bluuebunny/crossref_metadata_2025 huggingface dataset:
Making Pressure Measurements in Insert Earphone Couplers and Real Ears
Authors: Sachs Richard M. , Burkhard Mahon D.
Published: October 2005

When pressure measurements in couplers were made via a probe tube, it was often observed that the pressure frequency response would drop sharply at a single frequency. The frequency (f0) of this minimum depended on cavity dimensions and relative position and size of probe tube and sound inlet tube. An equation from Ingård [J. Acoust. Soc. Amer. 20, 665 (1948)] served to explain this phenomenon. Pressure was theoretically determined at various locations within a hard-walled cylindrical cavity when driven by a constant volume velocity inlet of circular symmetry. At each location, a transfer impedance was thus defined as the ratio of pressure to input volume velocity. In the region around the inlet port, each transfer impedance passes through zero from negative to positive reactance as frequency increases. Two hard-walled cavities were examined in detail: (1) the main cavity of a 2-cm3 HA-2 coupler and (2) a cavity approximating the dimensions of the external ear canal (between earmold tip and eardrum). Contours of constant f0 are given for these two cavities with experimental verification. The phenomenon can be modeled as a series inertance/compliance. [Supported by Knowles Electronics, Inc.]
Binaural Loudness Summation for Pure Tones
Authors: Del'Aune W. R. , Elfner L. F. , Franzen O. G. , Bothe G. G.
Published: October 2005

A two-alternative forced-choice paradigm was employed to assess the detectability of monaural and binaural presentations of threshold auditory stimuli. A 500-Hz tone was presented to the listeners in three possible configurations—left ear, right ear, or left and right ears—and the S was required to state whether the auditory stimulus occurred in a visually delineated “first interval” or “second interval.” From this data detectability estimates were determined for each of the different stimulus configurations, both when each stimulus configuration was presented in a discrete block and when the stimulus configurations were randomly alternated. Single and multichannel models for binaural hearing were evaluated. It was concluded that while binaural summation did occur in both the discrete blocks and the random alternations, a simple single-channel model could not fully explain the data.
Recommended High-Frequency Audiometric Threshold Levels (8000–18 000 Hz)
Authors: Northern J. L. , Downs M. P. , Rudmose W. , Glorig A. , Fletcher J. L.
Published: October 2005

The normal range of auditory sensitivity with high-frequency pure-tone signals (8–18 kHz) has been well bracketed by several laboratory studies using experienced listeners. Results from a field survey of high frequency hearing thresholds conducted at the Denver 1968 American Speech and Hearing Association Convention with 237 subjects agree closely with results reported in previous studies. The purpose of this presentation is threefold: (1) to report high-frequency field-survey hearing-threshold data as a function of age and sex; (2) to review and compare results of high-frequency audiometric studies of normal-hearing subjects; and (3) to recommend acceptance of the Zislis and Fletcher [J. Aud. Res. 6 (1966)] results obtained from 6th–12th-grade girls with slight modification as an arbitrary compromise for “most sensitive hearing” reference standards for 0 dB HTL in audiometric measurements at 8000–18000 Hz.
Simple Method for Converting Octave Band Data to Equivalent A-Weighted Levels
Authors: Gasaway Donald C.
Published: October 2005

Increased adoption and use of A-weighted sound levels for bioacoustic and psychoacoustic purposes and applications have progressively increased during the past decade. Newly proposed federal and state legislation employ A-weighted levels as measures of acoustic limits where hearing conservation and noise control measures must be adopted and enforced. Many bioenvironmental engineers, industrial hygienists, and others face the task of converting noise measurements recorded in octave bands to equivalent A-weighted levels. The author has devised a simple dial-type calculator which simplifies the task of converting octave band data to equivalent A-weighted values for the various octaves so that the over-all A-weighted level can be determined. The calculator provides five A-weighting corrections; two for data obtained using the old center frequencies and three for data recorded using the new preferred octaves.
Large-Scale Acoustic Testing of Gas Turbine Silencer Components and Reciprocating Engine Silencers Using a Dynamic Insertion Loss and Attenuation Facility
Authors: Halter E. J.
Published: October 2005

Since late 1970, the Maxim Silencer Product Center has been testing full-scale gas turbine silencer components and large reciprocating engine silencers under simulated field conditions of flow and intense soundpressure level. A 73-in. centrifugal fan and Ling Electronics EPT-94B electro-pneumatic transducer are assembled in a duct system to provide more than 100 000 SCFM flow and more than 2000 acoustic watts of shaped acoustic noise as input to test silencers. Full-scale gas turbine splitter panels are tested in a 4-ft by 4-ft duct at input acoustic levels corresponding to the unsilenced exhaust noise of a more than 30-MW gas turbine and at flows varying from zero to more than 150 FPS. A shaped random noise electrical input to the EPT-94B noise source is used. A circular duct transition section is used to modify the basic system for tests of large reciprocating engine silencers. Sine sweep and shaped random noise electrical inputs to the noise source are used.
Noise Measurements on Desk Calculators and Typewriters
Authors: Martin R.
Published: October 2005

