bluuebunny/crossref_metadata_2025 huggingface dataset:
Békésy Thresholds with Different Attenuation Steps
Authors: Young I. M. , Harbert F.
Published: October 2005

Békésy fixed-frequency initial thresholds were compared for pulsed and continuous tones for different attenuation steps (0.25 and 2.5 dB) in normals and ears with sensorineural hearing loss. For ascending method (starting at infrathreshold intensity), the initial threshold as measured by the bottom of the first spike showed no observable difference by varying attenuation step. For descending method (starting at suprathreshold intensity), thresholds for the tone interrupted 2.5 times/sec (Signal A) were best, those for continuous tone with an attenuation step 0.25 dB. (Signal C) worst, and continuous tone with an attenuation step 2.5 dB (Signal B) intermediate, in both normal subjects and ears with sensorineural hearing loss. The fact that the threshold obtained by the 2.5-dB stepped continuous tone is better than that by the 0.25-dB stepped continuous tone may be due primarily to greater recovery from adaptation. While there were arithmetic differences in threshold between three signals, the ratio for threshold difference between Signals A and B versus that between Signals A and C was constant. As the amount of separation in decibels between pulsed and continuous-tone tracings by conventional Békésy audiometry increased, difference in thresholds between Signals A and B and that between Signals A and C increased.
Comparison of Speech Perception Utilizing Monotic and Dichotic Modes of Listening
Authors: Zelnick E.
Published: October 2005

Two experiments were designed to compare speech perception, as measured by the Revised Peterson-Lehiste CNC word lists, for individuals with with bilateral approximately symmetrical sensory hearing losses, utilizing monotic and dichotic modes of listening. The monotic modes consisted of a monaural amplifier and an amplifying system of two channels to one ear (monotic V cord). Dichotic modes comprised a binaural system of amplification and a two channel amplifying system to each ear (double V cord). In Expt. 1, randomized word lists were presented through high fidelity amplifiers and earphones; in Expt. 2, commercial hearing aids were used. Statistical analysis of the data supported the following hypotheses for subjects with bilateral approximately symmetrical sensory hearing losses: (1) Dichotic modes were superior for speech perception to monotic modes of amplification; (2) The binaural mode was superior for speech perception to the two-channel modes (monotic V cord and double V cord systems) of amplification; (3) The two channel mode (monotic V cord system) was superior for speech perception to the monaural mode of amplification to the same ear.
Perception of Musical Pitch
Authors: Houtsma A. J. M. , Goldstein J. L.
Published: October 2005

In music, melodies can be recognized regardless of the instrument on which they are played. This is true even when the musical sounds have no energy at the fundamental frequency. This phenomenon was studied through identification of melodies, each note of which was played by a complex of two simple tones with adjacent harmonic frequencies and randomly chosen lower harmonic number. Subjects can perfectly identify melodies so played both when the two-tone complexes are presented to one ear, and when the two-tone complexes are presented to one ear, and when the harmonics in the complex are presented dichotically, one to each ear. Control experiments show that neither difference tone nor transformations based upon frequency difference per se can explain these phenomena. Identification errors began to occur for harmonic numbers larger than about 6 and for absolute stimulus frequencies in excess of about 4000 cps, for both the monaural and binaural paradigm. These results suggest that pitch perception is mediated by neural signals derived from spectral regions of the stimulus that are tonotopically resolved. [Work supported by a grant from the National Institutes of Health.]
Theory of Organ Pipe Sound Generation
Authors: Elder S. A.
Published: October 2005

By calculating force per unit area exerted by jet on a control volume extending from languid to edge and equating this to difference in acoustic pressure along pipe axis over this region, it is possible to derive an expression for acoustic particle velocity in the standing wave as a function of jet driving flow spectrum. The latter is proportional to initial jet speed and is further determined by fraction of time spent by jet below edge during each cycle, and phase of jet displacement upon arrival at edge. Over-all feedback loop can be closed by introducing superposed Rayleigh-Cremer type jet waves and finding solutions that give self-consistent asymmetry factor and phase of jet displacement fundamental. Interaction of partials occurs both in driving mechanism and in nonlinear mouth impedance. At least four nonlinear mechanisms are present in the process. Using a variational method, computer solutions are being obtained out to third harmonic. Theory predicts approximately equal acoustic volume flow out of both ends of pipe, explaining Coltman's result. Momentum conservation requires entrainment coefficient of approximately (2Q/πc) in agreement with slope of empirical entrained-flow curve of Cremer and Ising. [This work was supported by the Office of Naval Research.]
Self-Sustained Oscillations in Clarinet-Like Systems—Quantitative Results
Authors: Worman W. E.
Published: October 2005

