bluuebunny/crossref_metadata_2025 huggingface dataset:
An Algorithm for Locating Stressed Syllables in Continuous Speech
Authors: Lea Wayne A.
Published: May 2012

Local increases in fundamental frequency (F0) and large integrals of energy in the syllabic nucleus are known to be among the best acoustical correlates of stress. Major syntactic constituents have been shown to have archetype rapid-rise-then-gradual-fall F0 contours, with the rise into the maximum F0 often associated with the first stressed syllable in the constituent. An automatic procedure for detecting constituent boundaries and maximum F0 positions in constituents [W. A. Lea, “An Approach to Syntactic Recognition without Phonemics,” IEEE Trans. Audio'Electroacoust. AU-21, No. 3 (1973)] and sonorant energy and F0 functions, provided input data for an algorithm for locating stressed syllables. The first stressed syllable of a constituent was associated with a high-energy-integral portion near the rising F0 into maximum F0 position. Other stressed syllables were associated with high-energy-integral portions near local increases in F0 above a steadily falling “archetype line” from the maximum F0 position to the end of the constituent. For over 400 sec of speech, including written texts, and questions, commands, and declarations for man-machine interaction (involving 16 talkers), over 85% of all syllables perceived as stressed by a panel of listeners were correctly located.
On the Trading Relation between Time and Intensity for Intermittent Noise Exposures
Authors: Ward W. Dixon
Published: May 2012

Present damage-risk criteria (DRC) are based almost exclusively on studies of the effects of continuous 8-h/day noise exposures. However, most actual daily exposures are intermittent in nature. Therefore a series of 8-h exposures to intermittent noise was undertaken in order to determine whether the trading relation between level and time should be 3 dB per doubling time, as advocated by ISO, or 5 dB, as incorporated into present American DRC. The results of studies with on-fractions of 1, 12, 14, and 18 periods of 90 sec, 9 min, and 40 min indicate that a trading relation of 5 dB per doubling time will keep constant a 6- to 20-dB TTS2 produced by a 4000- or a 1000-Hz octave band of noise. In the case of a 250-Hz octave band, a TTS2 of 10 dB (the criterion for this octave band, one produced by continuous exposure at about 98 dB SPL) could not be reached even with a level of 115 dB as long as the on-fraction was 12 or less. It is clear that a trading relation of 5 dB per doubling time is more appropriate than 3 dB for intermittent exposures. [Research supported by the National Institute for Occupational Safety and Health, Public Health Service.]
Ambient Sea Noise Measurements near New Zealand
Authors: Bannister R. W. , Barker P. H. , Browning D. G. , Denham R. N.
Published: May 2012

The waters near New Zealand are in general characterized by a moderate sea state and low shipping density. The resulting ambient noise is relatively constant over the frequency range 10-1000 Hz. A summary is made of ambient noise collected at various locations in the South Pacific and Tasman Sea near New Zealand. An increase in the biological noise is observed in the morning and evening hours in some locations as well as transients which are attributed to underwater seismic activity and larger sea animals. Comparison is made with data from other ocean areas.
Some Effects of a Solid Bottom on Propagation Loss at Low Frequencies
Authors: Kutschale Henry W. , DiNapoli Fred R.
Published: May 2012

The fast field program (FFP) is a fast, convenient method employing the fast Fourier transform to compute propagation loss as a function of range. The FFP integrates directly the exact integral solution of the wave equation derived from point harmonic sources in multilayered media. In the past, the bottom has been represented by a layered liquid, but here the FFP is used to investigate some effects at low frequencies of a layered solid bottom on propagation loss as a function of range. Computations of propagation loss are compared between bottoms with the same layer thicknesses, compressional-wave velocity, and density but with and without rigidity. In deep water, the main effect in the band 8–30 Hz on propagation loss of a solid bottom is to alter the detailed fluctuations of loss with range in response to the multipath interference of the waves, but the smoothed loss with range commonly measured from explosive sources is not significantly different for the test cases over the range intervals up to 200 km. In shallow water, however, propagation loss as a function of range at frequencies below cutoff for the all-liquid guide may be significantly less when the rigidity of the bottom is included.
Sound Diffusion in Enclosures
Authors: Waterhouse R. V.
Published: May 2012

A review is made of some aspects of the theory and practice of diffuse sound fields in enclosures. The following topics are discussed: the need for diffuse field measurements; enclosure shape; normal and damped modes; modes versus frequency plot; lattice diagram; measurement of point-to-point response curves in the enclosure; excitation by single-frequency and narrow-band noise signals; stationary and moving reflectors; their mode of operation and effect on the sound field; interference patterns at reflecting surfaces; correlation measurements; statistical description of a diffuse sound field; and measurements of the sound power output of sources.
Diffusion, Room Shape, and Absorber Location: Influence on Reverberation Time
Authors: Schroeder M. R. , Gerlach R.
Published: May 2012

