Abstract: A resonant tube having an inlet fitting at one end for connection to the regulator hose attached to an intermediate pressure port on the first stage of a scuba diver's regulator and containing therein a sound generator responsive to pressurized air for generating an audible sound to be propogated against the wall of such tube. The outlet from such tube includes a normally closed air valve which may be selectively depressed to release air from such resonator tube causing incoming air to flow through such generator to generate such audible sound. Frequencies generated are propogated to the surrounding water or air.

Abstract: A resonant tube having an inlet fitting at one end for connection to the regulator hose attached to an intermediate pressure port on the first stage of a scuba diver's regulator and containing therein a sound generator responsive to pressurized air for generating an audible sound to be propagated against the wall of such tube. The outlet from such tube includes a normally closed air valve which may be selectively depressed to release air from such resonator tube causing incoming air to flow through such generator to generate such audible sound. Frequencies generated are propagated to the surrounding water or air.

Abstract: An improved outdoor warning siren comprising an electromechanical siren together with a multi-segment horn which effects an exceptionally smooth transition from a small high pressure area at the horn inlet to a larger low pressure area at the horn outlet thereby producing increased sound output with reduced power requirements.

Abstract: A horn assembly for installation within an opening in a boat structure having an exterior surface and an interior surface, is disclosed. The horn assembly includes a noise generator component whose output is directed through a trumpet member having an inlet section and an outlet section. A flared element adapted to extend through the opening in the boat structure has an inner end connected to the trumpet member and an outer end with a peripheral flange that bears against the exterior surface surrounding the opening. A grille element extends over and secures the flared element and thus the horn assembly to the boat structure leaving only the grille element visible on the boat exterior.

Abstract: The invention provides a new whistle, intended for sports referees, and for small boat emergency use, where a loud piercing sound is required without the possibility of loss of sound by "over-blowing" or by sticking of the freely-moving ball used in conventional whistles. The profile of the new whistle preferably is of flat-topped "mandolin" shape in side elevation, so that it is familiar and readily acceptable by established users, and yet includes three separate fipple-type whistle elements in a single whistle body, each with its own air column chamber and vibration-producing knife edge, at least two of which chambers are of slightly different lengths, so as to produce complex harmonics and beats that increase the piercing quality and audibility of the sound. This is done by providing two elements side-by-side and parallel to one another, with the third also parallel and below (or above in an inverted shape) the other two protruding into the space between them.

Abstract: A musical tea kettle is provided for playing a selected tune or the like when water within the kettle is heated to a boiling condition. The tea kettle includes a kettle body having an upper opening within which is mounted a steam driven whistle unit having a steam powered shuttle valve assembly for supplying steam to a plurality of steam whistles. When water within the kettle is boiled, the shuttle valve assembly drives a rotatable valve plate having valve ports therein for discharging steam to the plurality of steam whistles mounted on the shuttle valve assembly, wherein the valve ports are arranged in position and size to operate the steam whistles in a timed pattern to play the selected tune.

Abstract: A combined personal identification, sound producer, and repository device is of oblong hollow construction, including two chambers, one of which is formed as a whistle, and the other is provided with access through the body of the device for retaining coins or the like. The opening into the second chamber includes a door which can be selectively opened or latched closed.

Abstract: In a portable breath alcohol detector using a standard tubular mouthpiece, a breath direction and continuity sensor takes the form of a whistle mounted at a predetermined distance from the discharge end of the mouthpiece to leave a gap, open to the ambient atmosphere, between the discharge end and the whistle, the whistle being of sufficient sensitivity to be activated by a breath blown toward the whistle across the gap and the gap being of a size not appreciably to restrict the flow of breath, and permit air being inhaled to pass freely, whereby if the subject stops breathing, or inhales, the whistle stops sounding, and whereby residual alcohol in the whistle will not be drawn back into the mouthpiece when the subject inhales.

Abstract: Method and apparatus for increasing the turbulence in a gas exposed to low frequency sound. The gas is exposed to sound produced by a sound generator (10) which has a tubular resonator (11) having an open end and is operated at one of the resonance frequencies of the resonator having a maximum frequency of 150 Hz. The gas is flown into the tubular resonator through the open end thereof and is discharged from the resonator substantially in a region, where the sound pressure of the standing wave in the resonator has a node, after having passed through a substantial length of the resonator.