To get information on the state of the art and to find a basis for the preparation of a measuring standard, the noises of 32 desk calculators and 14 electric typewriters have been measured. Measured quantities were the sound-power level in the reverberation room and the mean A-weighted impulse sound level in the anechoic room. The mean level was derived from the dc-output of the impulse sound-level meter by a simple continuously operating device and was taken over one operation cycle of the machine under test at five microphone positions, each at a distance of 1 m from the surface of the machine. The results range from 61 to 73 dBAI for desk calculators and from 65 to 74 dBAI for typewriters. Since impulses like the printing noise of a calculator are not suited for reverberation room measurements and the directivity of the sound radiation is sometimes of interest, it seems appropriate to recommend for these measurements free-field conditions and the impulse sound level.
Acoustics of the Calvin C. Flint Auditorium, DeAnza College, Cupertino, California
Authors: Wetherill Ewart A. , Paoletti Dennis A. , Lewitz Joel A. , Walsh David P.
Published: October 2005

The recently completed 2571-seat Calvin C. Flint Auditorium on the DeAnza College campus is a community financed multipurpose performing arts facility located approximately 50 miles south of San Francisco. Uses range from lectures and speech-oriented presentations through a full complement of musical activities with primary acoustical design emphasis on orchestral performances. The hall is basically rectangular, with two balconies which are seven rows deep at the rear and two rows deep for the full length of the side walls. Acoustical variability is achieved by the inclusion of an orchestra enclosure and the use of longitudinally tracked sound-absortive curtains above a “visual” sound-transparent ceiling. Acoustical properties and subjective evaluations of live performances are discussed. In addition, special aspects of the sound-amplification and air-handling systems are also discussed. [Architects for the auditorium are Ernest J. Kump Associates of Palo Alto and Gwathmey, Sellier, Crosby Architects of San Francisco.]
Speech Privacy in an Open Office Landscape
Authors: Herbert R. Kring
Published: October 2005

The noise reduction of a number of source-receiver paths were measured in an open office landscape area. The articulation index (AI) was calculated from these values and compared with theoretical calculations for AI and subjective evaluations of privacy level.
Infrasound-Originated Seismic Waves at Long Range from Apollo Launches
Authors: Dalins I. , McCarty V. M. , Donn W. L.
Published: October 2005

Previously unpublished features of air-coupled seismic signals from Apollo launches as recorded with seismographs at long distances (370 km and more) will be presented, together with instrumentation used in this technical effort. The advantages and also certain apparent disadvantages of the seismic method for detection of weak infrasound signals will be discussed in detail. These studies indicate that the resonance mechanism, which occurs when phase-velocity matching at the atmosphere-ground interface exist, becomes very important in transfer of acoustic energy. The unique features of this resonance mechanism will be described.
Amplitudes of Gravity and Acoustic Modes in Air Waves from Nuclear Explosions
Authors: Donn William L. , Balachandran N. K. , Posey J. W.
Published: October 2005

Relative amplitudes of gravity and acoustic modes in the ground-level pressure fluctuations produced by acoustic-gravity waves at long range from nuclear tests show considerable variation. The acoustic modes have higher amplitudes than the gravity modes when stratospheric winds have strong components in the direction of propagation of the waves. When stratospheric winds are in the opposite direction, the acoustic modes have much smaller relative amplitudes. The results have been found to be valid for different test locations and various receiver locations. These observations have been verified theoretically by synthesizing infrasonic farfield pressure waveforms generated by nuclear explosions, using actual stratospheric temperature and wind data.
Observation of Infrasound Generated by Lightning Discharges
Authors: Goerke V. H.
Published: October 2005

Nearby lightning discharges produce pressure perturbations observable by ground-based microphones. The microphone system records infrasound at frequencies lower than 5 Hz. Each lightning flash produces a pressure pulse with a sonic-boom-like character with the predominant energy near 1 Hz. The peak-peak amplitude is near 1 dyn/cm2. The signals arrive at the microphones at elevation angles from about 45° to nearly directly overhead. Several hundred infrasonic arrivals observed over a period of a few hours on 28 June 1970 have been examined. Pressure variations versus time for some of these will be discussed. Lesser numbers of pressure perturbations have been observed at other times. On one occasion the lightning flashes were entirely intercloud types.
Generation of Anomalous Ionospheric Infrasonic Oscillations by Thunderstorms
Authors: Moo C. A. , Pierce A. D.
Published: October 2005

