bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of noise exposure during primary flight training on the conventional and high-frequency hearing of Naval Aviation Officer Candidates
Authors: Robertson R. M. , Williams C. E.
Published: October 2005

This investigation was part of a larger study conducted by Memphis State University. This laboratory's portion of the study focused on administering conventional audiometry (manual and self-recording), high-frequency audiomerry (4–18 kHz), and a speech intelligibility test in noise to 108 Naval Aviation Officer Candidates prior to and following primary flight training in T-34 aircraft. Hearing protection consisted of either the APH-6C or APH-6D flight helmet. Cockpit noise levels in the T-34 range from 96 to 115 dBA; during cruise the noise level is approximately 100 dBA. Results indicate no significant change in hearing sensitivity or speech discrimination that could be attributed to noise exposure during primary flight training. Pre- and post-primary hearing levels obtained for the high frequencies compare favorably with high-frequency hearing levels obtained by Northern et al. (1968) for males in the age range 20–29 years. Questionnaire data indicated that a considerabte number of the subjects had been exposed to potentially hazardous noise before entry into military service.
On the influence of the mechanical support on the hearing aid frequency response
Authors: Nabélěk Igor V.
Published: October 2005

Hearing aid frequency response measured in an unechoic chamber and in a hearing aid test box may differ appreciably. The usual explanation is that the difference in equipment and the sound field configuration cause the discrepancy. Often very small attention is paid to the effects of mechanical support used for fixing the aid in the desired position. The support is satisfactory if it does not disturb the distribution of the sound field and if it does not transmit mechanical vibrations. While the first requirement is usually fulfilled, the assumption that the second one is fulfilled also is often not justified. During the reported study, large alternations in hearing aid frequency responses caused by such vibrations were observed when measured, namely, in hearing aid test boxes. Even in commercial facilities considerable influenoe of mechanical resonances of supports was found in the low-frequency range (between lowest frequencies and approximately 1000 Hz). Some simple methods for improvement of the reliability of frequency response measurement are discussed.
On trying to disguise the voice with a dental appliance
Authors: Hamlet S. L.
Published: October 2005

As part of a beginning study on speech adaptation to dental appliances, four young adults were fitted with an experimental alveolar-palatal acrylic appliance similar to an orthodontic retainer. They wore the appliance for one week in an attempt to learn to speak normally with it. The appliance causes phonetic distortions in the beginning, and a slight voice quality change. The question is whether these speech alterations, both in the beginning and after one week's adaptation time, are sufficient to affect a listener's judgment of the speaker's identity. Paired voice samples representing different persons, the same person with and without the appliance, and the same person with or without the appliance were judged by phonetically naive persons. Judges were asked to indicate whether each pair was spoken by the same person or different persons, and in addition to indicate their confidence in the judgment. Results are reported in terms of the number and types of errors the judges made. [Supported by a University of Maryland Faculty Research Award.]
Measurement error in speech timing studies
Authors: Allen George D.
Published: October 2005

In recent years, studies of speech timing have begun to move from the purely descriptive into more hypothesis testing and model theoretic paradigms. Since a careful accounting for variance components is often necessary for such analyses, intuitively derived guesses as to the magnitude of measurement error are no longer adequate. This paper discusses various sources of measurement error, from the speaker's head to the experimenter's pencil, and suggests how such errors may have perverted some recent investigations. Methods for calibrating and controlling measurement error are described, and implications for future research are drawn.
Features of sounds produced by two- to eight-week infants
Authors: Stark R. E. , Rose S. N.
Published: October 2005

Sounds recorded on a longitudinal basis from infants of two to eight weeks were classified as cry, discomfort, or vegetative sounds. Five examples of each of these three classes of sounds were selected randomly from the output of three different infants. The selection was made for each of the three infants at two, four, and eight weeks of age. The cry, discomfort, and vegetative sounds were submitted to analysis of auditory and spectrographic features. Duration of segments, that is, portions of an utterance bounded by noise, and the temporal patterning of these segments, i.e., the number occurring in a series and the relative duration of segments within a series, were determined. Significant differences were found across the three sound classes, but not across age levels, with respect to (1) clustering of auditory and spectrographic features, (2) segment duration, and (3) temporal patterning. The possible importance of these findings for speech sound development after eight weeks of age is discussed. [Research Support by NINDS.]
Speech styles and pitch contours on negatives
Authors: Yaeger Malcah , O'Malley Michael H.
Published: October 2005

