Acoustic delay lines

Acoustic delay lines

Resonance matching in thin transition layers Aranovich, V. B., Prudov, I. A. Vol 17 No 4 (April-June 1972) pp 438-443 A technique of matching acoustic...

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Resonance matching in thin transition layers Aranovich, V. B., Prudov, I. A. Vol 17 No 4 (April-June 1972) pp 438-443 A technique of matching acoustic impedances at an interface, based on the utilization of resonance in a system comprising two transition layers of small thickness, is investigated. The matching efficiency is estimated for the cases of semi-infinite media and half-wave receiving-transmitting transducers at near-resonance frequencies. The theoretical results are obtained by the method of equivalent circuits in the one dimensional approximation, the matching resonator being represented as a system having lumped mass and compliance. Experimental data has been obtained for half-wave piezoelectric ceramic transducers in water and air, at atmospheric pressure.

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EVALUATION

Ultrasonic examination of welds: comparison of ASME and AWS procedures McGaughey, W. C. Vol 30 No 2 (February 1972) pp 44-48 Correlation of pulse-echo measurements with tensile strength of diffusion bonded joints Regalbuto, J. A. Vol30 No 3 (March 1972) pp 66-72 A simple mathematical model is constructed to calculate tensile strength of diffusion bonded joints from pulse-echo and attenuation measurements. Experimental data is presented which agrees well with the theoretical results. Attenuation, contamination and signal-to-noise ratio effects are discussed.

JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Multipath summability in ray-theory intensity calculations in the real ocean Neubert, J. A. Vol51 No 1 Part 2 (January 1972) pp 310-322 The conventions1 ray-theory intensity relation is extended to permit consideration of partial coherence in multipath problems by looking at the stochastic nature of microfluctuations. The partial coherence factor is shown to be a function of the curvilinear range, the frequency and the oceanographic conditions. A practical estimate for the standard deviation el of the intensity about its expected value is found; olis shown to depend on the partial coherence factor and to saturate as this factor approaches zero. Measured discrimination of boundary-layer pressure fluctuations by round, square and rectangular transducers Recine, E. C. Vol51 No 1 Part 2 (January 1972) pp 369-377 Pressure fluctuations obtained in a turbulent air pipe flow facility were measured using 19 flush-mounted transducers that varied in size and shape. Good agreement

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was found between experimental data and theoretical predictions. In the mid-frequency range, transducers that had their longest dimension parallel to the flow produced the greatest discrimination against pressure fluctuations. At high frequencies, the response became a function of size and independent of shape, as predicted. Performance degradation of deep-ocean transducers using onion-skin paper for acoustic decoupling Haan, D. E. Vol51 No 1 Part 2 (January 1972) pp 290-294 The acoustic decoupling behaviour of onion-skin paper is examined with emphasis on sonar transducer applications. Non-linear changes in the sound velocity of onion-skin paper with pressure are used to predict the degradation of both frequency and directional response. These results are obtained by computer analysis of a longitudinal-vibrator equivalent circuit. The results are in reasonable agreement with the measured characteristics of a specific transducer configuration. Acoustically induced gas bubble growth Skinner, L. A. Vol51 No 1 Part 2 (January 1972) pp 378-382 The diffusion problem governing gas bubble growth in oscillatory pressure fields, including growth through reasonance size, is solved by superposition of two sub-problems. Approximate solution of the growth-rate equation is shown to be independent of resonance behaviour details.

PATENTS Hightemperature ultrasonic device Bell Telephone Labs Inc US patent 3599123 (1971) filed 24 September 1969 Certain gold alloys, containing from about 12 to about 67% indium, when used in ultrasonic bonds, have been found to permit the operation of fused silica de$ty lines at temperatures from 200-550 C. This results in at least a 50% increase in frequency of acoustic waves transmitted for a given loss level as compared with room temperature operation. Electron-phonon resonator Wojskow Akademia Techniczna in Jaroslowa Dabrowskiege UK patent 1247622 (1971) filed 3 January 1969 Electra-acoustic transducer plastic diaphragm AKG Akustische & kino-Gerate GmbH UK patent 1246253 (1971) tiled 16 January 1970 Acousto-optic devices using lead molybdate and related compounds Bell Telephone Labs Inc US patent 3617931 (1971) fded 5 May 1969 Acousto-optic devices dependent for their operation on lead molybdate and related compounds show efficiencies comparable to that of devices made from alpha-iodic acid and superior to that of devices constructed of earlier materials such as lithium niobate.