Reverberation time, according to classical formulas (Sabine, Eyring-Norris-Waetzmann-Schuster, Millington-Sette, el al.) depends on room volume and total absorption and is independent of room shape and absorber location. Practical experience, as well as theoretical studies, show that both room shape and absorber location can have noticeable, or even large, effects on reverberation time. Can these effects be eliminated by sound diffusion and, if so, how much diffusion is required? Or do we need new reverberation time formulas that take room shape, absorber location(s), and amount and kind of diffusion into account? Preliminary results of scale-model experiments toward answering these questions are reported.
Comparative Evaluation of Test Methods to Simulate Acoustic Response of Shroud-Enclosed Spacecraft Structures
Authors: On F. J.
Published: May 2012

A comparative evaluation was performed on test methods to simulate the acoustic response of shroud-enclosed spacecraft structures. The evaluation was based primarily on vibro/acoustic test results obtained from a single “baseline” model of spacecraft, attach fitting, shroud, and “lower structure.” Emphasis was placed on (1) the magnitude of test input change required to generate comparable responses, both by a spacecraft/attach fitting “alone” acoustic test and a vibration test, to those responses produced by the shroud-installed acoustic test of the baseline model, and the difficulty in producing such a change, and (2) the degree of mis-simulation that can result from performing a particular “less than optimum” test. Conclusions are drawn with regard to the advantages and disadvantages derived from the use of input spectra adjustment methods and lower structure simulations. Test guidelines are also developed for planning and performing a launch acoustic environmental test.
Dynamics of a Rod-Fluid-Shell System
Authors: Chen S. S.
Published: May 2012

Flow-induced vibration and instability of fuel rods are of concern in the design and development of liquid-metal-cooled fast breeder reactors. Fuel rods in reactor cores are usually arranged in a hexagonal pattern. For the purpose of understanding fluid-solid interactions in rod bundles, this paper examines the behavior of a simplified model, a cylindrical rod located inside a cylindrical shell and subject to an axial flow. The system is described by the Bernoulli-Euler beam equation, Flugge's shell equations, and a linearized potential flow equation. The solution is obtained using the traveling wave type analysis. Frequency spectra are presented for steel rods and shells subjected to water flow. An approximate frequency equation is given and the effects of the flow velocity and various parameters are discussed. It is shown that the critical flow velocity of the coupled rod-fluid-shell system is smaller than that of a single rod subjected to an axial flow.
Radial Vibrations of Thin Rubber Rings
Authors: Gaunaurd G. C.
Published: May 2012

The equations of motion of linear elasticity in cylindrical coordinates are reduced to an axisymmetric plane-stress situation valid for thin elastic rings. The eigenvalue problem for the natural frequencies of the system is solved in two cases: first, when both rims of the ring are subjected to stress-type (third type for the displacement) boundary conditions having real coefficients; second, when the inner rim is stress-free and the outer rim is fixed. The characteristic equations in both cases are determined and solved numerically for almost incompressible materials of Poisson's ratio v very close to O.S. The first few roots are plotted in a nondimensional form versus the outer-to-inner radii ratio. The eigenwavenumbers of the first case are shown to be substantially below those of the second. The transient vibration problem for the elastic displacement field in the ring is then formally solved by means of eigen-function expansions in the first case only. The analysis is extended to viscoelastic rings (Kelvin-Voigt model) and under the same conditions, the effect of viscosity is to shift the eigenvalues from the real line into the complex wavenumber plane. Parts of this analysis are applicable to the design of (underwater) acoustic resonant coatings.
The Fluctuating Forces Appropriate for the Calculation of Discrete Frequency Noise Generation in Subsonic Turbo-Machines
Authors: Fleeter S.
Published: May 2012

Discrete frequency noise generation at blade passage frequency and its harmonics is a result of the aerodynamic interaction between successive rotors and stators. These interactions result in fluctuating forces on the rotor and stator blades which are equivalent to dipole sources radiating sound. This paper describes the importance of including airfoil cascade parameters and compressibility, even at low Mach numbers, in calculations of these fluctuating forces. The results are based upon solutions to the unsteady, compressible, two-dimensional partial differential equation which describe the flow disturbances generated by upstream obstructions being convected downstream past an airfoil cascade. The parameters include the cascade stagger angle, cascade solidity, reduced frequency, and the ratio of the number of upstream obstructions to downstream airfoils. The results indicate that isolated airfoil aerodynamics does not adequately describe these fluctuating forces; incompressible cascade aerodynamics is not adequate in the neighborhood of the resonance Mach number, but may be adequate at Mach number values both higher and lower than the neighborhood of the resonance Mach number. The extent of the neighborhood of this aerodynamic resonance, wherein compressibility and cascade effects are important, is a function of the flow and cascade parameters.
Noise from Ducted Rotor Interacting with Unsteady Inflow Fluctuations
Authors: Abdelhamid A. N.
Published: May 2012

