bluuebunny/crossref_metadata_2025 huggingface dataset:
Speaker Authentication Using a Formant-Tracking Vocoder
Authors: Richards J. R.
Published: October 2005

This talk describes some basic experiments centering around the use of linear discriminant functions to produce authentication judgments. A formant-tracking vocoder analyzer was used to reduce the speech waveform of key words to a set of eight time-varying parameters. Segmentations within the words were determined by noting rapid changes in the short-term power spectrum of each of the formants and changes in the state of voicing. Statistics derived from time-normalized segments within the words produced by a given speaker were used to generate an authentication mask for that speaker. The mask was automatically designed in a digital computer by utilizing Fisher's linear-discriminant function and some training utterances of the key words. After the masks were designed, they were used to classify new utterances and predict the likelihood that those utterances were uttered by a given speaker. The total system with the exception of the formant-tracking vocoder was computer simulated and testing was limited to a small group of five speakers. The system has the potentiality of being completely automatic in the learning and authentication phases, and the initial experiments were highly successful and indicate that reliable authentic results could be obtained using utterances from a set of five key words.
Field Transmission Loss of Some Unconventional Wall Panels Used in a HUD Experimental Low-Cost Housing Project
Authors: Hixson Elmer L.
Published: October 2005

In an attempt to make adequate single-family houses available to low-income families, the U. S. Department of Housing and Urban Development instigated a low-cost housing project in Austin, Texas. Ten houses using radically different materials and construction methods were completed in December 1968. The University of Texas at Austin was engaged to provide engineering, architectural, sociological, and psychological evaluations of these houses. In conjunction with the engineering studies the field transmission loss was measured for each type of wall panel. The data on these panels that range from plywood stress-skin sandwich with honeycomb core to conventional gypboard to 6-in. solid concrete “Stach Sac” will be presented.
New Reverberation Chamber, Rotating Vane, and Microphone System Improve Discrete Frequency Measurements
Authors: Guinter J. M.
Published: October 2005

A laboratory designed to help engineers produce quiet motors for automotive, household-appliance, and industrial-motor applications includes reverberation chambers of 16 000 cu ft, 8000 cu ft, and a semianechoic half-space. Numerous room proportions were investigated, and sizes adjusted to provide uniform modal spacing. In each reverberant room, ceilings and two walls were skewed, two tilted, to moderate the strength of axial and tangent modes and eliminate flutter. A rotating diffuser combining elliptical and conical sections for small air disturbance, a surface density of 1.8 lb/sq ft, projected dimensions of 14 ft × 15 ft or more from every view, and integral dc torque motor drive to 12 rpm without speed reduction was provided for the largest chamber. Variations in vane, source, and microphone locations and in acoustical absorption were investigated as were rate of vane rotation, of microphone distribution and sampling rate, and the effect of vane rotation upon the load seen by the source. Response is relatively good to 100 Hz, fair to 89 Hz, usable to 55 Hz.
Central-Heating Noise in a One-Family House
Authors: Strumpf F. Michael , Ovesen Kaj
Published: October 2005

For a long time, noise produced by the central-heating units (panel radiator, valves, pump, and others∥ in a one-family house was not considered as a noise problem. Complaints by inhabitants and later investigations done in Denmark concluded that the noise, although of a low level, was disturbing because of its continuous nature. One specific case is discussed in detail. Noise levels were recorded, and the sources of the noise were traced and investigated. Conclusions are drawn, and general advice as to noise control of a central-heating system is given.
Development of a Computer Program Directed towards the Design of a High-Resolution Cassegrainian Sonar Antenna
Authors: Simanyi Attila I.
Published: October 2005

The design techniques developed for predicting the pressure-distribution pattern of a Cassegrainian sonar antenna of 300-wavelength diameter (operating at 1 MHz) are discussed. Emphasis is placed on an economical formulation of the problem to allow the necessary computations to be performed on a high-speed computer (IBM 360-40/65) without excessive charges for execution time. The farfield pressure-distribution patterns show that the design goal of −30-dB sidelobe levels can be met utilizing a given, fixed, transducer pattern.
Vector-Impedance Plotting under Arbitrary Drive Conditions
Authors: Parvulescu Antares , Mitchell Dana D.
Published: October 2005

Circuitry has been developed to permit the examination of the vector impedance of individual elements within a large array, under real-life drive conditions that allowed neither the voltage nor the current applied to the individual element to remain constant. The circuits have used either of the two commercially available impedance plotters, as well as special-purpose resolvers, in an arrangement where an analog computer “multiplier-divider” normalizes the variable conditions so that the plotter, or the resolver, can operate as per its design specification. The equipment has also been rendered nearly automatic to allow a large number of elements to be studied in a limited amount of time. [This work has been performed while both authors were with Columbia University, Hudson Laboratories, Dobbs Ferry, New York 10522, and support from the U. S. Office of Naval Research is gratefully acknowledged.]
Directivity of Underwater Horns
Authors: Ripper A. P. , Finch R. D. , Muster D.
Published: October 2005

