bluuebunny/crossref_metadata_2025 huggingface dataset:
Wavenumber-Frequency Spectra of Turbulent-Boundary-Layer Pressure Measured by Microphone Arrays
Authors: Blake William K. , Chase David M.
Published: October 2005

Measurements of frequency spectra of pressure along a wind-tunnel wall have been made by single microphones and by a longitudinal array of four flush 0.8-in. circular microphones connected with alternating and with common phase. The alternating-phase array was designed to suppress by wavenumber filtering the background acoustic duct noise at frequencies near 3 kHz. Measured levels set upper limits on low-wavenumber boundary-layer pressure. Analysis indicates that the high-wavenumber (convective) contribution in this frequency range was probably negligible, but it could not be definitely established whether background noise dominated the spectra or whether the upper bound set on low-wavenumber boundary layer noise is a close one. On assumption of wavenumber independence in most of the pertinent low-wavenumber domain, an upper bound is given for the wavenumber spectral density of boundary-layer pressure, and its generalization by assumption of δ*, independence is discussed. At lower frequencies, in identifiable domains where single-microphone and array spectra are dominated by the convective-wavenumber component of boundary-layer pressure, satisfactory agreement is found with theoretical predictions based on current knowledge of the spectral density in the convective-wavenumber domain and on a measured facial-sensitivity distribution for the microphone. In general, salient features of the array spectra correlate well with expectation, and the array technique is demonstrated to be a useful one for the subject purposes.
Parametric Sonar Transmitting Array Measurements
Authors: Mellen R. H. , Browning D. G. , Konrad W. L.
Published: October 2005

Experimental measurements of intensities and beam patterns of a parametric sonar transmitting array are presented. For a mean primary frequency of 720 kHz, secondary source levels up to 90 dB//1 μbar at 1 m were attained at 50 kHz. At this level, however, saturation effects broaden the beamwidth to 8° compared to the unsaturated value of 3°.
Linear Wave-Vector Dispersion of the Shear-Wave Phase Velocity in α Quartz
Authors: Pine A. S.
Published: October 2005

We have observed a splitting in the Brillouin spectrum of the two shear waves that propagate along the c axis in α quartz. This is a consequence of a phase-velocity dispersion linear in phonon wave vector.
Brillouin Scattering and Dispersion and Attenuation of Hypersonic Thermal Waves in Liquid Carbon Tetrachloride
Authors: Stegeman G. I. A. , Gornall W. S. , Volterra V. , Stoicheff B. P.
Published: October 2005

Brillouin spectra of liquid CCl4 (at 20.0°C) have been investigated 20 scattering angles, from 40° to 145°. The spectra were excited by 6328-Å radiation from a He-Ne laser and analyzed with a pressure-scanned Fabry-Perot spectrometer. The measured frequency shifts and linewidths of the Brillouin component were used to determine velocities and attenuations of thermal waves in the frequency range 1.6–4.7 Gc/sec. A large dispersion (>10%) and corresponding change in attenuation were found, characteristic of a thermal relaxation process in this region. A broad new component in the spectrum of isotropic scattering was observed, which is also characteristic of a relaxation process. Analyses of these data were carried out in two ways: one is based on a simple extension of acoustic equations to light scattering, and the other, on Mountain's theory of light scattering in the region of a thermal relaxation. It is shown that the observed spectra and derived data agree with Mountain's theory in all respects. Also, from these data it was possible to evaluate the total internal specific heat CI = 11.6±0.3 cal/mole°C. Within experimental error, this relaxes in a single relaxation time τ = (6.5±0.5) × 10−11 sec.
Brillouin Spectra of Ethyl Ether and Carbon Disulfide
Authors: Gewurtz S. , Gornall W. S. , Stoicheff B. P.
Published: October 2005

Brillouin spectra of ethyl ether and carbon disulfide (at 20.0°C) were investigated for scattering angles of 20°–145°. A single-mode laser was used for excitation; scattered light was collected in a solid angle of 1.5×10−4 sr; and the total instrumental width was ∼100 Mc/sec. Linewidths of 10±5 to 215±10 Mc/sec were measured and velocities determined to an accuracy of ±0.5%. In ethyl ether the phonon velocity and attenuation were constant in the frequency range 0.8–4.1 Gc/sec, and the values agreed with acoustic measurements at 100 Mc/sec. In CS2 a considerable decrease in attenuation was observed in the range 1.7–6.1 Gc/sec, with the value at high frequency approaching the classical attenuation attributed to shear viscosity. This variation in attenuation is in good agreement with the theory of a single relaxation time for the total vibrational specific heat, as established by acoustic measurements in the frequency range 2–200 Mc/sec.
Testing for Isotropy
Authors: Scharf Louis L. , Schmid Charles E.
Published: October 2005

