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Nov 1978

Volume 64, Issue S1, pp. S1-S183

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back to top Session F. Engineering Acoustics I: Calibration and Transducers. (Part Précis‐Poster Session)
Invited Paper
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Review of acoustic research for telecommunication in Japan (A)

S. Yoshikawa

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S6-S6 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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Various acoustic researches for telecommunication are performed in the Electrical Communication Laboratory, NTT. Among these, researches on acoustic standard apparatus, acoustic measurements, electroacoustic transducers, vibrating systems, acoustic materials, room acoustics, and telephone networks are included. A new ½‐in. standard condenser microphone has been developed for precise sound measurement and sensitivity calibration of telephone sets. This new standard microphone, made of titanium alloy, has high sensitivity (−54 dB re 1 V/mgr;bar, high reliability, and wide frequency range (∼35 kHz). A precise calibration method using standard couplers, as well as a simplified calibration method using active coupler, are established. Research of room acoustics is important for telephone systems in the future, because the acoustic transmission characteristics of rooms may take an important place in the system. Transmission characteristics and the spatial correlation coefficients of various rooms are investigated. The results of these researches are especially useful in telephone loudspeaker design. Based on the results of various researches, several types of new telephone sets and systems are now being developed.
Contributed Papers
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A nearfield, underwater measurement system (A)

R. D. Marciniak

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S7-S7 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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A nearfield acoustic measurement technique for accurately computing the farfield radiation characteristics of underwater sound transducers was developed, implemented, and evaluated. The analysis was based on evaluation of a form of the Helmholtz integral which utilizes a Green's function that vanished over the surface of integration, thereby requiring only knowledge of the nearfield acoustic pressure for computing the farfield radiation. An experimental program was conducted to provide corroboration of the technique. Details of the automated, digital, nearfield measurement instrumentation are presented. Comparisons between conventionally measured farfield properties of four different types of test transducers and the results obtained by using the nearfield technique are given. The results showed that excellent agreement was achieved for the radiation properties compared. For the directional responses, the nearfield technique matched the conventionally measured results over the minor lobe structure as well as over the major lobe structure of the pattern. The results also showed that absolute sound pressure levels and directivity indices could be ascertained accurately and with relative ease. [Work supported by NAVSEA 034.]
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AN/FQM‐12(V) sonar test set. I: an automated acoustical measurement system (A)

James J. Truchard and L. Wayne Ashby

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S7-S7 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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In this paper we describe an automated acoustical measurement system. The system includes three minicomputers and a number of microprocessors for control and data handling. Multiprocessors are used to simultaneously handle all the processing functions. Interaction with the operator and overall timing and control for the system is handled by the central processor. Two peripheral processors are used for high speed data computation and processing. Several microprocessors provide intelligent control functions for the system. A sophisticated software operating system is used to integrate the hardware into a useable and flexible system. The user is offered a wide variety of options for display and output of measurement data. The software is designed to make implementation of any of these options as easy and convenient as possible for the user. [Work sponsored by NAVSEA 06H4D.]
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AN/FQM‐12(V) sonar test set. II: signal generation and processing for an automated acoustical measurement system (A)

L. Wayne Ashby and James J. Truchard

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S7-S7 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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This paper describes the signal generation and processing capabilities of an automated acoustical measurement system. The basic design goals for the signal generation and timing capabilities of the system were to provide the maximum flexibility for signal generation and reception while using sampling techniques that allow fast signal processing algorithms to be used in the data processing and analysis. The waveform and timing generator was designed to generate the conventional sinusoidal pulse waveforms used in many acoustical measurements along with special purpose arbitrary waveforms which can either be used directly as the transmit signal or to modulate the sinusoidal transmit pulses. The system timing technique allows a user to make simple single pulse measurements or to make multiple pulse measurements where data samples are summed either coherently or incoherently to maximize the signal‐to‐noise ratio. [Work sponsored by NAVSEA 06H4D.]
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Accuracies on pressure calibration of ½‐in. condenser microphones (A)

