bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements of the guinea-pig middle-ear transfer characteristic
Authors: Nuttall Alfred L.
Published: October 2005

The middle-ear transfer characteristic, defined here as the ratio of stapedial footplate displacement to constant sound pressure at the tympanic membrane, was determined for the anesthetized guinea pig with the aid of an electromechanical vibrator which applied displacement directly to the stapes. Magnitude and phase of the cochlear microphonic potential from the first cochlear turn were used as a common reference, first with the middle ear intact and later with the vibrator substituted for the middle ear. Under the assumption that the open-bulla middle ear has a second-order low-pass transfer characteristic, the data were simulated best by an overdamped system having breakpoint frequencies at 184 and 1358 Hz and a low-frequency transfer ratio of 6.16 × 10−7 m3/N. Closing the bulla results in a change in the low-frequency transfer ratio of −15 to −20 dB and a shift of the breakpoints to higher frequencies.
Input impedance curves for the reed woodwind instruments
Authors: Backus John
Published: October 2005

Equipment has been developed which will automatically plot the input impedance curves of the reed-excited musical instruments as a function of frequency. Sound from a regulated driver unit is passed through a high acoustical impedance into an adapter unit attached to the mouthpiece of the instrument. This impedance is in the form of a capillary of annular cross section, and is designed to have an approximately constant impedance magnitude over the frequency range used. The sound-pressure amplitude generated in the instrument is measured by means of a microphone whose output is applied to a chart recorder, so that a graph of input impedance versus frequency is obtained. Representative impedance curves were run for selected notes on the clarinet, oboe, bassoon, and saxophone. Input impedance values range from 400 to 1600 cgs acoustic ohms for the various instruments. For the low notes on the clarinet, the resonance frequencies are compressed in relation to the harmonics of the fundamental mode, the higher resonances having low frequencies than the corresponding harmonics. For low notes on the bassoon and oboe, the situation is the opposite, the resonances being stretched in relation to the harmonics. For high notes on the oboe and bassoon, the frequency of the blown tone may be considerably more than a semitone below the frequency of the resonance on which the instrument is operating.
Speed of sound and transmission loss in silicone rubbers at ultrasonic frequencies
Authors: Folds D. L.
Published: October 2005

The speed of sound as a function of temperature (0°–3°C) and the transmission loss in 2.5-cm-thick samples of 13 different RTV silicone rubbers have been measured in the frequency range 500 kHz–1 MHz. The range of measured sound speeds for the various materials was between 960 and 1110 m/sec at 0°C. The thermal coefficients of sound speed were approximately −3 m/sec °C for all samples. The transmission losses ranged from near 0 dB for RTV-602 to 14 dB for RTV-90 at 1 MHz.
Statistical correlates of the energy-equivalent sound level
Authors: Driscoll D. A. , Webster W. J. , Haag F. G. , Farinacci J. W.
Published: October 2005

The increased use of energy-averaged, single-number measures of environmental noise (e.g., Leq and LDN) makes desirable careful comparison with the more easily obtained and more frequently used statistical levels (e.g., L10 and L50). Analysis of a variety of environmental noise distributions, as well as a theoretical analysis of normal distributions, indicates strong correlation between several of the statistical levels (particularly the L10 and the L15) and the energy-equivalent sound level (Leq) for many types of environmental noise.
Paraholography—a new method for measurement of the directional distribution of sound waves in a reverberation chamber
Authors: Cook Richard K.
Published: October 2005

We describe a method for experimental determination of the complex of plane waves composing the sound field in a reverberation chamber. The basic holographic principle is comparison of the actual sound field with a family of reference plane waves having precisely known directions of propagation, sound pressures, and phases. The reference waves are not “real” waves but are created electronically, on the electrical side of microphones sensing the actual sound field, so as to be “parallel” to real waves.
Acoustic antennas for atmospheric echo sounding
Authors: Hall F. F. , Wescott J. W.
Published: October 2005

Utilization of acoustic waves for atmospheric studies through echo sounding requires an efficient antenna with high on-axis gain and suppressed sidelobes. The antenna pattern for a piston source, as it influences the evaluation of the acoustic radar equation, is calculated and the effective gain factor obtained. Existing microwave antennas and optical searchlights have been adapted for acoustic use and their performance measured. A conical horn-reflector antenna made of fiberglass gives excellent performance in the frequency region 1–5 kHz after being coated with a viscous dampening tar to shorten vibration time. This damping allows reception of weak echoes with minimum delay following the transmission of a high-power acoustic pulse from the antenna. Septum dampers have been used successfully on parabolic-dish antennas. Antenna beam patterns have been measured on an outdoor range, with some measurements being made across a canyon to avoid multipath ground-reflection effects. Mainlobe to 90° sidelobe ratios are 40 to 50 dB. The measured antenna pattern for the horn-reflector antenna agrees closely with predictions for a perfect piston source. The parabolic-dish antennas produce a more complex diffraction pattern. Absorbing cylindrical antenna enclosures have been found effective in further reducing sidelobe reception by 10 to 20 dB, in agreement with predictions. Attention to antenna design allows acoustic echo-sounder operation in a noisy urban environment, and keeps noise pollution from the sounder pulses below the annoyance threshold.
Long-distance propagation of infrasound from artificial sources
Authors: Liszka Ludwik
Published: October 2005

