bluuebunny/crossref_metadata_2025 huggingface dataset:
Introduction by Chairman
Authors: Audette R. R.
Published: October 2005

A brief introduction starting the purpose of this session, whom we are trying to reach, and how we plan to do this.
Noise of Homes
Authors: Schreinier John R.
Published: October 2005

Our homes are filled with products that provide comfort, convenience, and entertainment for the occupants and coincidentally produce noise. Most of these products operate only for short periods of time when users turn them on, but some cycle on and off continuously in response to automatic controls. Most are normally operated inside homes but some of the noisier ones are used outdoors and thereby contribute to community noise. Sound outputs vary widely between different types of products and to a lesser extent among different models of the same type, and many also vary with the mode or cycle of operation. The effects they produce also vary with the relative locations of the people exposed and their occupations at the time. While these factors add complications, considerable progress has been made on sound rating standards for many of these products, notably in the air conditioner industry, and quieter products will typically result from sound rating programs.
Industrial Noise in the Community—Current Views
Authors: Goodfriend Lewis S.
Published: October 2005

Noise from industrial plants has continued to be a problem for both the plant managements and their neighbors. Several recent studies have indicated that the majority of persons in residential areas are exposed to ambients set by transportation noise sources. This is of little comfort to the immediate neighbors of an industrial plant whose noise dominates a small region surrounding the plant. Recent acceptance of the A-weighted sound level to rate noise, results of several Federal studies, and an evaluation of the Normalized Community Noise Equivalent Level (NCNEL) have changed the community-industry situation little, but prepare the way to develop workable methods for rating noise situations in a manner similar to the earlier Composite Noise Rating, but without measurement of the spectrum. Furthermore, the interrelationship of a community and its industrial neighbors appears to play a major part in the acceptance of the noise levels surrounding the plant. This leads to the conclusion that there is no universal method of rating community noise that will satisfy any given percentage of neighbors in a community without first determining attitudinal factors that can be applied in the noise evaluation as weighing factors. Further research is currently under way. This effort is critical since current work to reduce transportation noise may lead to a situation where industrial noise becomes dominant in the major portion of many more communities.
The Citizen Response to Noise Since 1967
Authors: Baron Robert Alex
Published: October 2005

Since 1967, the citizen is on the offensive. He has learned how to intensify awareness of noise pollution. His educational techniques have become more sophisticated. Pressure points have been discovered and are being applied. Environmental noise is now being recognized by some acousticians and polluters. However, significant moves toward abatement have yet to be taken. While the hearing loss aspect of occupational noise is now being recognized in legislation, the nonauditory aspects are totally neglected. The citizen is, therefore, now including a concern for occupational noise while intensifying his battle against environmental noise exposure. The noise receiver is still asking the acoustician to move from measurement for the protection of vested interests to abatement for the sake of human interests.
Exposure of Communities to Low-Frequency Noise from Aircrafts and Rockets
Authors: Kiro D. , Fehr U. , Burnstein M. , Iron B. , Goldman J.
Published: October 2005

Data collections, in the low-frequency noise region (below 100 cps), in communities located near airports were analyzed for the purpose of volumetric coverage. The following factors, such as residential areas under influence, volume of noise, time of noise, and range of influence, have indicated the importance of these studies. Isosurfaces of SPL of jet planes at altitudes of up to 7000 ft are shells in the shape of pears, with the top directed towards the ground. The top covers a minimum area of 12 000 km2. The pearshaped envelope is pulled in the direction of the flight, and this produces a time delay and altitude dependence between the community exposure to radiated noise, and the instantaneous location of the plane. Typical time exposures for altitudes of 1000 to 7000 ft are 45–74 sec. This low frequency does not raise complaints because of the human ear's limitations; nevertheless they might be harmful. Furthermore, infrasonic frequencies (4 cps and below), having energies of 100 dB and more, cover 10 000 km2 and have durations of up to 30 min. Studies of physiological effects on animals and humans are of importance in this field. If these frequencies are harmful or bothersome, the jet engines should be designed to dissipate these energies at higher frequencies which attenuate strongly and do not propagate long distances in the atmosphere.
Aerospace Industry Applications of the Fast Fourier Transform
Authors: Galef A. E. , Mitchell D. H.
Published: October 2005

The advantages of the Cooley-Tukey technique for calculating the Fourier transform of a function were recognized immediately and universally; there is probably no other algorithm which was incorporated in program libraries so fast, and after only eight years it is now likely that there are no laboratories where current engineering work is being done that do not have an operational version of the fast Fourier transform. It would be reasonable to expect that this now universal ability to make the transform (and inverse transform) with great economy would have encouraged its widespread use and the development of new applications of this powerful technique. A cursory survey within the Aerospace Industry confirms that it is indeed being used widely, but suggests that the major use is the routine one of spectral analysis, where the Fourier transform is an end product rather than a tool. This paper attempts to encourage the wider use of the fast Fourier transform by describing some additional applications from the experience of the authors and others at the author's home company, and from the experience of others whose comments have been solicited.
Investigation of the Aerodynamic Noise Generating Region of a General Electric T-58 Jet Engine by Means of the Simple Source/Fluid Dilatation Model
Authors: Hurdle Patrick M. , Meecham W. C. , Hodder Brent
Published: October 2005

