bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation Speed and Attenuation Coefficient for Plane Coherent Acoustic Waves in a Turbulent Medium
Authors: Wenzel Alan R.
Published: October 2005

The results of numerical calculations of the propagation speed and attenuation coefficient for plane coherent acoustic waves propagating in a weakly stochastic fluid medium, based on equations derived previously, are presented. Two special cases are considered: waves in a randomly inhomogeneous fluid at rest, and waves in isentropic irrotational turbulent flow. In each case the medium is assumed to be statistically homogeneous and isotropic, and is assumed to have an exponential correlation function. The results for both cases indicate that the propagation speed of the coherent wave is less than the average sound speed of the medium; also that the attenuation coefficient increases, whereas the propagation speed decreases, with increasing wave frequency. The results obtained for waves propagating in motionless sea water (at 15°C, 1 atm, 35‰ salinity) are compared with corresponding results obtained by basing the analysis on the scalar wave equation. It is concluded that, in underwater acoustics, basing the analysis of the coherent wave in a quiescent medium on the scalar wave equation or stochastic Helmholtz equation, generally yields accurate results for the attenuation coefficient, but may lead to considerable error in the calculation of the propagation speed.
Acoustic Radiation Impedance of Caps and Rings on Oblate Spheroidal Baffles
Authors: Baier Roland V.
Published: October 2005

The acoustic radiation impedance of curved vibrating caps and rings located on hard baffles of oblate spheroidal shape is analyzed using eigenfunction expansion in oblate spheroidal wave functions. The numerical evaluation of the formulas is accomplished with the help of extensive computer programs. The results are presented in families of plotted curves showing the effect of curvature on the acoustic radiation impedance. Calculations are made for values of the acoustic size in the range 0.1⩽ka⩽20.0.
Wide-Range Calibration System for Pressure-Gradient Hydrophones
Authors: Bauer Benjamin B. , Abbagnaro Louis A. , Schumann Juergen
Published: October 2005

A gradient hydrophone calibrator consists of a precisely made water-filled tank, with ports to receive the hydrophones to be calibrated and the reference pressure hydrophones, which is set into axial oscillation with suitable drivers to develop a standing wave of sound in the water. An improved calibrator is described, which, by using a very rigid tank, covers a range of 3–2500 Hz. Measurements are simplified through use of electrical feedback, which maintains a constant pressure-gradient versus frequency function. The applications and limitations of this system to the measurement of sensitivity, frequency response, and phase response of pressure-gradient and pressure hydrophones, and for obtaining the polar patterns of gradient hydrophones, are described.
Underwater Shock-Wave Pressures from Small Detonators
Authors: Poché L. B.
Published: October 2005

Shock-wave peak pressures produced by exploding small (13.5-grain) detonators underwater were measured at ranges from 1 to 90 ft. Good agreement with the empirical pressure-distance scaling rule for TNT was found, and spreading of the pressure-time profile with range was found. Confidence limits for the predicted peak pressures at five ranges are given. The data were fitted to two other pressure-distance functions based on the Kirkwood-Bethe propagation theory.
A New Capped-Cylinder Design for an Underwater Sound Transducer (USRD Type F50)
Authors: Tims A. C.
Published: October 2005

A small broad-band transducer has been developed primarily for use as a receiver in the frequency range 1 Hz to 70 kHz, but it can be used also as a sound source in the frequency range 10–70 kHz. The nominal free-field voltage sensitivity at the end of a 30.5-m cable is −205.9 dB re 1 V/μPa at frequencies below 10 kHz. The sensitivity changes by less than 1 dB with hydrostatic pressure change from atmospheric to 6890 kPa and with temperature change from 3° to 30°C. As a sound source, the transducer is linear with driving voltage to 200 V CW at frequencies from 10 to 60 kHz. The broad-band characteristics are attributed to the novel design of the sensor element—a design that is applicable to a variety of cylindrical sensor configurations.
Detection of Noise Level Generated by a Grille in an Airflow
Authors: Sugiyama Akira , Tanaka Tadami , Nakamura Akira
Published: October 2005

Measurements were made in order to evaluate the pressure level of sound generated by a grille in an airflow. A streamlined probe microphone, which is covered by a solidified glass fiber of high density, was used for detection of noise existing in the airflow. Distributions in a flow duct of the turbulence-fluctuated pressure of the airflow and of the output level of the microphone were measured and then compared with sound transmission characteristics specified in the duct. It was found that the distribution of the microphone output agrees with the sound transmission characteristics, but not with the fluctuating pressure of the airflow. As a result, the levels of the sound pressure generated by a grille were about 50 dB (re 2 × 10−4 μbar) at frequencies greater than 200 Hz, with a maximum value of 65 dB at 1250 Hz, for a flow velocity of 8.4 m/sec. It was also found that the output of the probe microphone produced by the turbulence-fluctuated pressure of the airflow can be reduced to 40 dB below the turbulent pressure level by a covering of this type.
Binaural Interaction in Low-Frequency Stimuli: The Inability to Trade Time and Intensity Completely
Authors: Hafter Ervin R. , Carrier Samuel C.
Published: October 2005