Infrasound from distant artificial sources has been detected at 2 Hz by a chain of stations in Sweden. A number of infrasound sources were located and identified as hydroelectric power plants, industrial plants, and oil fields. The infrasound from distant artificial sources propagates with reflections in the upper atmosphere: during summer mainly with reflections in the stratospheric sound channel and during winter with reflections in the upper sound channel.
Vibrational relaxation in H2O vapor in the temperature range 373–946 K
Authors: Bass Henry E. , Olson John R. , Amme Robert C.
Published: October 2005

Vibrational relaxation in water vapor has been observed using both ultrasonic velocity dispersion and absorption. The raw data were corrected for real-gas effects and for classical absorption. Results are compared with those of other investigators. Observed relaxation times appear much too short to be explained by a simple V-T process, and are interpreted in terms of a V-R transfer mechanism. Values of kVR range from about 1×108 sec−1 atm−1 at 374 K to 6×108 sec−1 atm−1 at 946 K.
Noise reduction in transonic wind tunnels
Authors: McCanless George F. , Boone James R.
Published: October 2005

The phenomena of background noise generation in transonic wind tunnels are analyzed. In unsteady aerodynamic tests, background disturbances create problems because the instrumentation senses them in addition to the fluctuations generated by the aerodynamic flow over wind-tunnel models. Calibrations of 25 facilities show that the amplitudes of the background fluctuations are excessive. In porous-wall facilities, one noise source consists of porous-wall edgetones that are generated by the passage of air over the holes. A flow model is developed that yields the frequencies of these oscillations. Test section boundary layers and hole configurations govern the occurrence of these fluctuations. In slotted-wall facilities, a noise source is the slotted-wall shearing caused by the air flowing along the openings. In both types of wind tunnels, other flow mechanisms also cause disturbances, and these phenomena are described. Noise-reduction methods are outlined which will provide valid unsteady aerodynamic results.
Sound insulation design for buildings
Authors: Rettinger M.
Published: October 2005

A graph and an equation are presented for the ready evaluation of the required sound-transmission loss at any frequency for each of several components of a composite sound barrier, to economically achieve a desired interior noise spectrum, given the spectrum of the exterior noise and the areas of each of the significant boundaries of a room. It is also established that for common automobile and jet aircraft noises, the necessary insulation of such exterior room boundaries is not well represented by an STC rating.
Aerodynamic aspect of sensory deprived speech
Authors: Hutchinson John M. , Putnam Anne H. B.
Published: October 2005

The purpose of this study was to assess the effects of oral sensory deprivation upon the aerodynamic characteristics of consonant production. Three adult males with normal speech served as subjects and read a prose passage containing at least three occurences of 13 different stops and fricatives in a syllable-initial stressed position. Sensory deprivation was achieved through a series of nerve-block injections. Intraoral air pressure was obtained using a catheter passed through the nasal cavity. Air flow rate data were obtained using a tightly fitting face mask coupled to a pneumotachograph and a differential pressure transducer system. The results indicated that, during sensory deprivation, the intraoral air pressures, intraoral air pressure durations, and air flow rates were consistently higher than during the control condition. Very few qualitative changes in the aerodynamic patterns were observed during oral anesthesia. These results were interpreted as evidence of a mixed motor control model of speech. The temporal sequencing aspect of speech appears to be feedback independent. However, the elevated aerodynamic parameters were conceived as executive adjustments to provide increased sensory data necessary for precision in reaching appropriate articulatory targets.
Attenuation and speed of ultrasound in lung
Authors: Dunn F.
Published: October 2005

The frequency dependence of the ultrasonic propagation properties of canine lung inflated to a density of 0.4 g/cm3 are reported. The attenuation increases exponentially with frequency, and the speed of propagation increases linearly with frequency.
Deep scattering layer spectra in the Atlantic and Pacific Oceans and adjacent seas
Authors: Chapman R. P. , Bluy O. Z. , Adlington R. H. , Robison A. E.
Published: October 2005

The acoustic properties of deep scattering layers were examined using explosive sources at a few hundred sites in the main basins of the North and South Atlantic and the North and South Pacific, in the Labrador, Norwegian, Mediterranean, and Caribbean Seas, and in Baffin Bay. Representative day and night spectra of column strength are presented for these areas in the frequency band 0.8–25.6 kHz along with estimates of the effective radii of the swimbladders of the dominant scatterers. The spectra tend to fall into homogeneous groups, with the most pronounced changes in type taking place near known faunal boundaries. In mid-ocean, in the North and South Atlantic and the South Pacific, scattering is high near the equator and at mid-latitudes, with considerably lower values in between. Very low scattering strengths are also found in the cold waters at high latitudes in both hemispheres. In a number of cold water areas in the northern hemisphere there is a pronounced peak in sound scattering at low frequencies, caused by scatterers with effective radii of swimbladders of 1 cm or greater. As some of these relatively large scatterers are probably commercial fish, it appears that a measurement technique similar to that used in this investigation would be a useful tool in resource management of commercial fisheries.
Time-frequency-domain formulation of ultrasonic frequency analysis
Authors: Simpson W. A.
Published: October 2005