Abstract: A method and apparatus with which a sealed gas containing first container, which is disposed in a sealed inaccessible and not visually observable further container, can be detectably opened. A thermally inducible opening mechanism disposed in a gas flow or connecting path in the wall of the first container is actuated and the gas escaping through the connecting path is detected acoustically. Among other uses, the invention can be used, in particular, for containers having radioactive contents which can be manipulated, welded and leak checked only in hot cells. The method is particularly suitable for leak checking fuel element containers or molds containing highly radioactive vitrified waste since the closing member of the first container can be composed of a soft solder plug and this plug can be melted out by local heating.

Abstract: An electric horn, especially adapted for automotive vehicles includes a pole piece and adjusting cap for the driving motor. The pole piece and adjusting cap include a cylindrical shank and an enlarged head including a conical flange. The flange terminates in an annular rim which is in contact with and secured to the horn housing by resistance welding. A magnetic circuit for the motor extends from the pole face of the pole piece and adjusting cap through the shank and the head to the housing and the cross-sectional area for the flux path through the head is at least as great as that in the shank and sufficiently large to avoid undue magnetic saturation. The rim of the enlarged head has a diameter greater than that of the shank and less than the diameter of the housing coil cup to thereby obtain increased stiffness in the connection of the pole piece and adjusting cap with the housing.

Abstract: An ultrasonic horn assembly includes a horn with a bore tapering from a throat out to a mouth. An ultrasonic transducer is mounted in the throat of the horn. A beam narrowing insert includes a headpiece which tapers smoothly from a larger diameter base to a smaller diameter top. A stem projects from the base so that the base and stem define an annular shoulder which faces the transducer. A blind bore in the stem terminates at a flat bottom surface which faces the transducer. A ring receives the transducer and webs project inwardly therefrom to support the headpiece in spaced relationship to the transducer.

Abstract: A whistle having two chambers of different size so that each is capable of generating a sound different to that generated by the other. Each chamber is elongate and has an open mouth located at the same end of the whistle body. A mouthpiece extends angularly from that end of the body and has two open-ended passages extending therethrough, each of which has an open inner end located adjacent a respective one of the chamber mouths. The two passages are located in close side by side relationship and are arranged so that a stream of air emerging from their respective inner ends passes across a respective one of the two chamber mouths so that the two chambers generate sound simultaneously. The two chambers generate relatively high and low frequency sound respectively.

Abstract: An improved pneumatic pressure gauge used in inflating a pneumatic tire comprises an adapter means having a gas passage extending from a gas inlet end to a gas outlet end, and a gauge casing connected integrally to the adapter member. The gauge casing includes a gauge chamber, an opening intercommunicating the gas passage and the gauge chamber, a control chamber communicated with the gauge chamber, and a gas release passage opened to atmosphere and communicated with the control chamber. A first valve means is disposed to close the communication between the gas passage and the gauge chamber, and a second pressure responsive valve means is disposed in the control chamber to close the communication between the control chamber and the gas release passage. The valve means are opened when the pressure in the tire or the gas passage exceeds the predetermined pressure.

Abstract: A hydroacoustic transducer for generating and applying acoustic energy to a load coupling structure has a hydroacoustic amplifier with a driver stage and a power stage. The power stage includes a valve, which obtains high power conversion efficiency by operating to switch the flow of pressurized hydraulic liquid on and off thereby providing a switching amplifier which presents a pressure source of acoustic energy. This source is connected to a load coupling structure by way of an acoustic transformer and an inertive element in series with the source. The inertive element is provided by a liquid-filled bore and is terminated at its input end by the larger area of a stepped piston which provides the acoustic transformer. The smaller area of the stepped piston is in hydraulic communication with the power stage of the hydroacoustic amplifier.

