bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustics and the Concert Hall
Authors: Beranek Leo L.
Published: October 2005

Frederick Vinton Hunt profoundly affected the course of architectural acoustics. As the de facto successor to W. C. Sabine, he utilized the Sabine reverberation chamber in the early 1930s to introduce accuracy into reverberation-time measurements. Stimulated by P. M. Morse's “Chapter VIII” in Vibration and Sound (1936), Professor Hunt explored the sound field in a rectangular, marble-walled box and published in 1939 a new means for measuring sound-absorption coefficients of acoustical materials as a function of angle of wave incidence and the details of a high-impedance, research, sound source. With his students, he expanded the application of the normal-mode-of-vibration theory to full-scale rectangular rooms in which acoustical materials were present on one or more walls. Although he found other interests, his papers in this field touched off scores of published works and resulted in hundreds of engineered buildings by his students and their colleagues. Examples of his contributions that can be traced to today include techniques for reverberation measurement, the meaning of sound-field diffusion in spaces, the design of auditoriums, and the principles of sound reinforcement and music reproduction. This paper summarizes the present-day status of concert hall design, with emphasis on those elements of architecture that can be controlled after the basic shape of the auditorium has been established.
Refractive Effects in Acoustic-Echo Sounding of the Atmosphere
Authors: Clifford S. F. , Georges T. M.
Published: October 2005

In an earlier paper [J. Acoust. Soc. Amer. 52, 1397–1405 (1972)], we developed a simple model for estimating refractive changes of the quantities measured in active acoustic sounding of the atmosphere. Inhomogeneities in the atmospheric wind and temperature fields introduce refractive errors in measured Doppler shift, in the angular dependence of scatter by irregularities and in the location of the atmospheric volume being interrogated. We asserted that most refractive corrections, except possibly the change in scattering angle, are normally insignificant for sounding heights presently being probed (less than 1 km), but that refractive effects would become more important for greater heights. To illustrate this, we will present sample calculations for representative bistatic and monostatic sounding situations.
A Note on the Scattering of Sound in Jets and the Wind
Authors: Rudd M. J.
Published: October 2005

The theory of the scattering of sound by turbulence, as developed by Tatarski and modified by Monin, is used to calculate the scattering cross sections of two turbulent flows, jets, and the wind. The results indicate that strong scattering can occur under quite normal conditions. The strength of the scattering increases quite rapidly with the frequency of the sound and the length scale of the turbulence. The importance of acoustic scattering is then discussed in connection with methods of jet noise reduction and sound “attenuation” by the wind.
On the Collapse Mechanism of Finite Entropic Disturbances
Authors: Peter Abraham C.
Published: October 2005

The collapse mechanism of finite entropic disturbances is highlighted, based upon the previously obtained solutions of finite-amplitude entropic wave equations. It is shown how the thermal gradients caused by friction in the fluid undergo a constant steepening process due to the nonlinear change of type of the convected entropic perturbations. An expression for the time rate of change of the velocity space gradient along the path of the convected perturbations allows the determination of the lifetime of the entropic disturbance for a given initial state of the fluid. The physical relation between the frictional characteristics of the medium and its thermodynamic state is highlighted in view of the convection mechanism of the entropic disturbances. In addition, a more general aspect of the problem of finite-amplitude entropic waves is presented. Complete nonlinearized integrals of the equations for the thermodynamic states of the fluid in the direction of the physical-plane roots are derived and methods of general solutions are discussed.
Comparison of Detectability and Discriminability of Tones of Different Durations under Homophasic and Antiphasic Conditions
Authors: Blakeslee Edward A. , Robinson Donald E.
Published: October 2005

Using a two-alternative, temporal, forced-choice technique (2ATFC), the detectability of four (50, 60, 100, and 200 msec) 500-Hz signals in a continuous noise masker (50-dB spectrum level) was determined. The ability of the observers to discriminate the 50-msec tone from each of the three longer tones was also measured using a similar psychophysical technique. Psychometric functions for detection and for the discrimination of duration were obtained under both homophasic (N0-S0) and antiphasic (N0-Sπ) conditions. Under the homophasic condition, the observers required an increasing amount of signal energy as the difference in duration became smaller in order to perform as well in discrimination as they did in detection. With the antiphasic condition, a similar effect was observed, except that the displacement of the psychometric functions for discrimination toward greater signal energies was much more pronounced than in the homophasic condition. In addition, the slopes of the psychometric functions for discrimination were generally lower than the corresponding ones for detection.
Register Hole Design for Cone Woodwinds
Authors: Benade A. H.
Published: October 2005

