445 results about "Acoustic noise reduction" patented technology

The embodiment of the invention discloses a speech enhancement method and device based on a generative adversarial network model, and electronic equipment, and can solve the problems of how to more accurately and effectively reduce the noise influence and improve the definition and quality of an audio signal. The method comprises the following steps: acquiring to-be-processed voice data; performing convolution processing on the to-be-processed voice data by generating a target generator in the adversarial network model to obtain initial voice data, the target generator comprising an expansion convolution layer and a standard convolution layer, and the target generator being obtained by co-training an adversarial loss function, a perception loss function and a reconstruction loss function; through a target discriminator in the generative adversarial network model, the initial voice data and the to-be-processed voice data are discriminated to obtain a target discrimination result, and the target discriminator comprises a time domain discriminator and a frequency domain discriminator; and when it is detected that the target discrimination result satisfies a preset requirement, determining that the initial voice data is voice data after voice enhancement of the to-be-processed voice data.

The invention belongs to the technical field of regulating valve noise reduction, and particularly relates to a sleeve multi-stage noise reduction regulating valve system which comprises a sleeve multi-stage noise reduction regulating valve, a pneumatic diaphragm actuator, an air source control device, an intelligent control device, a butterfly valve, a reducing joint, a companion flange and a user pipeline. The sleeve multi-stage noise reduction regulating valve comprises a valve body. When fluid enters the valve, water flow is preliminarily dispersed through the first noise reduction holes in the outer layer, direct impact of the fluid on the valve body is reduced, noise is lowered, the water flow enters the upper sleeve and then falls onto the inclined buffer baffles, the buffer baffles are arranged in an up-and-down alternate multi-layer mode, and therefore the situation that the water flow vertically falls down and directly flushes the valve body is avoided, and noise is further lowered; and then the water flow passes through the second noise reduction hole in the inner layer, the water flow is further dispersed, direct impact of the fluid on the valve body is reduced again, formation of turbulent flow can be effectively restrained through the first noise reduction hole with the variable diameter, the second noise reduction hole with the variable diameter and the inclined buffering baffle, and therefore noise is reduced.

The invention discloses a multi-mode marine bearing fault detection method based on acoustic denoising. The method comprises the steps of obtaining marine bearing fault signal data; the marine bearing fault signal data comprises acoustic time sequence data and vibration time sequence data of corresponding bearing faults under different fault working condition types; the method comprises the following steps: constructing a multi-modal marine bearing fault detection model based on acoustic denoising, wherein the model comprises an input layer, a graph construction module, a feature extraction network, an acoustic noise reduction network based on a bidirectional long-short-term memory network, a nearest neighbor interpolation module, a feature fusion network and a classification prediction module; model training is carried out through marine bearing fault signal data to obtain an optimal detection model, and then multi-mode marine bearing fault detection based on acoustic denoising is achieved. According to the method, the problems of poor accuracy, robustness and early warning capability of fault detection under a complex ship working condition due to the fact that an existing method cannot effectively overcome strong noise environment interference of the ship and is insufficient in multi-source information fusion capability are solved.

The utility model discloses a noise reduction assembly applied to a cutting device. In an inner cavity of a cutting platform of the cutting device, a connecting piece is vertically arranged under the position where a cutting assembly carries out cutting action; one end of the connecting piece is connected with the top of the inner cavity, the other end of the connecting piece is pre-buried in the ground, sound waves can be conducted into the ground surface, and the inner cavity is filled with sound absorption cotton; the utility model further discloses a light steel keel cut-off machine, the cutting assembly is arranged on the cutting platform and can move synchronously with the position, to be cut, of the light steel keel, and in the moving process, the light steel keel is cut; the lead screw pair mechanism is arranged on the upper surface of the cutting platform and used for driving the cutting assembly to do reciprocating motion in the moving direction of the light steel keel. The light steel keel structure further comprises the noise reduction assembly, noise generated when the light steel keel is cut off is basically eliminated, the field operation environment is improved, and the harm of the noise is reduced.