The presence of isolated acoustic noise sources in the ocean produces an anisotropic noise field. Hence, a hypothesis test for detection of these sources can be formulated as a test of H0 (isotropic noise field) versus H1 (anisotropic noise field). The structured approach taken in this paper is to form M beams from N hydrophone elements and then measure the power in each beam. The test for isotropy reduces to acceptance of H0 if the spatial variance of the measured power is less than a predetermined threshold, and acceptance of H1 otherwise. This so-called spatial test is shown to be asymptotically uniformly most powerful invariant for a very natural group of invariance requirements, provided the measured powers are independent through design or suitable transformation. Strengths of the spatial test are that (1) no detailed specification of the anisotropic condition is required, and (2) the predetermined threshold is easily set without prior knowledge of noise levels. Performance curves for the spatial test are presented for specific models of anisotropy and are compared with performance curves of a conventional temporal test.
Comment on “Aerodynamic Sound as a Singular Perturbation Problem” [S. C. Crow, in Aerodynamic Noise, Arnold Goldburg, Ed. (American Institute of Aeronautics and Astronautics, New York, 1970), AIAA Reprint Series Vol. XI]
Authors: Ribner H. S.
Published: October 2005

A misinterpretation by Crow of one aspect of the dilatation theory of flow noise is clarified. It is pointed out that the theory remains valid even when the sound-emitting region is small compared with a characteristic wavelength of the sound. The theory ensures this by requiring that the radius of the region of integration be at least of the order of this wavelength and that the variation of retarded time throughout the region be taken into account.
SIMPLE METHOD TO PRODUCE AN EXPONENTIALLY MODULATED CARRIER WAVEFORM
Authors: Donato R. J.
Published: October 2005

The feedback system of a Brüel & Kjær level recorder is used to produce an exponentially reducing waveform. Such a waveform is useful for checking reverberation-time measurement equipment.
Ear Preference for Dichotically Presented Verbal Stimuli as a Function of Report Strategies
Authors: Gerber Sanford E. , Goldman Phyllis
Published: October 2005

A study was done to investigate lateral asymmetries in the perception of dichotic synthetic verbal stimuli in a group of 24 normal-hearing right-handed subjects. The subjects were tested under the following reporting conditions: (1) free recall, in which the subject reported the stimuli in any order; (2) ordered before, in which the subject was instructed which ear to report first before the presentation of stimuli; and (3) ordered after, in which the subject was instructed which ear to report first after the presentation of the stimuli. It was found that a significant right-ear preference for dichotically presented verbal stimuli existed regardless of the report strategy employed. In all three reporting conditions, the right ear showed a significant superiority of accuracy of response.
Binaural Unmasking of Vocalic Signals
Authors: Mosko James D. , House Arthur S.
Published: October 2005

Auditory unmasking was studied in an experiment that used natural and synthetic vowel sounds as target signals. In all listening conditions, the spectrum level of the noise was constant and the noise was in phase at the two ears, while the interaural phase relations of the signals were manipulated. The results support the idea that maximal threshold shifts occur when the components of the complex signal in the 250- to 500-Hz region are interaurally out of phase. However, the data do not support the idea that the magnitude of the unmasking is a simple function of fundamental frequency. Binaural unmasking of complex amplitude varying stimuli may be best accounted for by considering the amount of energy in the 250- to 500-Hz band relative to the characteristic spectral maxima in the signal. Interaural phase inversions outside the 250- to 500-Hz band have differential effects on unmasking depending upon the amplitude relations between the energy inside and outside this band.
Observations of the Vibration of the Basilar Membrane in Squirrel Monkeys using the Mössbauer Technique
Authors: Rhode William S.
Published: October 2005

The amplitude and the phase of vibration of the basilar membrane and the bony limbus of the cochlea were measured in living squirrel monkeys using the Mössbauer technique. In the middle ear, the vibration of the malleus (and occasionally the incus) was measured. The Mössbauer technique makes possible the measurement of very small velocities, e.g., 0.2 mm/sec. This sensitivity permits measurement of the motion of the malleus at sound-pressure levels (SPLs) of 90 to 110 dB and measurement of the motion of the basilar membrane at 70 to 120 dB SPL, depending on the frequency. The basilar membrane vibrates nonlinearly for frequencies which produce the largest deflections at the spot on the basilar membrane under observation. The ratio of the displacement of the basilar membrane to that of the malleus was observed to have the following characteristics: (1) As the frequency is increased from a low value, its amplitude increases at 6 dB/oct until just below the maximum ratio where the slope increases to about 24 dB/oct; (2) the maximum ratio was about 24 dB for the SPLs used; (3) for frequencies above that producing the maximum ratio, the drop-off rate was approximately 100 dB/oct; (4) the amplitude ratio did not drop off indefinitely but tended to level off; (5) the motion of the basilar membrane differs from the motion of the malleus by 90° at very low frequencies; (6) for frequencies below that producing the maximum ratio, the phase differences between the motion of the basilar membrane and that of the malleus is a linear function of frequency; (7) near the frequency corresponding to the maximum ratio, the phase difference decreases at a faster rate; and (8) the phase difference approaches a constant value (7π 8π or 9π) for high frequencies. Anatomical constraints allowed only a small portion of the basal turn to be studied (6.5–7.5 kHz produced maximum deflection of the basilar membrane in this region).
An Error in Helmholtz's Calculation of the Displacement of the Tympanic Membrane
Authors: Hartman William F.
Published: October 2005

