bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Acoustic Intensity Around the Limiting Ray
Authors: Crawley J. H. , Miller G. E. , Mohr C. M.
Published: October 2005

Measurements were made at sea of the changes in acoustic intensity in passing from a shadow zone through the limiting ray and into the directly ensonified region. These measurements were made under conditions where a strong negative velocity gradient, extending from the surface, caused downward refraction of acoustic energy from a near-surface source. The experiments were conducted in the Mediterranean off Corsica and in the Pacific off San Diego, using narrow-band signals centered at 3.5 and 11 kHz. In passing downward from the shadow zone into the directly ensonified region, changes in acoustic level of from 10 to 25 dB were observed in a 500-Hz band and over a depth interval of several hundred feet. Source levels of 73–77 dB/μbar and horizontal ranges of 1–6 kyd were employed. The shapes of the intensity profiles around the limiting ray are discussed in the context of previous theoretical work [C. L. Pekeris, J. Acoust. Soc. Amer. 18, 295–315 (1946); R. W. Morse, J. Acoust. Soc. Amer. 22, 857–860 (1950)]. [This work was supported by Code 00V1, U. S. Navy Ship Systems Command, under contract.]
An approach to the Eulerian-Lagrangian Problem for Sound Propagation in Continuous Stochastic Media
Authors: Neubert J. A.
Published: October 2005

The formal solution of the Eulerian-Lagrangian problem for sound propagation in continuous stochastic media is reframed so that the emphasis on the need for complete knowledge of the statistical nature of the Lagrangian functional of interest is shifted to the need for knowledge of the asymptotic behavior of certain stochastic Lagrangian integrals which result from the application of a central limit theorem for stochastic functionals. The resultant practical relation for calculating the Eulerian ensemble expectation corresponding to the Lagrangian functional in question is shown to depend in a natural manner upon the Lagrangian path spreading and, in the case of a statistically isotropic medium, to reduce to the proper nonstochastic limit.
Sonic Booms in the Sea
Authors: Urick R. J.
Published: October 2005

Sonic booms laid down by Navy fighter aircraft flying at Mach 1.1–1.2 have been observed below the surface of the sea by means of a string of hydrophones 195 ft long dangling from a surface ship. The underwater booms were found to decay about as the −32 power of the depth below the surface, to have the same spectral content as the boom in air, and to travel down the string with the velocity of sound in water. These findings contradict the theory of an “inhomogeneous” wave incident beyond the critical angle, as originally stated by Rayleigh and as recently extended to sonic booms by Sawyer [J. Acoust. Soc. Amer. 44, 523–524 (1968)] and Cook [J. Acoust. Soc. Amer. 47, 1430–1436 (1970)]. They suggest, instead, that the underwater sonic boom is a wave scattered by the rough sea surface into the sea below. Its decay with depth is so rapid that it is not likely to be perceptible against the ambient-noise background at depths greater than one or two thousand feet in the deep sea.
Measurements of Transmission and Penetration of Airborne Explosive Sound into a Body of Water
Authors: Waters John F.
Published: October 2005

Dynamite caps were detonated over a flooded quarry. Spherically spreading shock waves impinged upon the flat surface of the water. Microphones and hydrophones were placed to obtain simultaneous measurements of sound-pressure waveforms at various locations in the air and water. The shock waves incident upon the water had approximate N-waveforms, with periods of about 2 msec. Both the transmission and the penetration of acoustic energy into the water were observed. Measurements of the transmission of sound agreed well in amplitude with the predictions of ray theory [A. A. Hudimac, J. Acoust. Soc. Amer. 29, 916–917 (1957)]. Measurements of the penetration of sound agreed well in amplitude and in waveform with theoretical predictions for incident N waves, such as sonic booms [K. N. Sawyers, J. Acoust. Soc. Amer. 44, 523–524 (1968); R. K. Cook, J. Acoust. Soc. Amer. 47, 1430–1436 (1970)]. [Work supported by Department of Transportation and Office of Naval Research.]
Sound Transmission through a Statistically Rough Plane Interface between Two Dissimilar Fluids
Authors: Medwin H. , Hagy J. D. , Helbig R. A.
Published: October 2005

The dependence of sound transmission on the statistics of a randomly rough interface between two dissimilar fluids has been studied by Kirchhoff-Helmholtz theory, laboratory scale model, and ocean experiment. The analysis and verified conclusions for transmission in the Snell direction are very similar to those in the case of specular scatter from a randomly rough surface; for example, when there is a large impedance mismatch and low roughness, the intensity is coherent and is e−R times the smooth surface transmission; for large roughness, the transmitted sound is incoherent and depends on the surface correlation length. The roughness parameter for transmission is R = k22σ2[(c2/c1) cosθ1−cosθ2]2, where k, c, and θ are the propagation constant, speed of propagation, and angle with the normal; subscript 1 refers to the incident medium; and σ is the rms height of the surface.
The Acoustic Characteristics of Water-Saturated Fibrous Metals
Authors: Lastinger J. L.
Published: October 2005