The ultrasonic frequency spectrum is interpreted by Fourier analysis techniques. This approach leads to the same conclusions concerning flaw characterization as previous interference models; in addition, a number of other spectral characteristics are easily explained. Finally, the present treatment indicates that frequency analysis may be applicable to many additional problems, viz., timing measurements of any type (e.g., thickness or velocity measurements), wide-band attenuation measurements, and phase-shift measurements (e.g., determination of relative acoustic impedance).
Vibrational response of sonar transducers using piezoelectric finite elements
Authors: Allik Henno , Webman Kenneth M. , Hunt John T.
Published: October 2005

The finite element method is applied to the vibrational analysis of electromechanical sonar transducers of arbitrary geometry. Three-dimensional hexahedral finite elements which include the effects of piezoelectric coupling are formulated, and the solution of the resulting coupled electroelastic equations of motion is presented. The vibrational response of a particular transducer element is computed, and comparisons with experimental mesurements are made. The calculated deformations of the transducer are presented in the form of computer generated displays. A data reduction scheme is also utilized to clarify the physical meaning of the transducer response.
Two-tone distortion products in a nonlinear model of the basilar membrane
Authors: Hall J. L.
Published: October 2005

Two-tone distortion products were studied in a computational model of the basilar membrane into which second- and third-order nonlinearities had been introduced. The displacement patterns produced by distortion products f2 − f1 and 2f1 − f2 resemble, in the neighborhood of the characteristic place for the frequency in question, displacement patterns produced by tones delivered at the stapes. This is not the case for distortion product 2f2 − f1. The dependence of both the amplitude and phase of distortion products f2 − f1 and 2f1 − f2 on frequency spacing and amplitude of the two primary tones has features in common with results from psychophysical experiments. The 2f1 − f2 distortion product shows a nonmonotonic behavior similar to that demonstrated in psychophysical experiments. The phase of the 2f1 − f2 distortion product changes with intensity in a manner similar to that observed psychophysically. In the model, a cancellation-tone method overestimates the amplitude of the 2f1 − f2 distortion product, again in agreement with results from psychophysical experiments. These areas of agreement between the model and psychophysical data support the notion that psychophysically observed distortion products 2f1 − f2 and (under some conditions) f2 − f1 are the result of nonlinear mechanical properties of the basilar membrane.
Discrimination of auditory temporal differences by the bottlenose dolphin and by the human
Authors: Yunker Michael P. , Herman Louis M.
Published: October 2005

Difference limens (DLs) for standard tonal durations (T) of 0.3, 0.6, and 1.2 sec were determined underwater for a bottlenose dolphin, Tursiops truncatus, and for a human subject underwater and in air. For the dolphin, the temporal stimuli were either 9- or 25-kHz pure tones. A response on a paddle to the animal's left was reinforced following a standard duration signal, while a response on a right-hand paddle was reinforced following a longer duration signal, DLs being obtained for one standard at a time. The relative DLs (DL/T) generally remained between 0.06 and 0.08 for all three standards at each tonal frequency. Procedures for the human subject were similar to those for the dolphin, except that the temporal stimuli, in water and in air, were 1-kHz pure tones. No appreciable difference was found between the human in-water and in-air relative DLs, but their values were generally more than twice as high as those for the bottlenose dolphin. It was noted that temporal duration information could be useful to the echolocating bottlenose dolphin for the estimation of target distance.
Investigation of structural bonding forces in bacteriophage T2
Authors: Smith Réné J. , Cleary Stephen F.
Published: October 2005

The effects of laser-induced acoustic transients (pressure pulses) on the structure of bacteriophage T2 have been investigated. The acoustic transient is produced by transient heating of a dye solution resulting from the absorption of a ruby laser light pulse. Electron microscopy was used to evaluate the nature of the damage caused by the acoustic transients. Theoretical methods were used to estimate the magnitude of the stress induced in the bacteriophage T2 particle by the acoustic transient. Disruption of T2 was studied as a function of pH, urea, and glycerol concentration to obtain data on the structural stabilizing forces in this virus.
Multimode spherical hydrophone
Authors: Ko Sung-Hwan , Brigham Gerald A. , Butler John L.
Published: October 2005

An investigation is made of the multimode spherical hydrophone. The physical model considered in the present analysis is a piezoelectric ceramic spherical shell whose surface is sectionally electroded, with each section considered an electrically separated hydrophone. The induced voltage due to the incident acoustic wave is obtained for a radially poled ceramic shell. The maximum hydrophone sensitivities are calculated for both omnidirectional and dipole modes based on the present model, and the theoretical results are compared with the experimental results. The use of the multimode spherical hydrophone is found to be advantageous over the multimode cylindrical hydrophone in that (1) the resonant frequency of the omnidirectional mode of the spherical model is substantially higher in comparison with that of the cylindrical model for the same mean diameter, and (2) the sphere has identical dipole mode patterns in both directions of azimuth and elevation, whereas the cylinder has different dipole mode patterns unless the height of the cylinder is small compared with the wavelength. However, one possible disadvantage of the sphere is that an additional resonant frequency is encountered in the dipole mode, which is lower than the first resonant frequency for the cylinder.
Acoustic emissions in stressed soil samples
Authors: Koerner Robert M. , Lord Arthur E.
Published: October 2005