Experimental evidence recently reported by Georges, Davies, Detert et al. shows ionospheric oscillations during periods of thunderstorm activity. Spectrum analysis of RF Doppler perturbations indicates infrasonic periods between 2 and 5 min are present. These oscillations are coherent over lateral ranges of at least 35 km and throughout the lower ionosphere, frequently for many hours duration, consistent with their interpretation as acoustics waves of very long wavelength. The present paper examines the generation of such waves within the general context of Lighthill's theory of aerodynamic sound. Arguments and ground-based data are presented which suggest that the turbulent air motions associated with the thunderstorms lie principally within a range of time periods with marked enhancement at the Brunt-Vaisala period. The fact that the periods of the ionospheric oscillations are substantially lower than such natural periods are explained as being due to the doubling in frequency of generated noise relative to local turbulence predicted by the Lighthill theory.
Estimation of Nuclear Explosion Energies from Infrasonic Waveforms
Authors: Posey Joe W. , Pierce Allan D.
Published: October 2005

Previous theoretical interpretations of the microbarograph records of infrasonic waves generated by nuclear bomb tests have required some explicit knowledge of the average atmospheric temperature and wind profiles above the path connecting source to microbarograph. A derivation is given based on the authors' recent single-mode theory [Geophys. J. Roy. Astron. Soc. (1971)] of an approximate theoretical relationship between certain waveform features and energy yield which is insensitive to changes in atmospheric structure. In particular, it indicates that energy should be proportional to a given waveform's first peak to trough pressure amplitude and to the three-halves power of the time interval between first and second peaks. This result is compared with data presented by Donn and Shaw [Rev. Geophys. (1967)] and by Harkrider [J. Geophys. Res. (1964)] utilizing Bath's [Univ. Uppsala (1962)] yield estimates based on seismic data. The general trend of longer period signals being of lower amplitude than shorter period signals recorded at the same range from explosions of comparable yield seems amply substantiated by the data.
Dependence of Cylindrical-Geometry Acoustooptic Light Modulator Efficiency on Light Beam Diameter
Authors: Hargrove L. E.
Published: October 2005

This paper presents further results on the farfield diffraction of a Gaussian light beam that has passed axially through a cylindrical ultrasonic wave. Numerical calculations of the on-axis light modulation depth have been extended into the range where the light beam waist includes several nodes of the cylindrical standing wave. These results are characterized by the value A, at the waist radius, of the argument of the zeroth-order Bessel function which describes the radial dependence of the ultrasonic perturbation of refractive index. Previously [L. E. Hargrove, J. Acoust. Soc. Amer. 49, 120(A) (1971)], only results for A = j0, 1, where jn, m is the mth nonzero root of the nth-order Bessel function, had been obtained. These new calculations confirm that A≃j0, 1 results in maximum modulation efficiency and show the amount this efficiency is reduced when, for example, a nonoptimum value of A is determined by constraints of a particular application. Calculated farfield spatial distribution results will also be presented
Clinical Study to Evaluate Rock Music, Symphonic Music, and Noise as Sources of Acoustic Trauma
Authors: Barry John P. , Thomas Ian B.
Published: October 2005

Recent studies have implicated rock music as a potential source of hearing damage. The present study was designed to evaluate, under carefully controlled clinical conditions, the relative damage potential of rock music, symphonic music, and bandlimited white noise. Ten normal-hearing subjects were exposed to each program source for 60 min at an average SPL of 95 dB binaurally through electrostatic headphones. After each exposure a TTS5 was obtained by Békésy audiomerry at each of 10 frequencies. An octave-band analysis demonstrated that both the rock and symphonic music had very similar frequency spectra being within ±4 dB from 125 to 8000 Hz and having maxima at 500 Hz. The TTS5s for both rock and symphonic music were nearly identical with maximum TTS5s from 2000 to 5000 Hz and averaging 8–10 dB. The white noise, being richer in high frequencies, produced average TTS5s of 11–17 dB for the same test frequency range. Males showed generally higher TTS than females; for example the white-noise induced TTS5 at 4000 Hz was 22 dB for males and 11 dB for females. In conclusion symphonic music is just as potentially harmful as rock music if played at the same intensity and daily 1-h exposures at less than or equal to 100 dB SPL appear quite safe for the average listener.
Operational Noise Levels of Motor Vehicles
Authors: Hillquist Ralph K.
Published: October 2005

The noise emitted by motor vehicles varies in intensity as a function of speed and operating mode. For highway operation, the relative significance of the various vehicle noise sources is similarly dependent. Bounds of operational noise levels for representative automobiles are presented. The relevance of current test methods to typical vehicle operation is discussed.
Spectral and Directional Characteristics of Truck Tire Noise
Authors: Leasure William A.
Published: October 2005

The noise from tires predominate over engine/exhaust noise at moderate to high speeds provided the truck is equipped with an adequate muffler and is in a good state of repair. The noise generation characteristics of typical truck tires were measured during an extensive field investigation. The data were frequency analyzed in one-third octave bands and the A-weighted sound level was calculated from these data. Measurement and analysis techniques leading to the acquisition of these data will be discussed. Similarities and differences in the data among the various tread designs and the establishment of data trends associated with changes in speed, load, tread depth, or pavement surface will be discussed. Three-dimensional plots of sound-pressure level versus frequency and time clearly indicating the doppler shift effect will be presented. Equal sound-level contour plots of the data show major lobes to the front and rear of the truck as well as to the side. These spectral and directionality data will supplement existing data on total vehicle noise and serve as a basis for the prediction of noise levels in nearby communities at various distances from present and proposed highways.
“Noise Thermometer”: A Large-Display Sound Level Meter
Authors: Brammer A. J. , Toole F. E.
Published: October 2005

