The blower includes a pump and an alarm device. The alarm device has a buzzer, a lamp, a control unit, and a cover fixed to the pump. The cover comprises a plurality of sections including a first cover section and a second cover section, and the buzzer, the lamp, and the control unit are fixed to the first cover section.

An ultrasonic transmitter. The ultrasonic transmitter includes a first enclosure, a second enclosure, a piezoelectric transducer, a first piston, and a second piston. The first enclosure has an opening for directing an output of the ultrasonic transmitter in a first direction and a wall opposite the opening. The second enclosure has a first opening aligned in the first direction and a second opening opposite the first opening. The second enclosure is positioned in the first enclosure with the second opening directed toward the wall. The piezoelectric transducer is positioned in the second enclosure and movable relative to the first enclosure. When an ultrasonic electric signal is applied to the piezoelectric transducer, the piezoelectric transducer expands and contracts pulsing the first and second pistons to produce ultrasonic sound waves from the first and second openings which combine and our output by the ultrasonic transmitter.

A robotic cleaning appliance includes a housing to which is coupled a surface treatment item and a sensor assembly with first and second transducers and an acoustic interface. The first sonic transducer transmits sonic signals through an acoustic interface and out of a first acoustic opening toward a surface beneath the robotic cleaning appliance. The sonic signals reflect from the surface as corresponding returned signals received by the second sonic transducer via a second acoustic opening port of the acoustic interface. A first annular ring is defined around the first acoustic opening port and a second annular rings is defined around the second acoustic opening port. The annular ring attenuate direct path echoes between the acoustic opening ports. The first and second acoustic opening ports are coupled the first and sonic transducers, respectively, via first and second horns; and the horns are tilted from orthogonal with the surface.

Provided is a buzzer that sounds without noise contamination. Specifically, an inaudible frequency signal generation unit 22 generates an inaudible frequency pulse signal P0; an audio frequency signal generation unit 26 generates, from the signal P0, an audio frequency pulse signal P1: a signal synthesizing unit 28 generates a synthesized frequency pulse signal P2 having the signal P0 in an ON time of the signal P1; a first duty ratio setting unit 30 sets a duty ratio Di of the signal P0 in the signal P2 to gradually increase over a first predetermined period of the signal P2, and thus generates a buzzer driving signal P3; and a buzzer driving unit 40 makes a buzzer 60 sound with a pitch corresponding to a frequency of the signal P3 and volume corresponding to the duty ratio of the signal P3.

Provided is a buzzer that sounds without noise contamination. Specifically, an inaudible frequency signal generation unit 22 generates an inaudible frequency pulse signal P0; an audio frequency signal generation unit 26 generates, from the signal P0, an audio frequency pulse signal P1: a signal synthesizing unit 28 generates a synthesized frequency pulse signal P2 having the signal P0 in an ON time of the signal P1; a first duty ratio setting unit 30 sets a duty ratio Di of the signal P0 in the signal P2 to gradually increase over a first predetermined period of the signal P2, and thus generates a buzzer driving signal P3; and a buzzer driving unit 40 makes a buzzer 60 sound with a pitch corresponding to a frequency of the signal P3 and volume corresponding to the duty ratio of the signal P3.

A sound transmitting system for a motor vehicle has a sound generator (2) and a sound-conducting first sound duct (6). The first sound duct (6) has a proximal end (7) connected to the sound generator (2) to transmit sound and a distal end (21) facing away from the proximal end (7) and via which a sound from the generated sound enters a passenger compartment (19) or external region (20) of a bodywork (26) of the motor vehicle (12). To bring about a specific sound characteristic of the resulting sound, a first length (L1) of the first sound duct (6) and/or a first diameter (D1) of the first sound duct (6) and/or a first cross-sectional area (Q1) of the first sound duct (6) are/is adapted as a function of the generated sound.

An ultrasonic sensor includes a magnetic substance, a diaphragm, and an electromagnetic transducer. The electromagnetic transducer is disposed opposing the magnetic substance across an outer plate of a vehicle. The diaphragm has the shape of a thin film with a film thickness direction along an axial direction parallel to a directional axis. The diaphragm is able to ultrasonically oscillate by being joined to an outer surface of the outer plate at an outer edge in a radial direction crossing the directional axis. With the outer edge of the diaphragm joined to the outer surface of the outer plate, an internal space that expands and contracts along the axial direction in response to ultrasonic oscillation of the diaphragm is formed between the diaphragm and the outer surface of the outer plate.

A calibration method comprises adjusting an operating frequency of an air-pulse generating device, such that a sound pressure level (SPL) of the air-pulse generating device is within a specific range. The sound producing module comprises the air-pulse generating device configured to produce sound via generating a plurality of air pulses at a pulse rate corresponding to the operating frequency.

A calibration method comprises adjusting an operating frequency of an air-pulse generating device, such that a sound pressure level (SPL) of the air-pulse generating device is within a specific range. The sound producing module comprises the air-pulse generating device configured to produce sound via generating a plurality of air pulses at a pulse rate corresponding to the operating frequency.