Although acoustic emission techniques have been used in a wide variety of materials, scarcely any attention has been given to particulate systems such as soils. Yet, it is in such particulate materials where the concept of strain is quite fictitious and an alternate parameter is greatly needed. The results of this study suggest that acoustic emission might be such a parameter. Included herein is a laboratory study of the acoustic-emission response of a series of soil samples at different water contents and under different stress states. The stress states are hydrostatic compression and triaxial shear compression tests. In each type of test the soil samples are laterally confined by pressure which simulates the soil in its natural state. The results show that high confinement pressure and high water content both produce high levels of acoustic emission. The emissions begin instantaneously upon the application of the stress. In all cases, the emissions cease when the soil samples reach an equilibrium position under the applied stress state. Some insight as to the wide range of problems which might be solved using acoustic-emission techniques is also noted.
Omnidirectional Scattering of Acoustic Waves by Rough, Imperfectly Reflecting Surfaces
Authors: Parkins B. E.
Published: October 2005

The omnidirectional scattering of acoustic waves by a rough, imperfectly reflecting surface is described using the method of physical optics. The expression for the far-zone intensity is derived and then specialized to the case of surfaces that are sufficiently rough to neglect the specularly reflected power. For such surfaces, the average differential scattering cross section σ0 is calculated and compared with the results of bistatic measurements made under conditions that satisfy the assumptions of the theory.
Volume-Scattering Measurements at 12 kc/sec in the Western Pacific
Authors: Batzler W. E. , Vent R. J.
Published: October 2005

Acoustic volume scattering data at 12 kc/sec from 14 deep-water areas lying in the region 5°–45°N and 115°–175°E in the Western Pacific are presented. Results are shown graphically as volume-scattering coefficient (and scattering strength) vs depth. Volume-scattering-coefficient values (expressed in decibel form) range from about −50 to −95 dB. There is considerable variation from area to area; the more southerly areas have the lower scattering coefficients, and scattering layers observed there are less well defined. Most intense scattering occurred in an area northeast of Honshu, Japan, where layers 500 ft thick with a peak scattering coefficient near −50 dB were observed. Scattering levels show a rough dependence on latitude and a somewhat stronger correlation with estimates of organic productivity. Volume-scattering coefficients observed off Southern California are usually higher by 5–15 dB than those in the Western Pacific areas.
Free-Flooding Unidirectional Resonators for Deep-Ocean Transducers
Authors: Horita R. E.
Published: October 2005

An array of compound piezoceramic metal resonators can be made to radiate sound preferentially in one direction without auxiliary acoustic baffles if suitable geometries and material combinations are selected. This has the advantage that depth independence and high power-to-weight ratio are obtained. Expressions have been derived for the farfield front-to-back pressure ratio, the electromechanical coupling coefficient, and the mechanical Q for resonators with flared conical metal heads, cylindrical piezoceramic shanks, and tapered conical metal tails. The results of the analysis and supporting experimental work show that it is feasible to design practical, high-performance sound projectors for deep ocean operation attaining unidirectionality without the use of baffles.
Axial Focusing of Sound in the SOFAR Channel
Authors: Williams A. O. , Horne William
Published: October 2005

Approximating by a polynomial a standard “velocity profile” of sound speed near the axis of the SOFAR channel, we have used normal-mode methods to explore recurrent focusing when a receiver and a CW point source are exactly on the axis, for acoustic frequencies of the order of 100 cps. A certain range R exists—about 26 km in the North Atlantic—at which the few lowest and strongest modes of the sound field add nearly coherently. Focusing is to be expected near R and, decreasingly, near integral multiples of R. A velocity profile nearly symmetric about the axis would also produce focusing near R/2, 3R/2, etc. Numerical calculations 100 cps show no such effect at R/2, but a modest focusing enhancement of about 3 dB near R and 2 dB near 2R. Our results disagree markedly with recent analysis by Hirsch, partly because he dealt with a pulsed source but more because he assumed a symmetric profile of sound speed. Axial focusing is evidently very sensitive to the profile. Experimental detection appears almost hopeless because the depths of axis, source, and receiver must be known with great precision.
Elastic Surface-Wave Excitation, Using Parallel-Line Electrodes above Piezoelectric Plates
Authors: Yamanouchi Kazuhiko , Shibayama Kimio
Published: October 2005

The measurement of the velocity of the surface waves and the electric-field intensity over the piezoelectric plates, when the parallel-line type of electrodes are employed, are described. The characteristics of the higher-mode excitation are also described.
Reply to “Comments on ‘Detection of Random Acoustic Signals by Receivers with Distributed Elements: Optimum Receiver Structures for Normal Signal and Noise Fields’” [Burwell Goode, J. Acoust. Soc. Am. 39, 1193–1194 (L) (1966)]
Authors: Middleton David , Groginsky Herbert L.
Published: October 2005