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: A toy squirt gun which shoots a continuous high velocity stream of water. The squirt gun is configured as a structure facilitating partial filling with water leaving a void for compressed air. The squirt gun includes a nozzle for ejecting water at high velocity, a pressurization pump for compressing air into the gun to pressurize water contained therein, and a trigger actuated flow control valve for shooting the gun by controlling flow of pressurized water through the nozzle. A battery-powered oscillator circuit and a water flow powered sound generator produce futuristic space ray gun sound effects when the gun is shooting.

Abstract: A turkey call capable of realistically imitating both the gobbling and clucking sounds made by wild turkeys. A hollow body has an internal sound chamber covered at one end by a vibratile diaphragm. An air bulb is mounted on the opposite end of the body and can be squeezed to vary the gobbling sound produced by the diaphragm. A hammer and anvil mechanism in the sound chamber reproduces the clucking sounds made by wild turkeys and can be activated independently of the diaphragm.

Abstract: There is described a system for producing noise particularly for sonic testing of an article, such as a satellite, in a reverberation chamber. In one of its aspects the system comprises a low frequency high-level broad-band noise source; a tube means including a section formed as an acoustic horn connected at its small end to the low frequency source and at its large end to the chamber. A Hartmann-type air acoustic high level noise generator, or generators are located inside the tube at a predetermined position. In operation the generator is excited by the generated low frequency noise to provide an output of non-linearly modulated noise. Also described is a Hartmann-type noise generator which comprises a nozzle and an aligned acoustic tube spaced therefrom by an air gap. A reverberation cup is formed in the mouth of the tube facing the nozzle and a bridge member extends between the nozzle and tube and spans the air gap.

Abstract: A lid knob for a pressure cooker contains a whistle which informs the user when boiling has occurred. The lid knob is designed so that the whistle hole of the knob may be rotated into alignment with the steam hole of the lid of the pressure cooker during initial heating and then rotated out of alignment with the steam hole once boiling has occurred. The lid knob is simple in structure and is easy to disassemble for cleaning.

Abstract: A low-frequency sound generator for generating intense sound, which generator includes an open resonator tube. Pressurized gas is supplied to the resonator tube as pulses through a feeder system which includes a valve slide member which controls the pressure of the supplied gas. The gas pulses develop standing sound waves in the resonator tube which provides a varying gas pressure. Means in the resonator tube is operable in response to changes in the gas pressure to provide positive feedback of the sound pressure in the resonator tube to the feeder system at a resonant frequency of the resonator tube.

Abstract: A solid propellant gas generator operating with a calibrated tunable resonator produces a strong sonic field capable of affecting particle coagulation in an aerosol. The resonator is calibrated to produce a sonic field at the optimum frequency for a given aerosol and can be changed according to the aerosol involved. The resultant coagulation increases visibility and/or electromagnetic transmissibility within the sonic field. The device can be used to reduce obscuration during battlefield operations.

Abstract: A sonic cleaning device and method for removing accumulated fine particles from surfaces such as in heat exchangers using sonic energy vibrations. In the invention, a gas is passed through a tube having internally corrugated walls and having the tube outlet end attached to the inlet end of an expanding horn. The gas flows past the corrugations at high velocity and produces high intensity sonic vibrations within the tube, and the vibrations are amplified by passage through the horn. The horn outlet is directed at a surface to be cleaned and the accumulated particles are fluidized by the sonic energy and removed from the surface by the flowing gas and/or by gravity.

Abstract: A personal security device is disclosed which comprises a trigger actuated aerosol canister contained in a two-piece telescoping housing. The canister contains a pressurized offensive odor containing gas such as mercaptoethanol which, when ejected from the canister, emits a loud shrieking noise. Additionally, the gas may, as an additional additive, contain a suspension of fine solid or liquid particles of paint or stain so that the device when actuated, discourages a potential rapist or attacker with offensive odor and noise and also identifies him with a stain. In one preferred embodiment, the telescoping housing also includes a flash-type light which is actuated by the same triggers which actuate the canister. The telescoping housing has a key ring attached at one end and may also have a mechanical whistle at the other end.