Quantitative results are presented of calculations (based on the formalism discussed by the author at the 1968 Cleveland meeting) for a system composed of a clarinet reed and mouthpiece attached to a clarinet-like tube. The impedance curve of this tube has one peak (QZ0) and one dip (Z0/Q), which lie below the cutoff frequency supplied by a row of open holes. Above cutoff, the impedance Z ≅ Z0, the characteristic impedance of the tube. The Q of the tube is 13.5. Calculation deals with medium and small amplitudes of oscillation, i.e., when the reed does not beat. The frequency of steady-state oscillation and the pressure spectrum (amplitudes and phases) in the mouthpiece are found as a function of blowing pressure, starting from the measured impedance curve of the tube, and dynamical coefficients of the reed, with Backus' measurements of nonlinear flow through a clarinet mouthpiece as a function of reed opening and pressure difference across it. The threshold blowing pressure is also calculated. Numerical results are in accord with experimental observation.
Nearfield Solution for Spherical Waves of Finite Amplitude
Authors: Kurze U. J. , Madden R.
Published: October 2005

It is desired to determine theoretically the shape of an input pulse at a small spherical source that will distort into a single N pulse in the farfield. This has been accomplished by considering the effects of nonlinearities and pulse distortion in the nearfield of a sphere whose diameter is small in comparison to the characteristic wavelength of the pulse. Two approaches have been used: (1) a simple model based on the method of characteristics for an inviscid non-heat-conducting medium, and (2) a more refined weak shock approximation, which includes the effects of viscosity and heat conduction. Results are presented in terms of the waveform as it propagates for a class of input pulses with variations in shape and amplitude. [This study has been sponsored by the Dynamics Loads Division, National Aeronautics and Space Administration, Langley Research Center, Hampton, Virginia.]
Sonic Boom Simulation Model Study
Authors: Allen Clayton H. , Hayden Richard E.
Published: October 2005

As part of a feasibility study directed toward the design of a facility for generating full-scale simulated sonic booms over a test site approximately one-fifth of a mile square, tests have been made on a 1:100 scale model. This presentation describes the model, gives experimental data, and discusses implications that can be drawn from the data regarding the proposed full-scale facility. [This study has been sponsored by the Dynamic Loads Division, National Aeronautics and Space Administration. Langley Research Center, Hampton, Virginia.]
Fast Field Program (FFP) for Surface Duct Propagation
Authors: Chamberlain S. G.
Published: October 2005

The FFP is a numerical method, due to H. W. Marsh, of evaluating accurately and efficiently the solution of the acoustics wave equation. Presented here is a form of the FFP, due to W. S. Liggett, in which by proper choice of an integration contour the wave solution is expressed as a sum of residues plus a branch cut integral. By appropriate approximation, these can be evaluated using the FFT or Chirp Fourier Transform algorithms. A general numerical integration scheme, which allows arbitrary sound-velocity profiles that need not be approximated by analytic functions nor divided into layers, and which permits propagation loss computation as a function of both range and depth, is used to evaluate the kernel of the FFT. Although the FFP is more generally applicable, to illustrate the procedure, the propagation loss is computed for a surface duct case with no bottom returns. Our results are compared to those in the literature for this case, which were found by normal mode and ray trace computations and from empirical data. [This research was supported by the Office of Naval Research.]
Ray Tracing with Horizontal and Vertical Gradients
Authors: Wright Edward L.
Published: October 2005

Ray paths are found in a medium with a sound speed varying in two dimensions. The velocity field is approximated in a triangular region by a linear function of range and depth. The assumed velocity is continuous, but the gradient of the velocity is discontinuous across the boundaries of the triangular region. Results are compared with exact solutions for a tilted bilinear profile, and tilted and nontilted hyperbolic cosine profiles. The errors in ray position are due to the linear approximation of the velocity, not to the existence of horizontal gradients.
Computation of Long-Range Propagation Loss in a Duct
Authors: Raisbeck Gordon
Published: October 2005

An acoustic ray shows the direction in which acoustic energy flows, but not the intensity of the resulting field. The conventional way to estimate intensity is to infer the cross section of a narrow bundle of rays from the difference in the trajectories of a closely spaced pair of rays. Where (1) the distance is long, (2) the detailed sound-velocity structure is uncertain, and (3) multipath propagation exists, there are both practical and theoretical objections to this procedure. As an alternative, we can seek the average intensity at a given depth over a range interval about a nominal range. The resulting expression involves no differencing of ray trajectory parameters, only summing, which is computationally preferable. To a first approximation, the resulting expression depends only on the velocity profiles at the source and receiver and the distance between them, but not on the detailed velocity structure between. This conceptually simple space average can be shown to be equivalent to the average or expected value resulting, by much more profound arguments, from uncertainty or from special or temporal fluctuations in the sound-velocity structure. [Work was supported by the Naval Ordnance Systems Command.]
F1 Masking of F2 Transition Discrimination in Hearing-Impaired Listeners
Authors: Martin Eellen S. , Pickett J. M.
Published: October 2005

