Abstract: A submersible acoustic generator for projection of sound waves into a body f water comprises a tubular resonator, open at its lower end and closed at its upper end, and having a multiple-plate thermoacoustic stack located near the upper end between a pair of heat exchangers which set up a temperature gradient in the stack. The upper heat exchanger is heated by a chemical fuel, and the lower heat exchanger is cooled by the surrounding water. The resonator is gas-filled, and the wavelength of the oscillations produced is approximately twice the length of the resonator. A portion of the resonator tube can be surrounded by a coaxial tube which serves as an impedance matching stub. The stack plates can be made anisotropic by means of embedded copper wires. In alternative versions of the apparatus, the resonator can have two stacks, one near the open end and the other near the closed end, and the temperature gradient in the stack can be established cryogenically.

Abstract: An air horn and method of using such a horn is rechargeable by a conventional air pump for use when the air, acting as a propellant, is depleted from its container connected to the horn. The device may be connected to a bicycle or may be used, for example, on a boat. The device is sounded by depressing an activator or an actuator which releases air into a membrane of the horn to vibrate a diaphragm. When air is depleted from the container, an adapter having an inlet valve connected thereto permits connection of a conventional pump or a built-in pump for refilling.

Abstract: A single-tone inverted toroidal whistle for producing a uni-directional output of about 135 decibels at 100 feet on axis at a frequency of about 420 hertz. A hollow cylinder having a closed base end is combined with a toroidal body to provide an annular sound chamber the working length of which determines the wavelength of sound generated by passage of air or steam under pressure through an annular slit formed in the interior of the cylinder and impinging against a spaced tapered lip on the inner cylindrical wall of the toroidal body.

Abstract: The dropping of pressure for the gas supply in respirators, below a minimum pressure, is reported to the wearer by an acoustic alarm device. To make it possible for the wearer to check whether a warning signal heard comes from his own equipment or not, it is provided that the alarm device has a manipulator which adjusts the sound-generating region.

Abstract: A toroidal shaped closed chamber whistle produces a warning signal capable of being easily heard at relatively great distances from the whistle. The toroidal whistle emits a bidirectional sound which is phase-locked to a particular pitch. The toroidal whistle has a circular plate positioned within a hollow cylinder to form an air passage leading to an annular air slit. Incoming air under pressure flows through the air passage and out of the annular air slit into a toroidal chamber. Within the toroidal chamber, a sound wave is formed which passes out of the toroidal chamber through a chamber mouth. Optionally, two toroidal chambers can be used in combination to produce a dual-tone sound. Additionally, a tremulant device can be used to produce a warbling effect in the emitted sound.

Abstract: A piezoelectric audible sound generator having a feedback type piezoelectric transducer, an amplifier, and a phase compensator for adjusting the phase shift due to the combination of a bias resistance of the amplifier and equivalent capacitance of the piezoelectric transducer.

Abstract: A whistle audibly responsive to extremely small pressure differentials is described. The whistle has a cylindrical inlet portion, a cylindrical outlet portion and a cylindrical constriction that form a passageway between said inlet and outlet portions. The whistle produces audible sound having an intensity of about 80 DB in response to a pressure differential, across the inlet and outlet portions, that is in the range of about 0.005 to 0.02 psi.