John Alien [J. Acoust. Soc. Ant. 55, 396(A) (1974)] has presented data demonstrating that in read speech the work which carries a [+neg] meaning also carries the pitch peak of the sentence. Data from several multiparty conversations, of varying degrees of formality and from various dialect areas, have been analyzed to determine if some comparable statement can be made for “spontaneous” interactional styles. The data to be presented demonstrate that (1) most of the time, the unit which carries the negative is reduced; (2) there are cases in which the pitch on the negated syllable is not raised even though the amplitude is not reduced; (3) raised pitch on the negative occurs only in cases of emphatic agreement with one's coparticipants, or emphatic disagreement with an intimate (e.g., in these data, wife with husband). These data again demonstrate the relevance of stylistic variables to the study of speech production.
Nonphysiological variation in the pronunciation of Arabic by men and women
Authors: Kahn Margaret
Published: October 2005

Two spectrographic studies measured the acoustic difference shown by men and women in the pronunciation of Arabic pharyngealized and nonpharyngealized segments (emphatics). In the first experiment, native female speakers of Arabic (Cairene) showed significantly fewer acoustic cues for pharyngealization than male Cairene speakers. A second experiment contrasted male and female Arabic speakers using American students of Arabic as a control. This study showed American students modeling their male teachers' pronunciation, manifesting less than half the E factor [(F1e−F1)+(F2−F2e)] difference that was shown by Arab men and women. Furthermore, Arab women showed consistently higher vowel formants than American women, whereas Arab men and American men are quite similar. Among Arabs, the magnitude difference in formant frequencies between men and women was found to be much greater than anatomically predicted by Fant [1966], and the direction of the sex-related formant differences was opposite fo Fant's predictions. The results of these two experiments point toward nonphysiological bases of variation in vowel formants for men and women. [Supported by the Herman Fund.]
“Comfortable effort level”: an experimental variable
Authors: Brown W. S. , Murry Thomas
Published: October 2005

It is not uncommon to read in speech studies that subjects were instructed to produce speech samples at a "comfortable effort level." In many cases the experimenters have made the assumption that this level of effort is more or less constant over repeated occurrences. The purpose of this study was to test the constancy of comfortable effort level in speakers' utterances. Sixteen speakers were recorded each of five successive days while producing a series of vowels, phrases, and sentences. The only instruction to the speakers was to repeat the utterances at a “comfortable effort level.” Measures of speaking fundamental frequency (SFF) and vocal intensity (SPL) were obtained from the recordings. Initial results indicate that variability in both SFF and SPL occurred in the utterances; in many cases this variability was considerable. These results suggest that experimenters desiring constant vocal productions must be more specific in providing instructions to subjects since comfortable effort level can not be assumed to be constant from one experimental session to the next (especially from day to day).
Comparison of models with theoretical examples
Authors: Wood D. H.
Published: October 2005

Our confidence that computer medals are correctly programmed is greatly enhanced when we are able to test them against special theoretical examples which exert them to the (usually unrealistic) limits of their capabilities. Agreement of models with experimental data and agreement with other models are important but totally separate matters where disagreements are often “explained away.” The most useful theoretical examples, and the rarest, are the few known exact solutions of the reduced wave equation for media without boundaries. Some of these yield exact solutions for bounded media by using a slight generalization of the classical method of images. For testing ray tracing programs for nonlayered media, some theoretical examples can be found in three recent papers invoking analytic function theory. For some special layered media, there are well-known analytic evaluations of the ray tracing and normal mode expressions. Finally, for a few special media, there is a new technique which directly generates caustic curves.
Transmission loss for wide-band signals transmitted in a SOFAR channel
Authors: Leslie H. D. , Porter R. P.
Published: October 2005