Acoustic direction-finding Fried Krupp GmbH UK patent 1262900 (1972) fled 31 July 1968 The device calculates the angle of incidence of a sound wave-front, of predetermined frequency, relative to two spaced transducer groups, from the phase shift needed to compensate for the pl.ase angle between the output voltages of the two groups. Acoustic holography Holotron Group UK patent 1263093 (1972) fled 6 March 1968 Viewing optics are focused on the detecting surface itself to reduce the dependence of image resolution on the size of light source, and on irregularities in the ultrasonic detecting surface. Acoustic lenses Holotron Corp UK patent 1263749 (1971) filed 20 May 1968 An acoustic lens consists of two liquids having differing acoustic indices of refraction relative to air, and a stretched and curved synthetic polymeric film separating the liquids. Ultrasonic inspection devices Branson Instrument Inc UK patent 1264424 (1972) filed 23 May 1968 A pulse-echo device selects and indicates the shortest pulse transit-time in a series of measurements to prevent spurious readings due to increasing pulse propagation times when the temperature of a coupling medium between the transducer probe and a hot test object rises. Ultrasonic probes: ultrasonic inspection devices Shurtronics Corp UK patent 1267208 (1972) filed 26 September 1968 An ultrasonic probe has a generally cylindrical transducer element loosely retained by guides to permit limited radial axial movement of the element. Piezoelectric devices Minnesota Mining & MFG Co UK patent 1268141 (1972) filed 27 January 1969 Delay lines make use of transducer or delay elements cut from a single crystal of wurzite zinc oxide. The element has maior faces at right-angles to an axis which makes an angle of between 13 and 53 degrees with the crystallographic c-axis. Acoustic detection of gas bubbles in blood National Research Development Corp UK patent 1268640 (1972) filed 31 May 1968 Acoustic delay lines Motorola Inc UK patent 1268853 (1972) filed 26 August 1969 A delay line comprises a piezoelectric crystal shaped as a tube. The mean diameter of the

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tube is less than one-half wavelength highest frequency to be propagated.

of the

Acoustic detection finders: monostable circuits Freid Krupp GmbH UK patent 1269566 (1972) filed 12 July 1968 An arrangement for determining the direction of incidence of sound waves within a relatively broad angular region comprises: an array of transducers whose outputs are combined to form a plurality of relatively narrow beam patterns covering different adjacent sectors of the region; a device for periodically scanning received signals of all the sectors; a cathode ray oscilloscope; and a device for determining the incidence direction within any sector from the phase or travel-time difference between received signals in two beam patterns associated with that sector. Ultrasonic transducers: ultrasonic lenses F. Hoffmann La Roche & Co AG UK patent 1269869 (1972) filed 5 June 1969 An ultrasonic transducer assembly which can be used for investigating human arterial wall motion using the doppler effect, has an elongate preset curved printed circuit board supporting ultrasonic transducer units along its longitudinal axis. I

Transmission of ultrasound through the larynx as a means of determining vocalfold activity Hamlet, S. L., Reid, .I. M. Bio-Medical Engineering Vol BME 19 No 7 (January 1972) pp 34-37 A method of determining vocal-fold closure using continuous-wave ultrasound through the larynx is described. A frequency of 3.2 MHz and an applied acoustic power of less than 1 mV cm-’ is used. Phvsiological interpretation of received signals is discussed in terms of glottal closure, vocal-fold thickness, vocal-fold vibratory pattern, and thyroid cartilage ossification. Suggestions are offered for choice and arrangement of transducers for this application. Sonar (sound navigation and ranging) 1. Introduction Reith, B. C. Ingenieur Vol 83 No 5 1 (December 19 7 1) pp 180-183 (In Dutch) Sonar (sound navigation and ranging) II. Transducers foiactive sonar - -Rijnja, H. A. J. Ingenieur Vo183 No 51 (December 1971) pp 183-188 (In Dutch)

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Ultrasonic flaw detection Allegheny Ludlum Industries Inc UK patent 1269845 (1972) filed 22 November 1968 A flaw detector in which pulsed ultrasound echoes from boundaries transverse to the scanning beam are blanked out, utilizes an electron recording beam in a storage oscilloscope.