The control of urban noise by means of quantitative limits on the noise emitted by motor vehicles, while in some ways attractive, bears the problem that the populus has little understanding of the specified sound levels. As an experiment in public education a large-display sound level meter was constructed. The indicator is an 8-ft column of lights, the illuminated height of which registers the sound level, from 70 to 100 dBA, in 2-dBA steps. In a roadside installation this would be mounted on, say, a lamp post, with the microphone located 100–150 ft away at the distance from the traffic lane specified in the local noise regulation. Motorists passing the microphone see the thermometer-like display of sound level ahead and can compare the noise produced by their own vehicles with the maximum permitted level as indicated by a vehicle silhouette. A “hold” feature is built into the device so that there is ample time for the driver to observe his maximum noise level. The design, operation, and use of the device will be discussed.
Observations of 1–16 Hz Acoustic Aurora
Authors: Procunier R. W.
Published: October 2005

Acoustic aurora have been heard by long-term residents of the arctic. They have also been recorded on microbarographs. Acoustic events associated with aurora are now reported in the near infrasonic range (1–16 Hz) at Barrow, Alaska. These observations were made with the aid of a resonant detector achieving a high signal-to-noise ratio similar to that used in extending the rocket-grenade technique to 109 km. Over 100 impulsive events of a quasirepetitive nature were recorded on a patrol basis during January, 1970. Initial observations of acoustic events were correlated with disturbed magnetic conditions and optical aurora but uncorrelated with lower frequency auroral microbarograph events at College or Inuvik.
Separate Speech and Nonspeech Processing in Dichotic Listening
Authors: Day Ruth S. , Bartlett James C.
Published: October 2005

Temporal order judgment (TOJ) in dichotic listening can be a difficult task. Previous experiments that used two speech stimuli on each trial (S/S) obtained sizable error rates when subjects were required to report which ear led (TOJ-by-ear). When subjects were required to identify the leading stimulus (TO J-by-stimulus), the error rate increased substantially. Apparently, the two speech stimuli were competing for analysis by the same processor, and so were overloading it. The present experiment used the same TOJ tasks, but presented a speech and a nonspeech stimulus on each trial (S/NS). The error rate was comparable to that of S/S for TO J-by-ear, but did not increase for TO J-by-stimulus. This would be expected if the speech and nonspeech stimuli are being sent to different processors, each of which performs its analysis without interference from the other. The interpretation of the data given here is consistent with the results of standard identification experiments reported elsewhere: when asked to identify both stimuli on each dichotic trial, subjects made many errors on S/S, while performance was virtually error-free on S/NS.
Is the Left Hemisphere Specialized for Speech, Language, or Something Else
Authors: Papçun George , Krashen Stephen , Terbeek Dale
Published: October 2005

Experienced Morse code operators showed significant right-ear superiority, indicating left-hemisphere lateralization, for the perception of dichotically presented Morse code letters. No significant lateralization was found for rapid monotically presented Morse code words. Subjects who did not know Morse code did not show significant lateralization when dichotically presented with a set of stimuli which included all Morse code letters; however, they showed a tendency toward left-hemisphere lateralization with a set of Morse code letters which were restricted in duration and presented at relatively low intensity. Our results show that articulability is not a necessary property of stimuli lateralized to the left hemisphere in dichotic listening; a possible further interpretation is that it is language rather than speech that is lateralized to the left hemisphere.
Is Vowel Perception Non-Euclidean
Authors: Terbeek Dale , Harshman Richard
Published: October 2005

In continuation of an experiment described previously [D. Terbeek and R. Harshman, J. Acoust. Soc. Amer. 50, 147(A) (1971)], judgments of perceptual similarity and difference for 12 natural vowel sounds were obtained from native speakers of Turkish and Swedish. These new data, like the earlier data from English, Thai, and German subjects, were analyzed using the PARAFAC multimode factor analysis method [R. Harshman, UCLA Working Papers in Phonetics No. 16 (1970)]. The resulting perceptual spaces are roughly interpretable in terms of traditional vowel descriptions, but certain difficulties remain. The results for the five languages tested, together with results reported by other investigators, were subjected to several further types of analysis. The patterns which emerge suggest that the function relating perceived distances between vowels to their positions along underlying perceptual dimensions is non-Euclidean in two ways. First, the perceptual dimensions do not lie orthogonally to one another, implying that they are related in meaning. Second, they interact nonlinearly, producing a curved space, an effect which causes the extraction of an uninterpretable dimension when linear models are used.
Self-Demodulation of Predistorted Pulsed Carriers
Authors: Davy B. A. , Hixson E. L.
Published: October 2005