We present further results from a program of research to describe the auditory discrimination of persons with sensorineural hearing loss, using synthetic test sounds with speech-like formants. The present tests investigate F2 transition discrimination in the presence and absence of a low-frequency formant (F1). The task of the listener was to hear the occurrence of an F2 transition in contrast to no transition. An adaptive procedure was used to estimate the smallest amount of transition that the listener could discriminate; we call this amount the transition threshold. The transitions had a final frequency of 1500 Hz. Discrimination was measured both for rising transitions and falling transitions. When F1 was present, the amplitude relation between F1 and F2 was like that in natural speech. F1 was always held at the same steady frequency. F2 transitions were either 300 or 100 msec in duration. When F2 was presented alone, thresholds for sensorineural Ss were often as small as those of normal-hearing Ss. However, when F1 was added to the signal, the F2 transition thresholds for the sensorineural Ss became larger than normal, and day-to-day variability in threshold increased markedly.
Teaching /ba/ and /pa/ to Deaf Children by means of Real-Time Spectral Displays
Authors: Stark Rachel E.
Published: October 2005

Two groups, each comprising eight deaf children, were taught to produce the consonant-vowel syllables /ba/ and /pa/. One group was taught by means of visually displayed spectral information and the other by means of conventional speech-training techniques. Ability to produce these syllables was assessed before, immediately after, and six to eight weeks after training by means of (1) measurements of time of onset of voicing in relation to the release of the stop and (2) listener judgments. The scores obtained from both voice onset time measurements and listener judgments indicated that (1) most of the deaf children were better able to say /ba/ than /pa/ before and after training; (2) production skill improved with training, especially for /pa/; (3) the group taught by means of real-time spectral displays showed greater improvement in production skill than the conventional instruction group (this group superiority was maintained six to eight weeks after training. [Research supported by the National Institute of Child Health and Human Development and the Bell Telephone Laboratories.]
Discrimination of F2 Transitions in Speech and Non-speech Contexts
Authors: Syrdal Ann. K. , Mattingly Ignatius G. , Liberman Alvin M. , Halwes Terry
Published: October 2005

Second-formant transitions in both initial and final position are perceived differently in speech and non-speech contexts. Discrimination of stop-vowel and vowel-stop two-formant syllables, with second-formant transitions varied, was compared with discrimination of two types of non-speech: stimuli consisting of second formants only and isolated second-formant transitions. Subjects had to identify the stops of the syllables as /b/, /d/, or /g/; to discriminate between similar pairs of syllables; and discriminate between the corresponding pairs of nonspeech stimuli. There were two major differences in discrimination between speech and nonspeech. For the speech stimuli, there were peaks in the discrimination functions at phoneme boundaries; peaks for nonspeech stimuli were at other points in the functions. For the speech stimuli, discrimination was better for initial second-formant transitions; for nonspeech stimuli, the reverse was true. [Partial support by ONR, NICHD, and VA is acknowledged.]
Perception of Temporal Order for Speech Sounds
Authors: Thomas Ian B. , Hill Peter B. , Carroll Francis , Garcia Bienvenido
Published: October 2005

Following the technique described in the work of R. M. Warren et al. [“Auditory Sequence: Confusion of Patterns Other Than Speech or Music,” Science 164, 586 (1969)] concerning the perception of temporal order in a continuously repeated sequence of four sounds, we investigated the duration of the four (equal) segments necessary for correct perception of the temperal order of four vowel sounds. The vowels chosen were /i/, /ε/, /a/, /u/; all vowel samples were spliced from the enunciations of one speaker (PBH) and were controlled for pitch (125 Hz) and true rms intensity. The duration of each vowel segment, T, was varied from 75 to 300 msec; vowel order was randomized for each value of T. In identifying temporal order, listeners achieved near perfect scores (>90%) for T⩾125 msec; for T⩽100 msec, scores were near chance (16.7%). The marked difference between the segment durations (T) necessary for correct perception of temporal order for vowels (T≈100 msec) and nonspeech sounds (T from 300 to 700 msec) suggests that this technique can provide a sensitive measure of the “speechlikeness” of synthetic stimuli. [Work supported by NIH.]
Target Ranging by Echolocating Bats in Interfering Noise
Authors: Simmons J. A.
Published: October 2005

This author has previously reported evidence that bats using short-duration FM sonar cries determine the range of a target from the arrival time of its echoes, and that these bats process returning echoes for their arrival time information with a correlation receiver. Bats of the species Phyllostomus hastatus were tested for their range discrimination acuity at several different echo S/N ratios to find out whether the bat behaved in a manner similar to a receiver operating on the correlation properties of its input. S/N ratios from better than 100 down to about 0.3 were used on the bats. The acuity of range resolution was stable at about 12 mm as the S/N ratio declined to about 2–5, at which point the bats acuity abruptly deteriorated. This performance strengthens the assertion that these bats have an ideal sonar receiver as far as range or time resolution is concerned.
Temporary Threshold Shift Recovery from Impulse and Steady-State Noise Exposure
Authors: Fletcher John L.
Published: October 2005