The invention relates to the technical field of transformers, and discloses a noise reduction type intelligent large dry-type transformer which comprises a base, a sound insulation plate is fixedly connected to the left side of the base, a ventilation door is rotatably connected to the front portion of the sound insulation plate, a buffer spring is fixedly connected to the inner wall of the base, and a supporting frame is fixedly connected to the top of the buffer spring. A transformer body is arranged at the top of the supporting frame, a fixing plate is fixedly connected to the left side of a sound insulation plate, a chamfering plate is fixedly connected to the bottom of the fixing plate, a reciprocating lead screw is rotatably connected to the inner wall of the chamfering plate, and a U-shaped plate is in threaded connection with the circumferential surface of the reciprocating lead screw. And vibration generated in the operation process of the transformer body can be buffered, so that mechanical vibration generated in the operation process of the transformer body can be remarkably reduced, noise is reduced, and the comfort degree of the working environment is improved.

The utility model relates to the technical field of calcium silicate boards, in particular to a calcium silicate board waterproof structure which comprises a structure body, a first calcium silicate board layer is arranged at the top of the structure body, a colored surface is arranged at the bottom of the first calcium silicate board layer, an anti-corrosion layer is arranged in the structure body, a drying layer is arranged in the anti-corrosion layer, and a fireproof frame is arranged in the drying layer. A silencing structure is arranged in the fireproof frame and mainly comprises a silencing layer, a sound transmission hole, a silencing opening, silencing cotton and a silencing medium. Through the arrangement of the sound transmission holes, the silencing openings, the silencing cotton and the silencing medium, noise transmission can be reduced through the silencing layer, external noise is absorbed through the sound transmission holes, the absorbed noise is transmitted to the interior of the sound absorption medium, and the absorbed noise is circularly transmitted and reduced through the silencing holes in the sound absorption medium; and through the silencing cotton, the transmission of noise can be reduced, the volume of the noise is effectively reduced, and the sound insulation effect of the sound reduction layer is ensured.

This invention discloses a low-noise range hood, including a range hood body and a fan housing mounted on the range hood body. A sound-absorbing volute is fixedly installed inside the fan housing. The sound-absorbing volute includes a volute body and a damping layer on the inner wall of the volute body. Multiple baffles are mounted on the volute body, and these baffles are rotatably connected to the volute body via connecting components. A noise-reducing plate is installed inside the fan housing. An exhaust pipe is connected to the exhaust vent extending from the volute body to the outside of the fan housing. An oil fume filter plate is installed inside the exhaust pipe. This invention discloses a low-noise range hood that reduces noise while also filtering oil fumes.

The invention discloses a noise reduction and impact resistance gear structure and a transmission device. The noise reduction and impact resistance gear structure comprises a gear body, a buffering assembly and a noise reduction assembly, wherein the buffering assembly and the noise reduction assembly are arranged in the gear body; the buffering assembly is arranged in the gear body, and the noise reduction assembly comprises sound absorption cotton and is mounted in mounting grooves separated by the fixing frame. The gear box has remarkable noise reduction and impact resistance and can effectively protect gears. And the lubricating device in the gear box can accurately spray oil to provide continuous lubrication for the gear. In the operation process of the gear, the sound absorption cotton can absorb part of sound waves, and noise transmission is remarkably reduced. When the gear is subjected to large impact force, the gear body drives the fixing frame to extrude the telescopic rod, the whole gear body eccentrically moves, and therefore the impact force is dispersed, after the impact force disappears, the movable spring and the sliding spring release energy, the gear body is pushed to recover to the initial state, the service life of the gear is remarkably prolonged, and the operation stability of the gear is remarkably improved.

The invention belongs to the technical field of ventilation, and discloses a vehicle body acoustic superstructure noise reduction ventilation frame which comprises a ventilation frame body and an acoustic superstructure. The ventilation frame comprises a ventilation frame body and blades rotationally connected to the ventilation frame body, the ventilation frame body is provided with a pressure relief channel, and the blades can open or close the pressure relief channel under the action of external force; an acoustic superstructure body of the acoustic superstructure is fixedly connected to the ventilation frame body, the acoustic superstructure body is provided with a communicating channel communicating with the pressure relief channel, and at least two acoustic noise reduction cavities are formed in the inner circumferential wall of the communicating channel in a concave mode and distributed in the circumferential direction of the communicating channel at intervals. By the adoption of the vehicle body acoustic superstructure noise reduction ventilation frame, in the vehicle outer circulation process, on the basis that the ventilation and pressure relief efficiency of the ventilation frame is not affected, the intensity of noise transmitted into a vehicle cab can be effectively weakened, and therefore the riding experience of people in a vehicle can be effectively improved.

