bluuebunny/crossref_metadata_2025 huggingface dataset:
Adjointness properties for differential systems with eigenvalue-dependent boundary conditions, with application to flow duct acoustics
Authors: Kraft R. E. , Wells W. R.
Published: October 2005

When the boundary conditions at the two endpoints of a second order differential system depend explicitly upon the eigenvalues such that the system becomes non-self-adjoint, a generalized condition of orthogonality which includes endpoint terms can be developed. The generalized orthogonality condition is used to determine modal coefficients for the expansion of arbitrary functions in series of eigenfunctions. The method is applied to the particular ease of acoustic wave propagation in a rectangular duct with a uniform mean flow profile and walls with finite acoustic impedance. The ability of the eigenfunction expansion to converge to a plane-wave acoustic pressure profile is demonstrated under a variety of flow, frequency, and wall impedance conditions.
A new approach to acoustic filtering with lined ducts
Authors: Ingard Uno , Patrick William P.
Published: October 2005

We consider a lined duct which is divided into two parallel branches by means of a rigid partition. The phase speed of the fundamental mode in each branch depends on the liner configuration and can differ markedly from the free-space phase speed. If the liners in the two branches are not the same, the corresponding phase speeds will be different and a relative phase lag between the waves in the two branches results. This, in turn, leads to interference between these wave components (and their reflections), both at the exit and the entrance of the parallel branch pair. We have demonstrated both analytically and experimentally that this interference can be exploited for the purpose of obtaining a low-frequency attenuation which is substantially larger than the attenuation of the unpartitioned duct. [This work was supported in part by the U.S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-0019 and in part by the U.S. Department of Transportation under Grant Agreement DOT-OS-3011.]
Systematic method to determine the acoustical characteristics of series-parallel duct configurations using transmission matrices
Authors: Patrick William P.
Published: October 2005

The design of duct systems to minimize their transmitted sound requires a calculation procedure which can handle various duct geometries and liner configurations. Drawing upon the experience of electrical and mechanical engineers in applying matrix techniques to the analysis of electrical circuits and vibrating systems, a systematic method is developed to determine the acoustical characteristics of complicated duct arrays (“acoustical circuits”). By defining impedance, admittance, and transmission matrices for each component of the duct system, the sound transmission characteristics for the complete system can be obtained by the appropriate combination of component matrices. System optimization is facilitated because elements of the component matrices appear explicitly in the resultant matrices characterizing the overall duct system. The rules governing the combination of component matrices of lined duct sections joined in series and/or in parallel are set forth. Example problems are presented in which the transmission loss is determined for N ducts aligned in parallel and for a series-parallel lined duct combination. [This work was supported by the U.S. Department of Transportation under Grant Agreement DOT-OS-3011.]
Effects of ground cover and reflecting surfaces on sound-level meter measurements
Authors: Proctor Thomas M. , Magrab Edward B.
Published: October 2005

The effects of soft (grass) and hard (asphalt) horizontal reflecting planes on the measurement of the sound pressure level have been determined as a function of source-receiver distance for 15 one-third octave bands of noise from 250 to 6300 Hz and for several combinations of heights of the source and receiver relative to the reflecting surfaces. Comparisons are made between these measurements (semifree field) and measurements made in a free field (anechoic chamber). It is found that interference effects, characterized by the ratio of the difference between the distances of the direct and bounce paths to the wavelength, tend to dominate the semifree-field data and show strong noise-band dependency. Computed A-weighted sound pressure levels are compared for the various semifree-field and free-field source-receiver combinations. A second and more complicated configuration consisting of two orthogonal intersecting planes has also been studied. Again, comparisons to the free-field data have been made.
Some effects of the atmosphere and microphone placement on aircraft flyover noise measurements
Authors: Hosier Robert N. , Hilton David A.
Published: October 2005

The NASA Langley Research Center recently participated in a joint program with the FAA to study the effect of varying atmospheric conditions relative to certification type noise measurements. These tests were made under various atmospheric conditions at two test sites, Fresno, California and Yuma, Arizona, using the same test aircraft, noise, and weather measuring equipment, and personnel. The opportunity was taken to obtain flyover noise measurements under controlled test aircraft operating conditions for use in the NASA Langley Research Center in-house noise propagation program. Measurements were made to determine the effects of the atmosphere and of microphone placement on aircraft flyover noise. Presented in the paper are descriptions of the test setup and the type of measurements obtained for characterization of not only the acoustic signature of the test aircraft, but also specific atmospheric characteristics. Data are presented in the form of charts and tables which indicate that for a wide range of weather conditions, at both site locations, noise data were repeatable for similar aircraft operating conditions. The placement of microphones at ground level and also 1.2 m over plowed earth and concrete illustrate the effects of ground reflections and surface impedance on the noise measurements.
Effects of weather on sound propagation
Authors: Schomer P. D.
Published: October 2005