Subjects were presented with low-frequency tonal signals, leading in time to one ear but more intense to the other. For differing values of interaural time (Δt) and intensity (ΔI), the listener's task was to detect the difference between the dichotic signals and diotic tones of the same frequency. The shapes of the psychometric functions demonstrate that time and intensity do trade but that the trade is incomplete—a result shown to be in accord with other experiments where listeners presented with such signals report the presence of two distinct “images.” A model of time-intensity trading is presented in which it is assumed that differences of intensity are converted to time by two different trading mechanisms and that the two sums of Δt and converted ΔI act as different loci on a single interaural dimension. It is further suggested that the inner and outer hair cells may represent the site of the two trades.
Monaural Phase Effect: Cancellation and Reinforcement of Distortion Products f2−f1 and 2f1−f2
Authors: Hall J. L.
Published: October 2005

When two primary tones in the frequency ratio f1:f2 = 2:3 are presented to human listeners, a combination tone is audible at f1/2. The loudness of this combination tone depends on the phase angle between the two primary tones. We measured the amplitude and phase of the combination tone using a cancellation- plus probe-tone technique. The phase effect can be explained by interaction of a second-order distortion product f2−f1 and a third-order distortion product 2f1−f2 of approximately equal intensities. The intensity relative to the primary tones of both distortion products is influenced strongly by frequency of the primary tones and weakly by intensity of the primary tones.
Monaural Phase Effects for Two-Tone Signals
Authors: Hall J. L. , Schroeder M. R.
Published: October 2005

Effects of relative phase on subjective quality were found for signals with two components having a frequency ratio of 1:2 (octave). The data were analyzed by means of INDSCAL, a multidimensional scaling program. The subjective space corresponding to different phase conditions is a circle, and equal phase differences correspond to equal distances along the circle. These results confirm the sensitivity of the auditory system to waveform even when only two frequency components are involved, and they demonstrate that perception of the two-component signal falls into an orderly pattern.
Psychophysical Evidence for Lateral Inhibition in Hearing
Authors: Houtgast T.
Published: October 2005

Although there are some indications of the possible role of lateral inhibition in hearing, there has been no clear demonstration of it in psychophysical experiments. Either the phenomenon plays only a minor role, or it has escaped psychophysical verification. Accepting for a moment the second possibility, is argued in this paper that the threshold of a test tone presented simultaneously with a masker does not reflect clear lateral-inhibition effects since the inhibition affects both the test tone and the masker. Two different methods, in which the test tone and the masker were presented succsesively, give clear psychophysical evidence of lateral inhibition in hearing. Firstly, the threshold curve of short test-tone bursts presented in the gaps between repeated masker bursts (noise with a steep negative or positive gradient at a particular frequency) shows marked edge effects. Secondly, the results of psychophysical measurements on two-tone suppression indicate that the nervous activity due to one frequency component may be suppressed by another component. The effect at the edges of the frequency spectrum are comparable with visual Mach bands, and the interaction of two tones is suggestive of the two-tone inhibition found in auditory-nerve fibers.
Changes in Frequency Discrimination Caused by Leading and Trailing Tones
Authors: Ronken Don A.
Published: October 2005

Frequency discrimination for a tone of short duration may be strongly affected by the temporal proximity of another tone. One of the effects is unlike either masking or memory interference and may be related to the time required by the auditory system for frequency organization.
Directivity of the Bowed Stringed Instruments and Its Effect on Orchestral Sound in Concert Halls
Authors: Meyer Jürgen
Published: October 2005

The directional characteristics of sound radiation were investigated for violins, violas, cellos, and contrabasses. Each instrument group has a nondirectional characteristic in its lowest frequency range except the contrabass. At higher frequencies, there are regions of preferred radiation, which change their direction and anglewidth with frequency. These results suggest that different seating arrangements for the strings would be optimum for different concert halls and different styles of musical compositions. The European seating system is optimum for the radiation of the cellos; it has the advantage that the sound character of the first and second violins may be distinguished by the audience, but the sound of the second violins has no brilliance. The American system makes the second violins sound as good as the first violins, but it is difficult to distinguish both groups in contrapuntal passages of classical symphonies. The sound of the cellos is poor and without clarity. The validity of these findings is confirmed by measurements in concert halls, and they have been used for guidance in changing the seating arrangement of an orchestra to improve the instrumental balance with successful results.
The Timing of Utterances and Linguistic Boundaries
Authors: Lehiste Ilse
Published: October 2005