The propagation constants of six types of water-saturated Felt-metal, varying in fiber diameter and porosity, were measured in the NRL-USRD acoustic impedance tube at frequencies from 3 to 8 kHz and hydrostatic pressure to 34.5 MPa (5000 psi). The results consistently show effective sound speeds less than that in water, with attenuation constants ranging from 2 to more than 50 dB/m. Observed sound speed decreased and attenuation increased with decreasing porosity. The 10-μ-diam fibers also gave more attenuation with a lower sound speed than did the 100-μ-diam fibers.
Sound Propagation and Reverberation Measurements in Hudson Bay
Authors: Browning David G. , Jones Everett N. , Mellen Robert H. , Maples Louis C. , Thorp William H. , Ross John M. , Brochu Claude
Published: October 2005

An experiment was conducted in Hudson Bay during August 1970 to obtain propagation and reverberation data below 12 kHz. A listening hydrophone was suspended from an Amphibian stationed 90 miles east of Cape Churchill. Explosive charges were dropped from an aircraft along a 270-mile track to Coats Island. Additional charges were detonated close to the hydrophone to obtain the reverbetation data. BT information from along the propagation track indicated a sound channel with an axial depth of 150 ft over a flat hard bottom at an average depth of 500 ft. Propagation loss curves were obtained for 13-oct bands from 300 to 5000 Hz and reverberation levels for 1-oct bands from 200 to 12 800 Hz. Both the acoustic and oceanographic properties of Hudson Bay indicate a stable shallow-water sound channel during the summer months.
Physical Principles of Noise Control
Authors: Ingard Uno
Published: October 2005

After a survey paper on the principles of noise control, 10 contributed papers dealing with several areas of acoustics were presented in the session on physical principles of noise control. Radiation and propagation from sources of various kinds, analysis of vibrations, and studies of techniques for evaluating acoustic power were discussed. Of particular interest was a study of the radiation from incoherent sources, a holographic analysis of vibrations, and a paper on the visualization of the sound pressure distribution in a reverberant room [The work of U.I. is supported by the U. S. Navy Office of Naval Research.]
Environmental Noise
Authors: Franken P. A.
Published: October 2005

Eleven papers were presented in the session on environmental noise. Six of these included general discussions of engineering approaches for evaluating and controlling environmental noise (Franken, Goodfriend, Chalupnik, Karplus, Nowikas, and Senko). The need to utilize the appropriate degree of sophistication when analyzing an environmental noise situation was stressed. The political and social context, as well as the signal waveshape, statistical distribution, and frequency spectrum, must be considered. No simple rating system exists or is likely to be evolved, but complexities must be introduced in such a way that they clarify rather than confuse. New frequency-weighting scales are still being proposed. Although there seems to be a developing consensus that A-weighted sound levels are adequate for most problem descriptions, this view is by no means accepted by all. Three reports were presented on matters related to specific criteria (Flynn, Winzer, and Barnett). Performance requirements have been set for all acoustical aspects of multifamily housing. For another situation, the assessment of housing site acceptability, the requirements are expressed not in conventional engineering terms, but with descriptive information. Results of a psychoacoustic study (Barnett) showed that people consider artificial noises to be more bothersome than real-life appliance noises of the same over-all level, and that small but significant differences are observed among real-life noises from different appliances. Finally, two progress reports were given concerning specific noise sources: truck tires (Flynn) and synthesized spiral sound waves in a duct (Reethof).
Instrumentation, Measurement, and Assessment Techniques
Authors: Kundert W. R.
Published: October 2005

There were two significant themes in this session. One was that new electronic technologies allow more complex noise-rating criteria to be instrumented as practical, relatively inexpensive devices. It was suggested that it is no longer necessary to use the A-scale reading of a sound-level meter in place of a direct loudness measurement. A new loudness meter was proposed that includes a set of octave-band filters and is somewhat more complex than the present sound-level meter. Another device was discussed that simulates the TTS effect in normal hearing and can be conveniently worn. It would be used to assess the probability of hearing damage in a given noisy environment. In another paper, it was shown that a relatively simple analog circuit will detect the rms level over a wide dynamic range. The other theme of the session was the measurement of vehicle pass-by noise. Four papers considered various aspects of the measurement problem. Equipment must automatically monitor and collect data and it must be designed for continuous unattended use in adverse environments.
An Overview of Surface-Wave Methods and Devices
Authors: Shaw H. J.
Published: October 2005

Surface-acoustic-wave devices are presently under development in a number of laboratories as tapped delay lines and filters having unique properties for various signal-processing applications. Possible new devices involving surface-wave amplification, waveguiding, dispersive propagation, parametric signal processing, nonpiezoelectric propagation, and very long time delay are being studied, which have good prospects for future applications.
Energy Redistribution in an Ultrasonic Beam Reflected from an Interface
Authors: Smith James H. , Smith Richard F. , Breazeale M. A.
Published: October 2005

