Abstract: A piezoelectric buzzer directly secured to a portion of a wrist watch casing and driven to vibrate the casing and produce an alarm sound. Associated circuitry alternately drives the piezoelectric buzzer at two different frequencies having a frequency ratio of 4:5 and at monotonically decreasing amplitudes as to produce alarm sounds like chimes.

Abstract: In an electrodynamic speaker comprising a vibrating plate, a voice coil secured to the vibrating plate, a magnetic circuit portion having a soft magnetic member and a magnet and having a magnetic gap, a frame for supporting the peripheral portion of the vibrating plate and the magnetic circuit portion, and a lead substrate. The voice coil is secured to the vibrating plate after the vibrating plate is secured to the frame and then the magnetic circuit portion is assembled on the frame. As a result of it, the lead terminal of the voice coil can be connected to the lead substrate through the notch portion of the frame in the same process as mounting the voice coil on the vibrating plate wherey the factor of variation in the magnetic gap dimension which affects the efficiency of the magnetic circuit is reduced.

Abstract: A small acoustic device is provided with a housing, a first electrically actuated vibrating plate and a second vibrating plate. A support member cooperates with the housing for mounting the periphery of the second vibrating plate to the housing to define therewith an airtight chamber. The support member also supports the periphery of the first vibrating plate in the airtight chamber with a gap between the two vibrating plates and air chambers on either side of the second vibrating plate. In this way, the barometric pressure in the two air chambers on either side of the second vibrating plate are equivalent and the device is both waterproof and independent of ambient temperature changes.

Abstract: A waterproof construction around a miniature buzzer incorporated in an electronic alarm watch depends on a gasket alone. The construction is such that the gasket can secure a resonant plate without any storage of distortion in the resonant plate. This feature makes it possible to provide the electronic alarm watch having a stable performance for acoustic emission.

Abstract: An electromagnetic transducer in which one end of a coil terminal is connected with a step portion of a magnetic core body made of soft magnetic material such as pure iron and the other end of which is connected with a step portion of a supporting frame made of metal on the same plane by spot welding. An insulation between the supporting frame and the magnetic core body is made by interposing an insulator therebetween or by coating the surface of the magnetic core body with a resin film by evaporation.By treating the coil terminals on the same plane, the expensive substrate for making an electrical connection is not needed and the assembly cost is extremely reduced.

Abstract: An electro-magnetic type electric acoustic transducer comprising an exciting portion consisting of a back plate mounting a permanent magnet and a magnetic core winding an exciting coil therearound, a vibrating plate arranged opposite to said exciting portion leaving a certain space, and a vibrating plate supporting member which supports the periphery of said vibrating plate, characterized in that the resonance frequency of the vibrating plate is reduced while maintaining sound pressure by providing an air hole at a part of said plate or said vibrating plate supporting member.

Abstract: An alarm wristwatch comprises a watchcase having a back with an inclined peripheral portion and a watchband attached to the watchcase at opposite sides. A transducer for generating an alarm signal faces a cavity provided in a rear portion of the watch case. A plurality of sound holes provided in the inclined peripheral portion of the watchcase back open into this cavity. The second holes are located within an angle of 45.degree. on either side of the longitudinal center line of the watchband so that they are not blocked or muffled by the arm of the wearer. The cavity and sound holes are so proportioned as to constitute a Helmholz resonator by which the sound produced by the transducer is intensified and efficiently transmitted to the exterior of the watchcase.

Abstract: An alarm electronic timepiece comprises a time circuit including a time standard signal oscillator for generating a time signal fed to a time display portion for displaying time. An alarm device is driven by an alarm driving circuit to produce an audible alarm sound. An alarm signal compound circuit develops a plurality of signals having different duty cycles and having a frequency in the audible frequency range, and serially arranges the plurality of signals in a predetermined pattern to form an alarm signal composed of the serially arranged signals of different duty cycles which is applied to the alarm driving circuit to produce an audible alarm sound having a predetermined sound pressure variation pattern.

Abstract: An alarm watch has an electro-acoustic transducer with a sound releasing cavity containing a vibrating plate for releasing an audible alarm sound. The surface of the vibrating plate exposed to the open air is treated with a water-repellant material having the property to shed or repel water so that when water enters into the sound releasing cavity and wets the vibrating plate, the vibrating plate readily throws off the water thereby obtaining rapid recovery of the alarm sounding function.

Abstract: A miniature electronic buzzer for an electronic watch has two vibrating plates with a sealed space between them forming an air spring. One of the vibrating plates carries an amarature which is acted upon by an electromagnetic to vibrate said plate. Vibration is imparted to the other vibrating plate by the air spring. The two vibrating plates and coupling air spring constitute a vibrating system having two resonant frequencies in the audible range. The electromagnet is energized by current having a frequency in the neighborhood of these resonant frequencies. There may be a third vibrating plate coupled with the second vibrating plate by a second air spring. In this event the vibrating system has three resonant frequencies in the audible range.

Abstract: An electroacoustic transducer particularly for small small-sized portable equipment such as a wristwatch comprises a first vibrating plate which is vibrated by means of an electromagnet and a second vibrating plate which is coupled with the first vibrating plate by an airtight space which acts as an air spring. The first and second vibrating plates have different natural resonant frequencies so that the vibration system comprising the two vibrating plates and the air spring coupling them with one another forms a vibration system having two resonant frequencies. A resonant air chamber superposed on the second vibrating plate has a sound radiating port and has a resonant frequency between the two resonant frequencies of the vibration system comprising the first and second vibrating plates and coupling air spring. The electroacoustic transducer thus responds to a considerable range of frequencies.

Abstract: An electro-acoustic transducer of electromagnetic type is composed of an exciting part having a magnetic core wound with an exciting coil, a vibrating plate provided opposite to the magnetic core at an interval and a ferromagnetic thin plate mounted to the vibrating plate. The thin plate is provided on the surface of the vibrating plate on the side of the magnetic core, so that the thin plate is not exposed to the open air. Furthermore, the thin plate is connected to the vibrating plate at plural points more than three or at a part with some area. Such connection restrains undesirable vibration of the thin plate.

Abstract: An electronic buzzer comprises an acoustic vibrator comprised of a circular metal plate having its entire periphery rigidly secured to a support, and a piezoelectric element adhered to one face of the metal plate. A driving circuit applies electric driving signals to the vibrator to vibrationally drive it at a 1/N multiple of its natural frequency, where N is an integer, so that the vibrator emits an audible buzzing sound. The metal plate is preferably mounted to undergo vibration in a natural vibration mode having only one nodal circle. The drive circuit includes an inductor connected in a closed loop with the vibrator, which functions as a capacitor, and the circuit applies signals at a selectively variable frequency to the closed loop to accordingly vary the inductance of the inductor to thereby vary the period of oscillation of the acoustic vibrator and the resultant frequency of the buzzing sound.