Fifteen young male subjects with hearing levels in the range of 125–8000 Hz no worse than 25 dB ISO were exposed to impulse and continuous noise separately until a criterion temporary threshold shift (TTS) of 25 dB at any of the frequencies monitored was reached. Recovery from the TTS was then observed at frequencies from 3–14 KHz for time intervals of 15 min, 30 min, 1 h, 2 h, 4 h, and 7 h postexposure. Recovery curves from impulse noise induced TTS differed significantly from the continuous noise TTS curves, with recovery much slower from impulse TTS. Results indicate the need for further research in this area.
Comparison of Temporary Shifts Induced by 3500-Hz Tones in Air and Underwater
Authors: Smith Paul F. , Howard R. , Harris M. , Waterman D.
Published: October 2005

Six men were subjected underwater to 3500-Hz pure tones of 1250-msec pulse length repeated every 2.5 sec for a period of 15 min at SPLs of 168 and 178 dB re 0.0002 dyn/cm2 TTSs were measured and compared to TTSs induced by similar exposure at lower levels in air in a second group of five men. It was found that the SPL of 3500-Hz tones in water must be about 68 dB higher than tones in air in order to induce comparable magnitudes of temporary threshold shifts.
Eartip Noise Immunization in Stereo Pneumatic Headsets
Authors: Cohen Abraham B.
Published: October 2005

The new generation of passenger aircraft is determining a new level of performance for the passenger entertainment systems. What the passenger will hear via the pneumatic transmission system terminating in ear-insert tips will depend not only upon the reproducing characteristic of the electrical transducer, but be equally dependent upon the transmission characteristic of the tubing and the attenuation of the cabin noise as governed by the type of the ear tip and its fit into the ear. Using the ambient noise spectrum of the interior of the Boeing 747, the noise immunization of nine types of tips terminating the tubes were measured and compared with the ambient using 13-oct band real-time spectrum analysis. Normalized analysis shows that for all the ear tips tested, there is an attenuation of approximately 25 ± 4 dB between the bands with center frequencies of 50 to 400 Hz, a drop in attenuation to approximately 18 dB between 800 and 1000 Hz, then followed by a generally asymptotic sweep towards 8000 Hz, where the attenuation reaches 38 dB. Correlation of these noise immunization characteristics are made with the actual response performance of the transmission system in conjunction with the seat transducer under actual noise conditions
Acoustical Considerations in the Open-Plan School
Authors: Kalk J. H.
Published: October 2005

The problem of acoustical engineering in school buildings is of greater importance now than at any time in the past because of the changing character of the methods of teaching. The traditional school with classrooms lining both sides of the corridor is disappearing rapidly in favor of areas that handle a large number of students and teachers in one space. Also being provided are large numbers of small rooms for conferences, seminars, developmental reading, and typing. Sound control in cafeterias, auditoriums, gymnasiums, shops, and large laboratory spaces has become exceedingly critical. The use of new teaching aids, both audio and visual, by individual students as well as large groups presents new problems in planning. The increased use of carpeting, air conditioning, and acoustic ceilings has helped, but these are certainly not the final answers. Schools still encounter noise from ventilating machinery, including unit ventilators, air ducts, audio equipment, and conflicts between such noisy areas as shops and music studies, all of which need to be given serious consideration if the educational program is to move forward. Many movable partitions designed to give schools flexibility in the size of spaces have failed miserably in operation. These factors and others will be considered in this seminar.
Acoustics and the Open-Plan School
Authors: Finley R. M.
Published: October 2005

Many schools being built today are open-plan. Many problems with acoustics in these buildings have evolved. Criticism of the sound problems has come mostly from parents and teachers; rarely do students complain. To avoid such criticism, a preparation period of time is important for the occupants before occupying the building. Teachers must experience open space before using it. They must understand that noise is about us every minute. They must realize and understand that acoustical problems are not primarily the fault of the building but of how the people in the building use the space. Such normal noise problems can be psychologically eliminated by careful planning of space, color, lighting, movement, activity, carpeting, and furniture. The foremost need to assure ultimate success in the use of such open space is team planning. Time is needed to achieve this. This paper will discuss Chagrin Falls, Ohio, Little Red Schoolhouse, 1956, and Barrington, Illinois, Middle School, 1963.
Acoustical Variables in Open Planning
Authors: Pirn Rein
Published: October 2005

The articulation index (AI) has been widely accepted as an objective measure of environments for speech communication and/or privacy. It quantifies speech intelligibility in terms of the S/N ratio on a scale extending from 0 to 1. While more experimentation is required to verify the subjective equivalent of any given AI, the AI itself can be calculated and hence predicted. It has been found that in buildings without complete floor-to-ceiling partitions, the AI changes drastically with the following variables: speech effort, speaker orientation, background noise, speaker-to-listener distance, and barrier attenuation (if present and unflanked). This paper discusses the relative effect of these variables on the AI, and thus demonstrates the importance of each parameter when designing open-plan facilities.
Landscaped Office
Authors: Bach Fred
Published: October 2005