An experimental study of the directivity gain of underwater transducers with the attachment of horns was made, and factors influencing such directionality were established for exponential, tractrix, and conical horns. The influence of steel and aluminum for construction materials and the effects of polyurethane foam or air backings were determined. The directivity index was found to show sudden drops at discrete frequencies, and it was shown that this behavior was related to transverse modes of propagation inside the horn by the mouth of the horn for acoustic pressure and phase variations. The effect on directivity of various cell arrangements in a conical horn was studied. [This work is supported by the Office of Naval Research.]
Hydrophone Calibrator
Authors: Trott W. James
Published: October 2005

The USA Standard procedure for calibrating a hydrophone at low frequencies is the two-projector null method in which the two projectors are electrodynamic. A. N. Golenkov, USSR, developed a calibrator on the same principle using two piezoelectric projectors. A new calibrator, using piezoceramic cylinders for projector and receiver, has been developed that eliminates the null balance requirement and thus simplifies the calibration procedure. The reference is again a step change in water head achieved by a two-way valve that connects one manometer and then a second. An absolute calibration of a hydrophone can be made up to 4 kHz and for hydrostatic pressures from 0 to 2000 psi.
Bench Test Apparatus for Sonar Transducer Elements
Authors: Trott W. James
Published: October 2005

A self-reciprocity method of calibration has been developed using a water-filled tube, terminated by a reflector, to provide a controlled acoustic load for measuring the sensitivity of sonar elements. Means for simulating the acoustic load for one element or for one element interacting with others in an array have been devised. An absorber termination in front of the reflector enables one to measure impedance at high power and longer pulse duration. Efficiency can be computed. Hydrostatic pressure can be varied for failure analysis. [This work is in support of the sonar transducer quality control program of the Navy Ship Systems Command.]
Spectral Analysis of Cavitation Noise in Cryogenic Liquids
Authors: Mosse A. , Finch R. D.
Published: October 2005

Spectra of ultrasonic cavitation noise were obtained in liquid helium and liquid nitrogen. A subharmonic response at half the driving frequency was found to be present at all times. In the case of liquid helium, the relative intensity of the subharmonic showed a peak at the λ point. The background noise intensity was also higher in helium II. A tendency for the subharmonic to increase with static pressure was also found both for helium and nitrogen. A correlation between the onset of the subharmonic and the white-noise background was also found. The variation of the intensity of the background noise was found to be different in helium II than in other liquids. It is felt that many of these phenomena arise from the effect on bubble dynamics of the efficient heat transport.
Periodic Small-Scale Cavitation Process
Authors: Neppiras E. A. , Fill E. E.
Published: October 2005

A type of acoustic cavitation has been studied which occurs at the face of a vibrator with a small diameter. A gas bubble grows to near-resonant size by accumulation of microbubbles. The process then reverses and the parent bubble rapidly throws off a cloud of microbubbles. This phase is accompanied by severe surface distortion of the main bubble, with emission of strong harmonics and a good deal of white noise. Under suitable conditions, a cyclic process is set up at a very regular repetition rate that depends on the acoustic pressure and the liquid properties. Acoustic streaming has an important rôle in maintaining the cycle. High-speed movies have been taken, and these, along with measurements of the acoustic emission, show clearly the progress of the cycle. Techniques are discussed for using this process to generate bubbles of defined size. [Work supported by grants from the National Institutes of Health and from the Air Force Office of Scientific Research.]
Sequence and Bias Effects While Tracking Thresholds
Authors: Campbell Richard A.
Published: October 2005

The responses of human observers while tracking 75% correct thresholds using a block up-and-down adaptive procedure for different signals (wide-band noise, narrow-band noise, and a sinusoid) in a continuous or a gated wide-band masking noise with a two time interval or a YES-NO paradigm has been examined. There was a tendency for performance at the most frequently revisited level to depend on the signal level of the previous block. The extreme case was the narrow-band noise signal where the percentages correct were: 78% if the previous block was higher, 75% if the same, and 72% if lower. Each error and the preceding response was analyzed. A strong bias in favor of the “2” response in the two-interval paradigm and the “NO” response in the YES-NO paradigm was observed. This bias was reflected in higher percentage correct values for the second interval than for the first: as much as 55% for the first and 80% for the second or 44% hit rate and 93% correct rejection rates for a 2000-Hz signal. These and other results of the analyses will be presented and discussed. [This work supported in part by the National Science Foundation.]
Listener Judgments of Vocal Loudness and Effort in Continuous Speech
Authors: Brandt John F.
Published: October 2005

The direct magnitude-estimation technique was used in an attempt to investigate two psycholinguistic aspects of spoken speech, i.e., vocal loudness and vocal effort. Three tape-recorded experimental conditions were developed representing (1) normal changes in loudness and “effort” in 5-dB steps over a 35-dB range, (2) intensity constant effort varied, and (3) intensity varied, effort constant. The speech samples were judged by 20 listeners on (1) the magnitude of loudness and (2) the magnitude of the amount of effort used by the speaker in phonation. Exponents of the loudness and effort functions (1.12 and 0.57, respectively) suggest that vocal loudness and effort may be different percepts of the listener. An examination of the acoustic signals show a systematic increase in bandwidth with increases in vocal intensity that is related to both loudness and effort.
Relationship of Lingual and Intraoral Air Pressure during Consonant Production
Authors: Brown W. S.
Published: October 2005