This paper is concerned with the effect of morphological and syntactic boundaries on the temporal structure of spoken utterances. Two speakers produced 20 tokens each of four sets of words consisting of a mono-syllabic base form, disyllabic and trisyllabic words derived from the base by the addition of suffixes, and three short sentences in which the base form was followed by a syntactic boundary; this in turn was followed by a stressed syllable, one unstressed syllable, and two unstressed syllables. The sentences thus reproduced the syllabic sequences of the derived words. The duration of words and segments was measured from oscillograms. The manifestation of morphological and syntactic boundaries is discussed, and some implications of the findings relative to the temporal programming of spoken utterances are considered.
Experiment on Voice Identification
Authors: Tosi Oscar , Oyer Herbert , Lashbrook William , Pedrey Charles , Nicol Julie , Nash Ernest
Published: October 2005

A two-year experiment on voice identification through visual inspection of spectrograms was performed with the twofold goal of checking Kersta's claims in this matter [Nature 196, 1253–1257 (1962)] and testing models including variables related to forensic tasks. The 250 speakers used in this experiment were randomly selected from a homogeneous population of 25 000 males speaking general American English, all students at Michigan State University. A total of 34 996 experimental trials of identification were performed by 29 trained examiners. Each trial involved up to 40 known voices, in various conditions: with closed and open trials, contemporary and noncontemporary spectrograms, nine or six clue words spoken in isolation, in a fixed context and in a random context, etc. The examiners were forced to reach a positive decision (identification or elimination) in each instance, taking an average time of 15 minutes. Their decisions were based solely on inspection of spectrograms; listening to the identification by voices was excluded from this experiment. The examiners graded their self-confidence in their judgments on a 4-point scale (1 and 2, uncertain; 3 and 4, certain). Results of this experiment confirmed Kersta's experimental data, which involved only closed trials of contemporary spectrograms and clue words spoken in isolation. Experimental trials of this study, correlated with forensic models (open trials, fixed and random contexts, noncontemporary spectrograms), yielded an error of approximately 6% false identifications and approximately 13% false eliminations. The examiners judged approximately 60% of their wrong answers and 20% of their right answers as “uncertain.” This suggests that if the examiners had been able to express no opinion when in doubt, only 74% of the total number of tasks would have had a positive answer, with approximately 2% errors of false identification and 5% errors of false elimination. The different conditions existing between experimental trials of identification or elimination performed by the examiners of this study and the tasks performed by a professional examiner in real cases are discussed.
Horizontal-Angle Resolution by Echolocating Bats
Authors: Peff T. C. , Simmons James A.
Published: October 2005

Echolocating bats were trained to discriminate between two small, spherical targets, each separated by a different angle from a third spherical target fixed in one location between the other targets. The targets were all in the horizontal plane. The angle from the fixed target to one of the movable targets was kept constant at 19° of arc, while the angle from the fixed target to the other movable target was varied from 37° to 19° in small decrements. The acuity with which the bat could use sonar to discriminate the larger angle from the smaller, constant angle of 19° was experimentally determined to be 6° to 8° for Eptesicus fuscus and 4° to 6° for Phyllostomus hastatus. Phyllostomus has a nose-leaf through which it broadcasts its sonar cries, using a beamwidth (6 dB down) of 40° to 50° in this experimental setting. Eptesicus emits cries through its open mouth and, in the apparatus for angular discrimination, used a beamwidth of 55° to 65°. There are many other differences between these species in echolocation, but the data suggest that at least the width of a bat's beam of sound may be related to acuity of angular resolution.
Optimum Window Length for the Measurement of Time-Varying Power Spectra
Authors: Wang R. J.
Published: October 2005

In analyzing a nonstationary time series, one often encounters the problem of estimating associated time-varying autocorrelation functions and power spectra. This paper proposes a method of estimating the time-varying autocorrelation functions and power spectra whereby the nonstationary time series is first divided into a number of windows. The time-invariant autocorrelation function and power spectrum for each window are then determined under the ergodicity assumption. The most important step in this procedure—namely, selection of an optimum window length—is based on the equation derived by Berndt and Cooper [IEEE Trans. Inform. Theory IT-11, 307–310 (1965)]. Implementation of the equation for the purpose of establishing an optimum window length is described. A numerical example for the measurement of time-varying power spectrum is given to illustrate its application. The result of this example indicates that the optimum window length thus established coincides with the intuitively “best” window length.
Generation of Ultrasound by a Dielectric Transducer
Authors: Legros D. , Lewiner J. , Biquard P.
Published: October 2005

In this paper we report the generation of ultrasonic waves in solids, at frequencies varying from 10 to 200 MHz, using a dielectric transducer. It is shown that the dominant process involved is the effect of electrostatic forces acting directly on the propagation medium, and not piezoelectricity or electrostriction of the central dielectric.
Separation and Analysis of the Acoustic Field Scattered by a Rigid Sphere
Authors: Rudgers Anthony J.
Published: October 2005