Schoch has pointed out that an ultrasonic beam incident on a liquid-solid interface is displaced appreciably when the angle of incidence is such that Rayleigh surface waves are generated on the interface. This theory has been extended by Brekhovskikh. Examination of the reflected beam near this angle using a precision goniometer reveals that the energy is redistributed into multiple beams, one of which may be dominant. Experimental results obtained with a Gaussian amplitude distribution across the incident beam are discussed. [Research supported by the Office of Naval Research.]
Surface-Wave Radiation from Interfaces of Material for Which Large Finite Beam Displacements Are Predicted
Authors: Neubauer Werner G.
Published: October 2005

Acoustic pulses in water at megahertz frequencies were directed at several material surfaces over a range of incidence angles. Some of the material had either very high densities or high wave speeds compared with aluminum, indicating, according to a formula by Schoch, that large lateral beam displacement should exist. By means of schlieren photographs, radiation from the solid surface is indicated to be an attenuated surface wave traveling along the solid interface rather than a distinct beam displacement as formulated by Schoch.
Radiation from Thin Plates Illuminated by Short Acoustic Pulses in Water
Authors: Dragonette Louis R.
Published: October 2005

Schlieren observations of effects which occur when thin aluminum plates are illuminated by short acoustic pulses, in water, are presented. At specific angles of incidence, the formation of wavefronts pro-progressing along the plate is visible. A sequence of photographs showing the incident pulse, and at later times its effects, is made possible by the pulsed schlieren system. Meaningful predictions are made by Lamb's theory for infinite plates with stress-free surfaces even though the experiments involve water-loaded plates. Comparisons are made with previous results on cylindrical shells.
Real-Time Technique for Speaker Verification by Computer
Authors: Lummis R. C.
Published: October 2005

In previous work on computer speaker verification [Doddington, J. Acoust. Soc. Amer. 49, 139(A) (1971)], low error rates were obtained when nonlinear time transformation was used for temporal registration of sample and reference utterances. In that study, utterances were represented by their pitch, amplitude, and formant-frequency profiles. The present study considers how well one might do only with measures which can be obtained in real time. The procedure differs from that of the previous study in the following respects: (a) utterances are represented only by pitch and amplitude profiles, (b) these functions are smoothed by low-pass filtering, and (c) a greater number of dissimilarity measures are computed. Because formants are not extracted, the verification is accomplished about 100 times faster than in the previous study. Performance was measured with the same speech material used in the earlier study. Included are utterances from eight “true” speakers and 32 “casual impostors.” A casual impostor is one who makes no attempt to mimic the true speaker. The acceptance-rejection criterion was adjusted a posteriori for equal rates of false acceptance and false rejection. The resulting error rate, averaged over speakers, was 1.0%.
Strategies for Recognition of Spoken Sentences from Visual Examination of Spectrograms
Authors: Klatt D. H. , Stevens K. N.
Published: October 2005

The automatic recognition of spoken sentences involves the extraction of acoustic attributes and rules for transforming these acoustic data into linguistic descriptions. The aim of this study is to examine the nature of these rules and to develop a framework within which the rules can be stated. The problem of automatic extraction of the acoustic attributes (such as boundaries, formant frequencies, and fundamental frequency) is bypassed by identifying these attributes from visual examination of spectrograms. The strategy involves scanning the acoustic data from left to right. At a given point in time the recognizer is in a “state” that is described in terms of recent yet-to-be-processed acoustic attributes, abstract phonetic features, lexical items, and syntactic and semantic categories. For any given state, there are rules that (1) guide the scanning of future acoustic data, and (2) specify how this state, augmented by the new acoustic data, is transformed into a new state. A framework in terms of which these two kinds of rules are specified is described, emphasis being placed on the phonetic and lexical levels of description. The rules are necessarily extremely numerous and complex, and this study simply attempts to indicate the nature of the rules and to give a number of examples. [This work was supported by the Advanced Research Projects Agency. The authors are also at Massachusetts Institute of Technology.]
Glottal-Pulse-Waveform Effects in Line Analog Speech Synthesis
Authors: Rice Lloyd
Published: October 2005

A research tool is described for studying the effects of glottal-pulse waveform on the speech signal. The system is based on a line analog synthesizer program which uses an on-line glottal-pulse-waveform editor. This system allows specification of an arbitrary waveform, which is then taken as the source impulse to synthesize up to 1.5 sec of speech. This new tool has been used for generation of stimuli for listening experiments on glottal source effects.
Speech Synthesis and Editing System for Teaching Phonetics
Authors: O'Malley M. H. , Kloker D.
Published: October 2005

A command language for controlling a Glace—Holmes speech synthesizer has been combined with a system for displaying, editing, and modifying natural speech. Synthesis parameters may be typed, displayed, or plotted. The pitch, amplitude, and duration of natural speech may be changed using the techniques of Vanderslice and Rand. Speech may be displayed, edited, and presented as monotic or dichotic stimuli and its spectra may be displayed, plotted, and punched. Results of using this system with introductory students are presented.
Some Applications of a Small Digital Computer in Speech Processing
Authors: Suen C. Y. , Beddoes M. P.
Published: October 2005