Abstract: A device for generating warning signals consisting of sound waves at frequencies between 14 and 26 kHz, preferably intended to be mounted on a motor vehicle so that the device will be actuated by the wind. The device operates similar to a flue pipe and generates a subatmospheric pressure behind the sharp edge of the flue pipe. The subatmospheric pressure is created by a passage continuing to a resonant chamber, open at its rear end, the passage being larger in cross-section than the resonant chamber. The passage is formed in a body which has substantially the shape of a frustum of a cone and is formed with longitudinal through slots which extend from the passage. With this design, a subatmospheric pressure is generated which excites the pipe to vibrate even in a relatively slow wind.

Abstract: An impulse noise generator having means to store a volume of compressed gas and suddenly to release same to eject through a nozzle (14) comprising a body (4) having a hollow stepped piston (1) arranged to move forward by gas pressure admitted through an inlet (9) when a spring-loaded valve (15) is closed and including a pressure chamber (7) to which gas is admitted through the valve (15) when the piston (1) is at the forward and of its stroke, and gas release means to cause the piston (1) to move back rapidly to exhaust the gas from the chamber (7) to the nozzle (14).

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: Devices are disclosed for use in generating an acoustical warning signal in the event of an abnormal pressure in a pneumatic tire. A spring-loaded piston is mounted for reciprocation in a cylindrical chamber along an axis perpendicular to the radius of the tire for substantially eliminating the effects of centrifugal force on the operation of the device. The piston maintains the device closed until such time as the tire pressure drops below a predetermined limit at which point a small sampling of air is released into a whistle which produces a coded acoustical signal detected by an acoustical transducer mounted on the vehicle. The transducer converts the acoustical signal into an electrical signal which is processed and used to actuate an alarm for warning the driver. Cap seals are disclosed which protect the whistle from water dirt, etc.

Abstract: A group of nozzles are submerged in a tank of liquid to produce convergent-divergent vortices and cavitation in a liquid which in turn produce acoustic vibrations which assist in cleaning articles placed in the liquid, or in emulsifying a mixture of liquids. Each such nozzle comprises a body, with a central axis, an inlet at one end for supply of liquid under pressure thereto, and a plurality of discrete outlet ports at the other end transversely spaced from the central axis, the axes of the ports converging externally of the body towards the central axis whereby liquid supplied to the inlet under pressure emerges from the outlets in discrete jets directed to pass close to but not to intersect the central axis of the body.

Abstract: This relates to the provision of a vacuum indicator in a container wherein a product is vacuum packaged. Most specifically, an end unit for a conventional container is provided with a vent opening through which air rushes into the container when opened. There is secured to the underside of the end unit a whistle device in communication with the opening so that the inwardly rushing air actuates the whistle device and causes the whistle device to emit a whistling sound in accordance with the vacuum present within the container and thereby gives an audible indication of the freshness of the product.

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 plastic whistle including a main whistle body provided with a relatively narrow, elongated throat terminating at one end in a mouthpiece opening and at its other end, in an enlarged sound chamber. The throat and the chamber are open along a common side of the body. An orifice is located in the body and opens to the chamber and is disposed in the side of the body adjacent the common side mentioned above. A closure is provided for the common side and has a peripheral size and shape substantially the same as the periphery of the common side and mounts a tab extending partially into the throat so as to have opposite sides of the tab in abutment with opposed parts of the body at the mouthpiece opening to thereby support the body against an external clamping force applied by the teeth of a user of the whistle to prevent fracture of the throat.

Abstract: A low-frequency sound generator for generating intense sound, which generator includes an open resonator tube. Pressurized gas is supplied to the resonator tube as pulses through a feeder system which includes a valve slide member which controls the pressure of the supplied gas. The gas pulses develop standing sound waves in the resonator tube which provides a varying gas pressure. Means in the resonator tube is operable in response to changes in the gas pressure to provide positive feedback of the sound pressure in the resonator tube to the feeder system at a resonant frequency of the generator.

Abstract: A warning device for breathing apparatus which has a respiratory gas conduit through which respiratory gases are passed and which includes three interconnected chambers. Two of the chambers include diaphragm valves operable, responsive to pressure conditions therein, to actuate a piston in the third chamber which moves a signaling element into the gas conduit to signal a low pressure condition.