1. The name of this design product: sound-absorbing panel. 2. Purpose of this design product: used for sound insulation, to isolate sound and reduce noise. 3. The key point of the design of this product lies in its shape. 4. The picture or photo that best illustrates the design points: Stereoscopic drawing 1.

The invention discloses an ultra-wide-band noise reduction and bearing function integrated metamaterial structure sound barrier. The ultra-wide-band noise reduction and bearing function integrated metamaterial structure sound barrier comprises a multifunctional integrated screen body and a porous metamaterial sound absorber. The multifunctional integrated screen body comprises a composite non-uniform hollowed-out plate and a cavity, the composite non-uniform hollowed-out plate is arranged at the open end of the cavity, and partition plates are arranged in the cavity to divide the cavity into a plurality of sub-cavities; the porous super-structure sound absorber comprises a plurality of high-porosity sound absorption media arranged in the corresponding sub-cavities, and sound wave regulation and control channels are formed in the high-porosity sound absorption media. The metamaterial structure sound barrier is applied to the field of acoustic noise reduction, the metamaterial structure sound barrier can obtain low-frequency and ultra-wide-band efficient sound absorption performance, the overall rigidity of the sound barrier is improved, the longitudinal supporting area of the sound barrier is increased, the ultra-wide-band sound insulation performance of the sound barrier is greatly improved, meanwhile, the bearing capacity of a sound barrier body is greatly improved, and the noise reduction effect is good. The integration of the ultra-wideband efficient noise reduction performance and the high bearing function of the sound barrier with the metamaterial structure is realized.

The utility model relates to the technical field of hair driers, in particular to a hair drier capable of reducing use noise through a conical sound absorption structure. Comprising a blower body with an air inlet and an air outlet, a fluid channel which enters the air outlet along the air inlet and flows out is arranged in the blower body, a high-speed fan and a heating module are arranged in the fluid channel, the heating module is arranged at the air outlet and the high-speed fan, and a conical inner shell is arranged in the fluid channel. The end, with a small opening, of the conical inner shell is in butt joint with the air inlet, the end, with a large opening, of the conical inner shell is in butt joint with the high-speed fan, a plurality of evenly-distributed long holes are formed in the wall face of the conical inner shell in a surrounding mode, a sound absorption cavity is formed between the conical inner shell and the inner wall of the blower body, and a sound absorption layer is arranged in the sound absorption cavity. And the sound absorption layer arranged in the sound absorption cavity can play a powerful sound absorption role. When sound waves generated when the blower works enter the sound absorption cavity through the long holes, the sound absorption layer can efficiently absorb and convert sound wave energy, and therefore noise transmission is greatly reduced.

This utility model relates to a noise reduction structure for a DC motor, wherein the noise reduction structure (1) is disposed within a cavity for accommodating a commutator (2) and close to the sound source. The noise reduction structure (1) can be a honeycomb structure, a square structure, a circular structure, or a regular polygonal structure, and can be disposed on the bottom surface of the cavity, or simultaneously on the sidewalls and bottom surface of the cavity. The noise reduction structures (1) can be evenly distributed on the bottom surface and sidewalls of the cavity, or staggered. In addition, the noise reduction structure (1) can also be disposed within the cavity of a gearbox (5), including at the bottom of the gearbox cavity (6), or simultaneously on the bottom and cavity walls of the gearbox cavity (6). Using this noise reduction structure for a DC motor, the sound waves generated by the sound source are effectively reflected and canceled out by the noise reduction structure, thus reducing the noise of the DC motor and possessing certain practical value.

The utility model discloses an auxiliary tool for manually attaching mute sponge. The auxiliary tool comprises a fan-shaped guide groove, a guide rod, a handle, a first buckle, a lead screw, a supporting rod, a fixing base and a fixing screw. By adopting the auxiliary tool, the situation that the center position of the tire crown cannot be found by manually attaching the mute sponge can be avoided, and the mute sponge is prevented from being attached to one side or snakelike. In addition, no matter how the width of the sponge changes, the lead screw can be adjusted to advance or retreat to ensure the width of the mute sponge, it is ensured that the mute sponge is attached to the center of the tire crown, the noise reduction performance is achieved, and the guiding function is mainly achieved.