Experimental tests were carried out at NASA Ames Research Center. Crosscorrelation measurements were made between the static pressure fluctuations, as measured with a B & K 14-in. microphone fitted with a nose cone, and the far-field radiated sound. These measurements were made for two different probe positions and a large number of far-field positions at various angles. In addition, each test geometry was run for jet exit velocities at four different Mach numbers. The measured, normalized cross-correlation functions varied between 0.155 and 0.004. These values depended upon the angular position of the far-field microphone, the jet exit velocity Mach number, and the position of the probe. In addition, the cross-correlation technique was employed to study the symmetry of the farfield radiated sound. Third-octave analysis of both the probe signal and the far-field radiated sound were made. The results of these measurements will be reported.
Vehicle Noise Measurements and Community Noise Standards
Authors: Lawrence Anita
Published: October 2005

Although measurements of road vehicle noise emission made according to ISO or SAE or similar methods have the asset of consistency, their usefulness in predicting the noise annoyance caused by such vehicles is limited, particularly in the case of large commercial vehicles. For nonmotorway traffic in built-up areas, the stop-start condition is most common. Field measurements indicate that acceleration from a stationary start in the lowest forward road gear gives useful results. In addition, body noise may be measured by driving the vehicle at constant speed over a rubber “bump” strip. Vehicle noise limits should be related to community noise standards; however, the subjective equivalence between the annoyance caused by a continuous stationary noise source and that caused by a traffic stream is not easy to establish.
Properties of Liquid Crystals
Authors: Brown Glenn H.
Published: October 2005

Molecular geometry is important in interpreting the properties of liquid crystals. In addition, the molecular packing in different liquid crystalline structures will be presented and correlated with the properties of the liquid crystalline state of matter. This information on molecular packing will be focused essentially on thermotropic liquid crystals, but some information will be presented on lyotropic ones. A brief synopsis of some of the most interesting applications of liquid crystals will be presented.
Visualization of Ultrasonic Waves Using Liquid Crystals
Authors: Greguss P.
Published: October 2005

The search for a device that transfers acoustic wave information into equivalent light information began its rebirth after the first ultrasonic holograms were recorded on sonosensitive plates in 1964/1965. About the same time, the heat sensitivity of liquid crystals which shows up in color was introduced to NDT to find flaws. Since when an ultrasonic image is projected onto a suitable absorbing material it is converted into a corresponding spatial temperature variation over the absorber, it is clear that by coating the absorber with a layer of liquid crystals the intensity distribution of the ultrasonic field will be visualized. Examples of this technique will be presented. In nematic liquid crystals, five electrooptic effects—dynamic scattering, voltage-controlled optical activity, fast turnoff mode, deformation of vertically aligned phases, and guest-host interactions—can be observed, all of which may be affected by ultrasonic waves. Therefore, they can be used to transfer acoustical wave information into light information. The birefringent properties of a new specially prepared liquid crystal cell (AOCC) offer a new real time acoustical-to-optical display, which can also be used to record ultrasonic holograms. The pluses and minuses of the AOCC will be discussed in connection with a short movie.
Ultrasonic Measurements in Liquid Crystals
Authors: Letcher S. V.
Published: October 2005

Although ultrasonic measurements in liquid crystals were first made more than 15 years ago, only in the last few years has there been a dramatic increase in interest and in the rate of progress. Both longitudinal transmission and shear reflectance measurements have now been performed in smectic, cholesteric, and nematic liquid crystals. The following topics will be among those discussed: temperature and frequency dependence of absorption and velocity, absorption at nematic-isotropic phase transitions, and anisotropic propagation in oriented nematics.
Use of Encapsulated Liquid Crystals to Demonstrate Temperature Increases due to Large Stress Amplitudes in Piezoceramic Bodies
Authors: Kendig Paul M.
Published: October 2005

When unloaded piezoceramic bodies are driven at high stress amplitudes at their resonant frequencies, considerable heat is produced, with the maximum heating occurring at the nodes (regions of maximum stress). The resulting temperature increase is easily demonstrated by placing on or cementing to the vibrating bodies, films of encapsulated liquid crystals (ELC). The ELC is protected on the viewing side with a sheet of Mylar and covered with black ink on the other. Most suitable films are those with a relatively small temperature range for the visible spectrum. When the vibrating body is driven with large stess amplitudes, a bright colored spot (red end of spectrum) appears in the region of the node. The color rapidly moves through the spectrum to blue and the area of the colored region expands. Implications of this technique are discussed.
Ultrasonic Imaging for Underwater Viewing
Authors: Warner H. L.
Published: October 2005