T. Takahashi and H. Miura

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S7-S7 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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The accuracy of coupler calibration of ½‐in. condenser microphones, such as MR112 and B&K4134, was tested. The coupler used was a new 1‐cm3 coupler [A. Suzuki and S. Yoshikawa, J. Acoust. Soc. Jpn. 28, 475–484 (1972)], as well as the 20‐cm3 a coupler attached with B&K adaptor DB0225. Calibrations were carried out at the frequencies 50–12 500 Hz by the 20‐cm3 a coupler and 50–30 000 Hz by the 1‐cm3 coupler. Pressure response levels calibrated by the reciprocity technique using both couplers showed very good agreement. If the theoretically calculated correction values [H. Miura and E. Matsui, J. Acoust. Soc. Jpn. 30, 639–646 (1974)] are applied to measured values, the differences of the response levels calibrated by both couplers are within 0.05 dB in the frequency range 100–10 000 Hz. It can be said that the method of precise coupler calibration of ½‐in. condenser microphones has been achieved.
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Study on detection of steel bar in concrete with electromagnetic impact driving method (A)

S. Motooka and M. Okujima

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S7-S7 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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The authors devised a new detection method of measuring the location of a steel bar within concrete on the concrete surface through an electromagnetic impact driving method. Through this method, a steel bar within concrete is driven directly into vibration with occurred impulsive magnetic flux at a flat spiral coil set on the concrete surface. That is, a steel bar within concrete is regarded as a sound source. The location of a steel bar within concrete is determined by the measured propagation time within concrete of radiated sound from a steel bar and the sound velocity in the concrete block. The experiment on the detection of a steel bar at a depth of less than 25 cm under the concrete surface was performed. From these experimental results, this method is expected to be useful for the detection of a steel bar within concrete. Furthermore, the propagation characteristics of sound in the concrete block and driving conditions for a steel bar within concrete were also examined.
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A method to determine changes in sound levels by analytical and experimental simulation techniques (A)

A. V. Mehta

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S7-S7 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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A method is described to determine changes in the sound levels of an acoustical system due to changes in the variables internal to the system as well as external to the system. The method involves analytical and experimental simulation techniques to determine various partial factors which are then superimposed to estimate the resultant sound levels as a function of a desired variable. A practical approach is suggested for the applications of the method by approximations to save time, effort, materials, etc.
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A method for measuring electrostrictive properties of ultrasonic transducer material under high hydrostatic pressure (A)

S. Takahashi and K. Sato

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S8-S8 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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The motional impedance or admittance method cannot be applied to a test transducer contained in a small non‐sound‐absorbing pressure tank, because admittance or impedance loop does not make a circle due to sound reflection at the tank wall. The method we used is to excite a bar‐shaped test transducer in a pressure tank into longitudinal vibration by the use of a mechanical driving system, and to observe short‐circuit current or open‐circuit voltage of the test transducer. A transducer material for high power use was taken as a sample. Electrostrictive stress constants e31, h31 and dielectric constant ϵ31 were measured at hydrostatic pressures from 1 to 600 atm. Vibrational velocity dependence of e31 and h31 was also measured, varying driving velocity level at the test transducer end as high as 80 cm/s. The results are that e31 and h31 become slightly large as hydrostatic pressure increases but show no appreciable velocity level dependence.
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On the added mass matrix and acoustic pressure of multiple circular cylinders vibrating in a compressible fluid (A)

W. H. Lin and S. S. Chen

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S8-S8 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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The linear two‐dimensional acoustic wave equation is solved for multiple circular cylinders vibrating harmonically in an infinite compressible fluid. The solution is expressed in terms of series of cylindrical wave functions. To satisfy the interface boundary condition of a particular cylinder, all cylindrical wave functions are transformed to the coordinates associated with that cylinder. The resulting equations are a system of algebraic equations for the undetermined coefficients, which are solved numerically by digital computer. The velocity potential, pressure, and force acting in each cylinder are then obtained in terms of these coefficients. The added mass matrix is found symmetrical and dependent on the wave number, the cylinder radius, and the distance and orientation between cylinders. On the surface of each cylinder the pressure field also depends on those parameters as well as the orientation of point on that surface. Numerical values of added mass matrix and pressure distribution are obtained for many cases.
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The radiation impedance and radiation directivity of conical nozzles (A)