Energy calculations for long-range wide-band transmissions have been performed by the ray-mode method [J. Acoust. Soc. Am. 54, 1081–1091 (1973)]. Average energy spreading as a function of range is determined from ray theory. Eigenray cycle lengths are calculated for each range by successive polynomial approximations. Energy distribution as a function of depth is determined from modal wave functions approximated by the WKB method. A diffraction correction to the phase integral is applied near turning points. Loss can be calculated for any source and receiver spectrum if the time-bandwidth product of the dispersion is large. The implementation scheme produces loss as a function of depth for a given range. Intermediate ranges are not evaluated as they must be for a ray trace program. Results are presented for a bilinear SOFAR channel.
Possible effects of velocity profile shape and scattering loss distribution in SOFAR propagation
Authors: Guthrie K. M. , Denham R. N. , Bannister R. W. , Browning D. G.
Published: October 2005

A primary aim of SOFAR propagation experiments conducted recently has been to obtain measurements of the acoustic attenuation coefficient in the ocean. However, the interpretation of the data gained in these experiments has been the subject of considerable debate. In particular, the relative importance of the scattering loss contribution to the total observed attenuation at low frequencies is an unresolved problem: Apart from relatively localized regions of deep scattering associated with water-mass movement, the distribution of scatterers (which may be either physical objects such as marine life and air bubbles or small changes in oceanographic parameters due to turbulence) is assumed to be concentrated in the region near the ocean surface. A propagation model which includes such a stratified scattering loss has been developed. The theoretical attenuation coefficient is found to be dependent on the velocity profile shape. This may account for regional variations in the observed attenuation coefficient; however, regional changes of the scattering loss profile itself may be equally important. By comparison with experimental signals, the magnitude of the scattering loss profile is estimated.
Session W. Special Lecture on Ocean Acoustics
Authors: Shaw Edgar A. G.
Published: October 2005

Ocean acoustics is a rich field of study embracing unique modes of sound propagation, specialized means of acoustic transduction, meteorological, biological, and man-made noise, sophisticated signal processing, and exploration on a vast scale. This special lecture is intended to give all members of the Society a broad view of an important area of acoustics which is the primary field of interest for nearly one-fifth of the membership.
Development of noise reduction concepts for the 727 and 737 airplanes
Authors: Arctander C. L. , Hodge C. G. , Tate R. B.
Published: October 2005

A review is given of the various noise reduction concepts for the JT8D-powered 727 and 737 airplanes, with emphasis on acoustic technology employed. Acoustic treatment aimed at fan noise reduction results in production configurations consistent with existing FAR Part 36 regulations for new airplanes. Several jet noise suppression concepts have been aimed at further 727 noise reduction. An ejector-suppressor concept has been demonstrated on an FAA-sponsored ground and flight test program. Six to eight EPNdB suppression of jet noise was obtained at takeoff power. Airplane performance penalties, however, precluded a viable configuration. The refan concept is currently under development on a NASA contract in which the JT8D engine is modified to incorporate a higher-work-extraction fan. This modification will result in a lower jet noise and a nominal impact on airplane performance.
Validity Of aircraft noise data
Authors: Storey W. C. , Yates R. , Sekyra C. A.
Published: October 2005

An analysis of noise measurements taken at various distances from a number of aircraft during FAR 36 certification conditions is presented. Data scatter is shown to increase with distance and with decreasing aircraft/observer angle. Data normalization techniques, utilizing current standards, are inadequate at large distances and low airplane/observer angles. Aircraft noise measurements taken under uncontrolled situations are of doubtful value in predicting future community noise. Noise measurements obtained directly beneath the airplane flight path, under carefully controlled conditions, are highly repeatable and adjustable for moderate distances (within ± 1 EPNdB); however, when adjusted to sideline distances, these data lead to variations on the order of ± 5 EPNdR. The accuracy of this type of information is of prime concern, since it is used to determine aircraft noise footprints in noise exposure studies. When a 3-EPNdB change in EPNL can lead to halving or doubling of footprint area, it is concluded that the value of current footprints in community noise impact studies is extremely dubious.
Musical pitch variations caused by the Doppler effect
Authors: Kelly Robert E.
Published: October 2005