An ideal ultrasonic imaging system for undersea applications is described that would provide diffraction-limited performance at high resolutions (5002000) over a field of view of at least ±10°. The image surface of the ideal system would be an array of closely spaced sensors with the size of each sensor being determined by the image spot size. Each sensor would be connected via a discrete processing channel to an element in an electro-optical display. Each processing channel would provide either linear or exponential amplification in specified temporal frequency bands and signal integration with controllable or automatic selection of the integration time. The merits of dividing the passband into three overlapping bands to provide a color display will be explored. The need for broad spatial and temporal frequency bandwidths will be shown. Since an ideal system cannot be built at this time, an examination of the parameters and performance which must be compromised to obtain practical ultrasonic imaging systems will be made. A number of systems that have been developed for undersea applications will be reviewed.
Experiments in Ultrasonic Imaging for Weld Inspection
Authors: Turner W. R.
Published: October 2005

As part of a program for investigation of ultrasonic visualization techniqnes, a laboratory imaging system was used to determine some practical factors in weld inspection applications. The system used the Vitro-designed ultrasonic image tube, and experiments were performed both with and without imaging lenses. The test material was 24-in. steel plate containing a butt weld with flaws that had previously been radiographed for reference. Ultrasonic energy was introduced into the plate as a shear wave through a coupling block. Scatter from defects was detected on a monitor as a two-dimensional image against a dark background. Image distortion and phantom images were investigated in detail. System performance criteria for a high data rate inspection system were established, and system modifications were specified for meeting these criteria.
Experimental Ultrasonic Image Converter to Permit a Diver to See in Turbid Water
Authors: Rolle A. L.
Published: October 2005

An experimental ultrasonic image converter was developed to generate a television-like image inside a swimmer's facemask of a 60° viewing sector from 14 in. (arms length) to a maximum range of 10 ft. The converter consists of an array of transducers and a similar array of light emitting diodes affixed to opposite ends of a rotating cylinder containing the processing electronics. The transducer array both generates and receives high-frequency ultrasound which is focused by a miniature liquid lens to form multiple narrow beams. The processed transducer outputs are applied to the diode array to form the visual image, which is conducted to the facemask by fiber optics. Rotating the arrays effects both the scanning of the narrow beams over the object plane and the required synchronous display scan to form the visual image. Tests using hand tools, metal plates, and cylinders demonstrated the feasibility of generating useful images of even specularly reflecting objects with techniques applicable to free-swimmer equipment.
Time Dependent Root-Mean-Square Response to Nonstationary Random Excitations
Authors: Hart Gary C.
Published: October 2005

The nonstationary rms response of single-degree-of-freedom linearly elastic structural systems to several classes of nonstationary random excitations are summarized and compared. Particular emphasis is placed on shot noise, time-modulated white and correlated noise, and evolutionary and segmented nonstationary excitations. The influence of both structural system and nonstationary excitation parameters upon rms response is evaluated. Approximate response approaches are discussed.
Spectral Representations under Nonstationary Random Excitation
Authors: Mark W. D.
Published: October 2005

The essential concepts and equations associated with the spectral analysis of stationary random processes are the power spectral density, the autocorrelation function, their mutual relationship known as the Wiener-Khintchine theorem, and the power spectrum input-response relationship for linear systems. These concepts and equations can be extended in a natural and unified way to nonstationary random processes. To provide these extensions, it is shown that two time-dependent power spectrum definitions are required—both of which reduce to the same definition in the case of stationary processes. One of these spectrum definitions is essentially equivalent to the class of time-dependent spectra obtained by narrow-band filtering; hence, this definition possesses a clear physical interpretation. However, it does not possess a simple input-response relationship for linear systems. The second spectrum definition is the Fourier transform of a time-dependent autocorrelation function. Realizations of this second spectrum exhibit spurious behavior—e.g., they may be partially negative; however, this second definition possesses a simple, exact input-response relationship for linear systems. The exact mathematical relationship between the two spectrum definitions is explained and interpreted in terms of the uncertainty principle for Fourier transforms.
On Fatigue Life Under Stationary Gaussian Random Loads
Authors: Talreja R.
Published: October 2005

Power spectra are taken to represent stationary Gaussian random loads. Location, scale, and shape parameters are defined for power spectra and proposed as a convenient set of load parameters for random loads. The center frequency of a power spectrum, defined as its weighted average frequency, is proposed as a measure of fatigue life. A servohydraulic closed loop testing machine is used to load specimens of carbon steel under six different power spectral shapes. Test results are utilized to evaluate a fatigue life function formulated in terms of the load parameters. The concept of a shape operator introduced by Weibull for probability distributions, is employed to correlate fatigue lives under different power spectral shapes. Good correlations in the test results are obtained.
Reflections on Recent Efforts to Teach Chimpanzee Language
Authors: McNeill David
Published: October 2005