Variations of intraoral air pressure associated with the production of different consonants may be due to resistance created by the tongue to respiratory air flow. One indicator of tongue resistance is the pressure it exerts against other oral structures during speech. The purpose of this study was to obtain simultaneous recordings of lingual pressure and air pressure to aid in determining if a relationship does exist between these two intraoral pressures. Nine young adult males repeated syllables containing /t/, /d/, and /n/ consonants placed in the initial, medial, and final syllabic position. Measurement of these recordings showed greatest air-pressure values for /t/, less for /d/, and least for /n/. Lingual pressure values did not follow the same systematic trend; greatest pressure values were found for /t/, but no difference was found between /d/ and /n/. These results suggest that—whereas varying tongue pressures may account, in part, for variations in air pressure—other physiological systems such as respiratory, laryngeal, and velopharyngeal activity also interact to account for varying air pressures.
Vocal-Tract Characteristics of Voiced and Voiceless Stop Consonants
Authors: Kent Raymond , Moll Kenneth L.
Published: October 2005

The purpose of this study was to investigate supraglottal differences between voiced and voiceless stop consonants. Cinefluorographic films and throat-microphone recordings were obtained from three speakers for 18 pairs of utterances in which one member differed from the other only in a stop cognate; i.e., /p,t,k/:/b,d,g/. The utterances were of the forms VCV, VCNV, and VNCV, where V is the vowel /i/ or /ɑ/, C, the stop, and N, the nasal consonant that is nonhomorganic with the stop. Analysis of the data revealed that the stop cognates are similar in the gesture of the primary articulator but dissimilar in respect to supraglottal volume and velopharyngeal coarticulation. The results suggest that two components of volume increase may sustain transglottal flow, hence voicing, during a stop. The effects of the two vowel contexts on certain consonant characteristics, such as rate of articulator movement, also are described. [This research was supported in part by a grant from the National Institute of Neurological Diseases and Blindness.]
Method of Direct Determination of Subglottal Pressure
Authors: Koike Yasuo
Published: October 2005

A miniaturized solid-state pressure transducer was employed to record the subglottal air pressure during speech. The minute size and wide frequency response of this series of transducers provides a new approach to the study of the rapid air-pressure variations inside the vocal mechanism. Advantages of this technique are discussed in comparison with other methods of measuring the subglottal pressure, such as those that employ an esophageal balloon, a thin catheter through the glottis, or a tracheal puncture. Some qualitative data from preliminary experiments are presented. Limitations of the technique are discussed, together with the technical modification of the equipment needed for speech research. [This study was supported by U. S. Public Health Service grant.]
Auditorium Synthesis—Degree of Approximation to a Real Auditorium
Authors: Veneklasen Paul S. , Hyde Jerald R.
Published: October 2005

The degree of stimulation of the research tool is determined by comparing the synthesized echograms with those recorded in real auditoriums. Thus, the similarity of physical occurrences during the growth and decay periods of the sound is taken as reasonable justification for using the tool as a research device to explore the preferences of musical subjects for auditorium sound.
Auditorium Synthesis—Early Results of Listener Preference
Authors: Veneklasen Paul S. , Hyde Jerald R.
Published: October 2005

A number of musically astute subjects have attempted the judgments and adjustments required to define their preference for auditorium sound. Subjects are conductors, musicans, music critics, concert goers, and acousticians. Program samples include a great variety of typical events that must be accommodated in a multipurpose auditorium—symphony, string quartet, piano sonata, light opera, stage play, monologist, classical guitar, jazz music, cathedral pipe organ, and oratorio. In each case, the listener is asked to adjust the balance of direct/envelopment/reverberance to suit his taste, and his settings are translated into relative acoustical energy levels. A few examples have been accumulated for preference for the player atmosphere by allowing expert musicans to play their instruments into the system. A reasonable research question is whether the preferred player environment and listener environment will be mutually compatible and achievable.
Nonlinear Characteristics of Brass Tones
Authors: Beauchamp James W.
Published: October 2005

Computer analysis shows that there are quite stable nonlinear relationships among the amplitudes of cornet tones harmonics, unique for each pitch, over wide amplitude ranges. As amplitude increases, the general tendency is for amplitudes of higher partials initially to increase more slowly than those of lower ones and ultimately to increase more rapidly. This nonlinearity is a consistent feature and is certainly important for “brasslike” tone quality. In another experiment, trombone mouthpiece and radiated pressure waveforms were synchronously recorded and subsequently subjected to harmonic analysis. Although ratios between corresponding mouthpiece and radiated wave harmonic amplitudes would be constant if linear theory were assumed, the input-output relationships measured were emphatically nonlinear. Pressures in the mouthpiece were in the range 152 to 169 dB, whereas radiated pressures were 67 to 107 dB over the same pitch and dynamic ranges (117 to 349 Hz, pp to ff). Previous work [J. Acoust. Soc. Amer. 6, 275 (1934)] predicts that throat pressures of such high amplitude will propagate in a nonlinear fashion. Although mouthpiece signals retain a brass sound quality, their waveforms are very smooth and sound more mellow than normal trombone tones.
Effect of Noise from Passing Trucks on Sleep
Authors: Thiessen G. J.
Published: October 2005