Abstract: An automatic signaling device responsive to small pressure variation, said pressure variations being created by a restriction of fluid flow within a flow system. The pressure variation causes fluid to flow through a resonant; loading chamber, activating a longitudinal wave resonator. The generation of longitudinal waves is apparent by the production of an audible signal. The device is mounted to the flow system using attaching means designed as part of or appurtenant to the device. In some embodiments the dimensions of the respective components of the device are adjustable.

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.

Abstract: A launcher for a target pigeon having a central coreless ring and a pair of propeller-type vanes projecting therefrom has a launch head whose tip can be rotated about a head axis for spinning a target pigeon held on the tip by a pair of retractable holding fingers. This head can be swiveled about a horizontal axis from an upwardly directed launch position into a downwardly directed load position in which it is aligned with a stack of such pigeons carried on a vertically displaceable platform, while in the launch position the entire head is also oscillated about a vertical axis. The launch tip has a radially displaceable beak which is urged centrifugally outwardly to deflect a target pigeon that is released from the launch tip by retraction of the holding fingers by a solenoid, and which also is urged radially inwardly by a spring so that when the tip is not rotating during loading the beak is out of the way.

Abstract: An underwater transducer which includes a fluid circuit having a valve disposed in a plenum chamber having a small aperture open to the ambient water pressure. Fluid flow into and out of the chamber by way of the valve is governed by controlling the valve opening and closing in accordance with movement of an electrodynamic driver which receives an input signal to be transmitted.

Abstract: A hanger for womens purses, handbags, shopping bags, or other articles, is provided which consists of a pair of elongated hinged support arms with a rubber semi-cylindrical bail mounted at the distal end of one of the arms, and with some means at the distal end of the other arm from which a purse, or other article may be suspended. The hanger is constructed to extend over the edge of a flat or curved surface, such as a table, chair arm, or the like, with the rubber bail engaging the surface in a non-slip relationship and with the article being suspended by the hanger over the edge of the table top, arm, or the like. The hanger is foldable to a compact configuration when not in use, and when so folded, it is constructed so that it may be used as a police whistle to summon help in cases of emergency.

Abstract: A high pressure compressed air tank has an inlet and an inlet valve which is opened when a fitting of a service station air hose is pressed against the inlet. High pressure compressed air is then forced from the service station air hose into the tank. The inlet valve prevents compressed air from escaping from the tank. An outlet fitting connected to the tank has an outlet valve therein. The outlet fitting is pressed against the tire valve housing of a bicycle, causing the tire valve to open. High pressure compressed air from the tank is then forced into the bicycle tire, thereby inflating it. The tank is attached to a frame member of the bicycle by means of a quick-release bracket. An air horn operable by means of a button valve and a pressure gauge are attached to the high pressure air tank.

Abstract: A sound-producing, ornamental article formed from ceramic material having a shell-like housing defining a chamber, wherein a sound-producing element is fixedly concealed within the chamber, the housing including a first hole to allow air pressure to enter the housing chamber and a second hole to allow the air pressure to escape therefrom, whereby the flow of air through the chamber activates the sound-producing element therein; and wherein the method of making the article is disclosed utilizing a mold having a particular configuration in which the article is shaped, fired and glazed, wherein an insert section is formed having a sound-producing element attached thereto, after which the insert is secured to the shell housing, sealing the sound-producing element within the defined chamber.

Abstract: A horn flare has first and second plastics mouldings which are welded or adhesively secured together. The first moulding has an end wall having a central opening aligned with the space inside a first annular wall extending integrally from the end wall. A further integral annular wall surrounds the first annular wall and a collar having a stepped annular recess therein surrounds an additional wall. The second moulding has an end wall which overlies the first annular wall and the further integral annular wall. Extending integrally from the end wall of the second moulding are said additional wall and a further wall. The additional wall lies between the first annular wall and the further integral annular wall while the further wall of the second moulding lies outside said further integral annular wall of the first moulding. The second moulding further includes an open-ended flared sleeve which is integrally connected with the further wall of the second moulding by spaced lugs.