An increase in the rate and the intelligibility of sound is highly desirable in speech communication. Also, it is useful to have an accurate and efficient method of obtaining desired segments of a speech sample. In this paper, the use of a small digital computer in processing the speech signal to achieve the above purposes is described with illustrations. On-line simulation of the method of Fairbanks et al. [G. Fairbanks et al., IRE Trans. Audio 2, 7–12, (1954)] of increasing the speech rate has been achieved with flexible speed-up ratios and sampling intervals. Increase of intelligibility in speech signals by converting them into dichotic signals with an interaural time delay is discussed. These dichotic signals have been obtained from the computer for time delays between 0 and 1 sec. To obtain different segments of a speech sample, the computer is programmed to store the speech sample and display its waveform on an oscilloscope, so that various segments of the speech sample can be extracted and also joined together if desired. This segmentation method is very efficient and should replace the time-consuming and less accurate method of manual splicing and abutting a tape. [Work supported by the National Research Council of Canada.]
Digital Conversion of Adaptive Delta Modulation to Linear Delta Modulation
Authors: Flanagan J. L. , Shipley K.
Published: October 2005

A technique is described for direct digital transformation of the channel bit stream of an adaptive delta modulator to that for a linear delta modulator. The method is simulated on a computer, and the signal-to-noise performance is measured as a function of the bit-rate expansion factor (m) required to achieve the linear delta. The results suggest that, for a three-pole Butterworth desampling filter, the system is essentially transparent for m>16. Implications to digital switching and reformatting of the signal to PCM and DPCM are mentioned.
A Hardware Realization of an Exponentially Adaptive Delta Modulator
Authors: Cummiskey P.
Published: October 2005

A “2 bit” exponentially adaptive delta modulator, similar to the device derived by N. S. Jayant [J. Acoust. Soc. Amer. 47, 84(A), (1970)] has been implemented in integrated-circuit hardware. Two modulators were constructed in order to test independent operation of a transmitter and a receiver. Measurements on the hardware confirm results of earlier computer simulations and also show that modulator performance is insensitive to practical hardware imperfections. Data reported include measurements of signal-to-error ratio made with sine-wave inputs, and spectrograms of speech encoded at sampling frequencies of 60, 40, and 20 kHz. Tests were also made on the input speech with level reduced 20 dB below normal full load and with the transmitter and receiver power supplies offset by 4%. The results demonstrate the excellent dynamic range of the delta modulator and the lack of need for precision components.
Pitch Display for the Deaf
Authors: Savage C. J.
Published: October 2005

The speech of a deaf person usually sounds unnatural and may even be difficult to understand; one cause of this unnaturalness is the frequently grossly incorrect intonation of such speech. In the absence of the normal auditory channel, visual displays of intonation patterns have been used to provide the feedback to learn proper pitch control. Most effective devices of this type provide both instantaneous pitch display and pattern storage. While this combination of features does not raise the cost of such an instrument beyond the reach of institutions, the cost is prohibitive for individual home use. To provide a low-cost pitch display, various possible principles are considered with respect to their relative merits. Experimental results of implementation of the most promising solution are presented. [The research reported in this paper was sponsored by a grant from the Bureau of Education of the Handicapped, Division of Research, Office of Education, Department of Health, Education and Welfare, Washington, D. C.]
Visual and Auditory-Visual Reception of Speech by Deaf Children
Authors: Erber N. E.
Published: October 2005

A speaker recorded lists of words on video tape. These lists were presented to normal-hearing children and adults and to profoundly deaf children (average HTL greater than 95 dB ISO) for recognition through visual or combined auditory-visual (A-V) modalities. For the normals, the auditory stimulus was a 500-Hz octave-band noise amplitude-modulated by the speech signal. For the profoundly deaf observers, the acoustic signal was modulated noise or linearly amplified speech. Regardless of the type of acoustic signal they received, the A-V scores of the deaf were 5%–10% higher than their lip-reading scores. The normals also demonstrated small improvements (6%–9%) over visual reception when allowed both to lipread and to listen to modulated noise. These results and other studies of profoundly deaf children suggest: (1) that their A-V reception of words is about 7% better than their visual reception, (2) that they probably perceive time-intensity (envelope) rather than spectral information when provided with amplified acoustic cues for speech, and that vibrotactile rather than auditory receptors may mediate the acoustic speech signal.
Memory for the Pitch and Loudness of Pure Tones
Authors: Jesteadt W. H.
Published: October 2005

In order to facilitate a direct comparison of recent models of pitch and loudness memory, identical recognition-memory experiments were performed with pitch and loudness as the memory variables. A trial consisted of a roving standard, an interpolated interval of variable duration filled with a variable number of tones, a comparison tone equal to, higher, or lower than the standard, and a same-different decision on the part of the subject. For both pitch and loudness, criterion and performance measures were related to the position of the comparison tone relative to the standard and to the position of the standard relative to the set of standards. The loudness-memory model proposed by Durlach and Braida leads to a more adequate explanation of these results than the pitch-memory models proposed by Massaro or Wickelgren.
Contralateral and Ipsilateral Pitch Shift in the Presence of Wide-Band White or Pink Noise
Authors: Lovell John D. , Carterette Edward C. , Barnebey A.
Published: October 2005