It is known that nonlinear effects in water cause demodulation of a pulsed carrier such that a signal proportional to the second time derivative of the square of the pulse envelope develops in the insonified medium. Previous experiments [B. A. Davy, E. L. Hixson, and T. G. Muir, J. Acoust. Soc. Amer. 50, 132(A) (1971)] indicated agreement with theory for several pulse envelope shapes. An extension of this work is to predistort the envelope function by time integrating it twice and taking its squareroot. The resulting signal was then used to drive a 3-in.-diam circular piston at a depth of 10 ft in a fresh-water lake. Within the bandwidth limitations of the transmitter and receiver, the original signal was recovered. A low-pass filter was used to eliminate any of the carrier not already absorbed by the water. [This work was sponsored by the National Science Foundation.]
Shallow Water Investigations at Naval Underwater Systems Center
Authors: Sussman Bernard , Schumacher William R. , Kanabis William G.
Published: October 2005

The objective of these efforts is to formulate a model suitable for sonar performance prediction in shallow water. For this purpose, the BIF1 range, which is 18.6 miles long and 110 ft deep, was established with bottom-mounted acoustic sources and receivers and moored oceanographic telemetering buoys. Measurements of propagation loss, time smear, frequency smear, and, in addition, temperature profiles and salinity provided a data bank for average values and fluctuations of a number of shallow water acoustic and oceanographic parameters. These oceanographic data were supplemented by others obtained from hydrographic and aerial radiometer surveys and from geological studies. Evidence from tests using explosives as sound sources indicated that the lowest of the normal modes was predominant in the received signal. This led to the design and implantment of a normal mode source consisting of 25 hydrophones capable of transmitting any desired “low” mode in the frequency range 1–4.5 kHz. Normal mode theory and experiment helped resolve many previously noted anomalies. Scheduled additional studies should provide the data required for formulation of the shallow water model.
Fixed System Acoustic Measurements in the Straits of Florida
Authors: Steinberg J. C. , Kronengold M.
Published: October 2005

Relationships between variations of underwater sound transmitted across the Florida Current and variations in the medium are under study with fixed sound transducers and environmental sensors. Continuous-wave and pseudorandom-sequence signals of 420 Hz are transmitted on a continuous basis, and both the amplitude and the phase of the received signals are measured. Temperatures at two locations in the sound path and current transport across a 5.5-mile section of the path are also measured. Relationships between the measured quantities, which exhibit variations with periods from seconds to weeks and longer term trends, are investigated by correlation and coherence techniques. Variations of acoustic phase correspond to variations of temperature and transport but acoustic amplitude variations are noise-like without identifiable periods. Calculations with ray path models having plane parallel boundaries confirm the observations and indicate that their characteristic features arise from multipath interference relatively independent of effects of surface and bottom irregularities. For time intervals of a few minutes or less, phase variations are small and sound transmission is phase-coherent. Propagation in the Florida Straits, which has a maximum depth of 800 m, takes place primarily by refracted bottom-reflected rays. Tests with fixed instrumentation in the deep ocean off Bermuda indicated features of propagation by surface-reflected bottom-reflected rays which were similar to the features of the Florida Straits observations. [Work supported principally by the Office of Naval Research and partially by the Naval Ship Systems Command.]
Vibrating Shallow Shells and Solution Analogies to Vibrating Plates
Authors: Soedel Werner
Published: October 2005

A shallow-shell equation different from the Mushtari-Vlasov equations is derived by applying consistently the assumption that displacements tangential to the shell surface are of negligible contribution to strain for primarily transverse modes. Introducing coordinates that follow a plane projection of the shallow shell rather than the shell surface itself, a solution analogy to plates is developed for those cases where the two principal curvatures can be considered location-independent. The analogy applies to any combination of boundary conditions. Thus, natural frequencies and mode shapes of unorthodox shallow shell congfiurations, as for instance automobile roofs, can easily be estimated if the analogous plate solution is available. Certain analogy results are compared with solutions available in literature. Also, an analogy restricted to shallow spherical shells of arbitrary projected shape and combination of boundary conditions was developed for the Mushtari-Vlasov equations.
Random Vibration of Strongly Coupled Systems
Authors: Davies Huw G.
Published: October 2005

The response of two simple systems, such as beams or plates, strongly coupled at a point is discussed. Two models of a mass, spring and gyroscopic coupling mechanism are treated. It is shown that the SEA power flow-energy difference result can be obtained even when the coupling is strong. For one model of the coupling mechanism, the power flow can be expressed in terms of changes in modal resonance frequencies caused by the coupling.
Reduction of Farfield Pressure Radiation by a Constrained Damping Layer
Authors: Lai J. L.
Published: October 2005