Electroencephalograph signals from frontal electrodes on sleeping subjects are recorded on magnetic tape while a few truck passages are played back during the night. The EEG records are played back at increased speed and the filtered output level recorded on a level recorder that provides a good picture of the progress of the subject's sleep. Noise levels as low as 45 dBA can cause a change to a shallower stage of sleep or awaken some subjects from a light sleep. However, individual differences are very great both in response and character of records. For the same subject, successive nights' records vary greatly and so dues the response during different parts of the night. These factors make gathering of statistics a slow process.
Application of Statistical Energy Analysis to a Noise and Vibration Problem in a Small Motor Vessel
Authors: Sawley Roger J.
Published: October 2005

The response of structural systems to high-intensity sources of broad-band random noise and vibration has been the subject of considerable study in recent years. This work has led to the development of an analytical technique known as statistical energy analysis, whereby the spatial and modal averages of structural response are determined. Directed primarily towards the solution of vibration problems in aerospace vehicles, the method is finding increasing application in the general field of noise and vibration control. This paper looks at the application of the method to the analysis of a noise and vibration problem in a small motor vessel.
Vibration-Isolation Treatment of a Railroad Track Bed
Authors: Miller Laymon N.
Published: October 2005

A few years ago, a half-mile section of railroad track was given a vibration-isolation treatment under several new buildings in Boston. The treatment consisted of welding all rail joints, inserting molded rubber rail seats under the lower flange of the rail, and installing an extra-deep ballast bed under the ties. Recently, a simple measurement was made of the earthborne vibration reduction provided by this treatment. A vibration pickup was mounted on a concrete wall inside the track, and the signal was tape recorded for passages of several short passenger trains. At one position, the vibration pickup was located beside the welded and isolated track. On the following day, the same passenger trains were recorded with the vibration pickup located beside conventional unwelded and unisolated track, approximately 200 yd from the first position. Train speed, train makeup, wheel loads, earth conditions, and the geometry of the measurement conditions were quite similar for both locations, so it is believed that the measured 10 dB difference was due to the vibration reduction provided by this treatment.
Foam Acoustical Wedges
Authors: Gardinier R. E. , Nordby K. S. , Silsbee D. L.
Published: October 2005

Polyurethane-polyether foam wedges have been used for the first time in the United States to provide the sound absorption in a new semianechoic chamber, in place of the fiberglass or rockwool wedges that have been so used for several decades. The sound absorption of the polyurethane foam was investigated as to (1) effect of physical properties such as density, air-flow resistance, and resiliency; (2) effect of physical dimensions; (3) cost relative to that of the older materials. Today, polyurethane-polyether wedges can be manufactured at a cost considerably less than that of fiberglass or rockwool wedges yet show better low-frequency sound absorption than do fiberglass or rockwool wedges.
Tensor Ray Tracing
Authors: Eby Edward S.
Published: October 2005

A temporal metric tensor is defined by combining the sound-speed function with the spatial metric tensor for a Riemannian space. Fermat's principle implies that spatial rays are temporal geodesics. Ray equations generalized to Riemannian spaces are shown to be the temporal geodesic equations expressed in spacial terms. This geometric derivation leads to the consideration of geodesic deviation and its relation to three-dimensional spreading loss. Previous results [E. S. Eby, “Frenet Formulation of Three-Dimensional Ray Tracing,” J. Acoust. Soc. Amer. 42, 1287–1297 (1967)] are generalized to Riemannian spaces, and tensor expressions are derived for ray curvature and torsion.
Propagation Calculations for a Parabolic Velocity Profile
Authors: Nicholas N. C. , Überall H.
Published: October 2005

The normal-mode series solution for the parabolic velocity of sound profile Co2/C2 = 1 − a2Z2 is discussed. The full series representation was evaluated to exhibit focusing in both range and depth, show the effect of frequency on focusing, validate the series cutoff indicated by analysis, and test an asymptotic closed-form solution valid near the convergence zones [H. Überall and N. C. Nicholas, J. Acoust. Soc. Amer. 44, 1259–1261 (1968)].
Experimental Prediction of Acoustic Path Stability from Thermistor-Chain Data
Authors: Walsh George M.
Published: October 2005