The scattered field calculated when a plane acoustic wave is incident upon an ideally rigid sphere is considered as a composite and resolved into two parts. One part, which includes the specularly reflected contribution to the field, arises out of scattering by the bright hemisphere—the scattering sphere being divided into two regions by the boundary of the geometrical shadow. The second part, owing to scattering by the shadow side of the sphere, includes the major part of the radiation due to creeping waves. This separation is consimilar with the separation of the scattered field that is made in the creeping-wave formulation of scattering theory. The separation is made here, however, by treating the scattering sphere as a spherical radiator and solving a pair of boundary-value problems by classical means. Each of the boundary-value problems is related to one part of the scattered field. Both parts are found to yield scattering components that are related to “image pulses” such as are predicted when scattering problems involving transient signals are analyzed using theory based on the Kirchhoff approximation. It is found, however, that the image-pulse-type returns, which arise out of the exact classical theory, cancel when the two separate parts of the scattered field are added together, so that, in the complete scattered field, no image-pulse-type return is detectable. It is also found that a secondary creeping-wave component originates in the scattering from the bright side of the sphere. This result indicates that the generation of creeping waves may not be a phenomenon taking place solely at the geometrical shadow boundary. Moreover, it is found that the part of the scattered field which yields the specularly reflected return can be very closely approximated by the scattered field that would be predicted by calculations incorporating the Kirchhoff approximation. Interference between the various components, identified as a result of the separation, explain a number of features of the scattering behavior observed when long pulses are incident on the sphere.
Impact of a Spherical Tool against a Sonic Transmission Line
Authors: Feng Ching-Chiou , Graff Karl F.
Published: October 2005

The impact of a tool against a sonic transmission line is a subprocess of the impact coupling method of sonic power transfer. This process is modeled and the nonlinear governing equation developed in this paper. A probability density function is derived that enables the average rebound velocity of the impacting tool to be established. Numerical results are obtained, for selected material-geometry parameters, on the stress pulses resulting from several conditions of impact, for the rebound velocity as a function of phase angle of impact and for the average rebound velocity. Future work will consider the entire impact coupling process and tools of more complex shape.
Transient Analysis of Lumped and Distributed Parameter Systems Using an Approximate Z-Transform Technique
Authors: Stepanishen P. R.
Published: October 2005

An approximate Z-transform approach is presented to compute at discrete time intervals the time responses of lumped or distributed parameter systems which exhibit wave propagation or time delay effects. The approach was previously developed by Boxer and Thaler [R. Boxer and S. Thaler, Proc. IRE 44, 89–101 (1956)] as a numerical method of solving linear and nonlinear equations and is an extension of the more familiar Laplace transform technique which is used for the analysis of continuous linear systems. Rather than directly utilizing the inverse Laplace transformation to obtain the time function, a mapping of the Laplace transform of the function from the s domain to the z domain is performed via the transformation z = esT, where T is the desired sampling interval of the time function. Unlike the inverse Laplace transformation, which requires the pole-zero structure of the transform to obtain the continuous time function, the sampled time function is then obtained from its z domain representation without using the theory of residues. Numerical solutions to several problems are presented to illustrate the advantages of the approximate Z-transform approach.
The Sea Surface as a Random Filter for Underwater Sound Waves
Authors: Fortuin Leonard
Published: October 2005

When underwater sound waves propagate from a transmitter to a receiver, part of the energy reaches the receiver after reflection and scattering from the sea surface. This boundary effect can be called the impulse response of the sea surface if the incident sound field is caused by a delta pulse. In this paper the Helmholtz diffraction integral is used together with a perturbation technique for the derivation of a formula for the corresponding transfer function. The result is a random function that depends on the frequency of the incident wave, on time, and on the source-receiver configuration. Its validity is limited by three assumptions: (1) the medium is ideal (constant velocity, no subsurface layer), (2) source and receiver depth are many times larger than the surface elevation, and (3) the bottom is infinitely far away. For very high frequencies the formula indicates specular reflection from each surface “highlight.” In the Fraunhofer domain, the transfer function reduces to specular reflection with phase fluctuations. Some results of a statistical analysis are included for that frequency domain.
Sound Propagation in Voigt Fluid
Authors: Raichel Daniel R.
Published: October 2005

One-dimensional sonic propagation in the viscoelastic Voigt fluid is studied through the partial use of the single relaxation theory. The Voigt constitutive equation is shown to be a relaxation equation, and a relaxation time for the fluid is defined. The dispersion of acoustic velocity and the attenuation coefficient, which are compared with those of the Maxwell fluid, are found in terms of the physical parameters of the Voigt fluid and the wave frequency.
Statistics of Multipath Transmission of Finite Bandwidth Signals
Authors: Mark William D.
Published: October 2005

The statistical properties of a random variable E that denotes either the time-averaged power in a received band of noise or the total energy in a received transient waveform are studied for situations where the variablity in E is due to uncertainty in the detailed structure of the multipath transmission channel. The transmission channel impulse response function is modeled by a nonstationary Gaussian random process—a model that predicts the Rayleigh probability density for received amplitudes of transmitted pure tones. General expressions are derived for the mean and variance of E. These expressions are reduced to the practically important case of impulse response functions that are δ-correlated in time. Approximate expressions and bounds are derived for the relative variance of E. Special cases of the results are shown to be in essential agreement with results previously obtained in studies of the responses of rooms to bands of noise.
Observations of Acoustic Ray Deflection by Aircraft Wake Vortices
Authors: Burnham D. , Kodis R. , Sullivan T.
Published: October 2005