A review of two recent experiments in which chimpanzees have been taught forms of human language supports the conclusion that chimpanzee shares with man a number of basic linguistic and conceptual characteristics. In spite of these similarities, however, chimpanzee has difficulty with those aspects of linguistic structure that encode conceptual relationships (such as agent and action), and instead spontaneously adopts a novel form of syntax based on social relationships (such as addressee and nonaddressee). It is argued that this difference between man and chimpanzee reflects a difference in species endowment, the two species having a syntax that encodes distinctly different kinds of information, which can be traced to differences in life conditions. It is conceivable that free ranging chimpanzees are already using a linguistic system organized along the lines revealed in the experimental studies of language acquisition by chimpanzee.
A Comparison of Mysticete and Odontocete Cetacean Acoustic Signals and Their Behavioral Consequences
Authors: Winn Howard E.
Published: October 2005

Odontocete cetaceans produce echolocation clicks, whistles, cries, chirps, and similar sounds. Mysticete cetaceans produce low-frequency moans, grunts, and thumps, and at least one species produces cries and chirps. The production of clicks by mysticetes has been controversial to date, but recent evidence suggests they emit pure frequency clicks up to 25 kHz. Mysticetes do not produce whistles. The organization of sounds implies that odontocetes use the high-frequency clicks for capture of individual prey (fish and squid). Mysticetes may or may not use their clicks for feeding, but if so they may be used only to locate masses of plankton and fish—not in locating single individuals. Again, the variety of signals produced by odontocetes in all seasons suggests a more intricate social organization. The complicated song of the humpback whale, produced only three months of the year, may have a wide variety of functions, but suggests a less complicated social organization outside of this season. Some of the low-frequency sounds of this mysticete may be needed for long-range communication, perhaps related to their extended migration.
Perception of Temporal Order for Tones
Authors: Peters R. W. , Wood T. J.
Published: October 2005

Judgments of temporal order were obtained for three successive pulses, 500-, 1000-, and 2000-Hz tones, for various durations and intervals between pulses. The durations were 20, 40, 80, and 160 msec and the intervals were 0, 40, and 80 msec. Signal presentations were monaural with both signals and the collection of responses under computer control. The results indicated a bimodel distribution in that some individuals were often able to detect correct order even for the shorter durations and intervals. More typical, however, were responses that approached, but did not reach, complete accuracy for the longer durations and intervals. In fact, at the longest duration of 160 msec, most listeners only achieved about 70% accuracy. The results will be discussed relative to the interaction of pulse duration and interval as it relates to judgments of order [This research was supported, in part, by the University Research Council of the University of North Carolina.]
Models of Attention for Vibrotactile Stimuli
Authors: Craig James C. , Shiffrin Richard M. , Cohen Eli
Published: October 2005

The study of summation for vibrotactile stimuli between two loci on the skin has produced conflicting results. Craig [Perception Psychophys. 4, 351–354 (1968)] found evidence for such summation while Franzen, Markowitz, and Swets [Perception Psychophys. 7, 193–196 (1970)] did not. To account for their data, Franzen et al. proposed a single-channel model of attention for weak vibrotactile stimuli. The present experiment was designed to test models of attention for the skin. Two conditions were used to evaluate observer's ability to detect near threshold vibrotactile stimuli. In both conditions, a signal was presented at one of three skin loci, the observer stating which locus received the stimulus. In the simultaneous condition, there was a single observation interval during which a signal occurred at one of the three loci. In the sequential condition, there were three observation intervals presented successively with a signal presented at one of the three loci during one of the three observation intervals. Each observation interval was associated with a particular locus. Theories postulating attentional control predict performance to be inferior in the simultaneous condition since that condition requires sharing of attention among the three possible sources of tactile stimulation. The data showed performance to be identical in the two conditions. The results indicate that a single-channel model is not appropriate and, in addition, argue for an unlimited-capacity non-attention model of tactile perceptual processing. [Research supported by NIMH and NIH.]
Predicting the Detectibility of Complex Signals
Authors: Tanski W. J. , Andrews F. A.
Published: October 2005

A series of investigations have been conducted to determine to what extent one may predict the aural detectibility of a complex signal in a background of masking noise. Observers were tested binaurally using the two-alternative forced-choice procedure to obtain psychometric functions for simple signals. Modeling the auditory system as an energy detector preceded by a set of bandpass filters, and knowing the statistics of the masking noise and signal plus noise distributions, one may determine the difference distribution statistic upon which the auditory system bases its decisions. The psychometric functions allow one to determine the inefficiency factor for the auditory system and, combining this knowledge with the difference distribution statistics, it is possible to develop a procedure for predicting the detectibility of various complex signals. The results of tests with signals consisting of various combinations of tones and noise will be compared with predictions. Limitations will be discussed.
Aural Harmonics: Nonlinearity and Loudness
Authors: Erdreich J. , Clack T. D.
Published: October 2005