The propagation time stability of an acoustic path traveling from the ocean surface to the bottom is predicted by a ray-path analysis. The sound-velocity profile as a function of horizontal distance is derived from towed thermistor-chain data, with a representative stable structure assumed between the thermistor-chain data and the bottom. The fluctuations of travel time at various points along the ship track due to sound-velocity profile variations are predicted by calculating the ray path travel time. The spectrum of these fluctuations shows a slope of K−3, where K is the spatial wavenumber, for K in the region of 2×10−4<K <2×10−3. Measurement noise due to the 0.05°C resolution of the thermistor-chain data exceeds the predicted travel-time fluctuation for K>2×10−3.
Possible Relations between a Plane Wave and Waves Refracted from Large, Weak Inhomogeneities
Authors: Broek H. W.
Published: October 2005

A plane wave in an isovelocity medium was assumed incident on a single spherical inhomogeneity. Refraction by the inhomogeneity was studied by ray tracing. The refractive index of the inhomogeneity was assumed to have a constant value that was within 0.1% of that of the surrounding medium. The object of the ray tracing was to delineate the region (the overlap region) in which the refracted wave had amplitude comparable to that which would prevail without the inhomogeneity. Diffraction by the edge of the inhomogeneity was also studied, and the approximate extent of the shadow region described. The volume of the overlap region and of the shadow region may each be much greater than the volume of the inhomogeneity. Large, weak inhomogeineities in the ocean may be sufficiently numerous that a wavefront is transformed into a multiplicity of refracted wavefronts, each with nearly the same travel time and arrival angles. At low frequencies, the wavefronts may add constructively, but short transmissions (high frequencies) may be resolved in time. [Work supported by U. S. Naval Research Laboratory.]
Extrapolation Techniques for Predicting Structural Responses to Aeroacoustic Loads
Authors: Piersol Allan G.
Published: October 2005

Preliminary estimates for flight-vehicle vibration environments are usually desired early in the design cycle before structural details have been formulated. Such estimates are often based upon statistical extrapolations from data measured on previous vehicles. These extrapolations are commonly performed in one of two ways; the predictions are based upon data from a single vehicle of similar design (scaling procedures), or they are based upon an average frequency response function (FRF) computed from data for one or more general vehicles. A number of specific techniques for predicting flight-vehicle vibration environments by both scaling and FRF procedures have been proposed over the years. In general, scaling techniques predict vibration levels based upon differences in excitation pressure levels and structural weight densities between the new and reference vehicle. FRF techniques vary from those that use only airborne noise level as an input parameter to more complicated functions involving structural weight density, vehicle diameter, and/or dynamic pressure. All extrapolation techniques, however, have the common advantage of requiring only gross information concerning the excitation sound pressures and structural properties for the flight vehicle of interest. The disadvantage of such procedures is accuracy. It is generally agreed that extrapolation techniques should be employed only to make preliminary vibration predictions for future vehicles. Such predictions should be refined and updated by more accurate analytical procedures and/or direct measurements as soon as sufficient information is available.
Response of Ground Structures to Sonic Loads
Authors: Sutherland Louis C.
Published: October 2005

Within the last decade, intense low-frequency noise from large rocket boosters and sonic bangs from supersonic aircraft have become a source of significant sonic loading on building structures. Some of the basic principles of loading and response of ground structures to sonic waves are reviewed, including the effects of diffraction on three-dimensional structures, structural-acoustic wave coupling, and vibroacoustic response. Related experimental data obtained during the course of an extensive study of sonic loading on structures is also briefly reviewed for the first time. Some of the characteristics common to sonic loading by acoustic waves, sonic booms, and blast are considered.
Simultaneous Measurement of Intraoral Pressure, Labial Pressure, and Labial Electromyographic Activity During Production of the Bilabial Soops /p/—/b/
Authors: Lubker J. F. , Parris P. J.
Published: October 2005

Intraoral pressure, labial pressure, and labial EMG activity were obtained from 18 adult speakers to provide data relevant to the supraglottal characteristics of /p/ and /b/. Isolated nonsense syllables were used with the stop position and syllabic stress varied in a controlled manner. Results suggest that: (1) the labial gesture for /p/ and /b/ is monotypic, requiring no more forceful labial contact or EMG activity for one than for the other; (2) intraoral pressure provides good discrimination between /p/ and /b/, regardless of position or stress, while labial pressure and EMG activity provide poor discrimination; (3) with all three parameters combined, good /p/—/b/ discrimination is obtained, if essentially no vocalization follows the stop, while poor discrimination is obtained if a significant amount of vocalization follows; (4) considerable between subject variability is evident in all three parameters, emphasizing the need for caution when making generalizations from data of this type.
Closed-Loop Control of the Initiation of Jaw Movement for Speech
Authors: MacNeilage Peter F. , Krones Robert , Hanson Robert
Published: October 2005