Abstract: This invention has to do with an alarm used by persons engaged in high-risk activities. A can of propellant gas is used in combination with a means to generate a noise signal at approximately 120 decibels. A rotatable shaft is used to connect the pressurized container and the noise generating means during operation of the device. A flutter valve can be used in the noise generating means to produce an intermittent signal.

Abstract: A knob for a cooking vessel is a whistle which gives an audible signal that cooking temperature has been reached, and has a valve slide for shutting off the whistle. Supporting inside and outside knob parts incorporate halves of a resonance chamber, which makes the knob extremely simple to mold, assemble, clean, and disassemble. The valve slide rests in guides which make it impossible to assemble incorrectly, and overlaid by a knob cover.

Abstract: A sound producing device which can produce a loud sound is disclosed. The device includes a moveable frame and a flexible and hermetically sealed cylindrical bag enclosed in such moveable frame as well as a bellows extensible and compressible in the axial direction of the frame. The bellows is intermittently driven so as to compress air contained therein and to release it. The compressed air is abruptly released to break a sheet of paper and produce the loud sound.

Abstract: An ultrasonic wave horn adaptable to any desired radiation pattern varying in length-to-breadth ratio of intended detecting area. The horn comprises at least a horn body having gradually expanding caliber from a constricted throat to an expanded opening which is of a flat shape with an unequal length-to-breadth ratio, and an ultrasonic wave generating source of which wave emitting side is disposed adjacent the constricted throat of the horn body, wherein the constricted throat of the horn body is also of a flat shape having an unequal length-to-breadth ratio and the respective major axes of the flat-shaped constricted throat and expanded opening of the horn body are in a relation of intersecting each other at right angles.

Abstract: An improved apparatus for removing lubricating compositions from crankcase oil pans of internal combustion engines through the oil dipstick well of the engine involves signalling means, acting in response to the amount of vapor flowing to the vacuum chamber of the apparatus to signal, preferably audibly signal, the completion of removal of lubricating composition from the crankcase oil pan.An improved method for removing lubricating composition from crankcase oil pans is also disclosed.

Abstract: A smoke and heat detector alarm including a compressed gas, self contained, stored energy source. A T-fitting connects to the compressed gas tank through a fusible element activated valve and feeds separate conduit systems leading to individual sounding devices. One of the conduit systems receives compressed gas directly from the valve to automatically permit transfer of the compressed gas to a first sounding device upon the presence of elevated temperatures sufficient to fuse the fusible element. The valve includes a lever arm that is functioned by operation of the fusible element to trigger an additional electrical alarm circuit. A solenoid operated switch is interposed in the other conduit system to normally prevent the flow of gas. The solenoid is responsive to a smoke detector and is wired to open the solenoid valve upon sensing the presence of a predetermined concentration of smoke to permit transfer of the compressed gas to a second sounding device.

Abstract: A gas-actuated sound signal generator is provided to produce a simple, reliable sound signal of predetermined frequency, or combination of frequencies. The signal generator is intended for use primarily with a tire pressure sensing system on a vehicle as a means for transmitting the occurrence of a low tire pressure condition from a wheel to a microphone mounted in fixed position to the vehicle and connected via processing circuitry to an alarm near the operator. The device is operated upon the release of a small amount of air from the tire if the tire pressure drops, for example, below a preset limit. The air released from the tire flows into the signal generator and is converted into a sound signal for detection by the microphone. The signal generator is comprised of a cavity block, a shim and a cover. The block contains an entrance feed through which air is admitted as from the tire and a cavity spaced from the entrance feed.

Abstract: A transducer to monitor a parameter and produce an acoustic signal from which the monitored parameter can be recovered. The transducer comprises a modified Galton whistle which emits a narrow band acoustic signal having a frequency dependent upon the parameter being monitored, such as the temperature of the cooling media of a nuclear reactor. Multiple locations within a reactor are monitored simultaneously by a remote acoustic receiver by providing a plurality of transducers each designed so that the acoustic signal it emits has a frequency distinct from the frequencies of signals emitted by the other transducers, whereby each signal can be unambiguously related to a particular transducer.