The utility model relates to the technical field of noise reduction, in particular to a noise reduction device capable of reducing noise between equipment, which comprises pump body equipment and an equipment room for installing the pump body equipment, a base for supporting the pump body equipment is fixedly arranged at the bottom of the equipment room, and right-angle grooves consisting of vertical square grooves and horizontal round holes are arranged on two sides of the base. And right-angle bent pipes are pre-buried in the vertical square grooves, pipelines at the two ends of the pump body equipment communicate with the input ends of the right-angle bent pipes on the two sides correspondingly, the output ends of the right-angle bent pipes communicate with horizontal pipes, and a noise reduction compartment is fixedly arranged on the surface of the top of the base. According to the technical scheme, the right-angle bent pipe is pre-buried, so that the requirement for laying inlet and outlet pipes of pump body equipment is met without punching holes in the noise reduction compartment, punching holes in the noise reduction compartment are reduced, the noise reduction effect is improved, the upper layer of the base is the rubber layer, vibration of the pump body equipment can be reduced, noise is reduced from the source, and the noise reduction compartment is matched. And the equipment noise transmitted from the equipment room can be reduced.

The invention discloses a noise reduction type disrotatory fog gun, and relates to the technical field of environmental protection. The noise reduction type contra-rotating fog gun comprises an air guide barrel, a first sound absorption barrel, a contra-rotating air outlet device and a spraying device. The first sound absorption cylinder is arranged in the air guide cylinder, a first sound absorption cavity is formed between the first sound absorption cylinder and the air guide cylinder, a plurality of first sound absorption holes are densely formed in the first sound absorption cylinder, the first sound absorption holes communicate with the first sound absorption cavity, the contra-rotating air outlet device is installed in the first sound absorption cylinder, and the spraying device is installed at the air outlet end of the air guide cylinder; the contra-rotating air outlet device comprises a driving part, a first impeller, a reverse transmission assembly and a second impeller, the driving part is connected with the first impeller, the reverse transmission assembly is connected between the first impeller and the second impeller, and the first impeller and the second impeller are coaxially arranged. According to the noise reduction type disrotatory fog gun, long-distance water mist blowing can be achieved, the operation requirements of different scenes are met, noise can be effectively reduced, and noise pollution is relieved.

The utility model relates to the technical field of los angeles abrasion tester, specifically relates to a los angeles abrasion tester with noise reduction function, including base, the gearbox of setting on the base, two support frames and the drum of rotating control through gearbox, the drum includes inner tube and outer tube, the inner tube is polyurethane rubber material, and the inner tube and outer tube form the sound insulation cavity of sealing, and the cavity is filled with sound absorption cotton, and the lower portion of drum is equipped with screen frame, and the both ends of screen frame are rotatably installed on the corresponding pivot, the double -deck structure of inner tube and outer tube is used to the drum, and fills sound absorption cotton, and can effectively absorb the noise of the collision of sample and cylinder wall, the polyurethane rubber material can reduce the rigid impact of sample collision, reduce noise from the source, solve the problem that the traditional equipment is running noisy, the both ends of screen frame are rotatably installed on the pivot, and reciprocating swing along the pivot of screen frame can be controlled through the handle, realize the quick separation of coarse and fine aggregate, need not extra carry material and carry out screening, reduce the artificial labor intensity.

The invention relates to the technical field of loudspeakers, in particular to a full-band loudspeaker system with large front and back sound pressure level difference, which comprises a box body, a first mounting plate arranged in the box body, a second mounting plate arranged at an interval with the first mounting plate, a first loudspeaker unit arranged on the first mounting plate and a second loudspeaker unit arranged on the second mounting plate, the plurality of first loudspeaker units are arranged in a rectangular array, the plurality of second loudspeaker units are arranged in a rectangular array, and the plurality of second loudspeaker units are electrically connected with an external processor and an external multi-channel power amplifier. The sound pressure level output facing the residential area is effectively adjusted to be small, the sound pressure level facing the sound listening area is effectively adjusted to be large, the influence of noise disturbing residents is reduced, meanwhile, efficient information transmission is ensured, and use is easy and convenient.