Recent comments on our paper have motivated us to reassess the derivations and remarks that we make therewith. We show here that a typographical correction suffices to correct the difficulty of the causal filter, pointed out by Goode. We reiterate that the factorization that is a nontrivial part of our study is understood best in terms of the matrix-operator notation used in our paper.
External Surface-Absorption Cross Section of a Pipe Organ
Authors: Benade A. H.
Published: October 2005

The total sound absorption due to a rank of organ pipes arises chiefly from internal resonance losses and also from energy dissipation taking place at the external surfaces of the pipes. The first contribution has been discussed elsewhere [A. H. Benade, J. Acoust. Soc. Am. 38, 780–789 (1965)], and the second is reported here. Scattering of a plane wave incident obliquely on a long circular cylinder is calculated, and the results are used to find the energy absorbed via viscosity and also via the short-circuiting of the wave's temperature fluctuations produced by an isothermal boundary. It is shown that an absorption coefficient can be defined for the pipe surface that is approximately independent of the radius/wavelength ratio. The corresponding coefficient for viscous and thermal losses at a plane surface is also calculated. The result are ᾱcyl = 2.3⋅10−5(ω)12 and ᾱPLANE = 6.8⋅10−5(ω)12. The latter result agrees with a calculation by Walther [J. Acoust. Soc. Am. 33, 127–136 (1961)]. Computation of the absorption by a rank of pipes is simplified by using the scaling principles followed by organ builders. It is shown that the external absorption is negligible below 500 Hz, and is only about 0.06 m2 at 2000 Hz for a 73-pipe rank centered at middle C.
Time Adjustment in Speech Synthesis
Authors: Scott Robert J.
Published: October 2005

Fairbanks' speech time-adjusting device has been simulated, using a hybrid computer. This device discards or repeats recorded speech segments to compress or expand the time dimension. A dichotic method for time compression of speech was investigated in which odd-numbered time segments were presented to one ear and even-numbered segments to the other ear. A preference test suggested that speech compressed with the dichotic method may be more intelligible than speech compressed with Fairbanks' method. Potential applications for time-adjusted speech and possibilities for further research are suggested.
Ultrasonic Orientation Determination of Single Crystals
Authors: Green Robert E. , Henneke Edmund G.
Published: October 2005

A general method for determining crystallographic orientation by measurement of velocities of propagation of ultrasonic waves is given. The method supplements optical and x-ray techniques and is primarily designed for orienting crystals to be used in ultrasonic pulse experiments. Aluminum and zinc single crystals are used as specific examples of the method. The required accuracy for such measurements is discussed.
Exact Simplification of Time-Dependent Ultrasonic-Standing-Wave Light-Diffraction Equations
Authors: Hargrove L. E.
Published: October 2005

A considerably simpler mathematical form of the equations for the intensity of light diffracted by ultrasonic standing waves with arbitrary standing-wave ratio is derived from an existing solution. The simplification—which results from mathematical identity, not from approximations—reduces a double summation of Bessel function products to the square of a single Bessel function.
Perturbations of Synthetic Orchestral Wind-Instrument Tones
Authors: Strong William , Clark Melville
Published: October 2005

The relative significance of spectral and temporal envelopes for the synthesis of orchestral wind-instrument tones was evaluated by exchange of spectral and temporal envelopes among the wind instruments, by creation of artificial spectral envelopes, and by perturbation of the spectral envelopes. It was found that, for the oboe, clarinet, bassoon, tuba, and trumpet, where the spectral envelope is unique as regards the frequency of its maximum and the range in which the instrument is normally played, this envelope predominates in aural significance over the temporal envelope. Where the spectral envelope is not unique—as for the flute, trombone, and French horn the spectral envelope is equal or subordinate to the temporal one in aural significance. Interfamily confusions are fewer in those cases where the spectral envelope is of predominant importance: about 14% for the clarinet, oboe, bassoon, and tuba anti about 25% for the flute, trumpet, trombone, and French horn. The ratio between identification probabilities of synthetic and natural tones is 0.97 for the oboe, 0.90 for the clarinet, 0.86 for the French horn, 0.82 for the bassoon, 0.77 for the flute, 0.75 for the trumpet, 0.69 for the tuba, and 0.62 for the trombone.
Effects of Transmission Delay and Access Delay on the Efficiency of Verbal Communication
Authors: Krauss Robert M. , Bricker Peter D.
Published: October 2005