Acoustic ray deflection by aircraft wake vortex flows has been observed during landing operations of large aircraft. The phenomenon has been used to detect and locate vortex traces in a plane perpendicular to the runway centerline. The maximum deflection angles observed for a variety of aircraft show qualitative agreement with values predicted for a viscous core.
Natural Frequencies of Clamped and Hinged Bars Having Small Curvature
Authors: Rossettos John N.
Published: October 2005

An analysis of the vibration of slightly curved Bernoulli-Euler beams, which have constant initial curvature, is presented. A closed form general solution to the governing equation is derived, and the natural frequency, as it is affected by curvature and the type of end fixity, is discussed, with results given for the first three modes.
Free Vibration of Anisotropic Rectangular Plates
Authors: Whitney J. M.
Published: October 2005

Solutions for the free vibration of anisotropic plates with other than clamped edge conditions have been previously obtained by approximate energy methods in conjunction with classical beam mode functions. Because of the existence of cross-elasticity bending stiffness terms, however, the beam functions do not satisfy the natural boundary conditions. Numerical results presented for a simple supported anisotropic plate indicate that such an approach yields very slow convergence of the vibration frequencies for highly anisotropic materials, such as graphite-epoxy fiber reinforced composites. Improved results are obtained by using a classical Fourier analysis in which both the geometric and natural boundary conditions are satisfied.
Studies in a Reverberation Room with a Highly Absorbing Sample
Authors: Yegnanarayana B. , Balachandran C. G.
Published: October 2005

This paper relates to a series of measurements undertaken in the reverberation room (25×20×14 ft) at the Indian Institute of Science, Bangalore. It is a common practice with all laboratories install diffusing panels in reverberation rooms for absorption measurements from decay rates. However, it has been observed that diffusers are not entirely satisfactory under all circumstances and hence the need for a method for the proper identification of the initial slope related to the material properties and subjective experience. With this aim in view, measurements have been performed on a large area of a highly absorbing polyurethane foam sample, and the following important features have been observed: (1) Choice of proper writing speed of the high-speed level recorder is necessary to delineate the first part of the decay curve. (2) The loudspeaker location and directional characteristics will determine the proper excitation of the room modes giving rise to a correct initial slope. (3) The microphone should as far as possible be located close to the sample. From a study of the above factors it has been possible to establish an initial slope related to the sound-absorption property of the material.
Aural Harmonics: The Monaural Phase Effects at 1500 Hz, 2000 Hz, and 2500 Hz Observed in Tone-on-Tone Masking When f1 = 1000 Hz
Authors: Clack T. Dean , Erdreich John , Knighton Robert W.
Published: October 2005

At least two explanations can be offered for the monaural phase effects reported in previous tone-on-tone masking experiments. The aural distortion approach leads to the prediction that changes in the phase angle between masker and maskee will cause sensitivity variations only at harmonic intervals. The two-tone interaction approach suggests that phase effects should also be evident at nonintegral multiples of the masker. To test these predictions, six normal listeners traced their thresholds at 1500, 2000, and 2500 Hz in the presence of a 1000-Hz masker at each of five intensities: 50–90 dB SPL in 10-dB increments. Within each session, the phase was shifted in randomly ordered 60° steps through one complete period (of the maskee). When confusions due to a 500-Hz difference tone are avoided by including a narrow-band (270–510 Hz) masking noise, no phase effects are evident at 1500 and 2500 Hz. The thresholds for the 2000-Hz maskee, however, show the usual phase dependencies. These findings are inconsistent with the two-tone interaction explanation and support the interpretation that emphasizes nonlinear response of the auditory system and direct interference between the aural and acoustic harmonics. Furthermore, when estimates of the second aural harmonic are obtained, its magnitude appears to vary directly with f1 intensity at the 2 dB/dB rate predicted from the power law description of amplitude distortion.
Oxygen Availability in Tunnel of Corti Measured by Microelectrode
Authors: Lawrence Merle , Nuttall Alfred L.
Published: October 2005

A method is presented for the insertion of microelectrodes into the scala media and fluid spaces of the organ of Corti without injury to the capillaries of the membranous labyrinth. Electrode placement is made under complete visual control and monitored on a closed-circuit television system. Capillary blood flow and electrode position are constantly observed. With electrodes so placed, electrode current resulting from changes in oxygen concentration is measured as respiratory air to the animal is cut off and restored. Oxygen concentration in the tunnel of Corti decreases and returns to normal much more rapidly than does that of the endolymph of the scala media. These results furnish evidence that the spiral vessels of the basilar membrane (vas spirale) and spiral osseous lamina supply the oxygen to the fluids in the spaces of the organ of Corti.
Measurement of Specific Mechanical Impedance of the Skin: Effects of Static Force, Site of Stimulation, Area of Probe, and Presence of a Surround
Authors: Moore Thomas J. , Mundie J. Ryland
Published: October 2005