An inverse relation between the loudness of a 1000-Hz pure tone and the amplitude of the second aural harmonic it generates was reported last year. To investigate more rigorously, normal listeners (N = 12) produced individual absolute loudness scales from ratio (doubling and halving) and equisection (five points over each of three ranges) judgments. These scales have been interrelated using Garner's [J. Acoust. Soc. Amer. 26, 73–88 (1954)] method of corrected ratios. Estimates of the second and third aural harmonics of a 500-Hz pure tone were made from tone-on-tone masking measurements. A comparison of the doubling and halving ratios will be discussed together with the shunting hypothesis: i.e., energy shunted into harmonic production is subtracted from that available for conversion into the magnitude of the loudness sensation.
Loudness Evaluations of the Sound from an Electric Clock
Authors: Viebrock W. M. , Crocker M. J.
Published: October 2005

The noise from a consumer electric clock was studied to evaluate loudness estimating procedures. Eight different clock noises were tape recorded for presentation to a panel of people for loudness judgments. An electronic switch enabled the recorded clock noise and a 1000-Hz tone to be presented alternately via earphones for 12-sec durations with 12-sec silences in between signals. The person adjusted the 1000-Hz tone to match the loudness of the clock noise providing a correlation to the phon loudness scale. It was determined that Steven's method generally underestimates the loudness but is usually less than 10 dB in error. If ranking on a relative loudness scale is all that is desired, dB(A) measurements will suffice. [This work was supported by Westclox Division, General Time Corporation, LaSalle, Illinois.]
Equal Loudness Pressures and the Normal Ear
Authors: Victoreen John A.
Published: October 2005

Measurements are presented to show equal-loudness sound-pressure values for a number of ears. Observations are given as average values for a number of ears that are useful in defining how a “perfect average” ear would be expected to perform. Equal-loudness sound-pressure observations are also given for several individual ears showing how supposedly “normal” ears deviate from a “perfect average” normal ear. Measurements were made by means of damped wavetrain signals having a decrement of 0.90. Signals were applied to the ear by means of a Sointrex HA10 circumaural earphone, which was calibrated on a flat-plate coupler. A number of conclusions are suggested which relate this type of measurement to the behavior of the average normal ear as a standard of general comparison without attempting to define specific numerical values.
Examples of Spectral Analysis Techniques for Analyzing Speech and Hearing
Authors: Schmid Charles E.
Published: October 2005

Various stationary and nonstationary spectral analysis methods are utilized to analyze two-channel data obtained from the ear of an anesthetized guinea pig. One channel was recorded from a microphone placed in front of the ear, while the second was simultaneously taken from an electrode on the round window of the cochlea. A stationary white Gaussian acoustic source was used to obtain an estimate to the transfer function of the ear. This was accomplished through digital computer calculations of the auto and crosspower spectral density functions, along with the coherency function. Linear phase changes and resonances were observed in the frequency regions exhibiting high coherency. A spoken sentence was utilized as a nonstationary source. The balance between frequency resolution and time definition is illustrated on various displays of time-varying spectra. They include two-dimensional, three-dimensional, and ordinary spectrogram types of displays.
Temporal Order Discrimination: Recognition without Identification by Untrained Subjects
Authors: Warren Richard M.
Published: October 2005

Earlier work with unpracticed subjects has indicated that identification (naming) of temporal order for repeated sequences consisting of three or four successive sounds such as hisses, tones, and buzzes could not be accomplished at item durations of 200 msec and below [see Warren et al., Science 164, 586–587 (1969)]. In the present experiment, eight separate groups of 30 subjects were required to tell whether alternating sequences, each consisting of a reiterated presentation of the same three or four successive items, had these items in the same or different order. Identification of these orders was not required. Accuracy of same/different judgments depended upon details of the experimental procedure employed, but in general was significantly better than chance when all items lasted 200 msec. Extending the duration of each item in one of the two sequences beyond 200 msec made the task more difficult. When one sequence had items at 200 msec and the other at 670 msec, same/different judgments were at chance level. It appears that if identification of orders cannot be accomplished, then recognition of the identity of or difference between patterns requires a prior “temporal template” for comparison of both duration and order. [Research supported by NSF.]
Motor Vehicle Noise Spectra, Their Characteristics and Dependence upon Operating Parameters
Authors: Hillquist Ralph K. , Scott William N.
Published: October 2005