Closed-loop control of articulator positioning is necessary for the initiation of an utterance, either in assuming a constant “ready” or “neutral” position from varying previous positions (as Chomsky and Halle have suggested) or to reach a relatively invariant initial “target” position from varying prespeech origins, or perhaps both. This contention was examined in a study of jaw movement and the concurrent contraction of muscles controlling the jaw. The study showed that although there is usually a definite prespeech jaw movement, the resultant “ready” position varies considerably. Most of the closed-loop control is exercised in movement from this ready position to the considerably less varied initial “target” position. Preliminary findings on the relative rôle of open- and closed-loop control of the jaw within utterances, and the form of the motor control of jaw movements, is also presented. [This work was supported in part by the National Science Foundation.]
Method for Conducting an EMG Aerodynamic Study of Normal Voice
Authors: Shipp Thomas , McGlone Robert E.
Published: October 2005

In order to examine some of the critical relationships in the physiology of phonation, a study was designed to compare simultaneously acquired measures of activity from four intrinsic laryngeal muscles, air flow, subglottal air pressure, and the acoustic voice signal. Intramuscular wire electrodes were inserted to three of the four muscles under direct laryngoscopic observation, while placement in the cricothyroid muscle was verified by electrical stimulation of the muscle during sustained phonation by the subject. A special drug combination was administered to each normal adult male subject prior to the experimental procedure to minimize the discomfort associated with electrode placement while still maintaining his ability to produce the requisite phonatory tasks. Following transducer placement, each subject sustained phonation at five points within his frequency range and at two intensities per point. Data were also obtained on vocal fry and falsetto phonation. In addition to a presentation of some preliminary findings, a motion picture is shown depicting some of the complex techniques utilized in the study.
Temporal Relations in Pure-Tone Contralateral Masking
Authors: Stokinger T. E. , Lankford J. E.
Published: October 2005

Masking overshoot (increase in masking at either the transient onset or offset period) was measured at nine test frequencies surrounding a 1000-Hz, 50 dB SPL masker of 1000-msec duration. The brief maskees (5-msec duration at maximum amplitude) were presented near masker onset (initial position) at the midpoint of the masker (medial position) and near-masker offset (final position). Averaged across subjects and frequencies, onset overshoot was significant while offset overshoot was not. Onset overshoot occurred at all test frequencies and its magnitude was directly related to the magnitude of initial-position masking. The magnitude of onset overshoot was less than reported by Zwislocki et al. [Perception Psychophys. 2, 59–64 (1967) and J. Acoust. Soc. Amer. 43, 1257–1271 (1968)]. Offset overshoot appeared primarily at the lower frequencies but was not significant at any frequency. A follow-up study compared masking at the medial position with steady-state masking. The steady-state masker was more efficient than the medial-position masker at frequencies immediately surrounding the masker. [This study was supported by the Oklahoma City VA Hospital and was based on Lankford's dissertation completed at the University of Oklahoma Medical Center.]
On-Frequency Tonal Masking
Authors: Leshowitz Barry , Wightman Frederic L.
Published: October 2005

The detection of 100-msec, 1000-Hz sinuosids added in phase and in quadrature with a continuous, 80-dB tonal masher in the presence of wide-band noise was investigated in two experiments. Signal-energy splatter caused by abruptly turning on the tone was “removed” either by bandpass filtering the signals or by adding a noise floor. It was found that for low noise levels, masked thresholds (measured in signal level) for in-phase and quadrature additions are approximately equal. At threshold, whereas the increment in level off the signal frequency is nearly identical for in-phase and quadrature presentations, increment level on the frequency differs by more than 20 dB. The rôle of signal duration in tonal masking was examined in a second experiment. The expected tradeoff of signal power for duration failed to materialzie when the experiment was conducted in a noise-free background. The addition of a moderately intense noise and bandpass filtering the signals both gave rise to a 6 dB/decade reciprocity relation. The results of the present work are consistent with the hypothesis that the ear listens off the frequency of the signal (“detunes”) and detects the energy in the lobes of the sinx/x function. [Research supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Relation between Critical Bands and the Phase Characteristic of Cubic Difference Tones
Authors: Schroeder M. R.
Published: October 2005

Among auditory nonlinear combination tones, the lower cubic difference tone (CDT) is the most prominent. It occurs when the ear is stimulated by two primary tones closely spaced in frequency and is audible over wide amplitude ranges of the primaries. Both amplitude and phase depend strongly on the frequency difference of the primaries. Known mechanical processes in the ear cannot by themselves account for the observed frequency dependence. On the other hand, the additional frequency selective processing that governs masking and loudness summation phenomena and is summarized in the “critical band” concept may also be implicated in the perception, and possibly the formation, of the CDT. This connection between critical bands and cubic distortion in the ear is suggested by the phase behavior of the CDT when expressed as a 3-dB bandwidth of a “minimum-phase” filter. The bandwidths so computed match closely the critical bandwidth function in the entire frequency range for which phase data have been published [350 Hz–8 kHz, J. L. Goldstein, J. Acoust. Soc. Amer. 41, 676–689 (1967)]. The hypothesized connection between the CDT and critical bands is also suggested by Zwicker's [E. Zwicker, Acustica 20, 206–209 (1968)] measurements of the amplitude characteristics of the CDT.
Rôle of Vapor-Cavity Dynamics in Cavitation-Threshold Determination
Authors: Apfel Robert E.
Published: October 2005

