• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

SECTION LISTING

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Nov 1979

Volume 66, Issue S1, pp. S1-S89

Return to All Sections
back to top
RSS Feeds
back to top Session T. Engineering Acoustics IV: Transducers
Contributed Papers
FREE

Reciprocity calibration of transducers in a plane wave resonator (A)

Steven Garrett

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S39-S39 (1979); (1 page) | Cited 1 time

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
The recently published expression for transducer calibration in a plane wave resonator by the reciprocity method [I. Rudnick, J. Acoust. Soc. Am. 63, 1923 (1978)] has been tested against a Rayleigh disk. The resonator tube was terminated at one end by a dual electret transducer and at the other end by an electro‐dynamic transducer. All three transducers were reversible allowing three independent reciprocating calibrations which agreed to better than 1% (0.1 dB). The deflection of the disk was measured by monitoring the change in inductance of a coil surrounding the resonator and the disk. The disk angle detection system was self‐calibrating and permitted absolute measurement of the flow velocity in the vicinity of the disk when the moment of inertia of the disk and damping coil were known. [Research supported by the F. V. Hunt Postdoctoral Fellowship of the Acoustical Society of America with funds provided by the Office of Naval Research.]
FREE

Cross‐spectral method of measuring acoustical intensity—correcting phase mismatch error by calibrating two microphone systems (A)

G. Krishnappa

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S39-S39 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
The accuracy of measuring acoustic intensity using two closely spaced microphones by correcting the phase mismatch error by measuring the transfer function between the two microphone systems is examined. The two measuring microphone instrumentation systems were calibrated by flush mounting the two microphones in a rigid circular plate attached to the end of a long length of circular pipe. A random noise source was mounted at the other end of the piping system. The two microphones were exposed to the same noise (phase and pressure levels) over a wide range of frequencies. The accuracy of the measurement method was verified by creating a sound field in an anechoic room by a loudspeaker and generating plane‐wave propagation inside along length of pipe with an anechoic termination. The measurement accuracies were very satisfactory. This method has the advantage of eliminating the recording and processing of two sets of data required in circuit switching technique.
FREE

Carrier‐operated microphone preamplifier with self‐testing capability (A)

Edith L. R. Corliss and William B. Penzes

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S39-S39 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
In carrier‐operated preamplifiers, a condenser microphone can be placed in series with an inductor in one arm of a modified Van Zelst bridge circuit [M.D. Burkhard et al., J. Acoust. Soc. Am. 32, 501–504 (1960)]. The microphone capacitance and the inductor are resonant at the carrier frequency. Consequently, the impedance of this arm is relatively low, and the signal‐to‐noise ratio can exceed that of a conventional high‐impedance preamplifier circuit by an order of magnitude or more. Sound‐induced motion of the diaphragm modulates the carrier frequency; demodulation and amplification produce the output signal. Advances in microelectronic components since 1960 include the availability of temperature‐stable integrated circuits, small crystal‐controlled oscillators, and temperature‐compensated voltage references. These components were used to construct a carder preamplifier of small size suitable for use with “half‐inch” microphones. Since the bridge circuit balance is dependent upon the electrical impedance of the microphone, changes in this impedance associated with changes in microphone sensitivity can be detected by use of an audio‐frequency insert voltage. This insert technique provides a simple and convenient in situ check of the microphone and preamplifier. Tests for preamplifier battery supply and polarization voltage are also provided.
FREE

Transient response optimization of piezoelectric disk transducers by time domain techniques (A)

H. A. Wolf and J. M. Lawther

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S39-S39 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
The goals of this research have been to find and demonstrate design procedures for reducing the mechanical ringing of piezoelectric disk transducers under impulsive electrical excitation. The primary criterion of the optimization procedure is the minimization of face velocity ring‐down peaks under the constraint of limiting loss from the peak velocity. Improvements to the transient response have been sought through the determination of appropriate matching networks at the two mechanical ports and at the electrical port. The optimization is accomplished by performing a gradient search over a parameter space defining the port matching configurations. The transducer and front‐side mechanical matching sections are modeled with distributed parameters. Back‐side loading is restricted to being resistive. Conventional inductance‐tuned matching at the electrical port is demonstrated to be detrimental in reducing transient ringing. The findings indicate a natural division of the optimization process. Lightly backed and heavily backed transducers define the categories, each with an appropriate set of design criteria. Within each category, these new time domain optimization procedures result in improved transient performance over previously reported techniques based on frequency domain analysis. Experimental demonstrations are provided to verify the theoretical design improvements.
FREE

Advances in fiber interferometer hydrophones (A)

J. H. Cole and J. A. Bucaro

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S39-S40 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
Progress on the development of fiber interferometer hydrophones is presented. Baseline low‐frequency noise has been systematically reduced over the past year. A dramatic improvement in minimum detectable pressure of fiber hydrophones at frequencies between 200 Hz and 1 kHz was recently achieved by the incorporation of state of the art optical components. The potential for increased performance of fiber interferometers is discussed.
FREE

Pressure sensitivity amplification in interferometric fiber optic hydrophones (A)