Present highway motor vehicle noise levels are presented as a function of operating condition (idle, steady speed, normal acceleration, and coast). The variables that affect vehicle noise level, such as speed, throttle, road, location, and weather are considered. The spectral composition of motor vehicle noise is indicated, and, where possible, the prevalence and distribution of these levels is stated. The data represent both interior and exterior noise of such highway vehicles as trucks, buses, automobiles, and motorcycles. Some noise abatement approaches are discussed, including an order of priority for vehicle noise limitation, a rationale for light-vehicle maximum noise level, highway considerations, and operator responsibility.
Noise Radiation from Engine and Drive Train
Authors: Brammer A. J. , Muster Douglas
Published: October 2005

The rapid pressure rise within the cylinder accompanying spontaneous ignition of the fuel generates the characteristic “knock” produced by diesel engines. Noise is radiated primarily by nonstructural parts of engines such as the oil pan and valve covers, or by the crankcase. In contrast, the rate of change of pressure within the cylinders of spark-ignition engines is relatively slow, owing to combustion being nucleated at a point, and results in less radiation, especially at high frequencies. In air-cooled engines, the absence of a water jacket often results in additional radiation from the cylinder cooling fins. Other sources of importance in some engines are those with a mechanical origin such as piston slap or gear meshing. The significance of the contribution of these and other sources to the overall noise produced by vehicles will be indicated.
Calorimetric Method Tutorial Paper On The Calorimetric Determination of Ultrasonic Intensities
Authors: Sokollu Adnan
Published: October 2005

The rate of energy flux in an ultrasonic beam, propagating in a fluid medium, may be expressed for a single frequency and longitudinal oscillation by Eφ = 1T ∫ 0T A pudt, where T is the period of oscillations, A the cross section of the beam, p the instantaneous value of pressure oscillations, and u represents particle velocities causing the pressure oscillations. This is the basic equation with which, at the turn of the century, Lord Rayleigh calculated acoustic intensities in gases. Almost half a century later, Langevin was first to measure ultrasonic intensities in liquids by evaluating radiation pressures created by these intensities. A simple theoretical basis to these evaluations was already established two decades prior to his experiments. Further theories were later developed to express more closely the relationship between the radiation pressure and sonic intensities. The complexity of wave propagation phenomena in real media, however, has been preventive in establishing an exact theory, especially in cases of intense or pulsed radiations. Therefore, there is a serious need for alternative methods to determine sonic intensities without resorting to debatable postulations. Only after compilation of reliable data will it be possible, through these methods, to validate or modify the existing theories. The only reliable method, which can avoid debatable assumptions, appears to be the conversion of sonic energy into heat. The heat-conversion method is one of the oldest known to physics in terms of determining a multitude of radional energies. The so-called bolometers or radiometers were the standard instruments used in evaluating heat or light radiation more than a century ago. The purpose of this paper is to review various kinds of calorimetric methods and explore their feasibility to ultrasonic power measurements. Thus we hope to revive and perfect at least one of these classical methods as a primary standard toward the evaluation of newly established methods and theories.
Piezoelectric Transducers for Measurement of Ultrasonic Pressure
Authors: Berlincourt D.
Published: October 2005

The fundamental physical concepts of piezoelectricity are reviewed in some detail with emphasis on application to measurement of ultrasonic pressure. The physical constants of a variety of piezoelectric materials are given and discussed. These data are related to mechanical and electrical matching requirements and some recommendations are given. Various configurations for piezoelectric microphones are discussed with reference to frequency and the properties of the acoustical medium. Linearity of the ferroelectric (piezoelectric) ceramic materials is discussed briefly. Limitations with respect to static pressure and temperature are also considered.
Application of Correlation and Fourier Transform Techniques in Architectural and Building Acoustics
Authors: Tichy J.
Published: October 2005

This paper presents a historical review, summary, and discussion of existing problems of application of autocorrelation techniques and Fourier transform to measurements in architectural and building acoustics. Existing problems of sound field enclosures will also be discussed.
Combining Fourier and Correlation Techniques to Measure Acoustical Parameters
Authors: Schomer P. D.
Published: October 2005

The basic means of measuring an impulse response by employing correlation techniques and of extending this response into the frequency domain by utilizing Fourier techniques is reviewed. Particular attention is given to the problems inherent in this form of measurement. These problems include proper utilization and interpretation of the discrete Fourier transform, proper attention to flanking paths, and proper attention to what may be termed the acoustic version of the uncertainty principal. The ramifications of this uncertainty principal to other measurement methods are also considered. Sample results of recent laboratory and in situ transmission loss measurements are presented.
Time Delay Spectrometry
Authors: Heyser R. C.
Published: October 2005