This study attempted to investigate the mechanical response of skin-tissue systems under conditions commonly employed in psychophysical investigations of the tactile system. The influence of these conditions on the specific mechanical impedance was determined and evidence was found suggesting that if one desires to avoid altering the mechanical characteristics, then the parameters to be controlled are the pressure exerted by the probe and the area of the probe. The presence of a surround also influenced the mechanical characteristics when the site of stimulation was the volar forearm, but not when it was the finger or the thenar eminence.
Auditory Threshold in the Goldfish (Carassius auratus) as a Function of Signal Duration
Authors: Popper Arthur N.
Published: October 2005

Auditory thresholds were determined in the goldfish (Carassius auratus) for sound pulses with duty cycles from 1%–90% of 100- and 1000-msec periods. Thresholds were also determined for pulses from 10 to 500 msec in duration with at least 490 msec between pulses. Results indicate that there are no differences in threshold between short pulses and continuous tones and that thresholds are the same whether there is a long or short signal off-time between pulses. It is concluded that temporal summation does not occur in the goldfish and that enhanced sensitivity for long sounds, found in mammals, is unnecessary for fish since most fish sounds consist of short pulses. It is suggested that temporal summation most probably occurs in higher auditory centers in the brain of mammals and the lack of these centers is the reason for no temporal summation in goldfish.
Combination Tones and Their Origin
Authors: Smoorenburg Guido F.
Published: October 2005

Combination tones corresponding to f1 − k (f2 − f1), with k a small positive integer, are often audible during stimulation by the two frequency components f1 and f2 (f1 < f2). In this paper primarily the cubic difference tone (CDT) 2f1 − f2 (k = 1) is studied. The research reported is directed at the type of nonlinearity generating the CDT, and at the site of CDT generation. The first experiment shows that the generation of the CDT is affected by a dip (a threshold elevation in a narrow frequency region). The CDT was perceived only when the level of f2 exceeded the elevated threshold. In the second experiment the cancellation method is used. The results suggest that the high-frequency slope of the pattern of stimulation upon which the nonlinearity operates is comparable with the slope revealed in masking experiments. In the last experiments the cancellation method is reconsidered. Estimates of the CDT level found by various other measuring methods, in which the probe tone was presented nonsimultaneously with the stimulus f1, f2, were all lower than the cancellation level. The results are discussed in terms of a nonlinearity intimately coupled with a frequency selectivity. A simple compressing type of nonlinearity is proposed which accounts rather well for the CDT data. The lower estimates of the CDT level found for nonsimultaneous probe tones are attributed to suppression effects. These suppression effects might be introduced by the same nonlinearity.
Is Speech “Special”? Perhaps the Temporal Lobectomy Patient Can Tell Us
Authors: Berlin Charles I. , Lowe-Bell Sena S. , Cullen John K. , Thompson Carl L. , Stafford Marion R.
Published: October 2005

When dichotic nonsense syllables are presented to temporal lobectomy patients at equal intensities, the ear contralateral to the site of the lesion performs more poorly than the ipsilateral ear; if the ipsilateral ear is stimulated below threshold, the contralateral ear performs near 100%. However, if the intensity of speech in the ipsilateral ear is increased above SRT, the contralateral scores drop markedly as intelligibility increases in the ipsilateral ear. This “trade off” does not occur when noise is the competing stimulus. This phenomenon is interpreted as a sign of “speech identification” and is suggested as a potential technique for differentiating speech from nonspeech elements.
Experimental Investigation of Finite-Amplitude Acoustic Oscillations in a Closed Tube
Authors: Cruikshank Donald B.
Published: October 2005

This paper describes an experimental study of the pressure waveforms generated by a piston in a closed acoustic resonance tube. The study was prompted by waveform predictions of Chester [J. Fluid Mech. 18, 44–66 (1964)]. For the experimental system used, a high piston displacement amplitude is required to establish an experimental condition consistent with the approximations of Chester's analysis. Consequently, graphical comparisons between theory and experiment are made at resonance and at two frequencies bracketing resonance for three successively higher piston displacement amplitudes. Although better agreement is expected as the amplitude increases, this increasing agreement is observed only at the frequency above resonance, and not at resonance or below. However, good qualitative agreement between the shapes of experimental and predicted waveforms is found at high piston displacement amplitude. The pressure response curve of the experimental system is found to be asymmetric, i.e., skewed toward higher frequencies. On the basis of this observation, a qualitative argument is presented to account for the waveform inconsistencies between theory and experiment.
Radiation Impedance of a Long Narrow Rectangular Piston in a Plane Baffle
Authors: Lindemann Oscar A.
Published: October 2005