Two experiments were performed to investigate the effects of transmission delay and access delay, respectively, on the efficiency with which speakers verbally encoded information for transmission in a two-person communication task. Both experiments employed echo-free four-wire voice circuits in an attempt to isolate each delay effect and to avoid the delayed echo effect found in commercial circuits. In the first experiment, three values of pure roundtrip transmission delay were used: no delay, 0.6 sec, and 1.8 sec. Using 14 pairs of male subjects in each condition, it was found that, whereas 1.8 sec of transmission delay deleteriously affected the efficiency of communication, subjects performed as efficiently using the 0.6-sec delay circuit as with no delay. In the second experiment, three values of access delay were used: no delay, 0.25 sec, and 1.8 sec. Ten pairs of male subjects and 10 pairs of female subjects were run in each condition. The effect of access delay was found to be different for the two sexes. Access delay of 1.8 sec had a greater effect on males than on females, whereas at 0.25-sec delay female performance was impaired slightly and male performance not at all. With no delay, male and female performance did not differ. These results are supported by data based on subjects' responses to a postexperiment questionnaire. The findings are discussed in terms of their relevance to problems encountered in two-way voice communication over long transmission paths.
Cepstrum Pitch Determination
Authors: Noll A. Michael
Published: October 2005

The cepstrum, defined as the power spectrum of the logarithm of the power spectrum, has a strong peak corresponding to the pitch period of the voiced-speech segment being analyzed. Cepstra were calculated on a digital computer and were automatically plotted on microfilm. Algorithms were developed heuristically for picking those peaks corresponding to voiced-speech segments and the vocal pitch periods. This information was then used to derive the excitation for a computer-simulated channel vocoder. The pitch quality of the vocoded speech was judged by experienced listeners in informal comparison tests to be indistinguishable from the original speech.
Transient Electron-Inertia Field Produced by a Strain Pulse
Authors: Kennedy J. D. , Curtis C. W.
Published: October 2005

Conduction electrons, owing to their inertia, should move relative to an accelerated metallic lattice as they would in a stationary conductor if subjected to an electric field equal to the mass/charge ratio of an electron times the acceleration of the lattice. Since a strain pulse produces a transient acceleration, it should be accompanied by an electron-inertia field of this type. To demonstrate this effect, a torsional strain pulse was used to produce rotational acceleration of an insulated metal ring, and the electromagnetic signal, generated by the ring during acceleration, was detected by a pickup coil connected to an oscilloscope. The theory of a strain-induced electron-inertia effect is discussed, and calculations are carried out for comparison with measurements. Reasonable agreement between measurement and prediction serves to identify electron inertia as the cause of the signal.
Acoustic Turbulent Water-Flow Tunnel
Authors: Carey George F. , Chlupsa John E. , Schloemer Howard H.
Published: October 2005

The acoustic turbulent water-flow tunnel designed and constructed at the U. S. Navy Underwater Sound Laboratory has a clear plastic-pipe test section (312-in. i.d.) through which water is pumped at centerline velocities ranging from 9 48 knots. Noise-reduction techniques have prevented pump and piping noises from entering the test section through either structural or fluid paths. Measurements at centerline velocities between 9 and 48 knots with flush mounted hydrophones at several longitudinal spacings show that the ratio of convection velocity to centerline velocity ranges from 0.86 to 0.61. The curve of maximum space-time correlation in frequency bands versus hydrophone spacing in wavelengths is in good agreement with other published results. Frequency spectra measured from 200–10 000 Hz coincided when nondimensionalized with respect to centerline velocity and boundary-layer thickness. When corrected for hydrophone size, the spectral curve was similar to those reported for turbulent airflow and rising and falling bodies in water.
Echoes from Hollow Aluminum Spheres in Water
Authors: Diercks K. Jerome , Hickling R.
Published: October 2005

Recorded farfield echoes from precision hollow aluminum spheres in water, with different shell thicknesses and with either water or air in the hollow interior, are compared with calculated echoes. Steady-state echoes are investigated over a ka range of from 6 to 27, and individual pulsed echoes at ka = 20. Excellent verification is obtained for the features predicted by the theory. It is shown that the echoes are sensitive to changes in the elastic properties of the shell, particularly when the shell is thin. The experiments showed, moreover, that the echoes are dependent on the orientation of the sphere. This is due presumably to small asymmetries in the structure and properties of the shell and emphasizes again the strong interrelation between sonar echoes and the nature of the material in the target.
Computation of Farfield Radiation Patterns by Use of a General Integral Solution to the Time-Dependent Scalar Wave Equation
Authors: Ferris Horace G.
Published: October 2005

The computation of farfield radiation patterns by use of a general integral solution to the time-dependent scalar wave equation is considered. The use of this theorem in this connection appears to offer advantages that may have been overlooked. In particular, the general theorem is capable of interpretation in terms of an analogous network of linear systems whose inputs are the nearfield measured pressures and whose summed output is the desired farfield pressure. Moreover, the general theorem is valid for signals which are general functions of the time, including noise signals, as well as for signals having only a single frequency component. It may accordingly be applied to a much wider class of signals than may the familiar Helmholtz formula or the Green's formula, which have been used as the basis for most farfield computations in the past. The network interpretation of the general theorem is discussed in some detail and the forms of the network response function for both a plane and a spheroidal surface of measurement are given.
Criterion under Which the Standard Detector Is Optimal
Authors: Shapiro Arthur
Published: October 2005