In a woodwind the register hole produces a transition from low to second playing register in two ways. At low dynamic levels the hole must increase the damping of the first mode sufficiently that oscillation cannot be sustained. Oscillation then takes place on the basis of the second resonance peak. At high dynamic levels this effect of the hole is insufficient—intermode cooperation can still sustain the low register oscillation, so that the first mode frequency must be suitably shifted relative to that of the second mode to make their cooperation impossible. Optimum hole reactance raises the first mode frequency 25%. For an instrument whose low register half-wavelength is L, having a bore taper dR/dx = T, and provided with a (centered) register hole of radius b and effective length te≅(t+2b), the desired frequency shift is produced when (b2/te) − (π/4)2LT2. The damping requirement is best approximated by making the physical length t as small as is mechanically practical (1 mm on a saxophone or bassoon). Oboes and English horns traditionally have vent hole proportions in agreement with this design. Small modifications invariably give trouble. Most saxophones are dramatically improved by reworking the vent holes to the present specification. Similar principles apply to bassoons (and clarinets), but here the multiple use of the vent somewhat compromises the design.
Another Look at Vowel Duration in English
Authors: Kumar Anand , Ojamaa Koit
Published: October 2005

Acoustic measurements show that some vowel contrasts in English involve differences both in formant pattern and duration, e.g., bit versus beat. An experimental study with synthetic speech stimuli varied both in duration and quality indicates that native speakers of American English are insensitive to durational differences in vowels and respond only to differences in formant patterns in the identification of such pairs. Certain non-native speakers of American English do, however, make perceptual judgments based on both vowel quality and length, and this correlates in an interesting way with their productions of the same contrasts. The results of this study provide a criterion for evaluating some current ideas about the nature of human phonetic ability.
Temporal Acuity as a Function of Frequency
Authors: Green David M.
Published: October 2005

The ear can discriminate between two transient signals that have identical energy spectra but different phase spectra (hence different wave-shapes) as long as the total duration of the signals exceed about 2 msec. A natural question, but one impossible to answer on the basis of previous work, which used transient signals having a broad energy spectrum, is whether this value for temporal acuity is dependent on the frequency content of the signal. Two types of experiments were conducted to answer this question. In one experiment, the energy spectrum was broad but the temporal cues were restricted to specific regions of the frequency spectra. In the second experiment, two segments of a sinusoid (one 10 dB more intense than the other) were played in one order or the reverse. Both experiments confirm the finding that the value of temporal acuity is about 2 msec and that this value is largely independent of frequency. Also of interest is the fact that for the sinusoidal signals the percentage of correct discriminations of temporal order is a nonmonotonic function of the total duration of the two segments. [This research was supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Patterns of Palatoglossus Activity and Their Implications for Speech Organization
Authors: Bell-Berti Fredericka , Hirose Hajime
Published: October 2005

EMG recordings were obtained from the palatoglossus muscles of one Swedish speaker and three speakers of American English. The data indicate differences in the function of this muscle in nasal articulation for speakers of the two languages: palatoglossus activity in the Swedish speaker appears to be associated with nasal articulatory gestures while in the English speakers there is no apparent corresponding palatoglossus activity. Evidence is found, in speakers of both languages, of palatoglossus activity associated with tongue raising and retracting gestures. The activity patterns observed in different phonetic environments may provide a clue to the nature of the motor organization of speech. There are some speech sounds which show clear peaks of palatoglossus activity when they occur in environments otherwise free of palatoglossus activity. However, when several of the vowel and consonant sounds which exhibit palatoglossus activity occur serially, the activity may be fused or may remain separate, depending upon the order of the segments in the string of speech sounds. [Supported by NIDR Grant DE 01774.]
A Study of the Velopharyngeal Mechanism in 143 Repaired Cleft Palate Patients during Phonation of the Vowel /i/, the Plosive /p/, and an /s/ Sentence
Authors: Massengill Raymond , Brooks Rex
Published: October 2005

In the present investigation the vowel /i/, the plosive /p/, and a sentence with four words that start with /s/ were studied from the viewpoint of different aspects of presence or absence of velopharyngeal closure utilizing cinefluorographic analysis. The number of patients obtaining either total velopharyngeal closure or inconsistent velopharyngeal closure as well as those that manifested total velopharyngeal insufficiency are reviewed. The consistency of velopharyngeal closure or lack of closure during each production for each patient is also discussed. These overall results and their importance to research are also reviewed.
Location of Jet Exhaust Noise Sources from Cross-Correlation Measurements
Authors: Scharton T. D. , White P. H. , Rentz P. E.
Published: October 2005

The fluctuating pressures created by the mixing of a jet exhaust with the ambient air are viewed as the primary sources of radiated jet noise. Apparatus for measuring these in-jet pressures is described and measurements of the spatial and frequency characteristics of the in-jet pressures are presented. Jet pressure and radiated acoustic pressure cross-correlation measurements are used to determine the location of the jet noise sources as a function of frequency and jet Mach number. [Work sponsored by Air Force Aeropropulsion Laboratory.]
On Finite-Amplitude Waves in Horns
Authors: Blackstock David T.
Published: October 2005