Experimental and analytical determination of noise upstream and downstream of a 6-in. three-bladed ducted propeller interacting with controlled unsteady inflow distortion is conducted. The inflow distortion was induced by symmetrically mounting three 38-in.-diameter circular cylinders in the radial direction upstream of the propeller. The cylinders were rotated both in the clockwise and anticlockwise directions. The speed ranges of the propeller and the cylinders were 0-8500 rpm and 0-±800 rpm, respectively. Both velocity and acoustic pressure measurements are carried out in the duct and direct evaluation of the aero-acoustic transfer function is obtained. The amplitude of unsteady loading on rotor blades is shown to be affected by the frequency of the unsteady flow and the order of the flow spatial distortion. For distortion frequencies much lower than the rotor shaft frequency, the unsteady loading on the blade depends mainly on the spatial variation of the distortion. Frequency translation from blade passage frequency and its harmonics in the noise spectrum is demonstrated experimentally and the extent of translation is equal to analytical predictions. Comparisons between the experimentally determined aeroacoustic transfer function arhd analytical predictions indicate that the use of Sears function to calculate the unsteady loading on the rotating blades seems to be adequate for low values of Mach number. [Research supported by the National Research Council of Canada.]
Dipole Radiation from Rotor Interaction with Inflow
Authors: Rao G. V. R. , Chu W. T.
Published: May 2012

Rotor blade loading fluctuations have been recognized to be the dominant source of noise in subsonic fan rotors. Since the blade section drag force is of a lower order of magnitude than the lift force, the farfield sound is examined in terms of dipole radiation from the lift fluctuations on the rotor blades. These dipole sources can be classified into two catagories: (a) ordered sources arising from the effect of the deterministic component of the inflow distortion, and (b) random sources due to turbulence in the inflow. Theoretical analyses of both types of dipole radiation are presented. It is shown that even a small magnitude of steady-state inflow distortion can generate high levels of tone noise at blade passing frequency harmonics. For sufficiently large length scale of turbulence, the random lift force on the blades also gives rise to such discrete tone levels. [This work was supported by NASA Ames Research Center under Contract No. NAS2-6401.]
Comparison of Loudness Balances and Coupler Measurements for Insert-Type and Supra-Aural Earphones
Authors: Silbiger Herman R.
Published: May 2012

Loudness balances were performed between a supra-aural earphone and an insert-type earphone. Bandlimited white noise was used as the signal. Relative balances were obtained, with both test earphones sequentially balanced against a standard earphone. A double staircase method with variable step size was used to obtain the balances. The insert-type earphone used a plastic tube with ear tip to couple to the ear canal. Each of the ten subjects balanced with the properly fitted tip, and with one tip size larger and smaller. Objective loudness measurements were performed using the Electro-Acoustic Rating System (EARS) [Sullivan, Bell Syst. Tech. J. 50, 2663–2741 (1971)]. A modified type 3A coupler was used [Bryant, J. Acoust. Soc. Am. 52, 1599–1606 (1972)]. Since ear-insert couplers measure the sound pressure at the eardrum, and since the standard supra-aural coupler measures the pressure at the ear canal, a special “tympanum” coupler (Bryant, 1972) was used for the supra-aural earphones. The results of the objective measurements showed the ear-insert type to be 2.6 dB louder than the supra-aural type, which was in good agreement with the 2.5 dB obtained by the loudness balances, and supports the use of the “tympanum” coupler for comparative measurements.
Parametric Acoustic Lens Sonar
Authors: Muir T. G. , Folds D. L.
Published: May 2012

Sum and difference frequency parametric arrays are usually generated in the field of relatively large planar electroacoustic transducers by the transmission of two high-frequency primary waves. The approach taken in the present paper utilizes one or more small transducers located on the focal surface of a relatively large acoustic lens. Upon projection, the transducer (s) insonify the lens, which acts as a beamformer to radiate primary frequency sound in directions governed by the angular position(s) of the projectors on the focal surface. Narrow beams of sum and difference frequency sound are then generated by nonlinear interaction in the medium, in the usual manner. Echoes from targets in the field of view return to the lens, where they are focused on hydrophone aperture(s) located on the image surface. Some acoustic isolation between neighboring beams is affected by lens beamforming upon reception, thereby enhancing simultaneous multibeam operation. This capability is offset by the reduced power handling capacity of the smaller projections required for lens insonification. Experiments conducted in water with a solid polystyrene f/2 lens, 17 in. in diameter, at a mean primary frequency of 122 kHz and a difference frequency of 23 kHz are reported. Measurements of primary and secondary beampatterns, propagation curves, beam steering, and receiver channel isolation are discussed. [Supported by the U. S. Navy Office of Naval Research.]
Experiments on Parametric Arrays in Air
Authors: Widener M. W. , Muir T. G.
Published: May 2012

Recent measurements of parametric arrays in an air medium [see papers Q10 and Q11, 85th ASA Meeting J. Acoust. Soc. Am. 54, 297(A) (1973)] have been made with broad primary beams at short ranges. Some narrow-beam, long-range experiments are discussed in the present paper. A special mass-loaded ceramic projector employing a clamped-plate coupler was utilized as the feed to a large parabolic reflector The coupler's response was displaced from that of the mass-loaded ceramic to yield two sharp primary resonances centered at 16 kHz. Primary radiations at half-power beamwidths of 3.3° at extrapolated source levels in excess of 140 dB re 0.0002 μbar at 1 yd were generated. Detailed sound propagation and beam pattern measurements on a 1-kHz difference-frequency radiation having a half-power beamwidth of 4.2° were made and compared to theory. [This work was supported by the U. S. Navy Office of Naval Research.]
Radiative Sound Energy Transfer Formulation of Diffusion in Reverberant Rooms
Authors: Pierce Allan D.
Published: May 2012