This paper is concerned with the detection of a narrow-band signal using two hydrophones. Specifically, it addresses itself to the problem of finding the “optimal” linear combination of sample spectra, cospectrum, and quadrature spectrum to use as a detection-test criterion. The optimal detector is defined here as the one that maximizes the average probability of detection for given probability of false alarm and given observation time, where the average is taken over all possible noise-coherence and noise-phase-difference conditions. It is shown that, under not unrealistic conditions, the optimal detector, among all those that are linear in the sample spectra and the co- and quadrature spectra, is the one that adds the outputs of the detectors and squares the result. In other words, there are strong indications that if one restricts oneself to detectors of the form given, the best one can do, on the average, is to continue doing what is currently being done.
Auditory Spectral Filtering and Monaural Phase Perception
Authors: Goldstein J. L.
Published: October 2005

The fundamental relation of limited auditory frequency resolution to mortar phase perception is studied. Old and new results are discussed for experiments employing sinusoidally amplitude-modulated (AM) carrier tones and quasi-frequency modulated (QFM) carrier tones, which are related by a phase transformation. One experiment concerns AM and QFM modulation thresholds. A second experiment considers the quality differences between AM and QFM. Both experiments show that phase effects disappear for stimulus bandwidths that exceed a value roughly proportional to the critical band at the carrier frequency. The proportionality factor depends upon carrier level and differs greatly between experiments. A unified psycho-physical account is given with a model consisting of a quasilinear bandpass analyzing filter followed by ideal envelope detection, and concluding with either a peak-to-minimum or peak-threshold decision. Parameter values in the model are evaluated from the phase-perception data, and these values support the assumptions that underlie the model. It is shown that the critical-bandlike experimental data do not provide a measure of the commonly conceived critical band. Rather, the critical-band scale merely normalizes the analyzing-filter parameters. This work indicates that the model employed offers wider application.
Effects of Stimulus Duration on the Detection of Sinusoids Added to Continuous Pedestals
Authors: Leshowitz Barry , Raab David H.
Published: October 2005

The effect of stimulus duration on the detection of sinusoids added to continuous pedestals was investigated in two studies. Gated 1000-Hz sinusoids were added in phase with continuous pedestals in the presence of a steady background noise at durations between 10 and 500 msec. Plots of signal intensity necessary for approximately 75%-correct detections as a function of duration revealed enhanced detectability and an intensity duration reciprocity factor of 14 dB per log unit of time. In the second experiment, signal energy was held constant as duration of the probe was varied between 10 and 100 msec, and the proportion of correct responses was measured in a two-interval forced-choice procedure. Marked improvement in detectability obtained as signal duration was increased. When increment energy was held constant, discriminability remained unchanged in the face of a 10-dB decrease in signal energy. After correcting an energy-detection model for internal noise, the model accurately predicted the proportion of correct responses. Finally, it is argued that a description of detection data in terms of increment energy renders results obtained with pedestals simpler and more understandable.
On the Standard Reference Pressure
Authors: Bennett G. S.
Published: October 2005

Arguments are presented for the continued use of 1 dyn cm2 as the standard reference pressure for underwater-sound measurements.
Possible Inertial Period Time Dependence of Signal Transmission in the Ocean
Authors: Clay C. S.
Published: October 2005

The acoustic transmission between a fixed source and fixed receivers on the bottom of the ocean was monitored continuously for 27 h. The ray tracings indicate that the signal from the source was reflected at the ocean surface and refracted near the ocean bottom. Since the receiver was at the edge of the shadow zone, the signal level was very sensitive to small changes in the ocean. Some fluctuations of the phase and level of the signal had the same period as the ocean waves, about 9 to 10 sec. The signal level also changed from low to high after 14 h. This may have been a tidal effect, but the long observed period suggests that it can be ascribed to water motions having inertial periods (28 h at 25°N latitude). Other periodicities suggest that this experimental technique may be useful in studying deep-water movements.
Ambient Noise under Sea Ice and Further Measurements of Wind and Temperature Dependence
Authors: Milne A. R. , Ganton J. H. , McMillin D. J.
Published: October 2005

Measurements of underwater-pressure spectral density from M'Clure Strait (2–5 May 1966), the Beaufort Sea (31 July and 16 August 1965),and the Canada Deep (14 April 1965) are presented. The M'Clure Strait measurements, made under shore-fast sea ice, exhibited a variability related to air-temperature and wind-speed changes of a similar nature to those reported previously for midwinter under-ice noise. The great differences in the magnitude and variation with frequency, of the ambient noise observed under sea ice is again illustrated with three sets of measurements obtained during 1965–1966. The noise observed under the shore-fast ice of M'Clure Strait in the springtime appeared to be governed by air-temperature and wind-speed changes in a similar manner to noise observed previously in the midwinter [J. H. Ganton and A. R. Milne, J. Acoust. Soc. Am. 38, 406–411 (1965)]. On the other hand, measurements made under the moving ice cover of the Canada Deep in the springtime and of the Beaufort Sea in the summer appeared to be less amenable to description in terms of easily observable physical variables.
Proposed Detection of Dynamically Oriented Nuclei by Acoustic Nuclear Magnetic Resonance
Authors: Breitbart Mary Duns Scotus , Barker W. A.
Published: October 2005