When lecturing to students about horns, F. V. Hunt was fond of remarking that the throat of a horn is a place where the small-signal assumption is flagrantly violated. It is possible to assess the importance of this violation. Provided the horn flare is not great and the frequency not close to cutoff, the Webster horn equation with nonlinear terms retained may be readily solved. From the solution one may calculate the shock formation distance, the well-formed sawtooth distance, and the distance at which, because of absorption, the wave becomes a “small signal.” The relative magnitudes of these distances may be used to estimate whether finite-amplitude effects are important for any particular horn and consequently to decide the question about the importance of Hunt's “violation in the throat.” Rudnick [J. Acoust. Soc. Amer. 30, 339–342 (1958)] has used the (sawtooth) solution for strong waves to calculate the saturation amplitude, that is, the maximum output amplitude for a horn. Another application of finite-amplitude horn theory is in atmospheric propagation, where vertical variation in static conditions produces the same effect as variation in horn cross section. Upward propagation is analogous to propagation through a horn backwards, that is, toward the small end. [Work supported by AFOSR and ONR.]
Nonlinear Acoustic-Gravity Waves in the Upper Atmosphere
Authors: Liu C. H.
Published: October 2005

Acoustic-gravity waves play very important roles in the, dynamics of the upper atmosphere. One notable example is the quasiperiodic traveling disturbances that are observed almost daily in the ionosphere. They are believed to be generated by the acoustic-gravity waves in the neutral atmosphere. Also, there are indications that acoustic-gravity waves are responsible for certain thermospheric phenomena. For many situations, nonlinear effects on the propagation of these waves may be important. In this paper, some aspects of these nonlinear effects will be discussed. First, a general discussion on the various types of nonlinear effects will be given. Using an idealized model, the nonlinear oscillation of an air parcel is investigated next. The nonlinear dispersion relation for the internal gravity wave in a Boussinesq fluid is derived and stability of the wave trains will be discussed. Resonant wave-wave interaction of acoustic-gravity waves is studied with the emphasis on wave trapping. Possible interactions between acoustic-gravity waves and mean flow are also investigated. Finally, the possibility of long waves in the upper atmosphere will be discussed. Some experimental data pertinent to the discussion will also be given.
Transformations in Impulsive Stimuli Brought about by the Acoustics of the External Ear
Authors: Price G. Richard
Published: October 2005

Impulsive stimuli vary greatly in the hazard to hearing they represent. With the intent of determining the degree to which the interaction between the acoustic properties of the external ear and the frequency composition of the impulse could explain this variability, a number of measurements were undertaken. An ear model [R. Teranishi and E. A. G. Shaw, J. Acoust. Soc. Amer. 44, 257–263 (1968)] and cat ears instrumented with a condenser microphone next to the eardrum were exposed to a variety of impulsive stimuli ranging from live gunfire to speaker-produced clicks. Impulses in the open field were compared to the same impulses arriving at the eardrum position. At the eardrum position the gunfire impulses demonstrated a much longer rise time and all impulses showed a peak pressure that was higher by an amount dependent on the frequency composition of the impulse. The effect on the impulses was consistent with the sound-pressure transformation of the head, pinna, and auditory meatus that has been reported for continuous stimuli. It seems likely that an adequate damage-risk criterion for impulse noise should reflect this influence.
The Concept of “Effective Quiet.”
Authors: Ward W. Dixon
Published: October 2005

How quiet must be the intervals between high-intensity noise bursts if recovery from the TTS produced by the latter is to be unaffected? Listeners were given 8-h exposures to a 4000-Hz OB noise (2800–5600 Hz) that was at 90 dB SPL for 22.5 sec and then at some lower intensity for 67.5 sec (90-set duty cycle, ON fraction of 0.25). Under these conditions, the temporary threshold shift at the end of the 8 h was greater when the intervening periods were at 60 dB SPL than when they were 15–20 dB (ambient). Thus, for this particular octave band, “effective quiet” must be about 55 dB SPL. Implications of this result for damage-risk criteria will be discussed. [Research supported by the National Institute for Occupational Safety and Health, Public Health Service.]
Temporary Threshold Shift in the Goldfish, Carassius auratus
Authors: Popper Arthur N.
Published: October 2005

An avoidance conditioning technique was used to measure pure-tone auditory thresholds in goldfish before and after four hours of stimulation with intense pure tones (123 dB re 0.0002 μbar) at 300, 500, and 1000 Hz. Fish showed TTS when tested at the stimulation frequency. However, the shift was greater when fish stimulated at 500 Hz were tested at 800 Hz. After stimulation at 1000 Hz, TTS occurred at that frequency but not at lower frequencies, and after stimulation at 300 Hz there was more TTS at 500 Hz than at 800 Hz. Owing to technical limitations, TTS could not be measured immediately after stimulation, but over a period of two hours auditory sensitivity increased although normal thresholds were not shown during this time. Normal thresholds were shown 24 hours after stimulation. [Supported by National Institutes of Health.]
The Use of Prosodic Units for Syntactic Decoding
Authors: O'Malley Michael H.
Published: October 2005