The drum-leverage hypothesis of Helmholtz was apparently substantiated by measurements that he made of the volume displacement of the tympanic membrane. Later experiments by others indicated gross inconsistency with his reported results, and his hypothesis was rejected, but a proper explanation for the difference has been lacking. It is shown that his measurements were probably correct, but that he made a fruitful error in calculation.
Simultaneous Binaural Signal Detection: Comments on “Time Sharing in Auditory Perception: Effect of Stimulus Duration” [N. Moray, J. Acoust. Soc. Amer. 47, 660–661(L) (1970)]
Authors: Sorkin R. D. , Pastore R. E.
Published: October 2005

Moray's [J. Acoust. Soc. Amer. 47, 660–661(L) (1970)] experiment on binaural time sharing leaves several questions unanswered concerning actual differences between single-channel and binaural detectability. We cite recent evidence showing no decrement in the detectability of signals presented simultaneously to each ear, when the signals are of short duration and the same frequency.
Perception of Synthesized Isolated Vowels and h_d Words as a Function of Fundamental Frequency
Authors: Ainsworth W. A.
Published: October 2005

The effect of changing the fundamental frequency on the perception of two-formant vowels and h_d words has been investigated. Raising the fundamental by an octave caused a rise in the mean of F1 of about 5% and a rise in the mean of F2 of about 2%. Isolated and context vowels gave similar results except that the context vowels were recognized more consistently.
Mating-Call Sound Intensities of Anuran Amphibians
Authors: Loftus-Hills J. J. , Littlejohn M. J.
Published: October 2005

Mating-call intensities of five species of Australian anuran amphibians were measured under natural conditions. The sound-intensity values were consistent within species, and ranged from 88 dB for Crinia parinsignifera to 103 dB for Limnodynastes tasmaniensis (0 dB re 0.0002 dyn/cm2) at a distance of 50 cm. On the basis of published hearing threshold data, the maximal effective propagation distances were estimated for Crinia parinsignifera and Hyla ewingi; these were 4 m and 100 m, respectively.
Scattering Theory for Sound Absorption in Fibrous Media
Authors: Attenborough K. , Walker L. A.
Published: October 2005

A simple model consisting of a random array of parallel elastic fibers in air is considered for the purpose of deducing the acoustic behavior of flexible porous media. A scattering analysis is employed and the mechanism of internal dissipation is thus interpreted as the irreversible mode conversion of incident dilatational waves into viscous and thermal waves by scattering at the fiber boundaries. The analysis is initially carried out for a dilute suspension such that the presence of the fiber scatterers is considered only to increase the attenuation of the imbedding fluid. This treatment is subsequently refined to include multiple scattering effects. Expressions for propagation constant, specific characteristic impedance, and surface normal impedance are deduced as functions of fiber radius, fiber concentration, and various physical constants of the fiber solid and air. The phenomenological parameters required in other theories are thus avoided. Furthermore, for a typical glass-fiber material the multiple scattering theory is found to be in reasonable agreement with measurement.
Brillouin Scattering in Multiply Relaxing Liquids
Authors: Bhatia A. B. , Tong E.
Published: October 2005

The spectral distribution of scattered light is calculated for the model of a liquid in which the bulk and shear relaxation processes are each characterized by a multiplicity, or a continuous set, of relaxation times. The treatment is a generalization of that given by the authors previously [Phys. Rev. 173, 231 (1968)] in which bulk relaxation was ascribed to the relaxation of a thermodynamic order parameter relaxing with a single relaxation time. It is found that, in general, one has to introduce two independent distribution functions associated with the bulk relaxation times. Only when all the bulk relaxation processes are of the same type (pressure induced, temperature induced, etc.), does the expression for the spectral function contain just one distribution for bulk relaxations. This is in contrast to the results obtained by previous workers and may have significance in relation to a reported discrepancy in interpreting (in terms of a single distribution function for bulk relaxation) experimental data on Brillouin scattering and ultrasonic absorption in glycerine.
Forced Oscillations of Mixed Damped Symmetric and Asymmetric Systems
Authors: Sachs Herbert K.
Published: October 2005

The effects of nonlinear (mixed) damping forces (such as viscous and dry friction damping, combined and separately, on the forced vibration response of a system) are discussed. A recursion procedure is developed to determine the coefficients of the general solution of the equation of motion. This method is then applied to solve asymmetrically damped systems, such as those for which the damping parameters assume different values for forward and backward motion. The results of representative calculations are presented and their significance is discussed.
Axisymmetric Vibrations of Isotropic Composite Circular Plates
Authors: Stavsky Yehuda , Loewy Raphael
Published: October 2005