The acoustic pressure radiated from an infinite elastic plate excited by a time-harmonic point force has been reported [D. Felt, J. Acoust. Soc. Amer. 40, 1489–1494 (1966)]. It is shown that above the coincident frequency, the farfield pressure pattern becomes directive, and the peak pressure can be reduced by structural damping of the plate. This paper presents an analysis of farfield pressure radiation from an infinite elastic plate with a constrained damping layer excited by a time-harmonic point force. The plate system is considered as an infinite three-layered plate with each layer having uniform thickness. Transverse shear deformation and rotary inertia of each layer in the plate are considered in the analysis. Numerical examples for rubber as a damping layer and either aluminum or steel as a constrained layer added to a steel plate in contact with water are presented. The reduction of the peak pressure above the coincident frequency by using a constrained damping layer is discussed. Also, the effects of the thickness and the effective bending stiffness of the plate system on the farfield pressure radiation are shown and discussed.
Conversion of Midsagittal Dimensions to Vocal Tract Area Function
Authors: Maeda Shinji
Published: October 2005

A quantitative model for relating lateral cineradiographic measurements of vocal tract dimensions to the acoustic characteristics of the corresponding speech waves was investigated. The vocal tract dimensions were specified, at any point i along the vocal tract, by two variables, a midsagittal dimension di and a cross-sectional shape factor si; for the pharyngeal region an elliptical cross section was assumed and for the mouth cavity a parabolic (concave or convex) tongue contour combined with Heinz's approximation of palatal shape. Seven of the si values were determined as independent variables in an analysis-by-synthesis procedure. In this procedure the formant frequencies of natural utterances were matched against formants computed from the model using midsagittal measurements taken from simultaneously recorded x-ray pictures. An eighth variable was added to represent the effects of the nonrigidity of the vocal tract walls. Values of the eight derived parameters and their variability from articulation to articulation have been closely examined. Implications for speech analysis and synthesis will be discussed.
Vowel Formant Frequency Characteristics of Esophageal Speech
Authors: Weinberg B. , Sisty N. L.
Published: October 2005

Highly representative esophageal vowels (n ;= 191), selected from a listening experiment, were subjected to formant frequency analysis. The major results of this acoustic analysis showed that: (1) mean vowel formant frequencies for female esophageal speakers (n = 13) were higher than for males (n = 14); (2) the changes in formant frequency from vowel to vowel were systematic and were essentially the same for normal and esophageal speakers, and (3) average vowel formant frequency values for esophageal speakers were consistently higher than those reported for normal speakers [G. Peterson and H. Barney, J. Acoust. Soc. Amer. 24, 175–184 (1952)]. Laryngectomy results in wellknown changes in source-function characteristics. The present data provide strong support for the hypothesis that removal of the larynx also results in changed vocal-tract transmission characteristics. A reduction in vocal-tract length for laryngectomized persons using esophageal speech is suggested. [This research was supported in part by the National Institute of Neurological Diseases and Stroke.]
Unit Responses of Collicular Cells to Binaural Tones of Changing Frequency and Intensity
Authors: Clopton Ben M.
Published: October 2005

Units in the inferior colliculus of barbituate anesthetized cats were recorded with metal microelectrodes. 100-msec tone bursts of varied frequencies and intensites were used to generate frequency-time raster displays of unit responsiveness to sounds at the two ears. In addition, continuous tones of swept frequency and intensities sinusoidally modulated over 12 dB in or out of phase at the two ears served to estimate unit selectivity to time-varying sound parameters. Most units responding to tone bursts also responded to tones of changing frequency or intensity or both. Asymmetrical ranges of frequency responsiveness depending on the direction of frequency sweep and different ranges of frequency responsiveness for ipsi- and contralateral ears characterized some units. While contralateral facilitation was predominant, ipsilateral input was found to facilitate, inhibit, or have no effect for different units. The encoding of locus versus change of locus of sound sources was examined by means of the interaural intensity modulation. [Research supported by grants from the National Institute of Neurological Diseases and Stroke and Academic Senate, University of California at Santa Barbara.]
Responses of Single-Cells in Inferior Colliculus to Free-Field Auditory Stimuli
Authors: Leiman Arnold L. , Hafter Ervin R.
Published: October 2005

Naturally produced interaural differences of time and intensity rarely occur alone, but rather are present in different amounts depending on the shape and size of the animal's head and pinnae and on the acoustic frequency of the stimulus. This study was designed to explore that problem by examination of differences in the neural responses to sounds presented to animals from different locations in free-field space. Stimuli were tone bursts (500–5250 Hz), present in an anechoic chamber from speakers arranged in a semicircle around the animal's head. Minimum resolution was 20°. Frequency characteristics of the speakers were compensated for by a computer-controlled attenuator. Animals were held by a specially designed headholder on which all support members are placed well behind their heads. Extracellular microelectrode recordings were obtained from cells in the inferior colliculus of barbiturate anesthetized cats. Responses of these cells to auditory direction were varied, but it appears that the dominant type of direction sensitive cell shows an initial response which carries information about the presence of sound, with a later discharge that carries information about direction
Examination of the Variances in Sonic Boom Waveforms Recorded During Flight Tests
Authors: Kamali Give , Pierce Allan D.
Published: October 2005

