the impeller of a pump, which is an example of a rotor 3, has five blades (z=5), the blade passing frequency fn×z is 5fn. For example, when an operation sound of a blade passing frequency fn×z=5fn is generated from a pump, the additional sound generating device 6 generates an additional sound of four times the rotation frequency fn (N=4) and an additional sound of six times the rotation frequency fn (N=6). The frequency ratio of the operation sound and the two additional sounds is 4fn:5fn:6fn, that is, 4:5:6, and a consonant sound consisting of the notes C-E-G is generated. As a result, the pleasantness of the operation sound of the rotating machine 1 is improved.

[0033] Example 2 (Figure 6) In this example, a pump generates an operation sound with a frequency of 15fn, which is three times the blade passing frequency 5fn. When the additional sound generating device 6 generates an additional sound with a frequency of 20 times the rotation frequency fn (N=20) and an additional sound with a frequency of 25 times the rotation frequency fn (N=25), the frequency ratio of the operation sound and the two additional sounds is 15fn:20fn:25fn, i.e., 3:4:5, and a consonant sound consisting of the sodomy chord is generated.

[0034] However, it is highly likely that high frequency sounds such as 20fn and 25fn are not actually generated from the pump. Therefore, even if the chords of frequencies 15fn, 20fn, and 25fn are consonant, they are unnatural as the operation sound of the pump. Therefore, the additional sound generating device 6 adds sounds having frequencies of 9fn and 12fn, which are frequencies Nfn below the predetermined allowable upper limit. As a result, the ratio of the frequencies of the operation sound and the two additional sounds is 3:4:5, and a consonant sound consisting of the so-do-mi chord is generated. Moreover, this consonant sound is a sound that does not sound unnatural as the operation sound of the pump. As a result, the pleasantness of the operation sound of the rotating machine 1 is improved.

[0035] In one example, the allowable upper limit value is determined by multiplying the rotational frequency fn of the rotor 3 by the number of protrusions (e.g., the number of blades) z of the rotor 3, further multiplying the obtained value by a predetermined natural number, and adding a predetermined integer (including 0) to the obtained value.

[0036] FIG. 7 is a schematic diagram showing another embodiment of the additional sound generating device 6. The configuration and operation of this embodiment not specifically described are the same as those of the embodiment described with reference to FIG. 1 to FIG. 6, and therefore the overlapping description will be omitted. The operation control unit 20 of the previously described embodiment determines the frequency of the additional sound by multiplying the rotation frequency of the rotor 3 by N (N is a natural number), whereas the operation control unit 20 of this embodiment has a database 30 including multiple candidates for the frequency of the additional sound, and is configured to cause the sound source 7 to generate an additional sound having a frequency of a candidate selected from the multiple candidates. The database 30 is stored in the storage device 20a.

[0037] The multiple candidates in the database 30 are frequencies that are N times (N is a natural number) the rotational frequency of the rotor 3 and are equal to or lower than the above-mentioned upper allowable limit value. The additional sound having the frequency of each candidate is a sound that harmonizes with the operation sound of the rotating machine 1 to generate a consonant sound. That is, multiple candidates for the frequency of the additional sound that can generate a consonant sound are stored in advance in the database 30. In one embodiment, the operation control unit 20 selects one candidate from the multiple candidates and issues a command to the sound source 7 to cause the sound source 7 to generate an additional sound having the frequency of the selected candidate. In another embodiment, the operation control unit 20 may select two or more candidates from the multiple candidates and issue a command to the sound source 7 to cause the sound source 7 to generate multiple additional sounds having the frequencies of the selected candidates.

[0038] In one embodiment, the operation control unit 20 is configured to change the selected candidate to another candidate based on an input signal from the input device 21. While listening to a consonant sound consisting of the operation sound of the rotating machine 1 and the additional sound generated from the sound source 7, the user can operate the input device 21 to generate from the sound source 7 an additional sound that can generate a consonant sound with a higher degree of consonance.

[0039] The rotation speed of the rotor 3 may be constant or variable. When the rotation speed of the rotor 3 is variable, the database 30 includes a plurality of candidates corresponding to each rotation frequency of the rotor 3. The operation control unit 20 determines the frequency of the additional sound from the plurality of candidates based on the current rotation frequency of the rotor 3.

[0040] The operating sound of the rotating machine 1 may differ depending on the model of the rotating machine 1. As a result, the additional sound that is highly harmonious with the operating sound may also differ. Therefore, in one embodiment, the database 30 includes a plurality of groups corresponding to a plurality of models of the rotating machine, and each group includes a plurality of candidates for the frequency of the additional sound. The plurality of candidates in each group have a frequency that is N times (N is a natural number) the rotation frequency of the rotor 3 and is equal to or lower than the above-mentioned allowable upper limit value. The operation control unit 20 selects one group from the plurality of groups based on the model of the rotating machine 1, selects at least one candidate from the plurality of candidates included in the selected group, and causes the sound source 7 to generate at least one additional sound having the frequency of the selected candidate.