The office landscape, when considered as a management tool, has to include a thorough revision and adaptation of the information processing that goes on in the building, which is almost considered a factory, the product of which are decisions, and where, instead of material flow, we are concerned with information flow and processing. To make good use of this tool, the management, as well as the occupying personnel in general, has to be educated in its proper use; this must be done in the course of the planning. The planning method is designed to take care of this problem concurrently. This is an essential part of the over-all success because the office landscape will only give maximum benefits if the user has the know-how to use it for his own purposes in an optimal way. The planning effort has to address itself to various aspects of the company. Even though the development of a new environment may be the primary object and the reason for the planning, tools, and procedures used in the system, the social structure and the organizational structure all have to be reviewed so as to make sure that the total system can operate harmoniously.
Designing an Open-Plan Office
Authors: Lorimer A. Gordon
Published: October 2005

Experience with designing the office landscape test center in Port Authority Building is reported. Initial planning included studies of a number of open-plan offices in Europe and the United States. The detailed design included construction, furniture, and carpeting with special emphasis upon acoustical considerations. A study by an industrial psychologist evaluated the reactions of the occupants after one year in the test center. This was followed by modifications to permit the testing of other furnishing and equipment systems.
Acoustics in Office Landscape and Open-Plan Schools
Authors: Sulewsky James E.
Published: October 2005

The success of open-plan offices and schools is dependent on the acoustical environment in providing the privacy accomplished by and experienced in conventional partitioned rooms. The acoustical environment is provided by the extensive use of efficient sound-absorbant materials and constructions on all surfaces of an appropriate area, location of acoustical screens in relation to noise sources, conversational and business machine activity, and suitable mechanically or electronically produced background noise. The principle behind the use of sound-absorbent material on all room surfaces is to eliminate virtually all the propagation of sound energy by surface reflection. The over-all sound absorption within the area is dictated by the type of material and its surface extent and the application. In regard to acoustical efficiency, the ceiling is considered to be most critical, not only for sound absorption but also for sound diffusion, with acoustical screens, walls, and floor following in that order. Thus, the propagation distance for speech and/or business machine frequencies, the relative degree of privacy or speech intelligibility, can be determined quite satisfactorily by knowing the sound-absorbing efficiency of the area and introducing the appropriate mechanically and/or electronically produced background masking noise.
Airport Noise Zoning Ordinance and Building Code
Authors: Rose Thomas H.
Published: October 2005

Communities around the new 18 000 acre Dallas/Fort Worth Regional Airport are trying to plan ahead for the impact of the new airport facility. An “Airport Zoning Ordinance” was developed that included the control of land use by noise sensitivity, as well as the normal height restrictions. The types of land use permitted in areas exposed to aircraft noise are increased when a “soundproofing addendum” to the building code is utilized. The building code is a “material-oriented” code to assist the small builder. The Zoning Ordinance also contains performance specifications which can be used in lieu of the material specifications. If an architect elects to use different materials, he must prove to the city building inspector that the building was designed to meet the required performance by a person competent in the practice of architectural noise control.
Jury Ratings of Complex Aircraft Noise Spectra Versus Calculated Ratings
Authors: Wells R. J.
Published: October 2005

A set of 30 steady-state noises, comprised of 15 recordings of aircraft engine noise and 15 filtered recordings, was presented to a group of 35 jurors. All noises were heard at a computed tone-corrected perceived noise level of 90 PNdB, as specified by the new FAA noise certification rule. Jurors were asked to rate these noises against a single reference noise using a method-of-adjustment procedure. The resulting jury ratings spanned a 6-dB range. Data are presented showing how this range was influenced by spectral characteristics of the noise which included both strong individual tones and multiple pure tones. Better correlations were obtained between jury ratings and the measure ANL, as described at the San Diego meeting.
Study of the Effects of the Doppler Shift on Perceived Noisiness
Authors: Pearsons Karl S. , Bennett Ricarda L. , Fidell Sanford
Published: October 2005

Subjective judgments of the effects of Doppler shifts on perceived noisiness were made by 20 college students in an anechoic chamber. The stimuli heard in the test included both recorded and simulated air-craft flyovers. Computer controlled generation of the simulated flyovers permitted independent variation of the source frequency, apparent altitude, amplitude, and Doppler patterns. Data collection was governed by a computer-based adaptive technique known as Parameter Estimation by Sequential Testing (PEST). The results of the tests will be discussed and a recording of one of the simulated flyover noises will be presented. The major finding was that effective perceived noise level (EPNL) is a fairly accurate predictor of flyovers containing Doppler shifts, except perhaps at altitudes of less than 500 ft, for which flyovers it underestimates apparent noisiness. Compensation for the risetime of the stimuli (an onset correction) did not improve the accuracy of prediction provided by EPNL.
Direct Comparison of Lateralization and the MLD for Monaural Signals in Gated Noise
Authors: Hafter Ervin R. , Carrier Sam C.
Published: October 2005