A theory of diffusion in reverberant rooms of arbitrary shape is presented based on a directional spectral energy density S(x,ek,t,f) which represents the acoustic energy per unit volume per unit bandwidth per unit solid angle of propagation direction (unit vector ek). Energy conservation considerations give laws of propagation and reflection of S when a source is within the room with specified directional power output spectrum. These laws lead to an expression involving values of S on the walls which is stationary with respect to small variations. This variational expression, slightly resembling that derived by Sparrow and Haji-Sheikh [J. Heat Transfer (1965)] for radiative heat transfer in enclosures, is used to derive approximate equations such that, in the lowest order, S is presumed to be independent of x and ek and the Sabine equation holds, while a perturbation approach gives first-order corrections for the nonuniform nondiffuse contribution to S. Examples are discussed and it is suggested that the formulation affords a convenient method for quantitatively predicting the extent a given sound field may deviate from the Sabine ideal.
Effect of Local Signal Level on Differential Performance in Dichotic Listening
Authors: Crystal Thomas H. , House Arthur S.
Published: May 2012

Current studies have used a variety of dichotic listening tasks to demonstrate differential ear advantages in the processing of particular speech elements. The results have been used to draw conclusions about the roles of memory devices, feature processors, signal encodedness, and other factors in speech perception. In the belief that such interpretations are premature, we are conducting a series of experiments to evaluate the influence of the inherent levels of speech sounds on the results obtained from a variety of dichotic listening tasks. In particular, results are reported here for (1) dichotic temporal-order judgments involving three classes of speech sounds, and (2) dichotic discrimination and identification of sound features. The listening difficulty across sound categories was equated by using envelope masking that allowed the specification of local signal-to-noise conditions in the stimuli. In general, the results indicate that knowledge of local signal-level characteristics may be used to explain a variety of results obtained in dichotic listening. The implications of these results for a number of earlier experiments are discussed.
Right Ear Advantage for Vowels as a Function of Duration
Authors: Godfrey John J.
Published: May 2012

In a previous paper presented to the Society [J. Godfrey, J. Acoust. Soc. Am. 54, 285(A) (1973)], short vowel excerpts were shown to produce a right ear advantage (REA) of 4% to 8%, when the task was made sufficiently difficult. One parameter of “perceptual difficulty” explored was duration: whereas previous experiments with 300-msec vowels [Shankweiler and Studdert-Kennedy, Quart. J. Exp. Psychol. 19, 59–69 (1967)] produced no REA, the much shorter stimuli (10–60 msec) of my experiment did. To investigate further the relationship between stimulus duration and REA, a dichotic listening experiment was conducted using vowels of 50-, 100-, and 150-msec duration. Stimuli were sets of tense and lax vowels, presented with an S/N ratio of 0 dB. Results are discussed in terms of the “perceptual difficulty” hypothesis, i.e., that the REA is produced by the perceptual difficulty of the speech perception task, and that duration, within a certain range, constitutes one parameter of such difficulty.
“Same-Different” Reaction Times to Consonants, Vowels, and Syllables
Authors: Pisoni D. B. , Tash J.
Published: May 2012

It has been proposed that phonetic segments are encoded into perceptual units of syllable size. The aim of this study is to investigate how consonant and vowel information is transmitted (i.e., serial vs parallel), and to what extent auditory and phonetic levels of analysis may interact in perceptual analysis. Synthetic CV syllables, /ba/, /bæ/, /da/, and /dæ/, were arranged to produce four types of stimulus pairs: (1) consonant same-vowel same (CS-VS, e.g., /ba/-/ba/); (2) consonant same-vowel different (CS-VD, e.g., /ba/-/bæ/); (3) consonant different-vowel same (CD-VS, e.g., /ba/-/da/); and (4) consonant different-vowel different (CD-VD, e.g., /ba/-/dæ/). Same-different reaction times (RTs) were obtained separately for consonants, vowels, and syllables. In the consonant and vowel conditions, RTs for “same” responses were faster when the irrelevant feature was the same (i.e., CS-VS); “different” response RTs were faster when the irrelevant feature was different (CD-VD). In the syllable condition, RTs for different responses were faster when the vowel was different and the consonant was the same (i.e., CS-VD) than when the consonant was different and the vowel was the same (i.e., CD-VS). This suggests that vowel information may be more easily accessible for a comparison than consonant information. These results provide evidence for the parallel transmission of information about stop consonants and vowels in syllables, and an interaction of auditory and phonetic levels of processing in speech perception.
Standards for the Measurement of Aircraft Flyover Noise
Authors: Zwieback E. L.
Published: May 2012