Maglieri et al. (NASA TN D-5040) have previously reported on the variability in F-104 sonic-boom signatures measured at 42 separate microphones spaced along an 8000-ft linear array. The present paper, based on the same data, is concerned with the time variation of the variances in the waveforms. Each waveform recorded during a given overflight is assigned a time origin corresponding to that when the overpressure first reached 13 of its peak value. The average signature p̄(t) = 〈p(t)〉 and the variance 〈(p−p̄)2〉 are derived from the data as functions of time t. Our interpretation of the theory of S. C. Crow [J. Fluid Mech. 37, 529 (1969)] is that a log-log plot of variance versus time should give nearly a straight line over intermediate times with a slope of −7/6. The experimentally derived plots tend to be concave downwards with a slope −α varying between −0.1 and −1.5 over the time interval during which the assumptions of Crow's theory would appear to correspond. A typical segment of the curve gives 〈(p−p̄)2〉/(Δp0〉2 = (t/tc)−α, where tc varies between 0.1 and 2.0 msec. A discussion is given of the choice of time origin in the analysis and of the possible errors due to the limited number of samples.
Simple Pressure Source Model of Jet Noise
Authors: White P. H. , Scharton T. D.
Published: October 2005

The simple pressure source model of the sound radiated by a cold, subsonic jet is investigated analytically and experimentally. From the simple source model, the ratio of the frequency spectra of the radiated sound power and the jet pressure is derived for an assumed form of the jet pressure cross correlation. Measurements of the spatial distribution of the over-all jet pressure levels, the frequency spectra of the jet pressure fluctuations, the axial and radial separation cross correlations of the jet pressures, and the cross correlation between jet pressure and farfield sound pressure are presented. Some implications of the simple source model with regard to noise suppression are also discussed.
Model for Prediction of Ocean Surface Reverberation
Authors: DeAngelis F. E.
Published: October 2005

A model for reverberation is described which is based on a solution for scattering of a low-frequency acoustic plane wave by a time-varying trochoidal surface. It is shown that under certain approximations the Helmholtz integral for a time-varying pressure release boundary leads to the characterization of the surface as a continuum of uniform isotropic reradiators undergoing circular harmonic motion about fixed points on the mean-free surface. A farfield solution is obtained for the scattered field for arbitrary incidence and observation directions. The solution is seen to be dependent on the sea height, wave speed and direction, and the reradiating aperture size. The scattered field spectrum is, in general, asymmetric and consists of spectral lines positioned at multiples of the surface-wave orbital frequency. The model is employed to predict reverberation due to single-path propagation for a historic source-receiver configuration. These predictions are compared with spectra obtained from experimental data.
Reflection of an Acoustic Beam by an Infinite, Pressure-Release Plane Surface
Authors: Welton P. J.
Published: October 2005

It is shown experimentally that the image solution is valid for the reflection of an acoustic beam by an infinite, pressure-release plane surface in water. This result is then used to demonstrate the necessity of applying both the Fresnel phase approximation and a realistic source directivity approximation to the Rayleigh-Sommerfeld diffraction formula if good approximations to both the angular distribution and the range dependence of the reflected field are to be obtained. This solution will be called the “modified-Fresnel” solution. The modified-Fresnel solution is compared with the usual Fraunhofer and Fresnel solutions which assume an aperture type of directivity function, and is shown to give very good agreement with the image solution.
Backscattering of Acoustic Waves from the Ocean Volume between Vancouver Island and Hawaii
Authors: Scrimger J. A. , Turner R. G.
Published: October 2005

Column strength measurements of backscattering of acoustic waves from the ocean volume were obtained along a triangular track running west from the entrance to the Straits of Juan de Fuca then south to Hawaii, and then roughly northeast to the entrance of the Straits of Juan de Fuca. Thirty-four stations were occupied enroute alternately at midnight and midday. The data were analyzed to yield the spectral characteristics of the scattering for various column lengths at all station locations. The column scattering strength is seen to decrease and the daytime deep scattering layer to become shallower, as one proceeds north from Hawaii. Differences between day- and nighttime scattering and distinctive spectral characteristics associated with subtropic and subarctic water masses are illustrated.
Impedance Techniques for Soil-Structure Interactions
Authors: Crandall Stephen H. , Kurzweil Leonard G.
Published: October 2005

The dynamic interaction of a rigid body undergoing horizontal, vertical, and rocking motion on a soil surface can be characterized in terms of matrices of impedance or admittance functions. Measurements of these functions have been made for rigid circular disks on a Plasticine model soil facility. The results agree reasonably well with theoretical predictions based on idealized contact conditions between a disk and a linear viscoelastic half-space. The matrix of impedance functions is used to interpret surface measurements of free soil motions due to seismic noise and to predict the dynamic response to seismic noise of simple structures erected upon the soil. Measurement of the coupled impedances involves the use of a force gauge and an accelerometer (combined in an impedance head) plus two additional accelerometers. Disk excitation is provided by a miniature shaker acting directly or through an extension rod. Seismic excitation of the soil is achieved by a system of shakers which drive panels on the under side of the tube of Plasticine. Dynamic response is sensitive to actual area of good contact between disk and soil. Effective contact area (which may vary between 50% and 100% of the nominal area) can be determined an in situ dynamic test. [Work supported by NASA Langley Research Center.]
Mean-Value Characteristic-Impedance Method of Predicting Vibration and Sound Radiation
Authors: Skudrzyk Eugen
Published: October 2005