Sonar devices: sonar transducers Sparton Corp UK patent 1269751 (1972) tiled 14 April 1969 An acoustically sensitive transducer comprises a piezoelectric cylinder carrying two sets of electrodes, one set provides omnidirectional voltages and the other set orthogonal directional bearing related voltages.

Ultrasonic inspection devices International Research & Development Co Ltd UK patent 1270387 (1972) filed 7 June 1968

Acoustic detection devices National Research Development Corp UK patent 1270245 (1972) filed 11 June 1968 An apparatus for counting fish passing through a water channel beams ultrasound to illuminate the channel in two crosssectional planes, and counts only if echoes are detected from both planes.

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MISCELLANEOUS

Improved depthfinder display presentation bv use of MS1 Brede, R. Electroteknisk Tidsskrift Vol 84 No 20 (November 1971) pp 19-20 (In Norwegian) Equipment for the fine welding of electrical and electronic components Rub, F. Electrotechnik Vol 53 No 19 (October 1971) pp 20-24 (In German) An ultrasonic-microwelding method welding small synthetic components described. Diagnostic sonar Sabbagha, R. E. Instrumentation Technology (December 1971) pp 40-43

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Ultrasonics for ultra-clean surfaces Industrial Finishing and Surface Coatings Vo123 No 282 (December 1971) pp 26-28 Ultrasonic pressure gauge for static pressure Hoechli, U. T., Mueller, F., Nievergelt, H. IBM Technical Disclosure Bulletin Vol 14 No 5 (October 1971) pp 1629-1630 An ultrasonic pressure gauge will record static pressure between 1 and lo4 k? cm-’ with an accuracy of 0.17cfrom a few degrees Kelvin up to about 1000 K. Microstructure detection with the aid of ultrasound Wegel, G. Feinger’ate-Technik Vol 20 No 12 (December 1971) pp 563-566 (In German) A technique for determining the microstructure in cast iron from measurement of the speed of ultrasound in the material is described. A clear distinction can be made

between spheroidal and lame&r graphite structure. Advantages of the method include the facility for serial testing with negligible time delays. Automation of ultrasonic and eddy current methods Gunnell, R. A. Testing, Instruments & Controls Vo18 No 11 (1971) pp 13-17 Bat’s sonar simulator Escudie, B., Dziedzic, A., Barreault, G. Revue d’Acoustique Vol 5 No 18 (1972) pp 26-30 The study of bat’s sonar using spectral analysis and signal processing requires a generator emitting signals similar to those emitted by bats. A wide-band frequency modulated oscillator provides many of the emitted waveforms used by vespertillions and other bats. The experiments prove that the signals are similar to those recorded in nature. Proposals for the measurement of volume flow by ultrasonic methods Fitzhugh, H. A., Twidle, G. G., Richardson, J. R. National Physical Laboratory Report NPL-MS No 3-71 (October 1971) 4 pp A method of measuring the rate of volume flow in an air duct is proposed which depends on the downstream convection of an ultrasonic beam projected across the flow. The device requires no calibration, has a high frequency response and does not obstruct the flow. A method for digital measurement of attenuation Gavenda, J. D. Review of Scientific Instruments Vol 42 No 12 (December 1971) pp 1881-1882 Surface-wave amplifier with improved geometry Adler, R. Electronics Letters Vol 8 No 3 (February 1972) pp 65-66 A surface-wave amplifier is proposed in which an array of transverse conducting bars couples a narrow semi-conductor to a broad region of piezoelectric substrate. Ultrasonic determination of liver and spleen volumes Kardel, T., Holm, H. H., Norby Rasmussen, S., Mortensen, T. Scandinavian Clinical Laboratory Investigations Vol 20 No 2 (1971) pp 123-128 Nonlinear materials for acoustic surfacewave convolver Lim, T. C., Kraut, E. A., Thompson, R. B. Applied Physics Letters Vol 20 No 3 (February 197 2) pp 1277 129 Acoustic surface-wave convolution by nonlinear mixing has been observed in cubic, hexagonal and trigonal crystals. The magnitudes of the phenomenological nonlinear surface-wave coupling constants are tabulated and compared with the linear electromechanical coupling factor 2 @Y/v). It has been found that the basal plane of pzt-8 has a larger nonlinear coupling constant that that of the commonly used y-cut, z-propogating LiNbOs.

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