Pitch matches were made between a fixed standard tone at 100, 400, or 1600 Hz and a variable frequency tone occurring at different time periods in the right ear. A 40 dB SL wide-band white or pink noise occurred at the same time as the standard tone in either the right or left ear. When white noise was in the right ear, the results were similar to those of previous investigations [e.g., Schubert, J. Acoust. Soc. Amer 22, 497–499 (1950)]. Shifts of 100, 400, and 1600 Hz were, respectively, about 0%, 0.8% and 1.2% of the standard frequency, and were in an upward direction. When pink noise was in the right ear, pitch shifts were more negative by about 0.5% of the standard frequency. If pink or white noise were presented in the left ear, pitch shift was of a comparable magnitude to the case of the right ear, but the shift produced by pink noise was not consistently more negative than that produced by white noise. [Work supported by the United States Public Health Service and by the Patent Fund of the University of California, Los Angeles.]
Frequency Analysis in a Sequential Detection Paradigm
Authors: Gilliom J. D.
Published: October 2005

An experimental paradigm which requires the observer to monitor two frequency regions sequentially allowed the development of differential predictions from single-band and multiband models of the frequency-analysis process. Two visually marked observation intervals, each 250 msec in duration, were presented within each trial—the end of the first interval coincided with the start of the second. Observers were required to make two YES-NO detection responses concerning the presence of a sinusoidal signal—one for each of the observation intervals. Two complex conditions were run—a fixed condition in which the assignment of the two possible signal frequencies to observation intervals was fixed and known by the observer, and a random condition in which the two signal frequencies were assigned to observation intervals by a random process. Predictions from several single-band and multiband models were developed to relate performance measures obtained from each observer in simple YES-NO detection tasks to performance in the fixed and random sequential detection conditions. All single-band models consistently underestimated performance; multiband models were considerably more successful in predicting performance.
A Challenge to the Concept that the Auditory System Functions as a Frequency Analyzer
Authors: Mundie J. Ryland , Goldstein Allan J.
Published: October 2005

For a number of years, we have investigated auditory function with physiological and psychological measures and with electronic models. We have come to the conclusion that the auditory system must carry out its analysis in the dimension of time rather than the dimension of frequency. There is a simple relationship between frequency and time in signals composed of pure tones and simple combinations of sinusoids, so when these signals are used to test the auditory system the results may be interpreted as indicative of either time or frequency analysis. In complex stimuli composed of transients, such as speech signals, the simple relationship between frequency and time no longer exists. The auditory response to these signals can only be meaningfully interpreted in the dimension of time. Information in the primary auditory neurons is encoded in Pulse Density Modulation, a form not used by current engineering technology. The auditory system appears to be an analyzer ideally designed for processing brief transients.
The Varying Auditory Threshold of Normal Subjects
Authors: Young I. M. , Wenner C.
Published: October 2005

By using a Békésy-type audiometer, a comparison was made between pure-tone thresholds obtained with various attenuation rates and conventional audiometry for normal subjects. Tones with on-time of 300 msec and a rise-and-decay time of 25 msec were used for threshold measurements obtained by the frequency method. Tones were presented in random order with 1-dB steps. For Békésy audiometry, thresholds were obtained for continuous tones and interrupted tones with an on-time and off-time of 300 msec and a rise-and-decay time of 25 msec. Fixed frequency tracings were made with attenuation rates of 1, 2, and 4 dB/sec. Results indicated that thresholds measured by the frequency method correlated only with those measured at the midpoint of Békésy spikes by using an attenuation rate of 4 dB/sec. A faster attenuation rate, using the midpoint as the threshold value, provided a better threshold than did the random presentation. The reverse was true with the slower attenuation rates until a rate of 1 dB/sec was was reached. This rate showed that, regardless of the point on the Békésy spike the threshold was taken, it was always worse than that for the random presentation. Auditory threshold, then, is not definite value but varies with the method of presentation of the tone.
The Standard in Pure-Tone Auditory Amplitude Discrimination
Authors: Long G. R.
Published: October 2005

The role of the standard in a fixed-standard pure-tone amplitude discrimination experiment was examined by varying the proportion of trials on which it was presented. The results suggest that a different and slightly poorer strategy is used when the standard is absent and that uncertainty as to the nature of the trial interferes with the use of either strategy. These results conflict with the claim by advocates of the roving-standard method that the observer in the fixed-standard experiment does not use the standard but rather compares the variable with a stable long-term referent built up over many trials.
An Ear-Like Coupler for Calibration of Earphones
Authors: Zwislocki J. J.
Published: October 2005