There are a number of general statements dealing with sound propagation during certain weather conditions such as “sound ‘reflects' from low clouds,” “sound travels better downwind and over water,” etc. These effects are explained and conditions which limit these effects are explored. Turbulence is also sometimes described as a “sound absorber,” although this may not be the primary cause of amplitude reduction. As a summation, practical use is made of the above discussion to indicate those conditions conducive to sound propagation and those conditions which minimize propagation. This information can be used to minimize the noise impact of infrequent large amplitude sources, such as result from quarry operations, demolition, etc.
Use of reflecting panels to modify outdoor loudspeaker sound pressure level contours
Authors: Davy B. A. , Meyer N. J.
Published: October 2005

In an attempt to reduce sound entering communities surrounding a large open-air amphitheatre during rock concerts, a study was made of the loudspeaker system. A constraint on the problem was a lack of flexibility in locating, orienting, and phasing the speaker systems. To redirect some of the energy spilling out of the amphitheatre, large reflecting panels were mounted above the speakers extending upwards at a slight angle. A series of measurements were made to test a prototype panel. Tower mounted speakers were driven with octave bands of random noise between 500 Hz and 4 KHz. The measurement microphone was placed on a tower extendable from 10 to 50 ft, thereby allowing measurements from 5° below to 25° above the horizontal speaker axis. The results of these measurements indicated a potential reduction of A-weighted noise levels in the community of 3 to 4 dB with no apparent effect upon sound levels in the amphitheatre seating area.
Acoustic reflex threshold-duration functions for normals and noise-induced permanent threshold shift
Authors: Robinette Larry N. , Burchfield Samuel B.
Published: October 2005

Effects of temporal auditory integration on acoustic reflex thresholds were investigated for adult subjects with normal hearing and those with noise-induced permanent threshold shift (NIPTS). Threshold-duration functions were determined for 1-, 2-, and 4-KHz pure tones and for broad-band noise. Acoustic reflexes were monitored using an impedance technique for stimulus durations of 20, 50, 100, 200, and 500 msec. A measurement technique was developed which included observation of the impedance bridge output in conjunction with latency time to confirm the occurrence of reflex activity. Results indicated that there may be flattening of acoustic reflex threshold-duration functions for persons having noise-induced hearing losses. Acoustic reflex thresholds for 20-msec stimuli were found to be similiar for both the normal and NIPTS groups, and differences between the two groups increased as stimulus duration was increased. The hearing-impaired subjects seemed to have a decreased ability to utilize additional stimulus energy provided by increased stimulus duration.
Continuously variable binaural loudness balance procedure
Authors: Gelfand S. A.
Published: October 2005

Loudness balances obtained with a new procedure were compared to those of the classical ABLB technique for normal subjects and those with asymmetric sensorineural loss. The new technique involves a target tone in one ear, which rises from threshold at a set rate in decibels/sec; and a subject-controlled comparison tone which varies in intensity at a faster rate than the target, in the other ear. The tones alternate between the ears at a 50% duty cycle. The subject controls the comparison tone intensity to trace an equal loudness function between the ears by keeping it equally loud with the target using a Bekesy-like button. Parameters included comparison tone attenuation rate (1.25, 2.5 and 5 dB/sec) with the target intensity increasing at a set rate of 1 dB/sec; test ear (better or poorer for impaired subjects); and test frequency. There were no frequency or order dependencies for either group. The new test correlated well with the traditional one for normals; with the only dependency being that, as comparison tone speed increased, there was more variability, with “overshoot” at initial levels approximating an artificial asymptotic recruitment pattern at fast speeds. Subjects with asymmetric losses overestimated recruitment when the comparison tone was in the poorer ear, and underestimated recruitment when it was in the better ear. The most marked deviations were obtained when the better ear head the comparison tone at the 1.25-dB/sec rate. The new approach, while faster than the classical test, and while it quickly generates a complete loudness function, has several disadvantages. As an experimental technique, these lie in artifacts that modify the loudness function. As a clinical tool, these lie in the spurious over- or underestimates of recruitment. [Supported by the V.A.]
Monaural procedure for the psychoacoustic calibration of bone-conduction vibrators
Authors: Vaughan R. B. , Barry S. J.
Published: October 2005

An improved monaural loudness balance technique was used to derive transfer functions for three new bone-conduction vibrators. Six subjects adjusted a variable bone-conducted stimulus at each of seven frequencies to equal the loudness of an alternately presented air-conducted reference stimulus of like frequency presented at 30 dB SL. The mean force output levels at equal loudness, as measured on a Bruel & Kjaer Artificial Mastoid, were used to derive transfer functions for all possible vibrator pair combinations. These functions were compared with transfer functions derived from a threshold procedure employing the same subjects. With the exception of two vibrator pair combinations at 250 Hz, the differences between the two estimates of the transfer function for each vibrator combination at each frequency were less than 2.5 dB. It was concluded that the improved loudness balance procedure was suitable for the derivation of transfer functions between dissimilar bone-conduction vibrators.
Effects of abrupt intensity reduction on excursion size of Békésy tracings
Authors: Young I. M. , Wenner C. , Harbert F.
Published: October 2005