Human experience in the interpretation of sound strongly supports the concept of a time-dependent frequency spectrum. Acoustical testing of architectural structures must therefore be brought into alignment with joint time-frequency considerations to bridge the gap between subjective and objective performance assessment. Time delay spectrometry (TDS) is a method of measurement which directly yields the time-dependent frequency spectrum. This is done by transforming normal acoustic variables to a joint time-frequency coordinate system. By this means, acoustical properties that overlap in a pure-time or frequency domain measurement, as for example frequency-dependent multiple reflections, may be separated for analysis. Following separation of the signal of interest, the result is then transformed back to either the time or frequency representation for conventional evaluation, but with the difference that unwanted signals have been suppressed. Time delay spectrometry is a continuous coherent process that operates on a real-time basis allowing evaluation of system parameters in situ. The data obtained includes the complete response, both amplitude and phase, for either time or frequency. Measurements possible with TDS include direct and early sound anechoic spectra in a normally reverberant environment, reverberant energy as a continuous function of frequency and time, and joint time and frequency-dependent sound propagation through partitions.
Helium Speech Unscramblers: A Critical Review
Authors: Rothman H. B. , Hollien H. , Hollien P.
Published: October 2005

Man's attempt to probe and utilize “inner space” have, to a large degree, been hampered by inadequate voice communication. One of the specific sources of speech degradation is the use of helium as an inert breathing gas in the deep and/or saturation, diving situation. In turn, electronic devices have been developed which are designed to improve speech intelligibility distorted by the effects of high ambient pressures and HeO2 breathing mixtures. In order to evaluate the effectiveness of these HeO2 “unscramblers,” the Communication Sciences Laboratory at the University of Florida has undertaken a four-part project: (1) to evaluate available unscramblers on line; (2) to test them off line; (3) to develop a standardized test for evaluating all types of unscramblers; and (4) to establish guidelines for the development of optimum equipment of this type. The present paper will discuss the following: (1) techniques for helium speech unscrambling; (2) protocols necessary to conduct system evaluation properly; (3) development of the standardized off-line test for the evaluation of all types of unscramblers; and (4) results of several on-line and off-line evaluations. Finally, a discussion of the strengths and weaknesses of current approaches to HeO2 speech processing, and recommendations for the improvement of these devices will be presented.
Speech Dereverberation
Authors: Allen J. B.
Published: October 2005

A method for dereverberating speech based on linear prediction is developed in detail. By properly analyzing and resynthesizing speech that has been reverberated by a real room, it is possible to remove most of the reverberation. The algorithm will be described and tapes will be played.
Observation of Frequency-Dispersive High-Order Modes in Deep Sound Channels
Authors: Porter Robert P.
Published: October 2005

Large time spread of signal arrivals is characteristic of deep, sound-channel propagation of wide-band signals and is normally explained by ray acoustics; high-order mode theory predicts time spreading of the arrival and, in addition, predicts dispersion of the spectrum. For a given sound-velocity profile and transmitter-receiver geometry, only a few high-order modes are transmitted and received; it is possible to detect individual dispersion curves if certain time bandwidth requirements on the receiver are satisfied. Dispersed high-order modes have been observed at frequencies as high as 300 Hz and at ranges of 600 km for shots detonated and received on the axis of a SOFAR channel located in the western Mediterranean Sea. Spectrum analysis of shot records has revealed up to five identifiable group-velocity profiles that are accurately predicted by applying WKB high-order mode theory to sound velocity data. Group-velocity profiles for North Atlantic sound-velocity data typical of Bermuda water, Mid-Atlantic Ridge water, and Mediterranean overflow water are presented. These dispersion curves show the effects of multiple sound-velocity minima and near parabolic sound-velocity profiles on pulse structure. [This work was supported by the U. S. Navy Office of Naval Research.]
Behavior of Modified Ray Theory
Authors: Davis J. A.
Published: October 2005

Both modified ray theory [E. L. Murphy, J. Acoust. Soc. Amer. 47, 899–908 (1970) and J. A. Davis, J. Acoust. Soc. Amer. 52, 137 (1972)] and ordinary ray theory can be obtained from the method of stationary phase. Use of a WKB approximation leads to two points of stationary phase and the result is ray theory. Use of a generalized WKB approximation leads to an infinite number of stationary phase points and the result of using the first two is modified ray theory. The degree to which modified ray theory accurately includes frequency dependent diffraction effects depends on the contribution to the field by the remaining points of stationary phase. In sound propagation problems where there is a shadow region, the ray theory field may or may not contain a caustic, whereas the modified ray theory field always contains a caustic and in some cases a cusped or higher-order caustic. For ranges much less than the shadow boundary range the modified ray theory field approaches the ray theory field. For ranges much greater than the shadow range, the modified ray theory field (suitably extended to take the caustic into account) approaches either (1) the ray theory field (also extended), or (2) the field due to the first mode, depending on whether or not the problem parameters are such that a ray theory caustic is present. For ranges in the vicinity of the shadow range, the behavior can be very complicated.
Generating Parameterless Examples of Ray Acoustics
Authors: Wood D. H.
Published: October 2005