[0041] The multiple candidate frequencies included in each group are determined in advance based on the rotation speed of the rotor 3 and the number of protrusions of the rotor 3 (for example, the number of blades of the impeller or the number of blades of the Roots rotor). According to this embodiment, the frequency of the additional sound is determined based on the model of the rotating machine 1, so that a consonant sound characteristic of the rotating machine 1 is generated. As a result, the listening comfort can be improved for multiple models.

[0042] When multiple rotating machines are operated simultaneously and the operation sounds affect each other, the additional sound generating device 6 is configured not to generate an additional sound that is discordant with the operation sounds from the other rotating machines. For example, the operation control unit 20 is configured to obtain data on the rotational frequency of the other adjacent rotating machines and not to select a frequency of the additional sound that is discordant with the rotational frequency of the other rotating machines. The data on the rotational frequency of the other adjacent rotating machines may be a rotational speed command signal given to the other rotating machines, or may be a rotational frequency obtained by measuring the operation sound of the other rotating machine by the sound measuring device 25 shown in FIG. 2 and performing a frequency analysis on the measured operation sound.

[0043] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0044] 1 Rotating Machinery 3 Rotor 5. Bearings 6. Additional sound generator 7. Sound Source 10 Foundations 12 Bearing holder 15 Sound Wave Generator 16 Amplifier 17 Speaker 20 Motion control section 21 Input Devices 25 Sound Measuring Instrument 26 Rotational speed measuring device 30 Databases

Claims

1. An additional sound generating device for improving the sound quality of a rotating machine, comprising: A sound source that generates an additional sound; An operation control unit that controls an operation of the sound source, The operation control unit is configured to generate the additional sound that is consonant with the operation sound of the rotating machine from the sound source, thereby generating a consonant sound consisting of the operation sound and the additional sound, The operation control unit is configured to cause the sound source to generate the additional sound having a frequency equal to or lower than an allowable upper limit value calculated based on the rotational frequency of the rotor of the rotating machine and the number of protrusions of the rotor.

2. The additional sound generating device according to claim 1 , wherein the operation control section is configured to cause the sound source to generate the additional sound having a frequency N times (N is a natural number) the rotation frequency.

3. The operation control unit has a database including a plurality of candidates for the frequency of the additional sound, the plurality of candidates are frequencies that are N times the rotation frequency (N is a natural number) and are equal to or less than the allowable upper limit, The additional sound generating device according to claim 2 , wherein the operation control unit is configured to cause the sound source to generate the additional sound having a frequency of a candidate selected from the plurality of candidates.

4. the database includes a plurality of groups corresponding to a plurality of models of rotating machines; The additional sound generating device according to claim 3 , wherein each group includes a plurality of candidates for the frequency of the additional sound.

5. The additional sound generating device further includes a sound measuring device for measuring the operation sound of the rotating machine, The additional sound generating device according to claim 2 , wherein the operation control unit is configured to determine the rotation frequency by performing a frequency analysis on the measured operation sound.

6. The sound measuring device is configured to measure a sound pressure level of an operation sound of the rotating machine, The additional sound generating device according to claim 5 , wherein the operation control unit is configured to cause the sound source to generate the additional sound at a sound pressure level whose difference from the measured sound pressure level is within an allowable range.

7. The additional sound generating device further includes a rotation speed measuring device for measuring a rotation speed of the rotor, The additional sound generating device according to claim 2 , wherein the operation control unit is configured to calculate the rotational frequency from the measured rotational speed.

8. The additional sound generating device according to claim 2 , wherein the operation control section is configured to calculate the rotation frequency from a rotation speed command signal for the rotor.

9. A method for generating additional sound to improve the sound quality of a rotating machine, comprising: While rotating the rotor of the rotary machine, an additional sound is generated that is in harmony with the operating sound of the rotary machine; generating a consonant sound consisting of the operating sound of the rotary machine and the additional sound; An additional sound generating method, wherein the frequency of the additional sound is equal to or lower than an allowable upper limit value calculated based on the rotational frequency of the rotor and the number of protrusions of the rotor.

10. The method for generating additional sound according to claim 9, wherein the frequency of the additional sound is N times (N is a natural number) the rotation frequency.

11. The additional sound generating method further includes selecting at least one candidate from a plurality of candidates for the frequency of the additional sound included in a database; the additional sound has a frequency of the selected candidate, The additional sound generating method according to claim 10, wherein the plurality of candidates are frequencies that are N times the rotation frequency (N is a natural number) and are equal to or lower than the allowable upper limit value.

12. the database includes a plurality of groups corresponding to a plurality of models of rotating machines; The method for generating additional sounds according to claim 11 , wherein each group includes a plurality of candidates for the frequency of the additional sound.

13. measuring the operating noise of the rotating machine with a sound measuring device; The method of claim 10 further comprising: determining the rotational frequency of the rotor by performing a frequency analysis on the measured operating noise.

14. The additional sound generating method according to claim 13 , wherein the additional sound has a sound pressure level whose difference from the sound pressure level of the measured operation sound is within an allowable range.

15. measuring the rotation speed of the rotor with a rotation speed measuring device; The method of claim 10 further comprising determining the rotational frequency from the measured rotational speed.

16. 11. The method of claim 10, further comprising determining the rotational frequency from a rotational speed command signal of the rotor.

Images