Threshold measurements were obtained for fixed frequency Békésy pure tones on subjects having normal hearing and sensorineural hear Lug impairment. Following the threshold measurements using conventional Békésy audiometry, the intensity was abruptly decreased by 20 dB at the moment the subject pressed the switch indicating that he heard the sound stimuli. Excursion size was compared between the conventional Békésy tracings and the abruptly reduced intensity tracings. Results indicated that the excursion size obtained by the latter method was reduced by approximately 40%. This was true for both pulsed and continuous tones, and for normal and sensorineurally impaired subjects. Factors affecting this reduction in excursion are discussed and hypothesized.
Physical acoustics in quantum fluids
Authors: Rudnick Isadore
Published: October 2005

Superfluid helium is rich in the number of wave propagation modes which occur because it behaves as though it is composed of two fluids one of which is superfluid and the other a normal fluid. Four recognized modes are named first, second, third and fourth sound, of which all but the first occur only in quantum fluids. First sound is an ordinary compressional wave. Second sound is a propagating entropy wave. Third sound is a thickness wave which propagates in helium films and has been observed in films as thin as two atomic layers. Fourth sound is a compressional wave which propagates when the normal fluid component is locked as in the small pores of a rigid porous medium. These sound waves provide a powerful means of investigating the superfluid properties of helium and examples of such use is described. [Work supported by ONH and NSF.]
Ultrasonic attenuation in thin polycrystalline tin films
Authors: Free J. U. , Strandberg M. W. P.
Published: October 2005

Ultrasonic methods have been used to measure the low-temperature ultrasonic reflection coefficient of thin polycrystalline films of tin. In these experiments thin films of tin have been evaporated onto the end of an X-cut quartz rod. The opposite end of the quartz rod was excited piezoelectrically by means of an X-band re-entrant cavity. The reflected pulse was monitored as the film was switched between the normal and superconducting state in the frequency range of 8.9 GHz to 9.4 GHz. From the analysis of the reflected ultrasonic power with the film in the normal and superconducting state one can determine the reflection coefficient and attenuation coefficient for the film. For the data for evaporated tin films we find that the measured ultrasonic attenuation coefficient is in agreement with the results of Pippard. From the ultrasonic reflection coefficient we find that 10%–60% of the film is not in perfect contact with the quartz. [Work supported by Research Laboratory of Electronics, MIT.]
Nanosecond acoustic strain pulses from CdS phonon masers
Authors: Smeaton M. D. , Hughes R. C. , Vrba J. , Haering R. R.
Published: October 2005

Nanosecond acoustic strain pulses, generated by a mode-locked CdS phonon maser, have been observed through application of optical diffraction and spatial filtering techniques. Peak strains exceeding 5×10−5 have been measured. An analogy drawn between our device and a repetitive pulse generator has provided some insight into mode-locked phonon maser operation. [Work supported by the National Research Council and Defense Research Board of Canada.]
Acoustic wave propagation in a viscoelastic fluid undergoing a simple steady shearing motion
Authors: Schwarz W. H.
Published: October 2005

The theory for the prediction of the absorption and dispersion of forced acoustic waves propagating through a viscoelastic fluid in a steady simple shearing motion is presented. The stress tensor is represented by an approximate constitutive equation for a simple fluid, obtained by a functional expansion about the basic state of a motion with a constantstretching history. The linear term is written as a sum of integrals, having kernels identified as shear and compressional relaxation functions. The absorption and dispersion depends on the direction of acoustic propagation relative to the shearing axis. Two cases are examined and the appropriate relaxation functions, or alternatively, the complex viscosity functions, obtained. These forms are compared to the shear relaxation functions obtained from shear oscillation experiments. The special case of acoustic wave propagation through a viscoelastic fluid, otherwise at rest, is considered and the results are compared to existing theories and experimental data.
Perception of dichotic place contrasts
Authors: Repp B. H.
Published: October 2005

A pair of dichotic CV syllables that contrast only in the starting frequencies of their formant transitions is generally perceived as a single fused syllable. The identification and discrimination of such “psychoacoustic” fusions was investigated in a series of experiments. The stimuli were dichotic combinations of seven syllables from a “place continuum” ranging perceptually from /b / to /g /, with binaural “controls” interspersed. The aims of the experiments were (1) to examine whether identification responses can be predicted by an auditory averaging hypothesis, (2) to demonstrate that dichotic fusions show an average right-ear advantage which is as pronounced as that found with less completely fused syllables, and (3) to attempt a psychophysical (discrimination) approach to measuring ear advantages. The results are discussed primarily from a methodological viewpoint. Dichotic tests containing only voiced stop consonants seem to offer some advantages over tests containing all six stops: They require only a single response, are more homogenous and yield no “errors,” which greatly simplifies the scoring. They may be one step closer to the goal of constructing a standardized test for the precise measurement of ear differences in speech perception.
Acoustic similarity and dichotic listening
Authors: Benson Peter
Published: October 2005