Harry E. Plumblee, Jr., M. Salikuddin, P. D. Dean, and K. K. Ahuja

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S8-S8 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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An impulse technique for determining radiation impedance and radiation directivity of jet nozzles is discussed. Results for an unflanged pipe are compared with the theoretical results of Levine and Schwinger [Phys. Rev. 73, 383–406 (1948)] for the purpose of justifying the technique. Data are then presented to show the effect of nozzle size and jet velocity on both nozzle transmission and radiation impedance and radiation directivity. Conical nozzles are used and the results for 2‐ and 1‐in. diameter nozzles are compared with those for the 4‐in. diameter straight unflanged pipe. Effects of jet exit velocity up to 1300 ft/s are displayed and discussed in the light of available theory. Spectral energy is determined for the incident and reflected wave signals in the pipe, and the transmitted wave in the farfield and energy conservation for the system is discussed. Finally, it is shown that the test method can be usefully applied at frequencies above the plane mode regime.
Poster Papers
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An automated coupler calibration system for laboratory standard condenser microphones (A)

T. Fujimori., T. Takahashi, S. Sato, and H. Miura

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S8-S8 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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An automated coupler calibration system for laboratory standard condenser microphones is manufactured for trial use. Active couplers whose cylindrical wall vibrates as a sound source are designed. These couplers are used so as to get pressure response levels of microphones in a short time and to reduce manual transaction. A microcomputer controls the system, processes measured values, examines them, and stores final results in a diskette. In addition, many digital techniques are adopted for noise reduction and for the convenience of calibration. Accuracies were tested for 1‐in. condenser microphones, such as MR103, using a coupler which has the same dimensions as the 20‐cm3 a coupler. Pressure response levels calibrated by the system agree well with those calibrated by the ordinary precise coupler calibration system within 0.2 dB at the frequencies 100–10 000 Hz.
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Realization of the transfer function of a loudspeaker by optimization method (A)

M. Yoneyama and J. Fujimoto

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S8-S8 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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The purpose of this research is the synthesis of the transfer function of a loudspeaker. The characterization of a loudspeaker as a linear system is represented by its impulse response. It is assumed that the waveform of the impulse response is approximated by the summation of many different decaying cosine waves having four parameters (amplitudes, decay factors, frequencies, and phases). To minimize the root‐mean‐square error between the measured impulse response and the composed one, all parameters should be determined by computer optimization method. For the computer optimization method, Hooke‐Jeeves' method (one of the direct search methods) was adopted. By operating with a Laplace transform on the composed impulse response, it is possible to obtain the transfer function as the summation of function of the second‐order. From the computed transfer function, pole‐zero configuration can be obtained. As a result of our experiments using a loudspeaker with edge clamped circular radiating plate, the configuration of 28 poles and 27 zeroes was determined.
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A proposal of a method to evaluate the electrostrictive material for ultrasonic transducers (A)

H. Banno and H. Sobue

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S8-S9 (1978); (2 pages)

Online Publication Date: 11 Aug 2005

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The electrostrictive ultrasonic transducers operate under both high mechanical amplitude of vibration and high electric field. So far it has been measured either electrically or mechanically to evaluate electrostrictive materials for the ultrasonic transducers. Both methods cannot possibly justify their full legitimacy, because each does not always represent the actual use of material. We propose applying a new evaluating method of electrostrictive materials for ultrasonic transducers. This introduces the figure of merit A2/r1G1, involving both electrical and mechanical terms [where A is the force factor, r1 the mechanical internal resistance, and G1 the blocked conductance]. The figure of merit depending on the vibration velocity is described for several electrostrictive materials.
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Experiments in acoustic imaging with an isochronal convergence imaging method (A)