The radiation impedance of a long narrow rectangular baffled piston is investigated order to discover whether its frequency dependence is in any way markedly different from that of a disk. A first assumption that its width is negligibly small in comparison with a wavelength leads to an asymptotic expression valid for frequencies in a neighborhood of zero, and a second assumption that its length is infinite gives an asymptotic expression valid for frequencies in a neighborhood of infinity. For a finite rectangle of large aspect ratio the two approximations overlap and are compatible, enabling composite graph of the radiation impedance to be drawn over the entire frequency range. The result shows that the piston behaves differently in three distinct frequency bands, corresponding to spherical, cylindrical, and plane-wave radiation. The circular piston, in contrast, has no cylindrical middle band.
Comment on “Free Vibrations of Generally Orthotropic Plates” [D. Mohan and H. B. Kingsbury, J. Acoust. Soc. Amer. 50, 266 (1971)]
Authors: Bassily S. F. , Dickinson S. M.
Published: October 2005

In the above paper, characteristic beam vibration modes are used in Galerkin's method to determine the natural frequencies and mode shapes of flexural vibration of generally orthotropic rectangular plates. Three sets of edge conditions are considered: All edges simply supported; two parallel edges damped, the other two free; and a cantilever plate.
Useful Range of a Mechanical Impedance Technique for Measurement of Dynamic Properties of Materials
Authors: Edwards J. L. , Hicks D. R.
Published: October 2005

Many techniques have been developed to measure dynamic mechanical properties of viscoelastic materials. The purpose of this note is to verify the range of properties over which a point mechanical impedance measurement technique will give reliable data, by comparing results with those obtained by a simple resonance technique.
Comparison of Ray Theory and Modified Ray Theory near a Convergence Zone Caustic
Authors: Blatstein Ira M.
Published: October 2005

Modified ray theory was originally intended to be valid in caustic regions where ordinary ray theory is invalid. The two theories are demonstrated here to be in good agreement at relatively large distances into the double arrival region adjacent to a typical convergence zone caustic.
Ultrasonic Relaxation in Aqueous Acetic Acid Solution
Authors: Jackopin Leroy G. , Yeager Ernest
Published: October 2005

Ultrasonic absorption measurements have been made in aqueous acetic solutions at 15 to 85 MHz using pulse-echo and pulse send-receive techniques. A weighted nonlinear regression method has been developed for the computation of the relaxation parameters. A single relaxation has been found with a relaxation frequency at 13.2 MHz in 0.1M acetic acid and 66.1 MHz in 1.0M acetic acid at 25°C. These values and the maximum excess relaxational absorption per wavelength are in good agreement with the values calculated from equilibrium and kinetic parameters for the ionization of acetic acid as determined by non-acoustical techniques (density, conductance, electrode kinetics, and Wien effect II dispersion). The rate constants and reaction volume change of the ionization-association process, calculated from the ultrasonic absorption measurements in acetic acid, are kdissoc = 7.8 × 105 sec−1, kassoc = 4.4 × 1010 M−1 sec−1, and ΔVdissoc = −11.2 cm3/mole at 25°C.
Ultrasonic Attenuation and Velocity in Hot Specimens by the Momentary Contact Method with Pressure Coupling, and Some Results on Steel to 1200°C
Authors: Papadakis Emmanuel P. , Lynnworth Lawrence C. , Fowler Kenneth A. , Carnevale Edmund H.
Published: October 2005

The momentary contact pulse-echo method with pressure coupling has been extended to the measurement of ultrasonic attenuation in hot specimens. Previously, only velocity was measured. In the present method, the specimen is contacted momentarily by one end of a cool buffer rod about three times as long as the specimen. A piezoelectric transducer on the other end of the buffer rod transmits an ultrasonic signal and receives echoes from the buffer/specimen interface and from the free end of the specimen. The echoes are displayed on an oscilloscope and recorded by a camera. Three echoes are required to define both the attenuation coefficient in the specimen and the reflection coefficient at the buffer/specimen interface. Our results in steel show that the solution and precipitation of carbides affect the velocity drastically, while the attenuation is affected by at least one of the following: (1) magnetism, (2) recrystallization, or (3) carbon solubility, and also by grain growth at elevated temperatures.
Stability of Nonlinear Oscillations of an Elastic Rod
Authors: Haight E. C. , King W. W.
Published: October 2005

The stability of plane steady oscillations of a slender elastic rod subjected to lateral harmonic excitation is investigated. For certain values of excitation amplitudes and frequencies the planar response is unstable, and nonplanar motions are parametrically excited. Steady nonplanar motions are characterized by each point on the rod centerline tracing an elliptical path perpendicular to the rod axis. The investigation is restricted to cantilevered rods with nearly equal principal moments of inertia of the cross-section, and excitation is always in the direction of one of the principal axes of inertia. The effects of damping and of slight variations of the natural frequencies associated with motions in the two principal planes are investigated. Supporting experimental evidence is presented. Finally, the principal features of the transversely driven rod response are compared with the response for the same type rod excited axially.
Motion of a Spherical Obstacle Generated by Plane or Spherical Acoustical Waves
Authors: Sidman Robert D. , Handelman George H.
Published: October 2005