It is well known that in an unbounded medium having uniform speed, travel time is equal to the distance from a sound source and intensity is equal to its reciprocal. No ray parameters appear in the statement of these results. In general, ray parameters are a necessary but undesirable by-product of the standard technique for finding intensities. A new technique generates many parameterless examples by applying three principles to known parameterless examples such as uniform media. In one principle, limited to two-dimensional media, conformal mapping generates a new example having different wavefronts. For example, c=sinx is generated from c=x by the conformal mapping defined by f(x + iy) = tan(x/2 + iy/2). A second principle generates new examples having the same wavefronts. For example, c=x and c = 1 + x2 + y2 have the same wavefronts when a point source is located at (1,0). A third principle relates symmetric examples in two dimensions to cylindrically symmetric examples in three dimensions.
Utilization of a Transmitting Array Matched to Individual Modes
Authors: Kanabis W. G.
Published: October 2005

A vertical transmitting array was implanted in Block Island Sound in November 1970. A theoretical study was undertaken to determine the optimum utilization of such an array to excite individual normal modes. The results of this study are described. Amplitude and phase matching, the two basic methods to emphasize individual modes, are outlined. In matching to amplitude, either a course or more exact fit to the mode amplitude may be utilized. These three approaches to emphasize individual modes were considered. Simple cases of these approaches were evaluated for the physical characteristics of the implanted array using a computer program. BIFI velocity profiles typical for summer and winter were used. Propagation loss was calculated for individual modes when the array was matched in turn to modes 1–4 for each profile and mode. In this manner, the relative signal levels corresponding to each approach were obtained and their effectiveness evaluated.
Speech Intelligibility of Diving Masks and Mouthcups
Authors: Hollien Harry , Doherty E. Thomas
Published: October 2005

In order to speak underwater, SCUBA divers ordinarily must replace their mouthpieces with some sort of muzzle, mask, or helmet. The addition of such cavitites to the vocal tract usually results in distortion to the speech signal. Accordingly, it was the purpose of this research to investigate variation in diver/subject speech intelligibility resulting from the use of such devices. Included in this evaluation were all commercially available units plus several prototypes; they were (a) mouthpieces: double-hose regulator bit; (b) mouthcups: Bioengionics, Raytheon, U. S. Divers; (c) full face masks: Scott, MDL, Desco; and (d) helmets: Advanced, Kirby-Morgan. All units were evaluated under similar conditions, i.e., with double-hose regulators and (in most instances) with Aquasonics microphones placed in the breathing cavity. Two studies were carried out. The first in a hyperbaric chamber at the Naval Ship Research and Development Laboratory, Panama City, Florida and the second at NRL Underwater Sound Reference Division, Bugg Spring facility, Leesburg, Florida, and at Rainbow Springs, Dunnellon, Florida. In the first study, diver's speech intelligibility was assessed by standard procedure for five units (bit, Bioengionics, Raytheon, Scott, and MDL) at simulated depths of 0, 12, 50, and 100 ft; a small “wet pot” was utilized for the tests. The second study was carried out for all units in 12 ft of water at Bugg and Rainbow Springs. Divers were held in a fixed position and the speech signal was transmitted by “hard line” directly to a tape recorder at the surface. Data show considerable variability among the units evaluated; highest speech intelligibility was found for one of the mouthcups and for the helmets.
Estimates for the Reflection of Acoustic Waves Propagating through a Layered Thermocline
Authors: Elswick Roy C.
Published: October 2005

The oceanic thermocline contains a weak small-scale steplike structure (relative to scales of the overall thermocline) capable of producing at any given layer a weak reflection of an acoustic wave. By means of a two-variable asymptotic expansion technique, the cumulative effect of a series of such weak reflections is accounted for, indicating (similar to the Bremmer series for electromagnetic waves in a slowly varying and thus single-scaled stratified medium) that each higher-order contribution corresponds to a specific number of internal reflections. Simple first-order estimates can be derived for the loss due to an acoustic wave propagating through a stepped thermocline structure. Such order of magnitude estimates indicate that the cumulative effect of the weak reflections is indeed a plausible explanation for the apparent loss of acoustic energy across the thermocline region.
The Nature of Sound Fluctuation in the Upper Ocean. II
Authors: Neubert J. A.
Published: October 2005

Having reviewed and critiqued the nature of sound fluctuation in turbulent media and the upper ocean in Part I, it is now shown, on the basis of turbulent scaling, that the scattering theories of Bergmann, of Mintzer, and of Potter and Murphy are discrete-scattering, and not continuous-scattering, theories when Gaussian refractive-fluctuation correlations are imposed. Furthermore, turbulent scaling and the experimentally observed turbulent microstructure strongly suggest that the scattering mechanism in the Stone and Mintzer experiments is not the turbulence, but is more likely impurities (such as the ubiquitous, minute air bubbles which arise due to thermal degassing) that are shuffled about in a random manner by the turbulent fluid. It is strongly suggested that this is often the nature of sound fluctuation in the upper ocean. Finally, more effective methods of analyzing sound fluctuation in the real ocean are presented.