An audiotory-phonetic distinction has been used to explain both the right ear advantage (REA) and the feature sharing effect (FSE) obtained in dichotic listening tasks. The REA has been modeled as originating in the extraction of phonetic features from the auditory representation. It is susceptible to certain acoustic manipulations. The FSE, the increased number of double correct trials for stimulus pairs which share phonetic features, has been modeled as originating after these features have been extracted. This model was tested in a dichotic listening task in which phonetic factors were held constant and acoustic similarity was varied: two sets of stimuli, each consisting of six CV syllables, were used, one set in a male voice, one in a female voice. Stimulus pairs could have beth stimuli from the same voice or each from a different voice. The PEA was unaffected by these changes in acoustic similarity, indicating the competition for lateralized speech centers is unaffected by the acoustic differences between the voices. More double correct responses, however, were obtained when the voices were different. The model is modified to incorporate these data. [Work supported by NIH.]
Contribution of windows and doors to the acoustical integrity of wood-framed walls
Authors: Heebink T. B.
Published: October 2005

Noise intrusion through exterior walls containing windows and doors was studied in the laboratory. Although windows and doors are the weakest links in exterior facades, relatively simple modifications can improve the overall sound transmission loss property to satisfactory levels. Wood double hung and aluminum slider windows were evaluated as web as doors with solid wood and solid particleboard cores. Ordinary storm windows and doors proved to be reasonable solutions to improve walls in their capability to protect against outdoor noise. A useful family of curves is presented that makes possible the combining of wall, window, and door transmission losses.
Sound transmission through a double wall with studs
Authors: Garrelick J. M. , Lin G.-F.
Published: October 2005

A common structural configuration consists of two parallel walls, or partitions, structurally connected to each other via a periodic array of studs. The sound transmission characteristics of such a configuration are analyzed. In particular, the relative strengths of the parallel transmission paths, viz, the airborne path through the cavity space and the structure-borne path through the studs, are compared for common configurations. The mathematical model that is used consists of two plates infinite in extent, and governed by the classical plate equation, The cavity space between the plates as well as the surrounding spaces satisfy the wave equation. The studs are assumed to be infinitely periodic with translational impedances corresponding to those of line masses.
Fluid dynamics of floated floors
Authors: Ventres C. S. , Dym C. L.
Published: October 2005

In the design of a floated floor, it is important that no acoustic spring be set up in the air cavity between the floor and the supporting slab. An ingeneous heuristic analysis of this problem has been given [E.E. Ungar, Noise Control Eng. 5(1), 12–16 (Jul.–Aug. 1975)]. To rigorously define the acoustic problem of the response of a small cavity to a moving wall, first-order perturbations of the Navier-Stokes equations have been written, wherein viscous and thermal effects are included, in addition to the usual acoustic (potential flow) terms. The inclusion of viscous terms allows the satisfaction of tangential and normal velocity boundary conditions, thus accounting for the possibility of large lateral flow velocities when the cavity is vented at the lateral edges. When viscous and thermal effects are of comparable magnitude, the governing equations uncouple into a damped wave equation and a diffusion equation. The solution, for time-harmonic dependence, allows the prediction of the relative cavity geometry, i.e., size and venting of the cavity, in order to avoid generation of an acoustic spring.
Electroacoustic feedback in rectangular reverberation chambers
Authors: Lilly J. G. , Tichy J.
Published: October 2005

The effect of introducing an electroacoustic feedback system into a rectangular reverberation chamber has been determined in the low frequency region by modeling the individual system components as time invariant linear systems. Both electrical and acoustical coupling configurations are discussed in terms of the steady-state response of the system to a monochromatic point source. Special consideration is given to the stability requirements of the feedback system and how these requirements affect the system as a whole. The results indicate that both the frequency response and the spatial variations of the sound field can be significantly altered if the appropriate feedback control function exists in the electric portion of the feedback channel. If this control function can be physically realized, the techniques described herein could be used to increase the precision of reverberation chamber measurements in the low-frequency region. [Supported by US Naval Sea Systems Command.]
Impulsive sound level response statistics in a reverberant enclosure
Authors: Lambert R. F. , Dunens E. K.
Published: October 2005

An analytical model based on the experimental results presented in the preceeding paper has been developed which predicts the sound pressure level (SPL) exceedance probability distribution (EPD) of an enclosure to an impulsive noise source. The rms sound pressure is found by calculating the total energy per source impulse at the receiver. An energy partition method in conjunction with a method of images is used to calculate the total energy. Since a numerical or analytical calculation of the SPL EPD in a reverberant enclosure is not feasible, an equivalent 1 DOF system is predicted whose normalized EPD response is similar to that of the enclosure. The principal source parameters in the model are the impulse peak amplitude probability density, occurrence rate, and duration. The principal enclosure parameters are average sound absorption coefficient, volume to surface area ratio, shape, and location of barriers relative to the noise source and receiver, Generally, agreement between experimental and calculated results employing the model are very good. An example is included illustrating the use of such predicted responses in industrial noise applications. [Work supported by NSF Grant GK 4340.]
Duct liner optimization for turbomachinery noise sources
Authors: Lester H. C. , Posey J. W.
Published: October 2005