An acoustic cavitation event can be divided into three stages: the formation or nucleation of a small vapor cavity, the cavity's growth in size, and its violent collapse. In a recent paper, an estimate was made of pressure pn needed to nucleate a vapor cavity from an imperfectly wetted mote in a liquid (Stage 1). At low acoustic frequencies, the tension phase of the acoustic cycle is of sufficient duration that not only is the cavity nucleated at this pressure, but it also grows to many times its orginal size. If violent collapse ensues, then pn is equal to the cavitation threshold. At high frequencies, however, the cavitation threshold is greater than pn and is frequency dependent. In order to study the influence of viscosity, surface tension, and other parameters on this frequency dependence, we present an analysis of the motion of a spherical cavity in a viscous incompressible liquid that is subjected to an acoustic field. Numerical solutions of a nondimensional equation modeling this problem are given and can be applied to a broad class of liquids. [Work supported by the Office of Naval Research.]
Radiation into the Atmosphere by Underwater Infrasound
Authors: Cook Richard K.
Published: October 2005

The propagation of underwater sound through shallow water produces a radiated sound field in the atmosphere above the surface. At the land-sea edge of the shallow water, conical waves travel inland through the atmosphere. We present the results of an analysis giving the strength of the conical waves caused by the underwater infrasound. The latter is quantitatively defined by the normal modes for the shallow-water waveguide. The results of the analysis are applied to the “supersonic” atmospheric signal velocities observed for infrasound reveived at stations near the esatern seaboard of the United States, and arriving from Cape Kennedy at rocket launch times. The atmospheric sound is in the range 1.0–10 Hz, with signal velocities of at least 600 m/sec. The apparent “supersonic” signal velocities come about because much of the transmission is underwater, although the rocket source is in the atmosphere, and the microphones at a land station receive sound in the atmosphere.
Some Aspects of Frontal Infrasound
Authors: Bowman H. S.
Published: October 2005

Recently, infrasonic waves were related to certain frontal activity. The physical parameters of these waves and the nature of the meteorological conditions apparently responsible for such waves are being studied. Characteristic features of the low-frequency acoustic phenomena and the causal relations are explained. Results of experimental data comparisons are presented to show propagation properties of infrasound from a moving source. Meteorological disturbances that produce infrasound simulate point as well as line sources in motion. This in itself provides interesting areas of study of the generation and propagation of infrasound due to natural processes. Likewise, the study of meteorology dealing with frontal activity can be served by use of infrasonics when the cause and effect relationships are thoroughly understood.
Refraction of Sound by a Jet: A Numerical Study
Authors: Schubert L. K.
Published: October 2005

The equations appropriate to the propagation of sound in a realistic jet flow have been solved numerically for the case of a sinusoidal point source on the axis of a subsonic jet. The use of slowly varying quantities (related to phase and amplitude) as independent variables nonlinearized the wave equation but facilitated the application of finite difference methods. The difference equations approximating the partial differential equation were solved by nonlinear block relaxation using a Newton-like method. The solutions approach the results of ray acoustics in the high-frequency limit. For the most part, the finite frequency results agree well with experimental directivity patterns for a point source in a jet; they lend further support to the view that the downstream valley in jet noise is due to refraction. The computations have yielded detailed phase and amplitude data throughout the sound field. Unexpected findings are that the distortion of the constant phase surfaces is slight and that the flow beyond 100 nozzle diameters continues to deepen the refraction valley significantly. [Work supported by the Mechanics Division, AFOSR, OAR.]
A Farfield Study of Screech and Other Shock-Related Noise for Hot and Cold Jets
Authors: Simcox C. D.
Published: October 2005

A test is reported comparing convergent-divergent nozzles designed for Much numbers 1.2, 1.4, 1.6, and 1.8 to a convergent nozzle. Pressure ratios vary from 1.13 to 7.5 and temperatures from 520° to 2500°R. An array of eight microphones located at angles from 20° to 90° with respect to the jet axis has been employed. The C/D nozzles are shown to have a higher SPL than the convergent nozzle—a difference of 4–5 dB was measured—at certain off-design pressure ratios. Schlieren photographs demonstrate a close acoustic correlation with shock development. The data indicate that at high temperatures there is a “flooding” of background turbulent noise masking the shock noise. A 1/24-oct band analysis was used to determine the relative importance of the screech and its harmonics. Directivity, spectral distributions, and SPL are presented for total field, screech-free and shock-free data. The results show a significant broad-band contribution due to the presence of the shock structure and strong directivity effects resulting from the screech. A typical SPL breakdown for a cold off-design jet is: screech—133 dB, other shock-related noise—135 dB, and shock-free noise—132 dB.
Characteristics and Origin of Sound Emission from Turbulent Flames
Authors: Williams G. T.
Published: October 2005