A coupler for earphone calibration has been developed that mimics the acoustic properties of the outer ear and has a simple geometry. It consists of an outer portion corresponding to the auricle, a canal corresponding to the ear canal, and an acoustic network reproducing the acoustic impedance at the eardurm. The sound pressure is measured at the eardrum location by means of a 14-in. condenser microphone. According to comparative measurements, the acoustic impedance at the end of the coupler canal follows the average eardrum impedance with satisfactory accuracy within the frequency limits of 100 and 7000 Hz. The coupler also produces essentially the same pressure transformation between the microphone, midcanal, canal entrance, outer rim, and 1 cm outside the outer rim as the pressure transformation in an average ear between corresponding points. The coupler may be used for supraaural earphones as well as for insert and circumaural earphones. It can be manufactured according to rigorous specifications.
A Method for Acoustic Admittance Measurement
Authors: Arguimbau L. B. , Grason R. L.
Published: October 2005

In diagnosis of middle-ear hearing trouble, it is desirable to measure the acoustic admittance of the eardrum. In practice, the complex drum admittance is the difference between the complex admittance of the ear canal plus drum and that of the canal alone. If the drum is immobilized by a static pressure, the total admittance is essentially that of the canal alone. The difference with the drum free and immobilized is the drum admittance. The use of admittance permits the direct reading of drum susceptance and conductance. This can be carried out at more than one frequency by electrical null measurements. Null balancing is facilitated by a simple cross-correlation technique that separates the resistive and reactive components during manual operation and in automatic tympanometry.
A Redetermination of the Noy Contours
Authors: Ollerhead J. B. , Eldred K. M.
Published: October 2005

The subjective noisiness of bands of random noise was measured in the frequency range 31.5 Hz to 10 kHz and at sound-pressure levels up to 120 dB re 2×10−5 N/m2. The methods of paired comparison and individual adjustment were used in tests performed in both highly diffuse and progressive wave fields. Although certain differences were found which were attributed largely to different effects of head diffraction in the different fields, it was concluded that existing rules defining the variation of perceived noisiness with frequency and intensity are satisfactory compromises. Also, new data allow the noy contours to be extended to low frequencies with more confidence than was previously possible. Further research is recommended to define a standardized acoustic field in order to establish the most appropriate noy contours for practical use. [Work supported by the Federal Aviation Administration.]
Applied Macrosonics
Authors: Semmelink A.
Published: October 2005

Macrosonics is the field of nonlinear acoustics. Examples of the use of macrosonics are industrial processes which use mechanical vibrations at ultrasonic frequencies. There is no reason to limit our definition to such frequencies. Where large displacements are required to obtain deformation, lower operating frequencies may be essential to achieve the desired end. Thus mechanical vibrations of any frequency, ultrasonic, audible, or infrasonic, should be included. The medium to which the vibrations are applied may be solid, liquid, or gaseous. Examples of nonlinear processes are deformation in solids, cavitation and streaming in liquids, and turbulence in gases. The choice of frequency and power level depends on the medium, its dimensions, the effect to be achieved, and the time available for the process. Transducers of many kinds are used to convert electric, hydraulic, or pneumatic energy to mechanical vibrations. Velocity transformers may couple the transducer to the radiating face or tool tip. Measurements of acoustic power, exerted force, and displacement help in understanding phenomena involved in macrosonic processes. Recent developments include applications to many industrial fields, such as metal casting, building construction, chemical processes, etc.
Dislocation Damping in Macrosonic Fields
Authors: Langenecker B.
Published: October 2005

Attenuation measurements of high-amplitude ultrasonic waves (macrosound) in metal crystals contribute to a better understanding of the physics of crystal plasticity, as has been shown in earlier experiments. The study of the interaction of high-frequency mechanical waves with lattice structures (dislocations and grain boundaries) within the plastic range of acoustical stresses σ⩾ε′σ⩾τ (where τ is the shear stress necessary for extensive glide, ε′ the plastic strain, and σ the shear modulus) complements ordinary damping measurements at low amplitudes (a≲10−6) in metals after neutron (or other corpuscular) irradiation as well as the measurements during and after conventional plastic deformation. A satisfactory comparison and analysis of the data obtained at lower and higher amplitudes, respectively, was not possible as yet, owing to widely differing measuring techniques and materials. We therefore developed a new method of observation which provides continuous damping data ranging from low to high strain amplitudes, on high-purity copper and aluminum single crystals. Also, the modulus defect was observed in correlation with the influence of high-amplitude macrosound.
Comparison of Ultrasonic Power Measurement Techniques
Authors: Nicholson James E.
Published: October 2005

Ultrasonic devices are now used in a variety of medical and industrial applications where precise knowledge of the acoustic power output is required. Mechanical watt meters are available which measure radiation pressure and convert the reading to acoustic power. Acoustic power measurements can also be made by measuring the energy absorbed by a liquid medium which is irradiated by sound. In addition, the power output of ultrasonic devices can be estimated by measuring RF power out of the ultrasonic generator multiplied by the quoted acoustic efficiency of the transducer. These methods are reviewed and compared for a variety of transducers and acoustic watt meters.
Interactions between a Vibrating Object and the Surface of a Soft Solid
Authors: Frost H. M. , Fill E. E.
Published: October 2005