An acoustical field theory for axisymmetric multisectioned duct liners is combined with a numerical minimization algorithm to predict optimal one- and two-sectioned liner configurations producing maximum sound attenuation. Optimal inlet liner impedance properties calculated by this method are presented for a research compressor operating at about 0.4 Mach number. Kemp-Sears theory is used to describe the rotor/stator viscous wake interaction effects. Comparisons with data presented for point and plane-wave sources indicate that optimal liners for complex turbomachinery sources cannot be easily inferred from data based on these simpler source models.
Acoustic systems containing curved duct sections
Authors: Rostafinski W.
Published: October 2005

The analysis of waves in curved ducting of rectangular cross section is extended to the study of motion near discontinuities. This includes determination of the characteristics of the tangential and radial components of the nonpropagating modes, It is established that attenuation of the nonpropagating modes strongly depends on frequency and that, in general, the sharper the bend, the less attenuation may be expected. Evaluation of a bend's impedance and of impedance-generated reflections is also presented in detail.
N-port analysis of a projector consisting of a coaxial array of ferroelectric shells
Authors: Krile Thomas F. , Sabbagh Harold A.
Published: October 2005

The coupling between a coaxial array of six tangentially polarized, ferroelectric shells and the external fluid medium is analyzed by an application of N-port theory. Properties of the lowest (“breathing”) mode of the shells are ascertained by using three-dimensional finite elements, and this knowledge is utilized in defining an N-port representation of the array. An N-port representation of the external fluid is obtained by solving the Helmholtz integral equation that relates fluid velocity and pressure on the exterior of the array. The two N ports are coupled together in a standard circuit-theoretic manner to produce an equation for the electrical driving-point impedance of the loaded projector. Several frequency responses, which illustrate the effects of varying certain parameters, are presented.
Shock wave revisited—a second look at some measurements of explosive acoustic source levels
Authors: Maples L. C.
Published: October 2005

Updated information on system characteristics and underwater explosive parameters and new theoretical/empirical models have provided new insights into measurements of source levels of small TNT charges at shallow and moderate depths. Preliminary results, for the shock wave from a 3-lb charge of TNT, were presented at an earlier meeting of the Acoustical Society. In that paper, comparison with Weston's theoretical values showed differences of 2.5 to 5 dB. New evaluations of Weston's formulations, based on improved values of explosive parameters, show greatly improved comparisons and support measured values. Source levels for shock wave, bubble pulses, and entire wave train are presented for 3-lb charges detonated at 60−, 500−, and 1000−ft depths and compared with measurements of Weston and Stockhausen and later values from Bell Laboratories, Naval Ordnance Laboratory, Sac Lant ASW Research Center and Defence Research Establishment, Atlantic. To complete the survey, values from models of Weston, Christian, Gaspin and Shuler, and NUSC are included.
Design of broad-band transducer for high-temperature application to nuclear reactors
Authors: Karplus H. B.
Published: October 2005

Ultrasonic transducers are usually damped with metal powder-loaded plastic or lossy rubber materials, which are effective only over a narrow temperature region. A shear-wave transducer was designed using only materials capable of withstanding high temperature (650 °C, 1200 °F). The design employs a laminated stainless steel coupling block, a piezoelectric X-cut lithium niobate crystal, a laminated backing plate, and a clamp to force intimate mechanical contact between the crystal and the coupling block. Transmission of ultrasonic energy in the desired direction parallel to the interfaces of the coupling laminac is not affected by the laminated structure. However, subsequent reverberation in the coupling block is damped by Coulomb friction between interfaces after reflection at the third oblique surface of the coupling block. Radiation into the pressure pad forcing the crystal into contact with the coupling is strongly attenuated by laminating the pressure pad normal to the propagation direction. Uniformity of pressure is assured by applying pressure via a single ball bearing and thick solid blocks. The transducers were used to monitor flow in pipes by measuring sound velocity difference in the upstream and downstream directions. A time interval difference of 110 nsec for pulses transmitted simultaneously in both directions across a 4-in. Schedule 10 stainless steel pipe (108.2 mm ID) was readily measured to four significant figures, using a HP model 5345 Time Interval Averager for water flow at 500 gpm (31.5 l/sec).
Categorization of tonal intervals by musicians: Perceptual effect or response bias?
Authors: Siegel W. , Siegel Jane A.
Published: October 2005