Prosodic information such as intonation contour, stress, and juncture permits speech to have a complex grammatical structure. However, the relationship between grammar and prosody is confounded by nonlinguistic signals such as hesitation and by pragmatic information involving the talker's attitude toward his message. A full understanding of exactly what prosodic information is present, how that information can be extracted from an utterance, and what it signals is not yet available. Recent experiments indicate, however, that in careful, spontaneous speech, prosodic information may be used to reduce the number of syntactically incorrect parsings with a fair degree of reliability. This paper discusses the results of these experiments and suggests some ways in which they bear on a theory of the suprasegmental units of English.
Acoustic Analyses of Phonological Processes in Spontaneous and Read Speech
Authors: Yaeger Malcah
Published: October 2005

There are many reasons why most phonetic studies have been made based on data from read word lists or sentences. However, in doing so, it is interesting to know some ways in which this speech differs systematically from the informant's natural speech patterns. While for many studies reading passages or word lists will remain the only feasible practice, it is helpful to be able to hypothesize in what ways such data may differ from vernacular speech. It has been found in systematic parallel analyses made of natural speech and reading lists of the same subject, that, as would be expected, certain patterns of phones emerge which may differ from each other from style to style. For example, in recent analyses of sound change in progress, Labor has found that a phonological unit whose position within phonetic space is in flux will, in its progress toward a new target position, order its allophones in space according to the immediate phonetic environment. Often the environmental influence is much larger than mere coarticulation, and in many cases influences the phone in a contrary direction. This patterning of allophones has been documented for several speakers of a dialect in which the phone is changing. Yet before the change, or after it is complete, no such environmental influence is determinable. However, in the reading style of the same speaker with fine phonetic patterning of allophones in his natural style, these patterns will become obscured. [Work supported in part by an NSF Grant.]
Statistical Distribution Function for Interrupted Traffic Flow Noise
Authors: Green A. E. S. , Schwartz J. M. , Yost W. A.
Published: October 2005

A statistical time distribution model for interrupted and low-density traffic noise is presented. Noise measurements made in Gainesville, Florida, do not follow a Gaussian distribution. However, the three-parameter Fermi-Dirac distribution from statistical mechanics was found to characterize the actual data quite well. Graphical techniques are available for rapidly fitting the cumulative probability data. This statistical function has convenient analytic properties which should be helpful in its application to noise mapping and estimation.
Asymptotic Expansion of Freedman's Backscattering Integral
Authors: Eisler T. J. , New R.
Published: October 2005

By introducing the direction of an incident plane wave as the direction of integration, Freedman [Acustica 12, No. 11, 61 (1962)] has written the Kirchhoff integral for backscattering in a particular form and has developed a method for obtaining its asymptotic expansion in integral powers of the wavenumber when such an expansion exists. The expansion is expressed in terms of the magnitudes of finite discontinuities of the integrand and its derivatives. The method fails if the discontinuities should be infinite. We wish to point out that the integral in question is a special case of a Fourier integral and that its asymptotic expansion can be obtained by known methods, including the cases in which Freedman's method fails. These correspond to fractional powers of the wavenumber. As an example, the backscattering from a finite rigid cylinder is calculated. The terms in the asymptotic expansion can be identified with the physical edges of the cylinder and the shadow boundary.
Masking at One-Half Octave above 500 Hz
Authors: Clack T. Dean
Published: October 2005

Problems of spectral resolution, amplitude distortion, and musical consonance are all related to hearing tones with frequency ratio 2:3. Using the monaural tone-on-tone masking method with a 500-Hz masker, normal listeners trace threshold for an interrupted 750-Hz maskee as the phase angle between signals is changed systematically. For masker intensities of 50 and 60 dB SPL, thresholds shift but variation with phase is not apparent. At 70 and 80 dB, regular patterns of phase dependency are evident, indicating audible beats at twice/cycle. Such effects disappear when narrow-band noise centered at the difference frequency is included. Even at these low frequencies, therefore, the results contravene cochlear interaction explanations and support previous interpretations that the phase effects are due to nonlinear distortion. To rigorously test this idea, the quadratic and cubic coefficients of the power series are computed from estimates of the second and third aural harmonics. The predicted sum of f2 − f1 and 2f1 − f2 can then be calculated and compared directly with results from individual listeners.
Noniterative Computation of the Area Function for Given Lip Impedance
Authors: Wakita H. , Gray A. H.
Published: October 2005

Indirect determination of the vocal-tract area function has been studied on the basis of a lossless nonuniform acoustic tube model in which the vocal tract is represented as a concatenation of equal-length cylindrical sections with the reflection coefficient defined at each junction between sections. The transfer function of this model can easily be expressed in terms of a z-transformed polynomial whose coefficients are functions of the reflection coefficients. In the lossless case, the set of reflection coefficients cannot be obtained uniquely from only a given transfer function polynomial whose roots are given as the lip impedance zeros which correspond to the formants. However, given lip impedance poles as well as zeros, there is a simple noniterative way of determining a set of reflection coefficients uniquely in a recursive manner. This is the same information as Mermelstein used in his iterative solution to the inverse eigenvalue problem of Webster's horn equation [J. Acoust. Soc. Amer. 41, 1283–1294 (1967)]. The applications and limitations of this method are discussed. [The Office of Naval Research supported this work.]
Measured Jet Noise Compared to California Noise Codes and Health Criteria
Authors: Lane S. R.
Published: October 2005