Lateralization models of the masking-level difference (MLD) argue that detection under such conditions is of a lateral shift in the perceived acoustic image. We examined that assertion by presenting monaural 500-Hz signals in diotic noise (N0SM) and asking listeners to indicate the lateral position of the resulting auditory image. On randomly chosen trials, we presented a diotic signal in diotic noise (N0S0). Responses to these were assumed to represent perceived “center” and served as the standards against which the responses to N0SM were compared. Signal levels under N0SM and N0S0 were equally detectable as determined in a separate task. Both signals and noise were gated for a duration of 100 msec. As predicted from the model, the lateral scatter under N0SM was sufficient to account for the detection of those signals in an ordinary detection task. We did not find the loss in detection usually associated with gated noise; we attribute this to the fact that subjects had only to lateralize the signal-plus-noise, not to compare it to a remembered “center” or to judge the extent of the lateral shift.
Detection, Lateralization, and the Phase Angle α: Experiment II
Authors: Jeffress Lloyd A. , McFadden Dennis
Published: October 2005

By employing the same narrow band of noise (50 Hz wide centered at 500 Hz) as both masker and signal, and by introducing a phase-shifting network between the masking and signal channels, it is possible to control the phase angle α between the two. For a given signal-to-noise ratio, controlling the phase angle α controls the relative magnitudes of the interaural phase (time) difference and the interaural difference in level between the stimuli at the two ears. When α lies between 0° and 90°, and the signal is reversed at one ear relative to the other (N0Sπ), the interaural time difference and the interaural difference of level favor the same ear. However, when α is between 90° and 180°, the ear that leads in phase or time will receive the weaker stimulus, thus putting time and intensity into opposition as cues to the lateralization of the stimulus. Data will be presented on both detection and lateralization obtained for a variety of values of α, using the single-interval forced-choice procedures. Good detection was observed even at those values of α where time and intensity were in opposition, and where performance in lateralization was very poor. [This research was supported in part by a grant from the Public Health Service, National Institute of Neurological Diseases and Stroke.]
Binaural Discrimination Spaces
Authors: Gilliom J. D. , Sorkin R. D. , Langford T. L.
Published: October 2005

Discrimination performance was obtained using 500-Hz sinusoids containing various combinations of interaural amplitude and interaural-time cues. In one condition, the observer was required to discriminate between a 500-Hz binaural stimulus with an amplitude imbalance favoring the right ear and another stimulus with a time difference favoring the right ear. Other conditions required a discrimination between stimuli differing on both interaural-amplitude and interaural-time cue dimensions simultaneously. Observers were instructed to maximize the number of correct responses, and visual feedback was provided after each observer response. Performance was evaluated in terms of a distance measure analogous to d′. Lateralization performance when interaural time and intensity cues are consonant can be predicted by simple addition of the distances obtained in the corresponding single cue conditions. However, performance when the same interaural time and intensity cues are dissonant is a more complex function of single cue conditions. The results from the various conditions are discussed in terms of binaural discrimination spaces, time-intensity trading ratios, and recent MLD results using sinusoidal maskers. [Research supported in part by the National Science Foundation and in part by the Public Health Service.]
Masking Level Differences and Frequency Discrimination
Authors: Gebhardt Carol J. , Goldstein David P.
Published: October 2005

In 1967 at the 74th meeting of the Society, Robertson and Goldstein reported on changes in frequency-discrimination behavior in binaural listening in noise. The findings of that investigation are extended by this study in which binaural frequency-difference limens in noise were obtained for five frequencies: 200, 300, 500, 700, and 1000 Hz. A 275-msec tonal signal of either 5 or 10 dB SL above masked threshold (SLm) was employed under both homophasic (N0S0) and antiphasic (N0Sπ) conditions. A band-limited (100–2100 Hz) white noise with a spectrum level of 55 dB served as the masker. At each signal frequency and SL, the N0Sπ condition yielded larger DL than did N0S0. Two possible interpretations of these results are considered: (1) the larger antiphasic DL is a reflection of the larger bandwidth operative in the antiphasic configuration; and (2) the DL magnitude is dependent on the signal loudness and the larger antiphasic DLs are a reflection of the difference in the loudness growth patterns for each configuration as a function of SLm.
Stimulus Parameters of Apparent Movement in the Auditory System
Authors: Leftwich M. S. , Perrott D. R. , Elfner L. F. , Tomsic R. T. , Kornburger R.
Published: October 2005

Several stimulus parameters were manipulated to establish optimum conditions necessary to yield apparent auditory movement. Two successive auditory pulses were presented in a free field: a separate pulse from each of two speakers located at 0° and 60° relative to a listener's midline. The method of constant stimuli was used in determining apparent-movement thresholds with interpulse intervals of 5, 10, 20, 40, and 80 msec. No effect on threshold was observed with the following stimulus factors: (1) center frequency of a 1-oct narrow-band noise (c.f. 250, 500, 1000, 1500, 3000, and 5000 Hz); (2) bandwidth (pure tone, 13 oct, 1 oct, and 2 oct). Apparent-movement thresholds are inversely related to the following: (1) signal duration (150 and 500 msec); (2) rise/decay time (1 and 10 msec); (3) signal level (25, 50, and 75 dB SPL). A number of points of commonality can be described among tactual, visual, and auditory apparent-movement phenomena.
Comparison of Individual and Group Levels in Verbal Communication
Authors: Gardner Mark B.
Published: October 2005