K. Katakura, M. Kuroda, and Y. Takabayashi

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S9-S9 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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The method used in this study employs a multielement transducer. Each transducer element transmits successive cylindrical sound waves at a predetermined interval. During the transmission intervals, all elements receive echos from targets. A digital processor then distributes the amplitude data of these echos on elliptic addresses located in a digital memory system. The relation between sound propagation time and element location determines these elliptic addresses. The resolution power is estimated to be the same as that of a cylindrical transducer measured at the focal point for pulse echo mode operation. The results of numerical analyses agree well with the estimated values and indicate a high resolution power within the entire imaging plane. A prototype system utilizing this method, containing a 32‐element transducer and a minicomputer, is used to complete some experimental imaging of stationary targets, and the obtained images are discussed.
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An electrostatic transducer for absolute measurement of ultrasonic wave displacement amplitude in liquids (A)

John H. Cantrell, Jr. and Joseph S. Heyman

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S9-S9 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing which is sealed for immersion in a liquid environment. The membrane functions as the ground plate of a parallel‐plate capacitor, the other plate being a dc biased electrode recessed approximately 10 μm from the electrically grounded membrane. An ultrasonic wave incident on the membrane vibrates the membrane‐electrode gap spacing and generates an electrical signal proportional to the wave amplitude. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 12 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. A theoretical analysis shows that the coupling between the membrane and the contacting liquid is responsible for this frequency rolloff and that the absolute measurement of the ultrasonic wave displacement amplitude is possible with the ESAT when the correction for the rolloff is applied.
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Transformerless designs of broadband ultrasonic transducer equalizers (A)

J. Andersen and L. Augustine

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S9-S9 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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A promising new equalizer design for broadbanding ultrasonic transducers was recently presented [J. Andersen and L. Wilkens, Ultrasonics Symp. (1977)]. The design matches a resistive source to a piezoelectric transducer with power gain displaying a maximally flat (Butterworth) characteristic. Unfortunately, two undesirable restrictions are part of the existing algorithm: (i) The center frequency of the design is fixed, limiting the usage of the technique to certain passbands, and (ii) the design either requires a sacrifice in gain or is unrealizable without the use of an ideal transformer for certain source resistance and transducer combinations. The purpose of this paper is to present a generalization of the algorithm which broadens the applicability of the technique. The main result is an algorithm for the design of a lossless transformerless broadband equalizer with optimum power gain for a variety of ultrasonic transducers from which the exact latitude on passbands and source resistances is completely delineated. [Work supported by NIH.]
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Transmitting SAW hydrophone (A)

P. Das, C. Lanzl, and D. Barone

J. Acoust. Soc. Am. Volume 64, Issue S1, pp. S9-S9 (1978); (1 page)

Online Publication Date: 11 Aug 2005

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A transmitting hydrophone which remotely senses both absolute pressure and changes in pressure has been developed using a surface‐acoustic‐wave (SAW) oscillator. This oscillator is formed by placing a SAW delay line or resonator in the feedback loop of an amplifier. The pressure applied to the hydrophone is converted to a flexural loading of the piezoelectric plate which alters the surface‐wave velocity on the plate, consequently shifting the oscillator frequency. This frequency modulated signal is easily transmitted to a remote location for signal recovery. The piezoelectric plate thickness and length can be chosen to optimize the sensitivity of the SAW hydrophone. The surface‐wave element of the oscillator is a planar structure; therefore, it is simple and inexpensive to manufacture. Furthermore, the size and power requirements of the SAW hydrophone are small, typically less than 50 cm3 a and 300 mW. This paper presents performance data of a number of SAW hydrophones using SAW oscillators in the 40–100‐MHz range in conjunction with a versatile signal demodulation system. Extensive measurements of sensitivity and frequency response were made for both delay line and resonator hydrophones manufactured on LiNbO3 and S‐T cut quartz substrates and compared with measurements obtained from conventional hydrophones in the identical setup. [Work supported by Naval Electronics Systems Command Contract No. N00039‐78‐C‐0042.]
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