Siegel and Sopo [J. Acoust. Soc. Am. 57, 511 (1975)] presented data from a magnitude estimation study in which musicians judged the size of 20 tonal intervals spread over five semitones. It was found that some musicians showed five discrete steps in their magnitude estimation functions, that they used only five different numerical responses, and that they reported hearing the stimuli as “in tune.” We interpreted these findings as evidence for categorical perception of intervals. One could, however, infer that the step functions resulted from a simple response bias, a tendency to round off the numerical ratings to a value corresponding to the nearest semitone. Here we present data of other musicians in the same task who attempted to make finer discriminations, and used more than five response categories. The data showed that, even though these subjects detected out-of-tune intervals, their magnitude estimates had definite scallops corresponding to the chromatic scale in some musicians, and to the diatonic scale in others. Moreover, the variability of responding was cyclical, with the largest standard deviations occurring at the category boundaries. Our results converge with those of Burns and Ward [J. Acoust. Soc. Am. 55, 456 (1974)] which demonstrate categorical perception of intervals in a forced-choice discrimination task.
Selective auditory attention considered as a change in the effective level of the target sound
Authors: Watson C. S. , Spiegel M. F.
Published: October 2005

We have recently found that listeners' abilities to discriminate between temporally complex patterns (tonal sequences) depends more on foreknowledge of the stimulus than does performance on similar tasks with isolated tones [J. Acoust. Soc. Am. 55, S18 (1974)]. For example, the just-detectable change in the frequency of a single 40-msec, 1-kHz component of a 0.5-sec tonal sequence may be reduced from 150 to 6 Hz when stimulus certainty is increased, i.e., when the testing conditions allow the listeners to “focus their auditory attention.” In a new series of experiments, the level of the tonal component subject to change, relative to that of the other tones in a ten-tone pattern (the target-to-context ratio), was varied. Precise frequency discrimination could be achieved at target-to-context ratios as low as −40 dB in the minimal-uncertainty psychophysical procedures which favor selective attention. The same level of performance can be produced, when stimulus uncertainty is higher, by raising the target-to-context ratio to about +10 dB. There is thus a reciprocity between stimulus uncertainty and the relative level of a target sound which may operate over a range as great as 50 dB. [Work supported by National Institute of Neurological and Communicative Disorders and Stroke.]
Hybrid serial-parallel model for acoustic and phonetic processing: A re-evaluation
Authors: Pastere R. E. , Ahroon W. A. , Puleo J. S.
Published: October 2005

In a recent series of reaction time studies, Wood has claimed to have found evidence supporting a hybrid serial-parallel model for the processing of acoustic and phonetic information [e.g., C.C. Wood, Percept. Psychophys. 15, 501–508 (1974)]. According to this model, following a preliminary analysis, acoustic and phonetic information are processed in parallel. This paper describes a set of experiments using clearly non-phonetic stimuli which replicate and extend the basic results of the Wood studies. We reject the assumption of the involvement of phonetic processes in the Wood studies. Rather, we claim that Wood has described a basic characteristic of the auditory system which cannot be explained in terms of known recency or nonsimultaneous “recognition-masking” effects.
Low-frequency sound absorption in Pacific Ocean water
Authors: Simmons V. P. , Fisher F. H.
Published: October 2005

Using the 200-liter resonator, measurements of Pacific Ocean water (S=33.5%) taken from the Scripps Pier indicate agreement with Thorp that sound absorption below 1 kHz is about ten times greater than predicted considering only MgSO4 absorption. The low-frequency absorption which is primarily due to a multistate dissociation of boric acid is affected by interaction with the carbonate system. An effort to explain variations in absorption values from long-range propagation measurements in terms of the carbonate ion concentration is discussed. [This work was supported by the Office of Naval Research.]
Regional dependence of low-frequency attenuation in the ocean
Authors: Kibblewhite A. C. , Bedford N. R.
Published: October 2005

In a paper presented to the 87th Meeting of this society [K.M. Guthrie, R.N. Denham, R.W. Bannister, and D.G. Browning, “Possible effects of velocity profile shape and scattering loss distribution in SOFAR propagation,” J. Acoust. Soc. Am. 55, S45(A) (1974)], an oceanographic model of the South Pacific Ocean was proposed to explain the marked regional dependence of the attenuation observed in the experiment Project KIWI ONE. The effects observed were explained by introducing a regionally dependent, frequency-independent scattering loss, which decreased exponentially with depth, in addition to the usual 0.06f2 absorptive loss. This new attenuation term was explained in terms of mode coupling initiated by variations in the sound-velocity structure, leading to a redistribution of energy from lower order to more lossy higher-order modes. Results of another experiment are presented which also demonstrate a regional dependence of low-frequency attenuation coefficients and provide support for the theoretical basis to the scattering loss distribution function.
Observations of acoustic sidebands in CW tones received at long ranges
Authors: Shooter Jack A. , Mitchell Stephen K.
Published: October 2005