The utility model belongs to air conditioner compressor technical field especially relates to a kind of noise reduction structure of air conditioner compressor sound attenuation package, including frame, air inlet and air outlet are set up on frame, frame has sound attenuation chamber inside, noise enters from air inlet, to sound attenuation chamber inside, then noise passes through air outlet and enters into gas storage chamber, in turn through upper support plate, middle support plate and lower support plate, finally from exhaust port inside the noise is discharged, when noise spreads to sound attenuation chamber inside, will first collide with assembly component, noise will occur reflection, refraction and scattering and other phenomena in the process of collision, so that noise is in the bounce space Bounce back.And in the bounce process, the energy of noise will be gradually consumed and dispersed, because installation frame is installed at air outlet, to lengthen the path of noise, further reduce noise;Compared with prior art, the utility model thereby improves sound attenuation effect.

The invention discloses a multifunctional composite material and a preparation method and application thereof, and belongs to the technical field of composite materials. The multifunctional composite material provided by the invention is suitable for industrial scenes which need to meet the requirements of corrosion resistance, buoyancy support, light heat preservation and safety protection at the same time. Comprising but not limited to the fields of passive energy absorption protection, petrochemical engineering storage and transportation facilities, deep sea detection equipment, structure filling engineering in flammable and explosive environments, acoustic noise reduction engineering and the like. The multifunctional composite material provided by the invention is a material with multi-environment adaptability, and is particularly suitable for a composite functional material system with the characteristics of water resistance, oil resistance, chemical corrosion resistance, low heat conductivity, flame retardance, high-temperature adaptability, sound absorption, noise reduction and structural lightweight.

The invention discloses a voice guide and a voice guide system, and relates to the technical field of electronics. Noise can be reduced, and the use experience of a user on the navigation equipment is improved. The voice navigator comprises a hat body and a hat brim, the Bluetooth chip is arranged on the cap body and is used for starting a Bluetooth connection mode and a Bluetooth broadcast mode to carry out wireless communication; the audio processing module is arranged on the helmet body and is electrically connected with the Bluetooth chip; the first microphone is electrically connected with the audio processing module and is used for receiving a voice audio signal; and the second microphone is electrically connected with the audio processing module and is used for receiving an environment audio signal.

The utility model discloses a 500KV main transformer iron core noise reduction auxiliary tool belongs to transformer iron core noise reduction technical field, this 500KV main transformer iron core noise reduction auxiliary tool, transformer iron core subassembly sets up inside transformer body, the bottom of transformer iron core subassembly is installed to the noise reduction shell, and the top limiting installation of transformer iron core subassembly has the supplementary noise reduction cover board, one end of supplementary noise reduction subassembly sets up inside the noise reduction shell, and the bottom transmission connection of transformer iron core subassembly with supplementary noise reduction subassembly's another end, side first damping spring, side second damping spring and end damping spring, can effectively buffer and absorb the vibration energy that transformer iron core subassembly generates, reduce vibration transmission to reduce the generation and spread of noise. Meanwhile, the multilayer composite board and sound absorbing cotton in the supplementary noise reduction cover board can further absorb and block the noise, improve the noise reduction effect, and the supplementary noise reduction cover board is directly installed on the top of the transformer iron core subassembly and is not installed with the transformer body.

The application relates to the technical field of automobile silencers, in particular to a range-extender hybrid automobile silencer, which comprises a silencer body, the inside of the silencer body is sequentially provided with a first sound insulation plate, a second sound insulation plate, a third sound insulation plate and a fourth sound insulation plate from left to right and sealed with the inner wall of the silencer body, the first sound insulation plate and the inner wall of one side of the silencer body form a first silencing chamber, and the first sound insulation plate and the second sound insulation plate form a second silencing chamber. The first sound insulation plate, the second sound insulation plate, the third sound insulation plate and the fourth sound insulation plate are arranged, the first silencing chamber, the second silencing chamber, the third silencing chamber, the fourth silencing chamber and the fifth silencing chamber are formed in the inside of the silencer body, noise enters the first silencing chamber through one end of the U-shaped air inlet pipe, the kinetic energy of the noise is reduced through mutual collision, the kinetic energy of the noise is reduced again through mutual collision after entering the fifth silencing chamber through the U-shaped connecting pipe and the L-shaped connecting pipe, and the noise is finally discharged through the U-shaped air outlet pipe.

This application relates to a low-noise centrifugal pump and a pressure pulsation detection method, belonging to the technical field of water pumps. It includes a pump body, and the pump body is provided with an impeller chamber and a water inlet chamber. The water inlet chamber includes a water inlet flow channel and a connecting flow channel, and the connecting flow channel is connected to the impeller chamber. The boundary of the connecting flow channel is curved. The water inlet chamber includes several cross-sections that are circular. Let the smallest circular cross-section be S1 and the largest circular cross-section be S2, where S2 ≥ S1 ≥ 0.9S2. This application has the advantage of being able to reduce noise.