The actual measurements of aircraft flyover noise involve a large number of independent variables. The moving aircraft as a set of noise sources, the atmosphere as a nonhomogeneous and changing propagation medium, and the ground microphone station as a near-surface receiver represent a unique set of parameters for an individual measurements. The normalized data may take many forms, to include basic acoustic engineering data and psychoacoustic data. To encourage uniformity and minimum technical requirements for the measurements, a number of organizations world-wide, from the industry and the government, have long been active in formulating measurement standards. At the current time, there exist several comprehensive measurement standards. These standards differ in some respects, beyond the necessary differences for the different applications intended. Currently, several organizations, both international and national, are formulating revisions to existing standards to be more complete, incorporate technical advancements, and hopefully minimize unnecessary differences. The scope of these revisions is described.
The Auditory Receptor Organs of Birds
Authors: Smith Catherine A.
Published: May 2012

Birds have retained at least two reptilian features; one, the compact arrangement of sensory and sustentacular cells on the basilar membrane, and two. a kinocilium in many, if not all, of the hair bundles. The cytoarchitecture of the avian papilla Seems to be quite consistent between families. All the birds thus far examined (pigeon, chicken, parakeet, and sparrow) have two major types of sensory cells: tall hair cells and short hair cells. Each type has a characteristic distribution along the papilla, and a distinctive pattern of efferent and afferent nerve endings. The tectorial membrane is thick and bulky but highly cavitated. Only the tallest of the cilia appear to penetrate into its mass. It is also attached to all the sustentacular cells on the papilla. It appears that both birds and mammals eventually developed stabilized auditory receptor organs, but with a different organization. Even the most primitive of existing mammals (the monotremes) clearly point toward the direction of the organ of Corti and the cochlear duct which is found in the multitude of other living mammals. [Supported by NIH Grant No. 08813.]
Monte Carlo Method for Evaluation of Transducer Critical Components and Transducer Characteristics
Authors: Stec J. V. , Nelson R. A.
Published: May 2012

In the design and production of underwater acoustic transducers, two problems may arise. First, how does the design engineer specify the transducer component properties and their tolerances to best produce a cost effective transducer? Second, how does the production engineer determine if received transducer components will produce the desired quantity of acceptable transducers? The importance of these problems increases rapidly as the volume and production rate increase. This paper presents a Monte Carlo simulation capable of predicting the statistical variability of transducer characteristics from component variability data. The simulation consists of a power residue method of random number generation, a two-tailed chi-square test to insure that the numbers are random, a procedure which divides the probability density function of a component's property into equal area sections (equal chance for selection of property value) and a mathematical representation of the transducer. The simulation randomly chooses properties for the desired transducer components from their given (or assumed) distribution and generates the resulting transducer characteristics. Repetition of this procedure (Monte Carlo method) generates a series of random transducers which can be used to define the statistical variability of the desired transducer characteristic. An example of the results obtained using the simulation is presented.
Legal Aspects of Qualitative Municipal Noise Ordinances
Authors: Salter C. M. , Jones B-J. R. , Brittain F. H.
Published: May 2012

The most-favored of traditional approaches to statutory regulation of excessive noise has been the subjective or qualitative statute. We present an analysis of the legal problems of qualitative municipal noise ordinances. While such an enactment is a valid exercise of a state or municipality's police powers, a case study of the Provincetown, Massachusetts, experience demonstrates the statute's vulnerability on constitutional grounds. In Provincetown, prosecution under the subjective “disturbing the peace” ordinance was used to silence an unpopular retailer's amplified music. A sound truck ordinance in Kovcas v. Cooper and an auto muffler statute in Smith v. Peterson have been upheld out of apparent necessity rather than constitutional soundness. By prohibiting noise described merely as “unnecessary” or “annoying,” authorities leave a citizen without notice of precisely what conduct is violative of the statute, as is required by due process guarantees of the 14th Amendment. At the same time, there are obvious dangers of discriminatory enforcement where one noise may be less popular than another at equal emission level if measured on an objective decibel scale. A quantitative noise statute permitting objective measurement according to widely recognized acoustical standards obviates the legal pitfalls.
Legal Aspects of Quantitative Muncipal Noise Ordinances
Authors: Brittain F. H. , Jones B-J. R. , Salter C. M.
Published: May 2012

While quantitative noise ordinances eliminate many of the legal problems inherent in qualitative ordinances, certain potential legal problems are associated with writing and implementing a municipal ordinance. Specifically, limitations including the doctrine of state and federal preemption to municipal noise ordinances and the problems of enacting quantitative ordinances are developed and discussed. The costs of noise, noise legislation, and noise control upon the citizen, “polluter,” and municipal government are also discussed.
Microphone Requirements for Airport Noise Monitoring
Authors: Starr E. A. , Blanchard B.
Published: May 2012

The frequency response requirements for a microphone system to measure noise energy about an airport are reviewed. Several specifications, including the California Noise Regulations, for systems to perform such measurements have incorporated ANSI S1.4-1971 Type I requirements. In general, this standard is more stringent than required to make a reasonable measurement of HNL or CNEL. Alternate specifications are suggested, and typical data are used to compare various performance specifications.
Aberrant Temporal Summation Functions
Authors: Wright H. N. , Valerio M. W.
Published: May 2012