A Kirchhoff-type theory is established for axisymmetric motions of heterogeneous isotropic circular plates. It is shown that a coupled extensional-flexural inertia term exists, in addition to the classical extensional and rotatory inertia terms. An analogy is found between the composite plate problem and the vibrations of homogeneous shallow spherical shells. The obtained sixth-order system of equations is solved in closed form in terms of Bessel functions, with an argument determined from a characteristic cubic equation. A transcendental frequency equation is then derived for a circular composite plate with clamped edge conditions. Numerous examples are studied, showing the significant effect of plate heterogeneity on its vibrational response. Possibility of composite systems to transcend the frequencies of the individual constituents is clearly indicated by the theoretical results and checked experimentally.
Calculations of Underwater Explosion Pulses at Caustics
Authors: Blatstein Ira M.
Published: October 2005

A method for predicting underwater explosion shock-wave pressure histories in caustic regions is described. This method involves the incorporation of various propagation effects, i.e., finite-amplitude, absorption, and refraction effects, into a Fourier series representation of the initial shock wave from an underwater explosion. Refraction effects are accounted for by the use of a solution to the wave equation derived by Silbiger and Sachs. Pressure histories calculated using this method are compared with experimental results from ocean and flooded quarry tests. For the oceanic convergence zone case, quantitative agreement with the experimental pressure histories is demonstrated. This agreement is verified for a region 4000 ft wide surrounding the caustic. For the flooded quarry case, the peak pressure on and near the caustic is accurately predicted.
Analysis of Acoustic Wave Scattering by a Composite Rough Surface
Authors: Huang James C.
Published: October 2005

The effect of surface irregularities upon the scattering performance of a composite rough surface that consists of scattering elements of structure sizes in quite different scale uniformly superimposed one on the other is described and analyzed. The theory is formulated on the basis of the principles of both geometrical optics and physical optics through the introduction of the surface-slope distribution with a result clear in physical meaning and simple for analysis. Three factors determine the dominating role played by the component irregularities in wave scattering: surface slope, incident angle, and wavelength. An example showing the angular distribution of wave scattering by a composite rough surface at frequencies of 1 and 100 kHz about 7 oct apart is presented. At low frequency, the backscattering is confined to a narrow region of about 10° centered at the direction of normal incidence, while at high frequency, the angular distribution expands to about 150°. As for the bistatic scattering the angular distribution of the scattered acoustic wave increases from about 25° centered at specular reflection to 180°. This effect of the small-scale surface irregularities is to broaden the angular distribution of the scattered acoustic wave at high frequency.
Development of a Mathematical Model for the Class V Flextensional Underwater Acoustic Transducer
Authors: Nelson Ralph A. , Royster Larry H.
Published: October 2005

The purpose of this paper is to present development of a mathematical model for the Class V flextensional underwater acoustic transducer. The transducer is approximated through the consideration of three distinct problems. A thin piezoelectric disk with an arbitrary impedance on its edge is solved in terms of Bessel functions. The shell vibration problem is solved using a finite-difference model to approximate the shell. The acoustic radiation problem is solved by obtaining the source density distribution for a system of quadrilaterals representing the transducer. With the source density of each quadrilateral, the near- and farfield pressures and velocities can be found. Utilizing these three components, a model is then constructed for the transducer. A comparison of the results from the mathematical model is made with those obtained from experiments in order to validate the model.
Transient Radiation from Pistons in an Infinite Planar Baffle
Authors: Stepanishen Peter R.
Published: October 2005

An approach is presented to compute the near- and farfield transient radiation resulting from a specified velocity motion of a piston or array of pistons in a rigid infinite baffle. The approach, which is based on a Green's function development, utilizes a transformation of coordinates to simplify the evaluation of the resultant surface integrals. A simple expression is developed for an impulse response function, which is the time-dependent velocity potential at a spatial point resulting from an impulse velocity of a piston of any shape. The time-dependent velocity potential and pressure for any piston velocity motion may then be computed by a convolution of the piston velocity with the appropriate impulse response. The response of an array may be computed using superposition. Several examples illustrating the usefulness of the approach are presented. The farfield time-dependent radiation from a rectangular piston is discussed for both continuous and pulsed velocity conditions. For a pulsed velocity of time duration T it is shown that the pressure at several of the field points can consist of two separate pulses of the same duration, when T is less than the travel time across the piston.
Influence of Flow and High Sound Level on the Attenuation in a Lined Duct
Authors: Kurze Ulrich J. , Allen Clayton H.
Published: October 2005

The influence of turbulent flow on the sound attenuation in a narrow rectangular duct is calculated by a finite difference approximation of the differential equation for inviscid flow. The absorptive lining at one duct wall is characterized by a flow-independent wall impedance. Results are found in good agreement with experimental data from a duct with 1-in.2 open area lined on one side with a resistive layer of very fine metal fibers in front of a partitioned air backing. For resistive layers of fibers with larger diameter or of perforated plate used in the same configuration, the wall impedance depends greatly upon the flow velocity. A correlation is found between the nonlinearity of resistive layers due to turbulent flow and due to high sound-pressure levels in a duct. The influence of the nonlinearity due to high sound-pressure levels up to 160 dB is studied in the absence of flow. Measured attenuation data agree with those from a theoretical model, which correlates the varying attenuation along the duct with the varying sound-pressure difference across the resistive lining. By comparison of theoretical and experimental results, the influence of nonlinearity due to turbulent flow can be described by an equivalent level of sound-pressure difference across the resistive lining. A biasing effect of flow on nonlinear duct lining material linearizes the attenuation along the duct, if that equivalent level due to flow exceeds the actual sound level.
A Simple Way to Eliminate Diffraction Lobes Emitted by Ultrasonic Transducers
Authors: Martin Franklin D. , Breazeale M. A.
Published: October 2005

