Abstract: An improved depth sounder combines a multi-beam ultrasonic transducer with a multi-range selector switch with provisions for automatically selecting a particular beam pattern for a particular range setting. The relationship between beam patterns and depth ranges is uniquely chosen to provide equal areas of insonification at each full scale range setting. The inventive system also provides an additional scale on the multi-scale range dial which shows the diameter of the insonified region in the vicinity of the reflecting target in addition to the target depth.

Abstract: A plurality of ultrasonic flow meter measurement probes are located at spaced intervals along the length of a pipeline carrying a fluid and each probe measures the rate of flow of the fluid at each location along the line. If a leak develops at any point along the pipeline the nearest probe located upstream from the leak will read higher than the measurement being made by the nearest downstream flow meter probe. The difference in readings between the adjacent probes will be an indication of the magnitude of the leak and when the difference exceeds a preset threshold limit an alarm will sound and a coded command signal will be transmitted from the data monitoring center to initiate the immediate closing of the nearest upstream and downstream shut-off valves in the vicinity of the leak. This procedure will immediately isolate the damaged section of the pipe and prevent uncontrolled leakage of the fluid into the environment.

Abstract: A microphone is described for operating in dirty environments where a layer of dirt or mud may accumulate over the vibratile surface of microphone. The microphone is designed with its vibratile diaphragm having a mass greater than 0.4 gm/sq cm of diaphragm area so that an added layer of dirt over its surface will not cause any significant change in the sensitivity of the microphone over its prescribed frequency range of operation.

Abstract: A molded rubber tubular member includes a grommet-like flange at its open end for permitting the structure to be attached to a panel. A recessed nest portion is provided at the opposite end of the tubular member into which is inserted a transducer whose diaphragm serves as a closure at the end of the tubular member. The assembly serves as a flexible shock mount for the transducer and also as an acoustic amplifier which increases the acoustic sensitivity of the transducer by 10 to 20 dB in a selective frequency band within the audible range.

Abstract: An ultrasonic transducer employs a ceramic disc which, when excited by a d-c pulse, vibrates in its planar resonant frequency mode. The sensitivity is selectively increased for the second positive half cycle of the transient oscillation of the disc and a method is described for using the selectively improved transient response to greatly increase the precision of measurement of the time interval for a transient pulse of ultrasonic energy to travel the distance between an ultrasonic transmitter and an ultrasonic receiver.

Abstract: A comprehensive analysis of the effect of air turbulence on the acoustic performance of an ultrasonic intruder alarm system indicates that air turbulence does not cause Doppler frequency shifts in the received signal in the frequency region 2 - 100 Hz, as has been universally assumed in prior art systems but that air turbulence can only produce amplitude modulations in the received signal over this frequency region. It is also disclosed that changes in air velocity, or accelerations of the air flow, cause only very low Doppler frequency shifts in the signal, below 2 Hz for a 20 kHz carrier, and only moving targets can produce higher Doppler frequency shifts. A processing system is disclosed which is immune to false alarms in the presence of air turbulence without sacrificing threshold sensitivity and without introducing long time delays in the signal processing circuit as has been necessary in prior art systems.

Abstract: Electroacoustic transducers are nested to provide a centrally vibrating portion and a peripherally vibrating portion. The phases of the two transducers may be adjusted with respect to each other in order to provide a variety of beam patterns.

Abstract: The invention describes a low cost transducer construction utilizing a vibratile diaphragm to form a closure for a cylindrical tubular housing. The sound radiating surface of the diaphragm is of a concave shape to achieve an increased diaphragm thickness at its periphery. The concave diaphragm design permits the precise adjustment of the resonant frequency of large quantities of mass produced transducers by machining the surface of the thick rim portion of the diaphragm. Greater precision in the adjustment of the resonant frequency is achieved with this design because the frequency change is less critically dependent on the amount of material removed than is the case with a conventional flat diaphragm surface as used in prior art designs.

Abstract: An electroacoustic transducer uses a bilaminar vibratile element having at least two plate members which are bonded together in face-to-face relationship, at least one of the plates being made from a piezoelectric material. The bilaminar plate is supported within a frame-like structure by resilient pads which attach the bilaminar plate at its nodal points to the surface of the supporting frame.

Abstract: This invention provides an expendable velocimeter probe. High frequency transmitting and receiving transducers are mounted opposite to one another in axial alignment on the probe body and on a frame in front of the body. The mounting includes means for accurately adjusting the distance between the transducers in order to provide low cost, but highly reliable, means for calibrating the velocimeter during large scale manufacture of the instruments.