It is proposed that acoustic nuclear magnetic resonance be used to detect steady-state nuclear orientation achieved by the Jeffries Abragam effect. This is a new scheme for double magnetic resonance (ADMR) in contrast with conventional DMR, which employs the usual time-varying magnetic field to observe the enhancement of the nuclear resonance. The acoustic wave modulates the nuclear quadrupole interaction to induce double as well as single spin flips. Calculations for nuclei of spin I = 32 in weak dipolar coupling with paramagnetic electrons of spin S = 12 in an axial crystal indicate that both types of DMR should give positive and negative enhancements ∼g β /gnβn∼103 for 1° ⩽ T ⩽ 300°K in favorable circumstances. Suitable samples in which the effect might be demonstrated are iodine nuclei in NaI containing I2− centers and Al27 nuclei in Cr3+ or V3+ doped Al2O3. If the related experiments are performed, the effect of the electron paramagnetic resonance linewidth and of nuclear-spin diffusion may well reduce the enhancement by one or two orders of magnitude.
Variation of the Relative Intensity of Cavitation with Temperature
Authors: Ibisi M. , Brown B.
Published: October 2005

The variation of the relative intensity of cavitation with temperature has been determined by chemical and erosion methods. The endeavor was to employ both methods under identical conditions of transducer frequency, power input to the transducer, height of test samples over the transducer face, etc. The liberation of chlorine from a saturated solution of carbon tetrachloride in water with ortho-tolidine reagent as indicator was employed in the chemical method and cavitation intensity was expressed as the optical density of the resulting yellow solution for blue light of 436 mμ. An expression of optical density in terms of peak percentage absorption of the yellow solution was used to stress observations in this method of determining cavitation activity. In the erosion method, lead samples were used and the intensity of cavitation was expressed as the loss in weight of the sample after exposure to cavitation. The results obtained were fed into a computer and equations derived for the respective measurements. These results and other observations on the experimental work are discussed.
Instrumentation for an Array of Infrasonic- and Hydromagnetic-Wave Sensors
Authors: Fehr Uri , McGahan L. C.
Published: October 2005

A system is discussed for the instrumentation of infrasonic and hydromagnetic waves traveling through the atmosphere and the ionosphere. Two large missiles were used as the sources of energy. The advantages of the instrumentation system are: a minimum of manpower and time is required to calibrate and place the system into operation; the system is easily transported; and the system is very stable over long periods of time. A description of the missile engines as a moving source of energy in the infrasonic-frequency spectrum (20–0.025 cps) was obtained. It is concluded that the instrumentation system has the capability of providing reliable data on long period waves and that the equipment is stable.
Comparison of Experimental and Theoretical Sound-Attenuation Values in a Buried Network of Long Pipes
Authors: Michael Paul L. , Hogan Donn P.
Published: October 2005

Experimental and theoretical attenuation characteristics are presented for broadband and pure tone acoustical signals between 300–1200 cps traveling through long pipes with rigid walls. Close correlation was found between experimental and theoretical attenuation rates over the entire system; however, an unexpected, almost constant attenuation factor was found in 90° side branches. The experimental work was sponsored by the American Gas Association as part of a sonic-leak pinpointing project.
Guided Infrasonic Modes in a Temperature- and Wind-Stratified Atmosphere
Authors: Pierce Allan D.
Published: October 2005

The propagation of infrasonic waves in a realistic model atmosphere which includes a variable wind profile as well as a variable temperature profile is discussed quantitatively for wave periods between 1–10 min. The numerical method used for the computation of phase and group velocity curves and other characteristic quantities associated with the possible guided modes is an extension of the multilayer method used previously by Press and Harkrider and by Pfeffer and Zarichny for atmospheres without winds. The effects of winds on the propagation are assessed by examining computations carried out for various fixed directions of the horizontal group velocity and from the computation of deviations of the phase-velocity direction from group-velocity direction for the case of propagation crosswind. Pressure height profiles of various frequencies propagating in various modes are exhibited and excitation amplitudes for ground level sources (excluding the frequency spectrum of the source) are plotted versus frequency for various modes and various group-velocity directions. Qualitative explanations of the computed results are given, and the implications of the results to actual waveforms are discussed.
Separation of the Stress Equations of Motion in Nonhomogeneous Isotropic Elastic Media
Authors: Rao C. R. A.
Published: October 2005

Tensorial equations of motion are considered in order to attack the problem of the separation of the stress equations of motion in nonhomogeneous isotropic elastic media. We confine ourselves to the plane equations in a medium whose elastic coefficients and density are arbitrary functions of a single Cartesian coordinate. It is shown that the stresses are expressible in terms of a single function satisfying a fourth-order ordinary differential equation. The solution obtained may be useful in studying surface waves in nonhomogeneous media.
Some Energy Bounds for Randomly Excited Beams
Authors: Gray A. H.
Published: October 2005

An appropriate Green's function is used to obtain simple sounds on the average energies of randomly excited, nonuniform linear beams.