Diffraction lobes can be eliminated from the ultrasonic wave pattern emitted by an ultrasonic transducer by producing a Gaussian distribution of amplitudes across the transducer surface. A simple way to accomplish this is described.
Velocity Dispersion of the Lowest-Order Longitudinal Mode in Finite Rods of Square Cross Sections
Authors: Booker R. E.
Published: October 2005

The measured velocity dispersion of an isotropic square aluminium bar shows close agreement with that predicted by the modified theory of Nigro, except for one “displaced” harmonic which lies off the smooth graph, and another harmonic that is split into two resonances (a doublet). The displaced harmonic can be attributed to the proximity of an “end resonance,” and the doublet occurs at the frequency where the first complex mode becomes real for the equivalent cylinder.
Modification of the Bessel-Fubini Solution That Includes Attenuation
Authors: Cary Boyd
Published: October 2005

Burgers' equation is a nonlinear acoustical wave equation which approximately governs the propagation of finite-amplitude waves with dissipation and spreading losses. A new solution is derived for a spherically diverging sinusoidal waveform. By means of this solution, the amplitudes of the harmonic levels above the third can be more readily estimated than by successive approximation.
Stimulus Features in Signal Detection
Authors: Ahumada Al , Lovell John
Published: October 2005

Short bursts of computer-generated Gaussian noise were rated by observers for the presence or absence of a 500-Hz signal tone burst. A multiple regression analysis found for each observer the linear combination of the energies in narrow bands around the tone frequency that best predicts his total ratings. The estimates of the regression coefficients provide graphs of the “frequency responses” of the observers. Most of the reliable variance in the total ratings was accounted for by the regression analysis in terms of energy in narrow bands. Differences among observers are explained in terms of differential weighting by observers of features labeled “tone presence,” “pitch,” and “loudness.”
Effects of the Electrical Stimulation of the Crossed Olivocochlear Bundle on Cochlear Potentials Recorded with Intracochlear Electrodes in Guinea Pigs
Authors: Konishi Teruzo , Slepian Jacob Z.
Published: October 2005

The effect of electrical stimulation of the crossed olivocochlear bundle (COCB) on cochlear potentials was studied in anesthetized and immobilized guinea pigs. Sound-evoked responses and the endocochlear potential were measured simultaneously in the basal turn. The time course and the magnitude of the slow negative potential in the scala media produced by COCB stimulation can be modified by parameters of COCB stimuli. Augmentation of cochlear microphonic and inhibition of whole-nerve action potential were found to be dependent on the slow negative potential in scala media and on parameters of the acoustic stimulus. The summating potential showed increase of the positivity with COCB stimulation. The role of the positive summating potential on the inhibition of action potential was discussed.
Detection of a Narrow-Band Noise as a Function of the Interaural Correlation of Both Signal and Masker
Authors: Wilbanks W. A.
Published: October 2005

The signal, a 135-Hz noise centered at 250 Hz, was partially masked by continuous wide-band noise. The interaural correlation of both signal and masker was varied between +1.00 and zero. With a correlated masker (N0), detection is about 14 dB better with an uncorrelated signal (SU) than with a correlated signal. The masking-level difference (MLD) diminishes as the correlation of the signal is increased to unity and as the correlation of the masker is decreased to zero. The results imply that sizable MLDs are obtained under those conditions where the addition of the signal to the noise results in a decrease in the correlation between the stimulus events at the two ears.
Ultrasonic Scans of the Dorsal Surface of the Tongue
Authors: Minifie Fred D. , Kelsey Charles A. , Zagzebski James A. , King Thomas W.
Published: October 2005

Echograms of the dorsal surface of the tongue in the midsagittal plane and in coronal oblique planes are presented. Comparisons are made among tongue height measurements obtained from the transverse and longitudinal echograms and from lateral head x rays. It is concluded that ultrasonic scanning can provide information on the shape of the dorsal surface of the tongue during sustained utterances and in the articulatory rest position.
Effects of Interstimulus Interval on the Listener's Ability to Perceive an Intensity-Produced Lateral Shift
Authors: De L'Aune William , Elfner Lloyd , Leftwich Marilyn , Perrott David
Published: October 2005

The results of this study indicated that the interval between the standard and the test stimulus has little, if any, effect on the listener's ability to perceive an intensity-produced lateral shift in a binaurally fused auditory image at frequencies of 1 and 4 kHz.
The Auditory Threshold for Short-Duration Pulses
Authors: Tempest W. , Bryan M. E.
Published: October 2005