The threshold for 500-, 200-, 100-, 50-, 20-, and 10-msec tones was measured with the tracking method at 250, 1000, and 4000 Hz in a group of five listeners who simulated a hearing loss of about 40 dB. A sample of listeners presenting with temporal lobe lesions was also examined. The results on both groups of subjects were remarkably similar to one another. That is, where the threshold difference between a 20- and 500-msec tone is expected to be 10 dB, the differences observed here were in excess of 20 dB. In each instance, these aberrant results are interpreted not to be a result of a deficiency in the summing mechanism, but rather are due to a modification of the detection process.
Reaction Time as a Measure of Threshold and Supra-threshold Hearing. III. The Effect of Stimulus Duration
Authors: O'Connor T. , Hienz R. , Miller J.
Published: May 2012

White noise thresholds were investigated as a function of stimulus duration in a monkey performing an auditory reaction time task. Latency-intensity functions were obtained for six durations, ranging from S to over 200 msec. Threshold was defined for each duration from ogive functions relating percentage of correct responses to stimulus intensity. Increasing stimulus duration resulted in lower thresholds. The slope of the threshold-duration function was asymptotic to a minimum value as duration was increased. Suprathreshold hearing functions in the form of equal latency contours will be described. In addition, the effect of aspirin upon threshold was studied at three stimulus durations. The subject showed a temporary threshold hearing change similar to that observed using "brief-tone" audiometry in humans with a cochlear hearing loss. A general elevation of threshold was observed. The greatest change occurred with the longest duration stimulus. [Work supported by PHS Grants NS 08181, RR 00166, NS 50637, and GM 00260.]
Amplitude and Phase Fluctuations in Shallow Water
Authors: Barakos P. A. , Speidel S. L.
Published: May 2012

When an acoustic wave propagates through a turbulent medium, such as the ocean, the amplitude and phase of the incident wave experience fluctuations due to the variations of the acoustic index of refraction of the medium. Time series of experimental data of both the amplitude and phase fluctuations, the index of refraction, and the horizontal and vertical current components were obtained for a nearshore environment off Southern California. The acoustic signal output from a fixed narrow-beam ultrasonic source radiating in the CW pulse mode at 80, 90, and 100 Hz was received by a fixed directional receiver 25 m away. The vertical displacement between the two transducers was 17 m, and a sampling interval of 0.25 sec was used. This exercise was conducted in the presence of a strong seasonal thermocline separating water masses of different acoustical properties. The thermocline undergoes time- and space-dependent vertical motions related to internal waves. The projector was situated above and the receiver below the thermocline. Herein the line-of-sight propagation problem is considered and attention is given to the correlation functions and variances of the amplitude and phase fluctuations of the acoustic wave and their relation to the variation of the index of refraction along the path of wave propagation. It is shown that the turbulence near the transmitter has more effect on the fluctuation than the turbulence near the receiver.
The Effects of Horizontally Varying Internal Wave Fields on Multipath Interference for Propagation through the Deep Sound Channel
Authors: DeFarrri Harry A. , Yacoub Kamal
Published: May 2012

Fluctuations of CW signals transmitted through real ocean paths are characterized by smooth slow variations in phase and rapid noise-like variations in transmission loss. The variations are thought to be the results of internal waves, which perturb the sound speed field and thereby produce time-varying multipath interference. This study is concerned with modeling the effects of large-scale horizontal and vertical perturbation of the sound speed field on multi-path interference of CW transmission, for the particular case of long-range propagation through the deep sound channel. The vertical profile is approximated by two layers of linear sound speed gradient and arbitrary horizontal variations are introduced by numerical methods. Propagation is modeled for internal wave field which is invariant, coherent, or random in the horizontal. The travel times along individual ray paths are shown to be influenced by fluctuations of the internal wave field with horizontal scales which are (1) approximately equal to the cycle distance of the ray or (2) greater than several cycle distances of the ray. Both scales of disturbance induced multipath interference but the latter also induces temporally correlated phase shifts for all rays.
Broad-Band Surface Wave Attenuation for Structure Characterization
Authors: Graham L. J. , Alers G. A.
Published: May 2012

A broad-band acoustic instrument consisting of a white-noise generator and a damped piezoelectric receiver has been used to analyze the frequency spectra of 0–3 MHz acoustic surface waves on complex structures. By varying the path length, the frequency dependence of attenuation can be obtained. This attenuation data are used in the design of acoustic emission monitoring systems, where the frequency-dependent characteristics of the acoustic paths between possible acoustic emission sources and the detection transducer are needed. In addition, the data can be directly used in characterizing structures such as honeycomb sandwich panels where defects produce changes in the surface wave attenuation. The system used to make these measurements are described and results for a variety of structures are presented.
Error Analysis for Ultrasonic Flowmeters
Authors: Karplus Henry B.
Published: May 2012