The utility model provides a barrel type dust collector which comprises a main body, a dust collector body and a dust collector body. The dust collection barrel is detachably arranged in the mounting cavity, the dust collection barrel comprises an inner barrel and an outer barrel, the inner barrel is arranged in the outer barrel and is separated from at least one part of the outer barrel to form a sound insulation cavity, and the inner barrel is connected with the outer barrel to seal the sound insulation cavity. The double-layer dust collection barrel structure comprising the inner barrel and the outer barrel is designed, and the sound insulation cavity is formed between the inner barrel and the outer barrel, so that noise is reduced.

1. The name of the design product: earplug (full sleep posture without pressure). 2. The use of the design product: the design product is used to plug into the ear to reduce noise. 3. The design points of the design product: in shape. 4. The picture or photo that best indicates the design points: perspective drawing.

The invention relates to the technical field of voice recognition, and particularly discloses a building indoor acoustic noise reduction and sound absorption optimization system based on deep learning. The system comprises a sound field perception and data acquisition module, a cross-environment acoustic feature extraction module, a meta-learning driving model rapid adaptation module, a multi-target acoustic optimization decision module and a distributed sound absorption actuator control module, rapid model adaptation is realized through meta-learning, parameters are finely adjusted by using a small amount of field data, and the sound absorption performance is improved. And in combination with a multi-objective optimization algorithm, acoustic indexes such as voice definition, noise suppression and space sense maintenance are balanced, and finally, the sound absorption unit is dynamically regulated and controlled through the distributed actuator, so that efficient and accurate indoor acoustic environment optimization is achieved.

The utility model discloses a dustproof soundproof wall for municipal construction, which comprises a cement base, a soundproof wallboard, a spray dedusting component and a decorative plate, the soundproof wallboard comprises I-shaped upright posts, a dust blocking wall body fixedly mounted between the two I-shaped upright posts and inclined inwards, and a metal sealing strip fixed on the upper surface of the dust blocking wall body through screws, the first sound insulation wall body is fixedly installed between the two I-shaped stand columns and abuts against the lower portion of the top dust blocking wall body, and the second sound insulation wall body is fixedly installed between the two I-shaped stand columns and abuts against the lower portion of the first sound insulation wall body. The dustproof and soundproof wall for municipal construction has the advantages of being stable in structure, excellent in soundproof effect and outstanding in dustproof capacity, the soundproof wall board can effectively reduce noise, the inclined dustproof wall body and the spray dedusting assembly in the soundproof wall board can effectively block raised dust, and in addition, the dustproof and soundproof wall for municipal construction is high in adaptability and good in soundproof effect. And the requirements of different municipal construction sites can be met.

The utility model relates to the technical field of wall surface cloth, in particular to curved surface acoustic wall surface sticking cloth. The patch comprises a patch body, two convex grooves are formed in the surface of the patch body, strip-shaped plates are connected to the surfaces of the convex grooves in a sliding mode, connecting blocks are fixedly connected to the surfaces of the strip-shaped plates, flannelette is fixedly connected to the surfaces of the two connecting blocks, and the flannelette is attached to the surface of the patch body. The surface of the flannelette is fixedly connected with a plurality of flannelette points, the height sizes of the flannelette points are different, the surface of the patch body is provided with a plurality of sound absorption grooves, and a plurality of refraction protrusions are arranged in the sound absorption grooves. The problems that when sound waves meet a flat patch body, the sound waves on the surface of the patch body are intensively reflected, so that indoor sound interferes with each other, echo is obvious, voice definition is reduced, noise pollution is aggravated, normal communication, learning and rest of people are seriously affected, and even hearing fatigue is possibly caused are solved.

To provide a gear transmission device capable of reducing noise.SOLUTION: The gear transmission device includes a first gear pair, and a second gear pair for transmitting the rotation of the first gear pair. A first value as a ratio between a meshing frequency of the first gear pair and a meshing frequency of the second gear pair belongs to a consonance pitch, and a second value as a ratio between a frequency of gear sound which is caused by a tool mark of a first gear included the first gear pair or the second gear pair and a meshing frequency a gear pair including the first gear belong to a consonance pitch.SELECTED DRAWING: Figure 1