A rigid moveable sphere which is part of a mass-spring-dashpot system is constrained to move with one degree of freedom in an acoustical medium. The motion which ensues when the sphere is struck by a transient incident plane wave and, second, by a transient incident spherical wave, is studied. The motion of the sphere is computed and analysis is given for the inverse problem which seeks to determine the properties of the incident wave from the known motion of the sphere.
Speed of Sound in Sea-Water Samples
Authors: Del Grosso V. A. , Mader C. W.
Published: October 2005

Sound-speed equations having standard deviations between 0.013 to 0.101 m/sec are fit to 627 replicate observations on standard sea water modified to salinities between 30 to 41‰ S. Measurements were made for realistic conditions over a total range of 0°–40°C and 0–1000+kg/cm2 (15 000 psi) gauge.
Loudness Enhancement Following Contralateral Stimulation
Authors: Galambos R. , Bauer J. , Picton T. , Squires K. , Squires N.
Published: October 2005

The apparent loudness of a tone pip can be increased by 15 dB or more if it is preceded by a tone burst to the contralateral ear. The experiment is done by delaying the pip, S1, by a variable time, ΔT, after the offset of a contralateral tone; the listener assesses the loudness of S1 by adjusting the intensity of a second tone pip, S2, that follows S1 by 1500 msec. Some parametric explorations of the phenomenon are reported here.
Masking by Narrow Bands of Noise in Proximity to More Intense Pure Tones of Higher Frequency: Application to Measurement of Combination Band Levels and Some Comparisons with Masking by Combination Noise
Authors: Greenwood Donald D.
Published: October 2005

Combination bands generated by a pure tone and a narrow band of noise are detected and produce masking patterns in the frequency region below the primaries (Greenwood, 1969a, 1969b, 1970, 1971a, 1971b). Virtually identical masking patterns are produced by noise bands of external origin, situated on the low-frequency side of a more intense tone. Patterns in both cases take the form of elevations that merge with, or stand in isolation from, the low-frequency side of the masked audiogram produced by the tone, depending on the separation of the band from the tone. This study of masking by bands of external origin was undertaken (a) to measure the effect, if any, of the higher-frequency more intense tone on masking exerted by the noise of known intensity; (b) to permit, thusly, inferences to be made as to the effects of a lower primary on the masking exerted by a combination band below it; (c) to obtain signal/masker ratios for use in estimating combination band levels; and (d) to study one experimental situation bearing on the “additivity of masking” problem. Conclusions pertaining to these objectives are, respectively: (a) that the presentation of a higher-frequency more intense tone with a band of noise does not increase the masking maximum produced by the noise; (b) that it is plausible to assume that masking by combination bands is not affected by the lower primary above it; (c) that the obtained signal/masker ratios can be used to estimate combination band levels; and (d) that, although the tone does not increase masking by the noise, weaker lower-frequency noise can affect masking by the tone.
Study of the Acoustic Reflex in Human Beings. I. Dynamic Characteristics
Authors: Hung Ike J. , Dallos Peter
Published: October 2005

The contralateral acoustic reflex, elicited by wide-band noise and pure tones whose frequencies ranged from 200–2000 Hz, was measured and studied by using dynamic recordings of the change of the input acoustic impedance of the eardrum. Step and sinusoidal (envelope) stimuli with the above carriers at different sound pressure levels (SPLs) were used, and four human subjects with normal hearing were tested. It was shown that the dynamic properties of the acoustic reflex are both frequency- and magnitude-dependent. In general, within the dynamic range of the reflex, the speed of on-response (with step input) seemed to be proportional to the SPL of the stimulus. This proportionality was more clearly observed in the on-response of the reflex elicited by stimuli having pure tone carriers than wide-band noise carriers. The sinusoidal responses of the reflex tended to indicate that the apparent bandwidth of the reflex mechanism increases with SPL. The most distinct frequency-dependent characteristic of the reflex was observed in the on-responses of the reflex with different carriers, namely an underdamped oscillatory response was seen when the carrier frequency fell between 400–800-Hz range and an overdamped on-response outside this range. It was suggested that the magnitude dependence of the reflex could be attributed to a magnitude-dependent nonlinearity of the muscle mechanism, while the frequency-dependent characteristic was due to frequency-dependent attenuation of the sound transmission due to the activity of the acoustic reflex.
Preservation of Constant Loudness with Interaural Amplitude Asymmetry
Authors: Keen Keith
Published: October 2005

The intensity functions which preserve constant loudness under conditions of interaural intensity asymmetry are plotted for pure tones, random noise, and triangular transient stimuli. For all stimuli, the constant loudness function is positively accelerated towards greater decrease per unit increase at the contralateral ear. The rate of acceleration is a function of the binaural summation ratio for each signal. The significance of these data in the design of lateralization studies is discussed.