A muffler comprises a housing enclosed to form a hollow cavity, the cavity comprises a cylindrical chamber and a rectangular parallelepiped chamber, wherein one of bottom surfaces of the cylindrical chamber is connected with a first surface of the rectangular parallelepiped chamber, the cylindrical chamber communicates with an interior of the rectangular parallelepiped chamber, and the cylindrical chamber is provided with an air inlet and an air outlet.

A refrigerator includes a noise reduction device and a machine room that accommodates a condenser and a compressor. The noise reduction device includes a sensing unit configured to measure noise generated from the machine room of the refrigerator and a generating unit configured to output a sound signal having a frequency canceling or reducing the noise. The machine room is defined by a case that has a communication portion configured to communicate a fluid between an inside of the case and an outside of the case to thereby exchange heat between the fluid and the condenser and between the fluid and the compressor.

A sound-modulating device used in a confined space is provided. The sound-modulating device includes an event detector and an audio module in communication with each other. The event detector detects an event and generates a trigger signal in response to the detected event. The audio module plays a music segment in response to the trigger signal. The frequencies of the music segment range from 20 Hz to 20000 Hz. The intensities of the music segment are smaller than or equal to 75 dB.

A method of operating a motor driving a rotating member includes directing rotation of the rotating member at the motor at an initial speed, determining a first frequency of a first noise component generated by the rotating member at the initial speed, determining a second noise component having a second frequency phase shifted 180° with respect to the first frequency, determining a torque modifier of the motor to generate the second noise component from the motor, and directing activation of the motor according to the determined torque modifier.

A refrigerator includes a noise reduction device. The noise reduction device measures noise generated from a machine room of the refrigerator and outputs a sound signal having a frequency canceling or reducing the noise.

A muffler comprises a housing enclosed to form a hollow cavity, the cavity comprises a cylindrical chamber and a rectangular parallelepiped chamber, wherein one of bottom surfaces of the cylindrical chamber is connected with a first surface of the rectangular parallelepiped chamber, the cylindrical chamber communicates with an interior of the rectangular parallelepiped chamber, and the cylindrical chamber is provided with an air inlet and an air outlet.

A consumer appliance is provided herein. The consumer appliance may include a cabinet, an exterior panel, an electromechanical driver, an electromechanical receiver, and a controller. The cabinet may define an internal chamber. The exterior panel may be mounted to the cabinet. The electromechanical driver may be fixed to the exterior panel to generate a soundwave therefrom. The electromechanical receiver may be mounted within the cabinet. The controller may be configured to initiate a noise canceling operation. The noise canceling operation may include receiving a noise input signal at the electromechanical receiver and initiating an anti-noise wave at the electromechanical driver through the exterior panel based on the received noise input signal.

A refrigerator includes a microphone and at least one processor configured to identify a first driving noise level corresponding to first driving state information of the refrigerator, based on receiving an ambient noise through the microphone while operating according to the first driving state information, identify a reception noise level based on the received ambient noise, identify an external noise level based on the reception noise level and the first driving noise level, and based on a ratio of the external noise level to the first driving noise level being smaller than a threshold ratio, drive the refrigerator based on second driving state information corresponding to a lower noise level than the first driving state information.

A sound-modulating device used in a confined space is provided. The sound-modulating device includes an event detector and an audio module in communication with each other. The event detector detects an event and generates a trigger signal in response to the detected event. The audio module plays a music segment in response to the trigger signal. The frequencies of the music segment range from 20 Hz to 20000 Hz. The intensities of the music segment are smaller than or equal to 75 dB.

An indoor sound-modulating device is provided. The indoor sound-modulating device includes a low-frequency noise detector, an automatic actuator and an audio signal generator. The low-frequency noise detector detects low-frequency noise and generates a first modulating signal in response to the detected low-frequency noise. The automatic actuator issues a second modulating signal in response to a predetermined state. The audio signal generator generates a low-frequency audio signal for eliminating the low-frequency noise in response to the first modulating signal and generates a high-frequency repellent audio signal in response to the second modulating signal. The low-frequency audio signal has a frequency ranging from 20 Hz to 350 Hz, while the high-frequency repellent audio signal has a frequency not less than 8000 Hz.