In December 1971, maximum allowable limits on aircraft noise at California airports became effective in the Public Utilities Code (PUC). Noise exposure limits are specified in terms of a base parameter, Single Event Noise Exposure Level (SENEL), which is an integration of A-weighted noise energy with time. Measurements of conventional jet aircraft landing noise levels at Los Angeles International Airport (LAX) were made and compared to the PUC SENEL limits, and to the “standard” SENEL values used for mapping community noise exposure zones. The measurement survey indicated that at locations 1 nautical mile from landing threshold the standard SENEL criteria were exceeded by 5–15 dB 50% of the time, and the California SENEL limits were exceeded 35% of the time. Data from special flight tests for the FAA indicated that the SENEL limits would be effectively violated about 50% of the time. If violators were cited according to the PUC ($1000 per violation) the resulting fines for landing operations would be about $200,000 per day, or $70 million per year, at LAX.
Generative Theory of Segmental Duration in English
Authors: Klatt Dennis H.
Published: October 2005

This paper presents a framework for predicting the durations of phonetic segments in English sentences. The rules have been developed to work within the transformational cycle described by Chomsky and Halle. It is assumed that the rules of word-level phonology produce a set of basic phonetic segments, each having an inherent duration. Stressed and unstressed vowels are assigned different durations and are subject to different rules. Consonants appearing in prestressed position within a word are given durations that are longer than the durations of the same consonants in other phonetic environments. Other rules shorten segmental durations in consonant clusters, in multisyllable words, and in certain syntactic environments. Silent pauses are inserted at some types of syntactic boundaries and a prepausal lengthening rule is applied. Other related phonological processes involving aspiration and allophonic variation are discussed. [This work was supported in part by the National Institutes of Health and the U. S. Air Force.]
Coarticulation Effects in the Identification of Final Plosives
Authors: Lehiste I. , Shockey Linda
Published: October 2005

In a comparison of the relative contributions of releases and formant transitions to the correct identification of final plosive consonants, Wang [JSHR 2, 66–73 (1959)] found little difference between identification scores of released final /p t k/ and final /p t k/ whose releases had been eliminated by tape-cutting. The former ranged between 90 and 98%, the latter between 73 and 85%. The present investigation compares the perception of released final /p t k/ (following the vowels /i æ a u/) with the perception of final /p t k/ derived from VCV utterances (in which C = /p t k/ and V = /i æ a u/) from which both the second vowel and the consonant release were deleted by tape-cutting. In such VC syllables, the transition to the consonant is modified by the anticipation of the following vowel. For all consonants combined, listeners achieved correct scores of 80.67% for released and 39.00% for unreleased final plosives. The greatest number of misidentifications were associated with /a/. It appears that the anticipation of a following /a/ produces changes in transitions that prevent correct identification of the consonant without the presence of a release. By comparison, initial plosives and plosives derived from VCV utterances by the deletion of the initial vowel were equally easily identifiable: listeners achieved 89.22% correct identification under both conditions.
Auditory and Vestibular Effects of Helium-Oxygen Hyperbaric Chamber Dives to Convulsion Depths
Authors: McCormick J. G. , Higgins T. L. , Clayton R. M. , Brauer R. W.
Published: October 2005

Compressing at 24 atm/h, guinea pigs were dived in a helium-oxygen environment (0.5 atm oxygen) to a depth where the animals convulsed—2640 ft (80 atm) to 2970 ft (90 atm). A modified Haldane decompression profile was used (28 h, 11 min from 80 atm, 22 h, 18 min from 90 atm). Post-dive auditory function was assessed with cochlear potential measurements. Animals with myringotomies and tubes did not convulse significantly deeper than nontubed animals. One animal exhibited post-dive bends symptoms. This animal also had severe post-dive vestibular disorders and a severe neurosensory hearing loss. All other animals had severe or slight loss of auditory function. Much of this loss was conductive due to ear drum barotrauma. Some loss was probably neurosensory due to barotrauma or some yet undefined cause. The vestibular loss noted was similar to vestibular loss previously observed in four squirrel monkeys after two hydrogenoxygen dives.
Role of the Basilar Membrane Capillary in Control of Organ of Corti Physiology
Authors: Lawrence Merle , Nuttall Alfred L.
Published: October 2005

Through appropriate techniques, the basilar membrane of the guinea pig is exposed in such a way that the organ of Corti and the capillaries beneath the basilar membrane are trans-illuminated. Under these conditions the structures of the organ of Corti such as the Hensen cells, the Deiters' cells, the rods of Corti, and the two zones of the basilar membrane can be clearly seen. The blood coursing through the basilar membrane capillaries is visualized and under proper magnification, can be photographed by motion pictures and monitored on a closed-circuit television system. This report will be a brief report on the results obtained measuring relative oxygen tension changes with an ultramicro oxygen electrode placed in the tunnel of Corti or placed in the scala media next to the stria vascularis under conditions of whole body anoxia as compared with occlusion of the spiral capillary. The differences observed indicate the role of the spiral capillaries in the general physiology of the organ of Corti and demonstrate that the organ of Corti does have a blood supply. A movie related to this presentation will be shown in session EE2-1
Closely Spaced Two-Element Arrays
Authors: Schmid C. E.
Published: October 2005