A number of factors influence the level of vocal output that is employed in verbal communication. For a private exchange between two individuals who are also in visual contact, the level employed is influenced primarily by the level of the ambient noise and the nature of the communication task engaged in. On the other hand, little influence is introduced by changes in circuit gain when similar but visually isolated exchanges take place over a two-way loudspeaker system. For group situations, such as social hours, restaurant and theater environments, etc., the level employed is influenced primarily by the interference of surrounding vocal output to give an enhanced rate of increase of vocal output (with increasing numbers) not found in the privacy of the individual exchange.
Results of Canine Allogenic Vocal Cord Transplants
Authors: Coleman Robert F. , Cherry Jerrie
Published: October 2005

Unilateral vocal cord transplants were performed on a group of 15 dogs, which were then maintained for postoperative periods of from 2 weeks to 12 months. Five of the 15 dogs were kept for a full year, and the others were sacrificed at intervals prior to a year in order to observe possible histological changes in the transplanted cords over time. Acoustic analyses and perceptual monitoring by a group of judges indicated that the transplanted cords were not only viable, but that functional results were near that of unoperated dogs. Laryngoscopic slides utilizing normal color and infrared film, in addition to motion picture film of the dog's larynges, confirmed the impression of acceptable function and viability.
Position-in-Utterance Duration Effects
Authors: Oller D. Kinbrough
Published: October 2005

The duration of speech segments as a function of position in utterances (initial, medial, final) was studied. Seven English speakers read nonsense utterances of the form “say a bab, say a babab, say a babab,” etc. Spectrograms were used to determine the duration of speech segments in the readings. Final syllables were found to be longer than nonfinal syllables. Final-syllable vowel increments were about 100 msec. Final-syllable consonant increments were less than vowel increments, for instance, 20 msec for absolute final consonants. Also word-initial consonants were found to be lengthened by 20–30 msec. It is suggested that durational studies in general should be interpreted in the light of findings concerning position-in-utterance lengthening. Explanations of lengthening effects are discussed. One theory suggests that lengthening in certain utterance positions is a learned aspect of languages which cues listeners concerning the segmentation of utterances into words, phrases, or sentences. Explanations based on hypothesized properties of the articulatory control system are also discussed.
Introduction to a Wave Function Representation of Speech
Authors: Markel John D.
Published: October 2005

A study of several properties of a wave function representation for speech analysis/synthesis, developed by Culler at UCSB is presented. Starting from the formulation ü(t) + (2π/S)2(t − C)u̇(t) + (2π/S)2(N − 1/2)u(t) = 0, asymptotic time and frequency domain solutions are obtained which can then be used as the basis elements for fitting linear combinations to the filtered speech wave. Requirements for obtaining a wave function representation are discussed and algorithms for extracting wave function parameters from speech are presented. To obtain a better understanding of how the wave function parameters relate to the formant parameters of speech, several algorithms are presented for transforming the wavefunction parameters {A,S,C,φ,F} into the formant parameters {Fn,Bn}.
The Prony Method and Its Application to Speech Analysis
Authors: Markel John D.
Published: October 2005

Extraction of formant frequencies and bandwidths corresponds to extracting a best estimate (in the sense of ]east squares) of three or four exponentially damped sinusoids from an acoustic signal that contains these terms plus noise (e.g., glottal wave characteristics). Least-square optimal estimation of the formant parameters is a nonlinear problem and must be solved iteratively, as in the “Analysis-by-Synthesis” methods. Prony's method, originally formulated in 1795, is now becoming recognized as a very powerful method of obtaining near-optimal formant parameter estimates without iteration. The algorithms required in the Prony method are reviewed along with results from different applications. It is shown that, in many instances, formant parameter and pitch extraction comparable in quality to cepstral techniques can be obtained over the full range of male voices to children's voices. In practice, the method appears to have a convergence property in which the use of more terms leads to more accurate formant estimates.
Quieting of the Hydraulic Noise in the Lunar Module
Authors: Mullan H. R. , Goss R. , Dorland Wade
Published: October 2005

The water/glycol pump in the environmental control system is a major source of noise existing in the cabin of the Lunar Module (LM). The fluctuating pressure produced by the pump causes a fluid system line vibration and associated noise radiation in narrow frequency bands centered at 400 and 800 Hz. This cabin noise environment has evoked unacceptable astronaut responses during work and sleep periods. Since future lunar landing missions include twice the stay time on the moon, noise problems are expected to be more severe than in past missions. Accordingly, a project was initiated to obtain sufficient noise abatement to assure that the cabin environment did not compromise results of the extended lunar missions. This project provided design of an expansion chamber muffler which is installed in the water/glycol plumbing on the pump outlet. This treatment which has been applied to LM-9 reduces fluid-borne pump noise 30 dB and the resultant air-borne noise 12 dB (as measured in an earth ambient atmosphere).
Q/Star—Experimental Quiet Aircraft
Authors: Griffith E. D.
Published: October 2005