Theoretical predictions, as well as observations at relatively short ranges and steep grazing angles, show that a sound wave which is forward scattered from the ocean surface has its frequency components smeared by surface-wave motion [M.V. Brown and G.V. Fisk, J. Acoust. Soc. Am. 55, 744–749 (1974)]. The subject of this paper is the presence of observable sidebands in CW signals which are generated by a moving source received at ranges of up to 160 NM in the ocean. The sidebands are approximately 0.1 Hz from the (Doppler-shifted) source center frequency and are as strong as 15 dB below the level of the signal received at the source frequency. [Work supported by Office of Naval Research.]
Anatomical and physiological adaptations of marine mammals for the prevention of diving induced middle ear barotrauma and round window fistula
Authors: McCormick J. G. , Wever E. G. , Harrill J. A. , Miller H. E.
Published: October 2005

A small number of confirmed human diving induced round window fistula cases have been reported by Dr. Peter Freeman's group in Australia. This finding in man lends teleological support to the idea that marine mammals have protected their middle ears from diving barotrauma through an erectile arteriovenous plexus. In numerous cochlear potential experiments on live anesthetized porpoises (McCormick, Wever, and Ridgway, 1970, 1974) and sea lions (McCormick and Mattsson, unpublished), we have encountered this plexus and also noted a tough fibrous protective layer over the round window (unpublished). This protective “armor” and adjoining scala tympani trabeculae are not found in man or other land mammals. In addition to reviewing our previous gross anatomical studies, we will report new microscopic findings on the nature of the multiple-layered structure of the round window membrane in porpoise and sea lion as well as histological sections of the middle ear plexus and its relation to the round window. Our comparative marine mammal experience, along with the results from Australia, helped us to correctly make a preoperative diagnosis of diving induced round window fistula in a patient. The successful treatment of a flat 80-dB hearing loss in this patient will be described.
Auditory fatigue: Half-octave shifts in single-unit responses following pure-tone exposures
Authors: Lonsbury-Martin B. L. , Meikle M. B. , Vernon J. A.
Published: October 2005

Responses of single fibers in the cat's cochlear nerve were studied before, during and after exposure to intense auditory stimuli. Exposure stimuli were pure tones at the fiber's CT or at 12 octave above (+12 octave) or below (−12 octave) the CF. Exposure levels were 85 dB and 90 dB SPL. The various exposures were evaluated in terms of the reduction of responding to test stimuli at the fiber's CF. At the 90-dB level the exposures at −12 octave produced greater response decrements and more prolonged recovery times than exposures at the CF. Effects of the 85-dB exposures at the CF and −12 octave were less severe, and were about equal to each other. Only a slight effect on fiber responses was found for exposure stimuli at +12 octave, whether at 85 or 90 dB. None of these exposures produced changes in CM. The relevance of these data to “temporary threshold shift” and to basilar membrane mechanics is discussed. [Supported by the National Institutes of General Medical Sciences and Neurological and Communicative Disorders and Stroke.
Superdirectivity revisited
Authors: Kooij Theo , Cox Henry
Published: October 2005

The difficulty with superdirective arrays is well known to be their extreme sensitivity to errors and uncorrelated noise. This paper reviews the fundamentals of superdirective arrays. With this foundation, the problem of achieving modest superdirectivity without extreme sensitivity to errors is addressed. The tradeoff between gain and error sensitivity is illustrated by a number of examples. In addition to the usual case of a three-dimensional isotropic noise field, results are presented for some anisotropic fields more typical of the underwater acoustic environment.
INDSCAL study of the perceptual space of American diphthongs Dale Terbeek
Authors: Fox Robert A.
Published: October 2005

Previous MD-scaling studies of vowel perception [such as S. Singh and G. Woods, J. Acoust. Soc. Am. 49, 1861–1866 (1971)] have been concerned with monophthongs. In this experiment, the stimuli included three vowels with [i] off-glides, three with [u] off-glides, and three with level or [ə]-like off-glides. The nine vowels, namely, [ei ai oi u ou au ɪ æ ɔ], were spoken by a native American speaker in the phonetic context [♯ _ t]. Twenty-one American listeners performed paired-comparison similarity judgments using a nine-point rating scale. A different set of 21 listeners performed the task on the same vowel phonemes, recorded without any phonetic context. Both sets of vowel-by-vowel dissimilarity matrices were analyzed by INDSCAL [J.D. Carroll and J.-J. Chang, Psychometrika 35, 283–319 (1970)]. Both stimulus conditions gave the same major results: (1) The most salient property is the presence of rounding anywhere in the vowel versus complete absence of rounding. (2) The next most salient property groups vowels according to off-glide. (3) Vowel onset height is the least salient dimension to appear. (3) No backness dimension appeared at all. The results are offered as evidence relevant to proposals about distinctive features. For example, the relative salience of rounding over backness speaks against the psychological reality of a phonological rule in English which assigns redundant rounding values based on backness values.
Pitch of acoustically altered whispered vowels
Authors: McGlone R. E. , Manning W. H.
Published: October 2005