Deformation of the surface of a soft solid by an ultrasonically vibrating object (20 kHz) was studied by means of a displacement transducer. An ultrasonic horn with a suitably formed tip was vibrated at amplitudes of 1 to 25μ against agar gel, wax, plastics, and soft metals while penetration into the test sample was recorded as a function of time. As an interesting example, a hemispherically shaped vibrating tip of 0.1-mm radius of curvature penetrated into paraffin wax in two successive stages—fast and slow. After initial penetration due to loading, the sound was switched on and the penetration rate changed abruptly from zero to 500 μ/sec. After 40 msec, the fast rate then changed to a slower one that gradually decreased to zero. Somewhat similar results were obtained for other solids such as agar gel, tin, lead, and plastic. Sonic penetration may arise from high shearing stresses near the tip, which lead to plastic flow. Currently these stresses are being studied in plastics by means of stress birefringence. Findings may increase understanding of effects of ultrasound on solid like media in general. [Research supported in part by Hood Interdisciplinary Fellowship.]
Variation in Measured Automobile Pass-by Noise Due to Operator and Environmental Factors
Authors: LaBreche R. M.
Published: October 2005

Pass-by noise levels were repeatedly measured for four cars using different operators and different environments. The measurements were made according to the SAE J986a procedure, which has been used as a basis of the California Vehicle Noise Code. The level produced by each car was found to be affected significantly by ambient temperature and by differing crosswind and/or differing reactions of each operator at the various test sites.
Noise Levels Encountered in Air and Surface Transportation
Authors: Bray Don E.
Published: October 2005

Noise Levels have been obtained at passenger seat locations on airplanes, buses, and railcars while they were operating in regular service. The sound field at seating positions was found to be diffuse in most cases, and convenient measurements could be made with a hand-held sound-level meter. The data are graphically illustrated first as typical time histories, second as separate groups with cruise noise levels shown in decibels (A) and, finally, as a point graph with cruise levels in decibels (A) versus the difference decibels (C)—decibels (A). This last graph shows three distinct clusters and illustrates in compact form the comparative differences in the frequency components of each group. Special interest items included are STOL aircraft, the Metroliner, and PATCO cars from Philadelphia's new Lindenwold Commuter line. Some comparative data from other authors and a discussion of the particular noise sources are also included.
Design of Acoustic Barriers for Highway Noise Reduction
Authors: Anderson Grant S. , Gottemoeller Frederick
Published: October 2005

By a technique similar to that of the Highway Research Board Acoustic Design Guide, the acoustic impact of 20 miles of future interstate highway through a large eastern city was evaluated. Where the Design Guide criteria indicated that the impact was excessive, roadside barriers were designed. Barrier design involves breaking the highway into straight-line elements and calculating their individual contributions to the A level at the receiver position. In this manner, the varying effectiveness of a roadside barrier in attenuating the sound from each element can be used to determine the necessary barrier length and height (which may vary along its length). Roadside barriers and barriers that envelop the receiver may both be evaluated. Also, the method allows computation of the A level for highways of varying curvature, gradient, traffic count, and surface characteristics. The calculations are repeated for receivers at different positions and heights. The technique predicts the barrier attenuation of both the 50-percentile and the peak A level. One of the recommended barrier complexes is used to illustrate the method.
Noise Legislation and Regulation in Hawaii
Authors: Buggess J. C.
Published: October 2005

During 1970, legislation was enacted in Hawaii mandating the State Department of Health to develop and adopt standards concerning and regulations governing excessive noise for different areas of the State. This legislation allows the department to establish advisory noise-control committees for each country, and the director established the Advisory Committee on Noise Control for Oahu (Honolulu County) in September 1970. The committee decided to approach the total problem of noise control on Oahu by preparing and recommending separate regulations for separable kinds of noise source. The first of these recommendations concerns surface transportation noise.
Acoustic Filter Synthesis
Authors: Kessler F. M.
Published: October 2005

Mathematical programming has been applied to the synthesis of acoustic filters, eliminating the need for intuitive parameter selection and analysis. Variational methods applied through conjugate gradient techniques of Hestenes and Stiefel have been developed for two types of synthesis problems. Attenuation relationships presented for various muffler configurations by Davis et al. in NACA Report 1192, are used as the criteria function for which the filter parameters are optimized; that is, the use of a computational algorithm provides the length and area ratio which minimizes the difference between a desired attenuation and the available attenuation. Alternatively, a synthesis approach has been developed which provides the optimum parameters for an n-section filter, treated as cascaded sections of distributed parameter elements, subject to size and through flow constraints. This is an n-section generalization of the aforementioned approach and provides optimum parameters which minimize the difference between a desired output spectrum such as Walsh-Healey criteria and an output spectrum obtained for a given input. Results obtained using the two methods for a single expansion chamber are presented and compared.
Use of Nearfield Measurements to Determine Total Noise Power of Large Machines
Authors: Angevine O. L.
Published: October 2005