The ultrasonic flowmeter is attractive for permitting unob-structive flow, is easily maintained, and has the potential for an absolute instrument. Particularly attractive is the design utilizing transducers on the outside of the pipe conducting the fluid to be metered. Refraction errors at the pipe/fluid interface can be computed and the effect of temperature and temperature gradient must also be taken into account. The assumption that this refraction error is zero for the immersed transducer is not entirely valid because there is still a refraction between the stationary fluid around the transducer and the flow. The largest velocity measurement error is due to the uncertainty of the flow profile. This can be eliminated by a detailed profile measurement using several ultrasonic paths or averaged approximately by using a single path along a chord not passing through the pipe axis. Until a few years ago, the greatest difficulty was the measurement of time interval differences of a few tens of nanoseconds. Timing errors are kept low by careful control of signal amplitude and gate switching level. Random fluctuations of this are further minimized by averaging many measurements. Signals of large amplitude and rapid rate of rise are necessary to reduce effects of extraneous noise. High-output transducers capable of withstanding high temperatures for sodium flow measurements in nuclear reactors have been built.
Quasi-Turbulent Damping at Wind Instrument Joints and Tone Holes
Authors: Benade A. H. , Cuddeback John K.
Published: May 2012

The measured Q of air column resonance can fall quickly with playing level by a factor of three or more at fortissimo (SPL ≳ 143 dB inside first open tone hole) below the classical nonturbulent value associated with softer playing (SPL < 100 dB). The increased damping arises at all sharp-edged discontinuities in the bore, such as in mouthpiece receivers, valves, and tuning slides of brass instruments, and the sockets, tenons, and tone holes of woodwinds. Rounding these edges gradualizes the growth of the damping. Good instruments so treated become responsive and “flexible.” When an instrument is thoroughly warmed up, similar changes arise via the temperature dependence of the kinematic viscosity and thence of the Reynolds number. Rounding of even a single corner is noticed by many players. Rounding also produces a “darkening” effect on tone color, owing to reduction of nonlinear turbulent effects. Musicians recognize a tonal distinction between drawn and soldered tone holes on saxophones. Rounding the corners of the latter eliminates the distinction. Study of numerous instruments and modification of many confirm that rounding from long use is one way that age improves wind instruments, provided bore and tone hole dimensions are not deranged by wear. Care with rounding can eliminate many problems of “unvented” tone holes (such as hissing, stuffiness, and unclear tone) if they are also sized correctly to maintain uniformity of tone hole lattice cutoff frequency.
Cochlear Microphonic and Whole-Nerve Action Potential Changes after Long Exposure to Low-Level Noise in the Guinea Pig
Authors: Benítez L. D. , Pardavé M. A.
Published: May 2012

Behavioral temporary threshold shifts (TTS) have been shown in the chinchilla [Benítez, Eldredge, and Templer, J. Acoust. Soc. Am. 52, 1115–1123 (1972)] to be correlated with cochlear microphonic (CM) and whole-nerve action potential (AP) losses in sensitivity as well as in maximum voltage. The guinea pig ear differs significantly both anatomically and physiologically from the chinchilla's; as a result, it does not seem to be as susceptible to TTS at noninjurious noise levels, except at those frequency bands where middle-ear impedance (with auditory bulla closed) and other factors are more favorable. At times varying from 2 h to 48 h, after termination of noise exposures of 48 h duration to an octave band of noise (7–14 kHz) with a sound pressure level of 95 dB, the CM from the first three cochlear turns as well as the whole nerve AP were measured in guinea pigs. Losses in sensitivity as well as in maximum voltage were found in the CM recorded from the first turn; CM recovered gradually with time, reaching normal levels at about 40 h after termination of noise exposures. The AP showed similar losses. Microscopic examination of the organ of Corti of these animals showed no loss of hair cells.
Evidence for a Possible Genetic Influence on Noise-Induced Cochlear Damage
Authors: Walloch Richard A. , Brummett Robert E.
Published: May 2012

Two strains of guinea pigs were exposed to a 1-kHz tone at +50 dB re 1 dyn/cm2 for 30 minutes. One of these strains was genetically homogeneous, while the other strain was genetically heterogeneous. A 1-µV isopotential curve for the ac cochlear potential was obtained immediately before exposure to the damaging sound, as well as 10 minutes and 56 days after the sound exposure. The isopotential curves obtained from the homogeneous group were significantly less variable than the curves obtained from the heterogeneous group. This difference in variability was more pronounced 10 minutes after the damaging exposure than it was 56 days after the exposure.
A Study of the Relationship between Consonant-Vowel Ratios and Speaker Intelligibility
Authors: Hecker Michael H. L.
Published: May 2012

Recordings by two male speakers of the 300 monosyllabic words of the Modified Rhyme Test were digitized, displayed, and phonetically segmented using an interactive computer system. For each speaker and consonant under test, a consonant-vowel ratio was computed from measurements of the energy in the appropriate consonant and vowel segments. It was found that Speaker 1 had consistently higher C-V ratios than Speaker 2. The words of Speaker 1 were then modified in amplitude so as to reduce his C-V ratios, and the words of Speaker 2 were modified so as to increase his C-V ratios. Analog recordings of the modified and unmodified words were prepared and presented as intelligibility tests to 20 listeners at two signal-to-noise ratios. The results show that (a) Speaker 1 (with the naturally higher C-V ratios) was more intelligible than Speaker 2, and (b) reducing the C-V ratios of Speaker 1 reduced his intelligibility while increasing the C-V ratios of Speaker 2 increased his intelligibility. Responses to individual words were analyzed to determine which consonants contributed most to these changes in intelligibility.
Two “Voiceprint” Cases
Authors: Papçun George , Ladefoged Peter
Published: May 2012