The present authors have hypothesized that the perceived pitch characteristics of whispered vowels are related to their second formant frequency [McGlone and Manning, J. Acoust. Soc. Am. 57, S69(A) (1975)]. This assumption was based on the rank-ordering of vowels by judges from highest pitch to the lowest pitch which corresponded directly with the frequencies of F2 of the speakers. To further test the above hypothesis, F2 of vowels /ɪ i, u, ɔ, æ/ in whispered hV syllables were electronically filtered from the speech signal. These altered signals were played in pairs to a group of judges who simply indicated which of the pair had the highest pitch. The vowel quality of the speech sample disappeared but pitch judgments were possible. The order of pitch differed considerably from the unaltered condition. F2 does appear to influence the pitch perception of vowels.
First-formant onset frequency as a cue to stop-consonant voicing
Authors: Summerfield Quetin
Published: October 2005

Both we and Stevens and Klatt have suggested that a voiced first formant (F1) transition following voicing onset in a stop-vowel syllable is a positive cue to stop voicing. Lisker et al. [J. Acoust. Soc. Am. 57, S50(A) (1975)] pointed out that the salient perceptual cue could alternatively be the F1 frequency at voicing onset as low values directly indicate synchrony of glottal vibration with vocal tract closure. Phoneme boundaries were determined by an adaptive PEST algorithm firstly on seven VOT /g-k/ continua with identical F2 and F3 but differentiated by the frequency of a steady transitionless F1. Phoneme boundary values in VOT increased monotonically as F1 frequency was reduced from 400 to 200 Hz. Secondly, phoneme boundaries were determined on seven VOT /g-k/ continua in which voicing always onset at 250 Hz in F1 and was followed, irrespective of VOT, by 0, 6, 12, 18, 24, 30, or 36 msec of linear F1 transition at 5 Hz/msec to a variable steady state. With increasing F1 transitions, phoneme boundaries shifted unexpectedly towards shorter VOTs. Thus the trading value against the ether cue, VOT, varies in the expected direction with onset frequency but not with transition extent, supporting Lisker et al. [Work supported by J.S.R.U., U.K.]
Chest wall dynamics in singers
Authors: Hixon Thomas J.
Published: October 2005

Behaviors of the chest wall and its parts (rib cage wall, diaphragm, and abdominal wall) will be considered as they are revealed through stress-strain analyses. Data will be charted in relative motion diagrams and various motion-pressure diagrams which enable graphic solution for muscular pressures exerted by each part during singing. For most singing, the effort of the chest wall is expiratory, control being vested in the rib cage wall and the abdominal wall in the upright body position and typically in the rib cage wall alone in the supine position. For phonations encompassing most of the vital capacity, chest wall effort is at first net inspiratory and later net expiratory. The former is governed predominantly by the rib cage wall in the upright position and by the diaphragm in the supine position. The latter is regulated mainly by the rib cage wall and the abdominal wall in both body positions. Stress-strain analyses of this type reveal chest wall function that is highly dissimilar to that described in previous electromyographic accounts of function. Possible reasons for the discrepancies will be explored.
Studies of larynx position in singing
Authors: Shipp Thomas
Published: October 2005

Singers and non-singers appear to have markedly different patterns of vertical larynx position for vocal frequency change. In general, non-singers position their larynx higher in the neck with increased fundamental frequency, while singers tend to depress their larynx below a physiologic rest position for any phonatory attempt and maintain this low position or even exaggerate it as vocal frequency is raised. In contrast to this pattern for frequency, singers and non-singers position their larynx similarly as a function of vocal effort lower larynx for high effort and higher larynx position for low effort. Larynx position can be affected by tongue and jaw movements as well as by hydraulic forces involved in respiration. This paper will attempt to present some additional data and propose an hypothesis of vertical larynx position function in sustained phonation.
Functioning of the larynx and articulatory organs of professional singers
Authors: Dmitriev Leonid B.
Published: October 2005

Our x-ray studies with highly qualified opera singers have shown that the larynx position on prolonged tones in singing is the same for all vowels in a two-octave range. With light sopranos, the larynx position in singing is always higher than its rest position; with basses and baritones it is always 2–3 cm lower. A larynx shift from its rest position to the singing position is caused by the necessity of having the buccopharyngeal tract correspond to the type of voice in question. If, by nature, this tract is too short the singer lets the larynx go down. If, on the contrary, it is too long, the singer lets the larynx go up. Owing to these larynx shifts, a ratio between the length of the vocal folds for each voice type and the needed length of buccopharyngeal tract in singing is found; it is equal to 1 : 10. The adjustment of larynx which is characteristic and necessary for singing on a supported and trained tone is a contraction of its opening observed with opera singers for all vowels and in all voice ranges including the covered upper range. Owing to this contraction, there is formed a small cavity the function of which is like that of a premegaphone chamber in acoustic amplifier megaphones. A proper contraction of the larynx opening and an adequately found length of the buccopharyngeal tract create an impedance indispensable for a supported professional voice.