Data on the variation in quiet threshold with stimulus duration for tone pulses have been used to examine the validity of an integration model of the ear's behavior. It is found that the ear responds to short-duration tone pulses in approximately the manner expected of a single time constant integrator, but that there is a significant frequency effect. It is concluded that, within the limits of experimental accuracy, the results can be described either by a reduction in integration time with increasing frequency (from 200 msec at 125 Hz to 100 msec at 10 kHz), or by a constant integration time of 200 msec with a reduction in slope of the integration function as the frequency increases from 125 Hz to 10 kHz.
Regulation of Vocal Intensity during Vocal Fry Phonation
Authors: Murry Thomas , Brown W. S.
Published: October 2005

As yet, there are no data concerning the regulation of vocal intensity over a range of frequencies in vocal fry phonation. The purpose of this study was to examine changes in vocal intensity and fundamental frequency during vocal fry phonation. Subjects sustained vocal fry for 3 sec at three points in their total vocal fry range and the intensity was recorded. Thereafter, the subjects sustained vocal fry at the three recorded intensities previously obtained and the fundamental frequency recorded. The findings indicated that vocal fry is produced at low intensities in relation to intensity levels noted by previous investigators for the modal and falsetto registers. Furthermore, a dependency between the intensity level and the fundamental frequency of fry phonation for each subject was noted.
Sinusoidal Horns
Authors: Nagarkar B. N. , Finch R. D.
Published: October 2005

It is pointed out that a sinusoid satisfies Salmon's criterion for a good horn shape. Calculations have been made of the throat impedance of sinusoidal horns of various dimensions, including the case of a single globe terminating in a cusp. Depending on the relative dimensions at the mouth and throat, the device may be used as an impedance transformer. Experimental determinations of directivity of an underwater horn have been made and were found to compare favorably with conical horns. Finally, it is demonstrated that several musical instruments employ sinusoidal cavities, the bell of the English horn being discussed in particular.
Analysis of the Transient Excitation of a Transversely Isotropic Rod
Authors: Mengi Y. , McNiven H. D.
Published: October 2005

The response of a semiinfinite transversely isotropic rod to a time-dependent input on the end of the rod is found using the method of characteristics. The rod is of circular section and the material of the rod is arranged so that the axes of isotropy are parallel to the axis of the rod. To reduce the problem to one where motions depend on only one space variable and time, use is made of an approximate theory developed by the authors in a previous study. Numerical results are found for an input which has a step distribution in time and for two different materials, magnesium and a fiber-reinforced material. For each material the response is found in terms of four quantities: radial strain, axial strain both on the lateral surface and along the axis of the rod, and the generalized axial stress.
Vertical Cross Correlation of Noise from a Horizontal Surface
Authors: Rein Charles R.
Published: October 2005

A theoretical study of the cross correlation of noise from a horizontal surface is presented. Only spatial separations in the vertical direction are considered. The ratio of the depths of the receivers is a parameter considered in the analysis so that the results might apply near the surface of the deep ocean, in the regions of shallow water where there is no bottom reflection, or where the receivers are not sensitive to signals from below. In previous work only receiver depth ratios close to unity were considered, so the results applied only to special cases such as surface-noise cross correlation in very deep water. The results indicate that the cross-correlation function depends very strongly on spatial separation of the receivers but very weakly on the ratio of the depths of the receivers. It is suggested, therefore, that the literature which applies to vertical correlation of surface noise in deep water can also be applied when the receivers are close to the surface.
Transverse Horizontal Coherence of Explosive Signals in Shallow Water
Authors: Wille P. , Thiele R.
Published: October 2005

Transverse horizontal cross-coherence lengths as a function of signal frequency were measured by a hydrophone array 80 m long under homogeneous winter conditions with heavy sea state. The decrease of the normalized coherence length with the acoustic wavenumber is shown as an example of sound propagation parallel to the wave crests and is compared with published reverberation measurements. The cross-coherence length is interpreted in a simple model computation as the reciprocal of a medium-dependent angular uncertainty.
Helicopter Noise due to Blade-Vortex Interaction
Authors: Widnall Sheila
Published: October 2005

The generation of impulsive sound, commonly called blade slap, due to blade-vortex interaction for helicopter rotors is discussed. The unsteady lift on the blades is calculated using linear unsteady aerodynamic theory for an oblique gust model of the blade-vortex interaction. A theoretical model for the radiated sound due to the transient lift fluctuations is presented. Expressions for the directivity, frequency spectrum, transient signal, and total power of the acoustic signal are derived. Typical results are presented and discussed. Calculations of the transient signal are presented in comparison with recent experimental results. The agreement is very good.
Experiments on the Fluid Mechanics of Whistling
Authors: Wilson T. A. , Beavers G. S. , DeCoster M. A. , Holger D. K. , Regenfuss M. D.
Published: October 2005