The evidence presented in two recent California “voiceprint” cases is reviewed. In one, the defendant, Nehemiah Jackson, was accused of making a telephone call to the Riverside police station as a result of which two policemen were murdered. The call was recorded on a 24-hour tape recorder with a very low signal/noise ratio and an apparent upper frequency limit of about 2300 Hz. Copies of the recordings will be played, and the spectrograms which were used for comparing the voices of the accused and the unknown caller will be displayed. The case ended in a hung jury. In the other case the defendant, Stephen Chapter, was accused of making a bomb threat. The Court found the defendant not guilty, and the evidence “not reliable in this particular case due to: (a) Mistakes and errors in preparation of the spectrograms used in making the identification. (b) Failure to ascertain the existence of such errors. (c) Demonstrated listening errors in court while under cross-examination. (d) Tentative misidentification of the court ordered exemplar. (e) Failure to maintain adequate records/logs during conducting of tests.” These two cases raise the issue of how to extrapolate from laboratory studies to forensic situations.
The Hazardous Noise Exposure to Which Airline Passengers are Subjected
Authors: Lane S. R.
Published: May 2012

Babies and children, in particular, and adults should not be exposed to the noise levels inside commercial aircraft. The passenger cabin noise levels during flight equal or exceed even the inappropriately high legal limits which have been shown not to protect hearing and health. Studies have shown that airline pilots have above normal hearing loss. Thus, each day (in the U. S.) about 400,000 airline passengers are exposed to long periods of excessive and hazardous noise radiation. This unfunded study shows that cruise flight noise levels inside Boeing 737 and 727, Lockheed L-1011, and McDonnell-Douglas DC-10 aircraft are in the 85 to 100+ dBC (or 80 to 90+ dBA) range. A few data released by the EPA indicate there are similar noise levels in all commercial aircraft. Despite the seriousness of the problem, the Cumulative Indices for JASA and contemporary literature on acoustics for the years 1948 to 1972 show no published reports on jet aircraft cabin noise. Consequently, airline passangers have not been informed about the noise levels and effects, and have been deprived of information necessary for making rational judgments about the acceptability of air travel noise environments.
Development of Community Noise Ratings for Railroad Operations
Authors: Swing J. W. , Pies D. B.
Published: May 2012

The noise environment of railroad line operations (on-track operations between yard facilities) has been analyzed and expressed in the form of the CNEL (Community Noise Exposure Level). This involved over 60 field measurements of locomotive- and freight-car-generated noise over a variety of operating conditions at varied locations. Empirical relationships were developed to account for the effects of speed, train length, grade (up or down), track conditions, degree of track curvature, elevated or depressed right-of-way, and presence of acoustic barriers. These factors were combined to synthesize, by a computer, train passby time histories and time-integrated noise exposure levels (SENELs-Single Event Noise Exposure levels). SENELs from actual time histories have shown good agreement with the computer-synthesized versions. Additional work has been accomplished in the areas of propagation of railroad noise into surrounding communities. Air absorption and excess ground attenuation correction factors have been included in the method to allow prediction of noise levels out to distances of over 1000 ft. Finally, attempts have been made to correlate CNEL contour values to the degree of expected community reaction based upon previous Wyle community noise studies.
Combination Tone 2f1—f2 in Responses of Single Cochlear Nerve Fibers: Evidence against Essential Non-Linearity
Authors: Kim Duck On , Littlefield Warren M. , Pfeiffer Russell R. , Molnar Charles E.
Published: May 2012

Fourier analyses have been conducted upon period histograms of responses of single cochlear nerve fibers to a pair of phase-locked, equal-amplitude tones whose frequencies f1 and f2 in relation to the characteristic frequency (CF) of the nerve fiber under study are given by the ratio CF:f1:f2 = i:j:k, where i, j, and k are positive integers satisfying i<j<k and i = 2j−k (typically i = 10, j = 11, and k = 12). For moderate-to-high stimulus levels, the relative level of the 2f1−f2 component with respect to the primary components changes only slightly, which is consistent with the previous report by Goldstein and Kiang [Proc. IEEE 56, 981 (1968)]. Confirming the prediction of a nonlinear basilar-membrane model which showed the above high-level property of the distortion component 2f1−f2 as well as a smooth transition into effectively linear response characteristics for sufficiently low input levels [Kim et al., J. Acoust. Soc. Am. 53, 324 (1973)], we have observed that the 2f1−f2 component in cochlear nerve responses decreases with decreasing stimulus levels faster than the primary components for low stimulus, levels. The low-level characteristic of the 2f1−f3 component leads to a theoretically important conclusion that the 2f1−f2 combination tone in responses of a cochlear nerve fiber is not a result of an essential nonlinearity, and supports the linear characterization [Littlefield et al., J. Acoust. Soc. Am. 54 (1973) (in press)] of single cochlear nerve fiber responses for the most sensitive region of the response area corresponding to low stimulus levels.