A home appliance comprising: a cabinet (10A, 10B); an object receiving chamber (11A, 11B) defined in the cabinet to receive an object therein; a door (100A, 100B) pivotally coupled to the cabinet to open and close the object receiving chamber, wherein the door has a see-through window; a lighting device (600, 610, 620) for illuminating an interior of the object receiving chamber; a sensor disposed in the door for detecting an acoustic wave, wherein the acoustic wave is generated by an application of a knock input to the door; and a controller configured to activate the lighting device upon detecting the knock input, such that the object receiving chamber may be visible to an outside through the see-through window, wherein the door includes a front panel (110A, 110B) provided on a front face of the door so that the knock input is applied to the front panel, an inner frame ( 210A, 230B) coupled to the front panel (110A, 110B) on a rear of the front panel (271, 471, 110A, 110B), and a printed circuit board, PCB, assembly coupled to the inner frame on a rear of the inner frame, characterized in that the sensor includes: a sensor device module including a sensor device for sensing the acoustic waves and a sensor device receptor constructed to receive the sensor device; a housing for receiving the PCB assembly; a holder provided on the housing, wherein the holder receives the sensor device therein such that a portion of the sensor device protrudes; a fastener provided on the housing for coupling the housing to the inner frame (210A, 230B), a coated-solution invading hole for allowing the coated-solution to penetrate the housing to protect electrical components from moisture; and a connector provided on a bottom of the housing, wherein the sensor and a controller of the PCB assembly are connected to each other through the connector, wherein the sensor device is provided to contact the front panel (110A, 110B). a cabinet (10A, 10B); an object receiving chamber (11A, 11B) defined in the cabinet to receive an object therein; a door (100A, 100B) pivotally coupled to the cabinet to open and close the object receiving chamber, wherein the door has a see-through window; a lighting device (600, 610, 620) for illuminating an interior of the object receiving chamber; a sensor disposed in the door for detecting an acoustic wave, wherein the acoustic wave is generated by an application of a knock input to the door; and a controller configured to activate the lighting device upon detecting the knock input, such that the object receiving chamber may be visible to an outside through the see-through window, wherein the door includes a front panel (110A, 110B) provided on a front face of the door so that the knock input is applied to the front panel, an inner frame ( 210A, 230B) coupled to the front panel (110A, 110B) on a rear of the front panel (271, 471, 110A, 110B), and a printed circuit board, PCB, assembly coupled to the inner frame on a rear of the inner frame, characterized in that the sensor includes: a sensor device module including a sensor device for sensing the acoustic waves and a sensor device receptor constructed to receive the sensor device; a housing for receiving the PCB assembly; a holder provided on the housing, wherein the holder receives the sensor device therein such that a portion of the sensor device protrudes; a fastener provided on the housing for coupling the housing to the inner frame (210A, 230B), a coated-solution invading hole for allowing the coated-solution to penetrate the housing to protect electrical components from moisture; and a connector provided on a bottom of the housing, wherein the sensor and a controller of the PCB assembly are connected to each other through the connector, wherein the sensor device is provided to contact the front panel (110A, 110B). a sensor device module including a sensor device for sensing the acoustic waves and a sensor device receptor constructed to receive the sensor device; a housing for receiving the PCB assembly; a holder provided on the housing, wherein the holder receives the sensor device therein such that a portion of the sensor device protrudes; a fastener provided on the housing for coupling the housing to the inner frame (210A, 230B), a coated-solution invading hole for allowing the coated-solution to penetrate the housing to protect electrical components from moisture; and a connector provided on a bottom of the housing, wherein the sensor and a controller of the PCB assembly are connected to each other through the connector, wherein the sensor device is provided to contact the front panel (110A, 110B).