Experiments to investigate the fluid mechanics of whistling are reported. A model, consisting of a cylindrical cavity with rounded holes at each end, is used to simulate human whistling. It is found that the frequency is very near the Helmholtz resonator frequency, and that the resonator can be excited by flow through the smooth-edged orifices bounding the resonant cavity. Furthermore, it is found that the flow velocity of the jet which excites the resonator must lie between limits that are proportional to frequency and that increase with both diameter and thickness of the orifice. It is concluded that whistling can be included in the same class of sound sources as the Rayleigh bird call and the Pfeifentöne, since the essential mechanism for exciting them depends on the instability of a jet to the formation of vortex rings and the interaction of the rings with a rigid boundary in the flow.
A New Equation for the Speed of Sound in Seawater
Authors: Frye H. W. , Pugh J. D.
Published: October 2005

A set of data was extracted from the reported sound-speed measurements of Wilson by including only those combinations of temperature, salinity, and pressure that naturally occur in seawater. After eliminating Wilson's later (October) measurements [W. D. Wilson, “Equation for the Speed of Sound in Sea Water,” J. Acoust. Soc. Amer. 32, 1357(L) (1960)] as incompatible with his original (June) set [W. D. Wilson, “Speed of Sound in Sea Water as a Function of Temperature, Pressure, and Salinity,” J. Acoust. Soc. Amer. 32, 641–644 (1960)], an 11-term equation was derived which fits the remaining data with a standard error of estimate of 0.10 m/sec, a significant improvement over the published equations of Wilson. Some features of a data set that will aid in the derivation of an empirical sound-speed equation are mentioned.
On the Propagation of Infrasound from Rockets: Effects of Winds
Authors: Balachandran Nambath K. , Donn William L. , Kaschak George
Published: October 2005

Acoustic signals received in the northeast coastal regions of the United States from rockets launched at Cape Kennedy show strong seasonal effects. For the Saturn V rockets, strong signals are received in winter, very weak signals in summer, and weak signals in the transitional months of early fall and spring. These seasonal effects are attributed to the winds in the stratosphere (around an altitude of 50 km). In winter, when strong signals are received, the stratospheric winds have strong components in the direction of propagation of the signals. These components are weak during the transitional months, and during summer the stratospheric winds have components in the direction opposite to that of the signal propagation. It is shown that calculations of horizontal trace velocities provide an indirect method of estimating upper atmospheric winds.
The Measurement of Loudness Level
Authors: Bauer Benjamin B. , Torick Emil L. , Allen Richard G.
Published: October 2005

This paper is a survey and a progress report on present and potential instrumentation to measure loudness levels of sounds. The development of the sound-level meter (SLM) in the 1930's, its technological and psychoacoustical evolution, and its evaluation as a measurement device are discussed. A loudness-level monitor, designed to measure the relative loudness level of broadcast programs directly on an indicating instrument, and the development of a new set of equal-loudness contours are described, together with a new law of loudness-level addition for combined bands of noise which was discovered during the research. An experimental loudness level meter, devised by adapting CBS Laboratories' loudness level monitor and the potential development of an accurate and practical loudness-level indicating device are discussed. The results of psychoacoustic evaluations of the loudness level meter versus sound-level meter are given.
Localization and the Law of the First Wavefront in the Median Plane
Authors: Blauert Jens
Published: October 2005

Test persons having their heads held in a fixed position were stimulated simultaneously from the front and the rear with identical broad-band (music and noise) signals. Between the front and rear signal, a time delay of maximum ±880 μsec could be set. It was found that the direction of the sound sensation coincided with the angle of incidence of the first wavefront for delay times greater than about ±550 μsec. For smaller delay times, however, the direction of the sound sensation depends on the spectrum of the ear signals and can be predicted by applying the concept of directional bands.
Aural Combination Tones and Auditory Masking
Authors: Greenwood Donald D.
Published: October 2005

In experiments mapping pure-tone masked audiograms at low to moderate masker intensities, in which the signal is either a pure tone or a narrow band of noise, a notch appears on the high-frequency side of the masker with a low point at a frequency one critical bandwidth from the masker frequency. The evidence indicates that this notch is caused by the detection, on the lower-frequency side of the masker, of the cubic combination tones that are produced by the addition of masker and signal. At higher masker intensities, the difference tone may also be involved in accordance with the conclusions of Wegel and Lane [Phys. Rev. 23, 266–285 (1924)]. Similar results are obtained when a very narrow band of noise masks a pure-tone signal. The implication that the same process that creates combination tones creates combination bands further supports other evidence as to the mechanical nature of combination tones. The immediate further implications that combination bands or tones arising from complex maskers should produce low-frequency masking effects in the same way as external stimuli also has been tested and confirmed over a wide range of masker intensities and spectra. The maskers consisted of pairs of tones, tones plus narrow bands of noise, pairs of narrow bands of noise, and single bands of noise. Some of the implications of these results for cochlear physics and critical bandwidth are outlined.
Spectral Basis of Auditory “Jitter” Detection
Authors: Pollack Irwin
Published: October 2005