Some properties of arrays with small d/λ ratios are investigated, where d = distance between point receiving elements and λ = wavelength in air or water. Two traditional two-element arrays are the pressure gradient array [weights (+1:, −1), directivity index ∼4.77 dB] and the cardioid [weights (1+jπd/λ, −1+jπd/λ), directivity index ∼4.77 dB]. Optimum array theory shows the “best” weights for isotropic noise are approximately (1+j13πd/λ, −1+j13πd/λ). This weighting produces a beam pattern of (13+cosθ) and a directivity index approaching 10 log104=6.02 dB, which means the performance of a two-element closely spaced array approaches that of a four-element half-wavelength array. However, the performance of superdirective arrays is known to be very sensitive to uncorrelated noise such as preamplifier noise. This sensitivity is discussed quantitatively as a function of uncorrelated noise power to isotropic noise power.
Mathematical Model for a Parabolic Cylinder Reflector
Authors: Rogers Peter H.
Published: October 2005

A mathematical model is developed for an ideal parabolic cylinder reflector driven by a line source coincident with its focal line. The parabolic cylinder is assumed to be infinite in length but of finite width. This two-dimensional model enables one to quickly ascertain the major features of the farfield when given only the acoustic size of the aperture, the focal length, and the type of reflector (rigid or pressure release). The model, which utilizes a quasigeometrlcal acoustics approach, is based on the following two assumptions: (1) there exists a definite shadow zone behind the reflector, and (2) the field “within” the reflector depends primarily on the boundary conditions on the inside surface of the reflector. By means of these assumptions the problem is reduced to solving a boundary value problem where the radiating surface is an infinite circular cylinder. The reduced problem is then solved using the fast Fourier transform algorithm. The results are compared with available experimental data.
Subharmonic Signals during Acoustic Cavitation
Authors: Eller Anthony I.
Published: October 2005

Past experiments have indicated that underwater bubbles in a sound field can help to generate acoustic signals at subharmonics of the driving frequency. Furthermore, theoretical evidence indicates that a likely mechanism for subharmonic generation is the nonlinear pulsation of the driven bubbles. This paper describes a computer study of subharmonics that occur in nonlinear bubble pulsations. The threshold sound pressure for exciting the subharmonic of order 12 was calculated as a function of driving frequency for various chosen conditions. The results show that the subharmonic of order 12 can be excited over a broad frequency range, and not just for a driving frequency of twice the bubble resonance frequency. In addition, the amplitudes of the fundamental and subharmonic components in the bubble motion were calculated for pressures above threshold. The computed results are compared to available experimental results.
Fluctuations in Tidal Modulations of Acoustic Transmission, Water Temperature, and Current Transport
Authors: Yacoub Kamal , Almeida Jose
Published: October 2005

As a result of underwater acoustic transmission experiments with a fixed system in the Straits of Florida, tidal modulation of acoustic phase was observed and reported as a measure of tidal fluctuations in sound speed structure and of current doppler effect. Twenty-five months of continuous measurement of acoustic phase, coupled with eight months of temperature measurements at five depths, and six months of current transport measurement across a 5.5-mile section of the sound path, showed that tidal modulations of these measured parameters are timevarying. The three major tidal harmonic bands O1 (25.82 h), K1 (23.93 h), and M2 (12.42 h) were separated by digital narrow-band filtering and then phase coherently demodulated with reference to their respective tidal harmonic. Thus the strength of the tidal modulation (envelope E) and its lag (phase θ) were obtained as a continuous function of time for each parameter and band. Comparison of these functions for two parameters such as temperature and phase give the Gain = E2/E1 in phase cycles/degree centigrade and the Relative Lag = (θ1−θ2) in radians of the tidal cycle or the equivalent time lag in hours. Describing the time variations in the gain and lag contributes to understanding the basic oceanographic phenomenon and helps to establish a prediction model relating acoustic and oceanographic parameters. The coherence and transfer function for each pair is evaluated for each band. [Work supported by Office of Naval Research Code 468.]
Limit of Spherical Spreading in the SOFAR Channel: Recent Experimental and Theoretical Determinations of R
Authors: Mellen R. H. , Browning D. G. , DiNapoli F. R. , Cable P. G.
Published: October 2005

Previously reported values of R0 for the SOFAR Channel have been orders of magnitude larger than theoretical predictions [D. C. Webb and M. J. Tucker, J. Acoust. Soc. Amer. 48, 767–769 (1970)]. Recent experiments conducted in the Red Sea and Hudson Bay which have relatively shallow sound channels yield values of R0 considerably nearer to the predictions. Comparison is made to computation of the transition range utilizing FFP techniques.
Digit Concatenation from Simple Rules
Authors: Olive Joseph P.
Published: October 2005