The paper describes an experimental investigation of the noise characteristics of premixed and diffusion flames carried out as part of a continuing study of noise generation and suppression in turbulent flames. Sound-pressure levels and spectra of the noise emitted from flames stabilized on a variety of cylindrical burners were measured and analyzed in terms of burner size, level of turbulence, and burning velocity of the combustible gas. The results permit a comparison to be made of the thermoacoustic efficiencies of premixed and diffusion flames. A simple model has been used to obtain an understanding of the relationship between combustion noise and turbulence-induced changes in flame structure. It is shown that the source of sound generation is located in the flame-reaction zone, and that a turbulent flame may be represented acoustically by a collection of monopole sound sources, of different strengths and frequencies, distributed throughout the reaction zone of the flame. The strength of noise generation by a flame is shown to be directly dependent on the speed of changes in the rate of combustion.
Study of the Acoustic Effects Caused by the Insertion of Strip Flow Spoilers into a Model Air Jet
Authors: Simpson M. A. , Gordon C. G. , Reddingius N. , Meecham W. C.
Published: October 2005

Strip spoilers of varying size have been inserted into the 112-in. diam exit pipe of a model jet system, 6 in. upstream from the exit plane. Measurements of the noise radiation as a function of flow velocity and spoiler dimension have been made. It was expected that the noise radiation for these configurations would be dominated by dipole-like sources arising from turbulence-generated surface forces. However, the expected levels were greatly exceeded by a tone of narrow bandwidth occurring near the resonance frequency of the pipe for cross modes (5 kHz), with additional tones appearing at multiples of this frequency. Experiments have been conducted to determine whether the resonances are driven by acoustic feedback or by the turbulent wake of the spoiler. [This work is partially supported by the Air Force Office of Scientific Research.]
Methodology for Highway Noise Prediction
Authors: Nelson Dan L. , Gordon Colin G. , Galloway William J.
Published: October 2005

There is increasing interest on the part of local and national authorities in the impact of new highway projects upon the noise environment in communities through which these highways pass. There is particular interest in developing tools whereby the highway designer and local authority together can optimize the design by judicious selection of route location and geometry and by developing appropriate zoning restrictions and building guidelines. This paper discusses a methodology whereby the pertinent parameters can be combined to arrive at a prediction of the highway generated environmental noise. The form of the prediction is such that it can be related in a meaningful way to the subjective acceptability of the environment. Parameters considered include density and mix of traffic, roadway geometry, details of propagation path, etc.
Statistical Study of Aircraft Landing-Noise Levels
Authors: Ortega Jose C.
Published: October 2005

Recent work related to the aircraft noise problem has presented the opportunity to obtain a great deal of measured data of the landing noise produced by present day jet aircraft. The quantity of the measured data allows a statistical evaluation of the results. This paper presents the results of noise-level measurements made underneath the landing flight path at Los Angeles International Airport. The study study included measurements of noise spectra produced by 142 four-engine turbofan and 100 three-engine turbofan aircraft. Statistical analysis based on the measured data shows that the noise levels produced at a given ground station beneath the landing path are not part of a parent distribution that is Gaussian. The analysis also shows that the variation in noise levels is not correlated with aircraft altitude variations; i.e., the noisiest aircraft are not necessarily the lowest in altitude. The conclusion is reached that noise levels on the ground are greatly dependent on aircraft engine power setting during final approach to landing.
Vertical Coherence of Shallow-Water Reverberation
Authors: Urick R. J. , Lund G. R.
Published: October 2005

During a field experiment in 200 ft of water off the west coast of Florida, the vertical coherence of the reverberation following a small explosive charge was measured by recording, and later correlating, the outputs of a string of vertically separated hydrophones. The reverberation coherence, in terms of the cross-correlation coefficient between the sound pressures on hydrophone pairs, was found to increase with time after detonation, so as to indicate that the reverberation reaches the hydrophone string within an ever-narrowing vertical angle as time or range increases. The equivalent vertical angle of the reververation—here called the coherence angle—was found to lie in the range 5°–30° at frequencies between 200–8000 Hz. It is so small that only an extremely long vertical array can yield an appreciable array gain for active sonars operating in a background of shallow-water reverberation.
Incoherent Hydrophone Arrays to Reduce Variance in Underwater Noise Measurements
Authors: Mark W. D. , Watters B. G.
Published: October 2005

Surface thermal layer, and bottom interference effects are common in underwater noise measurements. The reflected sound rays which cause interference increase the total sound pressure above the value that would be present in a reflection-free ocean. This total or average increase can often be evaluated and its effect removed from the data. However, for sufficiently narrow noise bands, or for pure tones, a variance in the measured sound pressure must also be anticipated owing to the statistical nature of the transmission paths. For some frequencies and source-receiver geometries, the measured sound-pressure level will be many decibels above or below the average value. This variance often can be reduced either by frequency averaging or by spatial averaging. We will discuss the statistics of multipath sound fields for both pure tones and noise bands of various widths. Lloyd mirror type interference (usually encountered at fairly close ranges) and more random, multipath interference (often found at longer ranges in shallow water) will be considered. The use of multiple hydrophone arrays with incoherent summation of the individual signals will be described, and typical experimental results will be presented. [Work supported by U. S. Naval Ordnance Systems Command.]