R. Hughes and J. Jarzynski

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S40-S40 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
The induced optical phase change when a pressure is applied to a fiber optic hydrophone is examined both theoretically and experimentally. The induced phase change is calculated both with and without a plastic jacket around the glass fiber. It is shown that the phase change predicted from a detailed three‐dimensional analysis can be adequately described in terms of the much simpler two‐dimensional generalized plane strain approximation. Sensitivities calculated assuming hydrostatic boundary conditions are shown to correspond closely in value with static pressure‐sensitivity measurements. The application of a plastic jacket can substantially increase the pressure sensitivity of the fiber. The increased phase shift is due primarily to the tendency of the jacket to increase the axial strain experienced by the glass fiber. It is predicted that maximum pressure sensitivity (up to 30 times that of the bare fiber) will be achieved by jacketing with Teflon.
FREE

Silicon rubber for optical hydrophones (A)

Peter Shajenko and James Flatley

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S40-S40 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
Elasto‐optic properties of materials can be used for modulating the laser beam by the acoustic pressure. The compressibility and the change of index of refraction with pressure of silicon rubber were measured using the technique of interferometry, and the results were applied to determine the voltage sensitivity and minimum detectable pressure of an optical hydrophone. Both values compare favorably with those of a conventional piezoelectric hydrophone.
FREE

Studies of PVF2 transducers (A)

E. F. Carome

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S40-S40 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
Thin film polyvinylidine fluoride (PVF2) polymer transducers are being used for various applications over the frequency range 0.2 to 30 MHz. Operated in the thickness mode, they have been employed as sources and detectors of longitudinal and surface waves. Wideband impulses are easily generated and detected with these elements, so that a transducer's performance can easily be evaluated by examining its direct and Fourier transformed response. Detailed data are presented on the sensitivity, frequency response, and other characteristics of various PVF2 transducer configurations. [Work was partially performed at Stanford University and supported by ONR.]
FREE

Utilization of semiconductor strain gauges in pressure gradient sensor designs (A)

F. W. Cuomo and D. J. Hilliker

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S40-S40 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
The performance of a pressure gradient sensor of the fixed baffle type embodying semiconductor strain gauges is discussed. The output is optimized by the utilization of a bridge circuit providing good linearity and temperature compensation. Experimental data are obtained by means of a low‐frequency acoustic calibrator similar in design to an earlier device [T. H. Ensign, J. Acoust. Soc. Am. 50, 108(A) (1971)] and compared with identical gradient transducers employing ceramic elements.
FREE

Optimization study of a parametric hydrophone with a slow waveguide (A)

J. Jarzynski and R. D. Corsaro

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S40-S40 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
The performance of a parametric hydrophone with a cylindrical slow waveguide between the pump and receiver transducers was calculated as a function of the waveguide dimensions and material properties. The computer program used is described by Corsaro and Jarzynski [J. Acoust. Soc. Am. 66, 895–904 (1979)]. The parametric conversion gain and beam patterns were calculated for waveguide lengths in the range 0.1 to 9λ, where λ is the low‐frequency wavelength in water; for waveguide radius/length ratios in the range 0.03 to 0.5; and for waveguide materials with sound speeds in the range 400–1500 m/s. The general conclusion is that large gains in parametric conversion efficiency (∼20 dB) and in directivity are achievable for geometries less than a few wavelengths long, with diameter/length ratios no less than 0.1, and with material sound speeds in the range 800–1200 m/s. With longer or thinner cylinders, or with materials having speeds less than 800 m/s, the side‐lobe levels increase, and both efficiency and directivity are typically reduced. These effects are predictable from Jacobi's analysis of sound propagation in slow waveguides [J. Acoust. Soc. Am. 21, 120 (1949)].
FREE

The motional impedance of an electro‐dynamic loudspeaker (A)

F. M. Murray

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S40-S41 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
For many years the electrical equivalent of the motional impedance of an electrodynamic loudspeaker has been represented as a lumped parallel resonant circuit with the tacit understanding that circuit elements do become distributed and that such complications are “beyond the scope of this course.” Recent experiments with high efficiency compression drivers show that these distributed elements can be analyzed and may be very important; in some cases causing cutoff characteristics similar to M‐derived filters rather than the classic constant‐K filters normally assumed. The author recently presented qualitative results (F. M. Murray and H. M. Durbin, Audio Engineering Society 63rd Technical Meeting, Paper D8) of experiments to control higher‐order modes of the motional impedance of such transducers. This paper presents a quantitative analysis to further understand this phenomenon. Some still unresolved questions will be discussed. When fully developed this new theory promises to provide better insight into gross anomalies sometimes attributed to other sources.
FREE

Ultrasonic bond evaluation in multilayered media (A)

R. M. Havira

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S41-S41 (1979); (1 page)

Online Publication Date: 11 Aug 2005

Full Text: | Download PDF

Show Abstract
This paper discusses a spectroscopic and time domain method for the evaluation of bonding and the determination of thickness in multilayered media using broadband ultrasonics. Mathematical modeling of multilayered media based on Z‐transform and scattering matrix techniques are presented. Experimental results using 500 KHz pulses are presented for water‐steel‐cement boundaries, water‐steel‐water boundaries and for a fluid‐filled delamination between the steel and cement. The comparison between experimental and theoretical results are discussed.
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close