The measurement of noise generated by large machines is often restricted by the necessity to make the measurements in a small semireverberant room. Sound-pressure levels can only be measured very close to the machine in such cases, at distances which appear to be well within the nearfield of the machine considered as a single large noise source. But large machines are actually composed of a number of smaller incoherent noise sources. Arrays of such sources show the farfield beginning at distances comparable to the measuring points at 1 m from the machine used in the CAGE standard, or the prescribed path of ISO Recommendation 495 and ISO Draft Recommendation 1680. Measurements made by this method corrected to a uniform radius and used to determine total sound power agree quite well with those on the same machine measured by the diffuse-field method.
Recent Advances in the Design Analysis of Acoustical Enclosures for Machinery and Appliances
Authors: Copley L. G.
Published: October 2005

Machinery and appliances are usually enclosed by a panel structure, one of whose functions is to reduce the sound power radiated by the equipment. The theory employed in building acoustics for sound transmission through walls and partitions is not generally adequate for these situations since the sound field inside the enclosure is rarely diffuse, owing to the geometry of the machinery or appliance with respect to the enclosing surfaces. This paper outlines a theoretical approach that does not assume a diffuse sound field within the enclosure. Rather, it models the close dynamical coupling between the enclosure panels and the vibrating machinery inside. Also recognized is that the sound power radiated by the machine is affected by the enclosure, a fact that can be generally ignored in building acoustics. The theory shows the effect on acoustical performance of structural damping of the panels, acoustical absorption inside the enclosure, and the space between the machinery and the enclosure.
Experiments with Superfluid-Helium Persistent Currents Using Fourth Sound
Authors: Rudnick I. , Kojima H. , Veith W. , Kagiwada R. S.
Published: October 2005

Persistent currents can be established in superfluid helium in cylindrical or ring-type containers which are packed with superleak. These circulatory states are metastable and have been observed to persistent with little or no decay for periods of many hours. In the absence of this motion, the fourth-sound azimuthal modes of the containers are degenerate. The degeneracy is lifted when the superfluid helium circulates and the velocity of the current can be determined by the frequency splitting of the modes. The velocities of persistent currents have been determined in this way. Experiments have been carried out on the effect of temperature, sound frequency, and other parameters of the system on the persistent-current velocities with sometimes surprising results.
Acoustic Modeling of Hydrodynamic Waves
Authors: Parvulescu Antares , Hart David N.
Published: October 2005

The effect of storm waves upon harbors, channels, and break-waters is generally studied by reduction of nonlinear hydrodynamic problems to a linear one described by a Hemholtz equation. Experimental work is generally carried out in a model wave basin under corresponding linearized condition. As was shown earlier by R. P. Shaw and A. Parvulescu (1970), a model using sound waves as an analog to the storm waves follows the same linearized laws. We have constructed such a model. It consists of an acoustical two dimensional anechoic chamber of dimensions 240 cm×120 cm×2 cm operating in air. An array of miniature loudspeakers generates a plane wavefield simulating incident storm waves. Two-dimensional models of various harbors are cut out into a block of reflecting material representing the coast line. We show results obtained with our models and compare them with previous results obtained with the classical approaches for the same harbor. The advantages and limitations of the acoustical models are also shown.
Evaporation and Diffusion Effect on an Oscillating Bubble
Authors: Wang Tunglu , Hsieh D. Y.
Published: October 2005

The effect of diffusion and evaporation on the oscillation of a bubble is analyzed. It is found that the modification due to diffusion alone is significant only when the diffusion length is large compared with the size of the bubble. The modification on the temperature field due to the evaporation process is important even at room temperature except for very small bubbles. Based on these results, a theory on the rectified heat diffusion is developed. A second-order net heat transfer into the bubble is found when the thermal diffusion length is either large or small in comparison to the bubble radius.
Ultrasonic Attenuation in Hot Specimens by the Momentary Contact Method with Pressure Coupling
Authors: Papadakis Emmanuel
Published: October 2005

The momentary contact method previously used for ultrasonic velocity measurements and flaw detection in hot specimens has been extended to the measurement of ultrasonic attenuation. In this method, a cool buffer rod is brought into contact with the hot specimen for a few milliseconds. A transducer on the cool end of the buffer rod transmits an ultrasonic pulse down the buffer rod and receives the echoes from the buffer/specimen interface and from the multiple reflections within the specimen. From the first three returning echoes, the attenuation in the specimen and the interface reflection coefficient are computed. Acoustic coupling at the interface is brought about by pressure alone for both longitudinal and shear waves without any bonding agent. The utility of the method is illustrated by measurements on SAE 52100 alloy steel in which the curie temperature was detected by a peak in attenuation in the ferromagnetic region followed immediately by a dip in attenuation in the paramagnetic region. At higher temperatures, grain growth is detected. [This work was supported by the Office of Naval Research, Code 468.]