The mean-value characteristic-impedance method predicts the mean line through the frequency-response curve and the sound pressure of a vibrator in terms of its mode mass and the average frequency difference between successive resonances with a few slide-rule computations, regardless of the complexity of the vibrator. This mean line can easily be supplemented with the curves that represent the height of the resonant peaks and the depth of the antiresonant mimima. If the vibrator is excited by white noise, the amplitude of the vibration becomes proportional to the local mean square root of the energy density. The radiation resistance above the coincidence frequency is ρc. The sound radiation below the coincidence frequency consists of a force component and an edge component both of which can be predicted. The theory makes it possible to compute, for example, the sound pressure that is generated by a spring-mounted motor in a cage inside a housing, taking into account all the resonances of cage, housing, and mounting. In applications of this theory to praccal situations, the results agreed with experimental results within a few decibels. [This research was performed for the Ordnance Research Laboratory and the Physics Department at The Pennsylvania State University under contract with the Office of Naval Research.]
Stress Patterns and Types of Perceptual Errors
Authors: Bond Zinny
Published: October 2005

The suggestion has often been made that stress serves an organizing function in speech perception. The present study attempts to investigate this idea by examining the relationship between stress patterns and the frequency of occurrence of substitution errors and order errors in the perception of obstruent clusters. Eighteen disyllabic CVCCVC nonsense words were selected to serve as stimuli. Only the medial consonant cluster was varied so that all combinations of p, t, and k with s were presented under three different stress patterns: stressed first syllable, stressed second syllable, and equal stress on both syllbales. Preliminary results indicate that, although the number of correct responses is the same under all conditions of stress, the ratio of ordering errors and substitution errors is different for the three stress conditions.
Acoustics of Thunder
Authors: Ribner H. S. , Lam F.
Published: October 2005

A phenomenological model of the acoustics of thunder has been briefly explored with the aid of a computer. A conceptually simple program yields the thunder signature in time for a given lightning signature in space. A Fourier transform then yields the frequency spectrum. A few cases of real-life lightning have been tried and plots of thunder signatures and power spectra obtained. The model assumes a lightning stroke to be a spatial distribution of point explosive sources; each one simultaneously generates a disturbance that is idealized as evolving independently of the others. For simplicity, an N wave is used as the elemental wave that evolves by nonlinear distortion from each point. The results suggest that the ensemble average of thunder power spectra, suitably normalized (e.g., total power), resembles the spectrum of the basic N-wave building blocks. Additionally, the model, over-simplified as it is, appears to yield pressure-time signatures of thunder that resemble measured signatures.
Focusing of Finite-Amplitude Cylindrical and Spherical Sound Waves in a Viscous and Heat-Conducting Medium
Authors: Chu T. C. , Seebass R.
Published: October 2005

The focusing of cylindrical and spherical pulses of finite amplitude in a medium of small viscosity and heat conductivity has been studied by dividing the region of interest into three parts: converging, interaction, and diverging regions. In the converging region, the flow field is governed by the radial Burgers equation with a small parameter multiplying the term with second derivatives. The method of matched asymptotic expansion is found applicable to this equation with an N wave as an initial condition; a composite solution obtained describes a converging N wave with increasing amplitude and wavelength. The front and rear shocks of the N wave are locally described by Taylor's shock structure. In the interaction region, no small perturbation solution exists for the shocks. However, the flow field between the front and rear shocks satisfies to first order the inviscid linear wave equation, which is solved by the Fourier transform technique. The treatment of the diverging region is similar to that of the converging region, except for trivial changes in the analysis. It is shown that the effect of entropy increase on the failure of the solution at the focus is inconsequential if certain restrictions on the initial strength and wavelength are satisfied.
On the Mechanism of Finite-Amplitude Entropic Waves (Part II)
Authors: Peter Abraham C.
Published: October 2005

This study is a continuation of the work presented at the 81st meeting of the Society in April 1971. The previously derived governing differential equations are integrated under conditions of simple wave motion. It is shown that along the path of the convected antropic perturbations, the pressure and temperature increase whereas the density decreases. Thus, due to the nonlinearity of the solution and the resultant constant change of type, the “cold” regions of high density but low temperature and pressure are constantly gaining on the “hot” regions of low density and high temperature and pressure. Under these conditions, low density and high pressure and temperature regions are formed in front of the convected ever steepening “wave.” The subsequent collapse of these hot “bubbles” causes a density fluctuation, which varies as a function of the adiabatic exponent γ and the local Mach number. For γ = 1.4 and vanishingly small Mach numbers, the density varies as the fourth power of velocity, decreasing to the second power as the Mach number reaches the value of 2.58.