A previous paper by Olive and Nakatani [“Quality Judgments of Spliced Synthetic Telephone Numbers,” J. Acoust. Soc. Amer. 50, 145(A) (1971)] described an experiment to evaluate the relative importance of pitch, timing, and formant coarticulation rules in digit concatenation from isolated digits. That paper concluded that pitch was the most important aspect of concatenation while the other two parameters did not contribute much to the quality of the concatenated speech. This paper will describe the simple concatenation rules that were based on the recommendations of the previous paper, and evaluate the results. A digit recall test was administered to measure comprehension and its results prove that the rule-concatenated numbers are at least as recallable as the same numbers spoken naturally. A subjective preference test revealed that the rule-concatenated speech was judged to be close to speech resynthesized from natural speech. Half the subjects preferred the rule-concatenated speech to speech spliced from isolated digits even when the isolated digits were naturally spoken; the other half disliked any form of synthetic speech.
PARAFAC2: Extensions of a Procedure for “Explanatory” Factor-Analysis and Multidimensional Scaling
Authors: Harshman Richard
Published: October 2005

Recently developed techniques for factor analysis and multidimensional scaling (PARAFAC-INDSCAL) allow discovery of a unique orientation of axes and thus “more explanatory” factors or dimensions. A certain price is paid for these advances, however. In multidimensional scaling applications, the price is a restriction of the possible form of the solution to orthogonal “nonrelated” as opposed to oblique “perceptually related” dimensions. In factor analytic applications, the price is a limitation to those three-way data sets showing “system-variation” [Harshman, UCLA W.P.P. No. 16 (1970)]. An extension of PARAFAC to summed-cross-product matrices (e.g., covariance matrices) overcomes both of these limitations. For factor analysis with PARAFAC2 it is only necessary that the average effect of a given factor change, relative to the other factors, from one covariance matrix to the next. For multidimensional scaling, PARAFAC2 describes the perceptual space in terms of orthogonal dimensions only when this best fits the data. Otherwise, it will recover the stimulis projections on oblique dimensions and also give the angles between these dimensions. Advantages of PARAFAC2 are explored by comparing its results with those of PARAFAC. Both factor-analytic and multidimensional scaling applications are demonstrated using data from speech physiology and perception.
Review of Legislation and City Planning Session
Authors: Gatley William S.
Published: October 2005

Trends and implications of urban noise legislation in the United States are discussed. Three invited and four contributed papers are reviewed and summarized. Subjects include development and use of performance codes for community noise; an airport zoning ordinance; requirements for community noise control programs; the Chicago comprehensive noise ordinance; and measurement and legislative control of vehicle noise.
Noise and Vibration Control
Authors: Cohen Raymond
Published: October 2005

This session consisted of nine contributed papers all dealing with different aspects of noise and vibration control. St. Hilaire and Vaidya described the mechanism of sound generation caused by the metal reed in a reed organ, and in another paper described the response in a small room due to a sound source in a larger room connected by an opening between them. Davies applied statistical energy analysis to systems with strong but point coupling. Tseo presented a farfield formulation for sound pressure and radiation intensity from a simply supported rectangular plate. Jai-Lue Lai showed mean-square displacement responses of an axially moving belt for loadings of special random processes. Prediction methods for sound power radiated by several classes of rigid flow-discontinuities in low-speed air ducts were presented with experimental evidence by Hayden. Requirements on scanning rate and detection time constant were presented for space-averaged acoustic measurements by Wooten and Cary. Nitsche presented a survey of spectral analysis techniques for moving sound sources. The use of Helmholtz resonators for acoustic absorption was presented by Czarnecki.
Propagation in a Time-Dependent Shallow-Water Channel
Authors: Clark John G. , Yarnall James R.
Published: October 2005

A ray approach is used to model transmission fluctuations for a 7-NM propagation path in the Straits of Florida. The model is based on simplifying restrictions consistent with the following assumptions: (1) Transmission fluctuations on the time scale of a few minutes and longer are attributable to time-dependent multipath interference effects. These effects are associated with variations in the channel of spatial scale larger than the source to receiver separation. (2) The bottom contributes significantly to the mean loss but insignificantly to fluctuations. For transmission loss, comparison with experiment is made on the basis of smoothed spectra, covering fluctuation periods of a few minutes to many days. The agreement is good. Time series of observed and computed phase, treated as a variable continuous over multiplets of 2π radians, also show favorable agreement. [Work supported by Acoustics Programs, Office of Naval Research.]
Acoustic Holography for Underwater Viewing
Authors: Mueller R. K.
Published: October 2005