The contribution of high-frequency and of low-frequency spectral information to the detection of temporal variability or “jitter” of auditory pulse trains was examined. Pulse trains were subjected to low-pass, to bandpass, and to high-pass filtering. Jitter discrimination for low-frequency pulse trains is substantially poorer than for high-frequency pulse trains. The reason is not that the low spectral frequencies within low-frequency pulse trains interfere with jitter discrimination, nor that low-frequency pulse trains contain insufficient high-frequency spectral information. Rather, it appears that the spacing between high-frequency spectral components of low-frequency pulse trains is too close to permit effective resolution.
Recognition of Phase Changes in Octave Complexes
Authors: Raiford Carolyn A. , Schubert Earl D.
Published: October 2005

It is generally accepted that even trained listeners have great difficulty perceiving static phase differences in two-tone stimuli. However, if the waveform with the changed phase is “inserted” into a longer signal, most observers can reliably detect whether the change has been made. This study used this “insert” method to compare a series of waveforms which differed from a standard waveform by 15°, 30°, 45°, 60°, 75°, 90°, 102°, 150°, and 180°. The standard waveform was A sin2π(250)t+B sin[2π(500)t+90]. By the time the comparison waveform differed from the standard by 60°, observers could perceive the phase change correctly on over 75% of the trials. An attempt is made to identify the cues which permit the system to recognize such nonenvelope phase changes, but the data do not permit positive identification of these cues.
Intracochlear Potential Recorded with Micropipets. III. Relation of Cochlear Microphonic Potential to Stapes Velocity
Authors: Weiss T. F. , Peake W. T. , Sohmer H. S.
Published: October 2005

Cochlear potential response to tones of known sound pressure was recorded with micropipets from the three scalae of the basal region of the cat's cochlea. By using an average transfer function for the middle ear of the cat, we calculated the complex ratio of cochlear potential response to stapes velocity, E/Ẋs. |E/Ẋs| is approximately constant for a decade or two of frequency in the range 100 Hz–10 kHz. As frequency decreases below 100 Hz, |E/Ẋs| decreases and ∠ (E/Ẋs) becomes positive. As frequency increases above a few kilohertz, |E/Ẋs| decreases and ∠ (E/Ẋs) becomes negative. The dependence of E/Ẋs on frequency for potential in scala media is somewhat different from that in scala tympani. To interpret our measurements, we postulate a model that relates cochlear microphonic potential, V(x, f), to stapes displacement, Xs(f), in terms of three cascaded transformations: mechanical, H(x, f); transduction, T(f); and electric, W(x,f). According to the model, the transfer function can be expressed as V(x,f)/Xs(f) = H(x,f) ⊗[T(f)W(x,f)], where ⊗ denotes convolution on x (distance from stapes). Special cases of this relation are discussed and compared with experimental data.
Auditory Critical Bandwidth for Short-Duration Signals
Authors: Srinivasan R.
Published: October 2005

A new experimental technique is proposed to estimate the bandwidth of the auditory-filter mechanism when detecting short-duration sinusoidal signals masked by wide-band noise. The experiment requires the use of only wide-band noise and two signals of the same frequency, power, and duration, but having different energy density spectra. The special feature of this technique is that the subjective impression made by the masking noise remains the same throughout the experiment unlike experiments that employ progressively changing bandwidths of the masking noise. This avoids the possibility of any change in the parameters of the detection mechanism due to changes in the subjective impression made by the noise. The analysis makes use of the energy detection model consisting of a bandpass filter, square-law rectifier, and an integrator to describe the auditory detection system. A rectangular filter and an LCR single tuned filter have been considered in the analysis. From the experimental results it is found that the rectangular filter provides a better description of the auditory-filter mechanism than the single tuned filter. The bandwidth estimates show an increase with signal frequency. The results also support the idea of a minimum auditory-filter bandwidth for a continuous or long-duration signal and increased values for short-duration signals depending on the signal duration.
Detection of Binaural Tones as a Function of Masker Bandwidth
Authors: Wightman Frederic L.
Published: October 2005

Several experiments have shown that the difference in masked threshold between signals in the S0M0 and SπM0 conditions, the masking-level difference (MLD), increases markedly with reduction in masker bandwidth. However, there are two inconsistencies this result. First, apparently similar experiments conducted by different laboratories have produced quite different results. Second, the MLD-bandwidth relation appears to be nonmonotonic; with very narrow-band maskers (e.g., a pure tone), the MLD is often small. The results of the experiments reported here suggest that these problems arise from anomalies in the S0M0 data alone. It appears that in some narrow-band masking conditions the SπM0 threshold is spuriously low, resulting in deceptively small MLDs. The proposed explanation is that observers detect signal energy which falls outside the masker band, for when this energy is attenuated by filtering the signal, the S0M0 threshold rises dramatically. The SπM0 threshold is unaffected by this manipulation. With specially filtered signals, the nonmonotonicity of the MLD-bandwidth relation is considerably reduced, and MLDs with continuous pure-tone maskers are observed which are nearly as large as the largest narrow-band noise MLDs ever reported (28 dB).