An experimental quiet aircraft has been developed by LMSC for research in quiet aircraft technology. This company-owned aircraft, designated the Q/Star, had minimum acoustic signature as its principal design goal. To achieve this goal several significant noise-reduction features were employed. A relatively clean aerodynamic design reduced aerodynamic noise. A “Wankel”-type rotary combustion water-cooled engine was selected to avoid noise-reduction problems associated with air-cooled engines. The muffler system was designed to be most efficient at cruise flight conditions and the system was “tweaked” in the field for maximum performance. The propeller is driven through a 5.34:1 reduction system to provide propeller tip speeds less than Mach 0.2. Over all, these design features have produced an exceptionally quiet airplane. A series of flight tests have been conducted using a variety of propellers including one designed specifically for acoustic noise performance. Data are presented to show aircraft flyover acoustic noise signature as functions of propeller configuration, engine rpm, and air speed.
Noise Levels of Large Industrial Fans
Authors: Bies D. A. , Sawley R. J.
Published: October 2005

There is an increasing trend in industry toward the use of large fans, particularly in their application to air-cooled heat exchangers. Available procedures whereby the sound power levels of fans may be estimated are based primarily on the results of laboratory measurements on comparatively small fans. This paper compares the results of field measurements on some large axial fans with various estimation procedures.
The Use of A Spinning-Mode Synthesizer to Analyze Complex Modes in Ducts
Authors: Oslac Michael J.
Published: October 2005

Tyler and Soffrin and others have shown that the analysis of spinning waves in ducts revolves around the solution of the wave equation in cylindrical coordinates. This solution yields the radial, axial, and circumferential dependents of the waves as they propagate of decay in the ducts. When utilizing the spinning mode synthesized coupled to an inexpensive terra cotta duct (12 in. in diameter by 8 ft in length), spinning waves were generated and measurements made of their radial, axial, and circumferential behavior. The resulting waves were plane, one- and two-lobe spinning waves having phase velocities capable of up to 18 000 rad/sec. Also important was the investigation of duct cut-off and duct expansion sections to reduce higher-order spinning waves to lower and even plane waves.
Ultrasonic Absorption in Hydrogen Sulfide
Authors: Bass H. E. , Winter T. G.
Published: October 2005

Ultrasonic absorption has been measured in H2S in the temperature range 300° to 683°K. This data was analyzed to obtain vibrational and rotational relaxation times. The vibrational collision numbers seem to increase with temperature from 300° to 473°K and then decrease with temperature. This behavior can be explained by the v-r theory of Shields and Burks. The rotational collision numbers compare favorably with thermal-transpiration measurements.
Ultrasonic Orientation and Elastic Constant Determination of Single Cubic Crystals by Minimization of Functions
Authors: Johnston J. D. , Cook B. D.
Published: October 2005

A general method has been investigated for simultaneously solving a system of equations for the elastic constants and orientation of single crystals from measured wave velocities. Applicability of the method to cubic crystals has been studied in detail. The minimum number of velocity measurements required is equal in number to three for orientation parameters plus the number of elastic constants inherent to the crystal. Additional velocity measurements and a least-squares minimization of the equations decrease the influence of individual random errors in the velocity measurements.
Waveform and Frequency Spectra of Acoustic Emissions
Authors: Pollock Adrian A. , Stephens Raymond W. B.
Published: October 2005

Stress waves generated internally by deforming materials provide information about the operative deformation mechanisms. These stress waves are known as acoustic emissions. Acoustic emission stands alongside conventional ultrasonic methods as a useful technique of nondestructive testing. The frequency spectrum of the emissions varies according to the nature and location of the deformation, and it may also provide information about the integrity of the structure under test. On fundamental grounds we conclude that the emission waveform at source is a stress pulse (displacement step) whose frequency spectrum extends from zero up to a frequency which depends on the duration of the source event. Between generation and detection, the spectrum is modulated by structural resonances which tend to obscure the information contained in the source waveform. These effects should be borne in mind during the design of practical emission detection systems. Experimental results from adhesive bonds confirm the validity of our theoretical approach and show how information about the source event may be gained from the spectrum by looking beyond the structural resonances.
Theory of Acoustical Wave Propagation in Porous Media
Authors: Smith P. G. , Greenkorn R. A.
Published: October 2005

A theory is developed for the propagation of sound waves in a rigid, isotropic, and homogeneous porous medium filled with a compressible fluid, including both the effect of viscous dissipation and the effect of thermal comduction. With a capillaric model assumed, an expression for the permeability as a function of the frequency is also given. For very low frequencies (isothermal case) and very high frequencies (adiabatic case), the results reduce to those of a theory presented by Morse [J. Acoust. Soc. Amer. 24, 696 (1952)]. The present theory can be used to determine the structural parameters of a porous system at a given frequency. Attenuation and phase factors are plotted as functions of a nondimensional frequency parameter for various combinations of the characteristic constants.