Acoustic holography enjoyed its peak of activity in the late 1960s, resulting in a wealth of new approaches to acoustic imaging and image data processing. Now that much of the work in innovation is reaching completion, the field is evolving more toward demonstrating the feasibility of the holographic approach for various applications as, for example, underwater viewing. The present paper discusses some new results obtained with a real-time holographic system for underwater viewing. This system consists of a transmit-receive array of 20×20 piezoelectric transducers, some data processing electronics, and an electro-optical image reconstructor.
Binaural Critical Bandwidth as a Function of Signal Bandwidth
Authors: Wightman Frederic L. , Houtgast Tammo
Published: October 2005

There are data in the literature which suggest that the critical band, as measured in masking experiments, may be wider for short signals than for long signals. Our data agree with this result. However, we suggest that it is the bandwidth of the signal and not only its duration that determines the critical bandwidth. Three types of signals were used: a 100-msec burst of 500-Hz sinusoid; a 100-msec burst of noise, bandpassed at 500 Hz; and a 0.1-msec click, bandpass filtered at 500 Hz. Signals were presented in both the S0N0 (signal and masker interaurally in-phase) and SπN0 (masker in-phase, signal inverted at one ear) configurations. The critical bandwidth for each signal was estimated by measuring its masked threshold in bands of noise of various widths. The important results are as follows: in S0N0 conditions the critical bandwidth for an octave-band filtered click is almost an order of magnitude larger than for a 100-msec sinusoid. Moreover, the critical bandwidth for a 100-msec octave-band filtered noise is about the same as for an octave-band click. This suggests that it is signal bandwidth that determines the width of the critical band, not its duration. In SπN0 conditions none of the above effects is observed. The critical bandwidth appears to be nearly independent of both signal duration and bandwidth.
Speed-Accuracy Trade
Authors: Green David M. , Luce R. D.
Published: October 2005

The study investigated the speed-accuracy trade for detecting a weak 1000-Hz tone presented in continuous noise. Reaction times were measured in a YES-NO design with a fixed response deadline and various payoffs for the four stimulus-response combinations. The deadline was varied from 300 to 2000 msec in various experiments, and the payoff schedule was varied at a fixed deadline to determine different points on an ROC curve. With 300 msec deadline, performance is near chance; with a 2000 msec deadline, performance is practically perfect. With a fixed-response deadline imposed on both signal and noise trials the data favor a counter model, since the mean reaction time for all events is roughly the same, and the ROC curve has a slope less than unity. When the deadline is imposed on only signal trials, the data favor an interarrival time model, since the mean reaction time on noise trials is a linear function of the mean reaction time on signal trials and the ROC curve has a slope greater than unity. [This research was supported by a grant from National Science Foundation.]
Prototype Standard and Index for Environmental Noise Quality
Authors: Goldstein S. N.
Published: October 2005

A prototype technical standard for environmental noise is proposed in terms enabling an index of noise quality to be defined and calculated. The standard takes into account the damaging aspects of chronic exposure to loud noise as well as psychologically disturbing aspects of typical community noises which are not loud enough to be physically dangerous. Inasmuch as the standard is intended to portray environmental quality rather than to reflect damage risk criteria, it is generally conservative with respect to work-related noise standards such as those specified by the Walsh-Healey Act. The basic standard specifies a distribution of noise intensities to which an individual might be exposed in a 24-h period. The distribution may be approximated by the composite of three Gaussian distributions with means and standard deviations of (30 and 3), (50 and 8.5), and (70 and 14) dB (A). These component distributions correspond to 8-h periods for sleep, miscellaneous daily activities, and work, respectively. Alternative strategies for obtaining data for calculating the related noise quality indices are discussed. [The work was sponsored by the Council on Environmental Quality as part of a larger study on monitoring the environment of the nation.]
Estimating the Noise Environment in the Vicinity of Small General Aviation Airports
Authors: Bishop D. E.
Published: October 2005

Noise is of growing concern at many smaller airports particularly when expansion or new airport development is planned. To aid in evaluating the noise impact of changes in airport operations, sets of noise exposure forecast (NEF) contours have been developed for a generalized small airport. Design charts for estimating changes in the size of the NEF contours with increases in volume of operations or the introduction of business jet aircraft are also presented. The potential for drastically reducing the deterioration in the noise environment which often accompanies the introduction of business jet aircraft at small airports by use of small jet aircraft equipped with new design high bypass ratio turbofan engines is illustrated. [Work supported by the Regional Airport Systems Study, Association of Bay Area Governments.]
Noise Encountered within Small Utility-Type Aircraft Used by the Military Services
Authors: Gasaway Donald C.
Published: October 2005

The military services use several types of small aircraft to perform a variety of missions. Most of these aircraft are obtained from commercial manufacturers and after receiving certain modifications, these vehicles are then used to accomplish a wide range of missions. This paper identifies primary and secondary sources of noise encountered within various utility type aircraft and features of bioacoustic and psychoacoustic concern are identified and discussed. Generally, three primary problems of aeromedical concern are evident in most of the aircraft studied; speech interference, potential auditory risk, and general fatigue induced by having to use increased vocal effort to achieve and maintain successful communications. Time (duration) files are also described that illustrate how the ambient noise environment changes with alterations in flight operations.