An analysis is made of the change in pitch expected because of relative motion of a musical performance and a listener. The Doppler shift is combined with the definition of the cent to result in a simple equation giving pitch changes as a function of velocity. The results show a typical pitch variation of 2.25 cents/mph. Wind, temperature, and humidity have negligible effects. Brief discussions of reflections, arbitrary observation angles, and small asymmetries inherent in the Doppler shift are included.
Mechanism of multiphonic tone production in woodwinds
Authors: Benade A. H.
Published: October 2005

In normal (as contrasted with multiphonic) woodwind tone production, the nonlinear flow control characteristic of a reed transfers energy between components of the spectrum by heterodyne action. The frequency of oscillation is that which maximizes the net oscillatory energy production by suitably matching several spectral components to input impedance peaks whose frequencies are in an approximately harmonic relationship. The resulting spectrum is strictly harmonic. So-called “multiphonic” tones are produced by a generalization of the same process. A typical multiphonic tone is sustained by the reed's collaboration with (for example) three reasonably strong input impedance peaks lying at frequencies fp, fq, fr These peaks have no harmonic relationship. The sound spectrum is made up exclusively of heterodyne components of the form αP ± βQ, μP ± νR, etc., where P, Q, R are the basis components (α, β, etc., integer). Here P ≃ fp, Q ≃ fq, R ≃ fr, the exact values being those which give the largest net oscillatory energy input over the entire spectrum. Unambiguous correlations of oscillatory regimes made up of up to 25 spectral components have been made. Examples are given showing the interpretation of several multiphonic tones on the oboe and clarinet.
Effect of varying relative humidity and removal of wood on response curves and eigenmodes of free-free violin plates
Authors: Hutchins Carleen M.
Published: October 2005

Variations in the damping, amplitude, and frequency of certain resonances in free-free violin plates with changes in relative humidity and removal of wood have previously been measured by means of response curves. This study correlates these measurements with the relative activity of various plate areas as displayed by means of Chladni-type patterns showing changes in the eigenmodes under differing conditions of temperature and humidity, as well as the effect of removal of wood in certain areas of the plates.
Can spruce be replaced?—a guitar with a graphite-epoxy top plate
Authors: Haines Daniel W. , Chang Nagyoung , Thompson Donald A.
Published: October 2005

A modern composite top plate has been installed in an otherwise conventional acoustic guitar. The design principles were essentially those proposed for wood substitutes by Schelleng [J. Acoust. Soc. Am. 35, 326–338 (1963)]. A graphite-epoxy was selected for its very high stiffness-to-weight ratio and its ability to achieve the orthotropic symmetry of a spruce plate. Further control was provided by the use of a low-density core. Tests indicate this sandwich plate construction closely matches the areal density, principal bending stiffnesses, and damping of a finished spruce plate. Attachment of the plate to the body has posed some difficulties, but the results of this first attempt are promising. A demonstration of this instrument will be given. [Supported by the National Science Foundation. Assistance from C.M. and M.A. Hutchins and J.C. Schelleng. Materials supplied in part by Hercules Inc.]
Generation of harmonics associated with amplitude-dependent damping
Authors: Mason W. P. , Jon M. C. , Beshers D. N.
Published: October 2005

Internal friction and harmonic generation have been studied at 22.5 kHz and very high strain amplitudes ε in samples of annealed and deformed α-brass. The observations of Q−1 and An, the amplitude of the nth harmonic, suggest several regions of behavior as a function of ε. In the first, Q−1 is independent of ε, and only A2 can be observed, proportional to ε2. At higher ε, A3 and A5 were also observed, but A4 was not detected. At small deformation the next region, hysteresis, has Q−1 rising to a maximum and then decreasing slightly; concurrently, An goes as εnm, where m2 = 2, and 2< (m3, m5) <3, all passing through maxima at somewhat different values of ε. The next region, plastic, has 3 ⩽ mn n = 2, 3, 5. At large deformations, the hysteresis region decreases with increasing deformation, with the plastic region moving to smaller ranges of ε, thereby obscuring the maxima. In both the hysteretic and plastic regions, the harmonic generation—acoustic emission—is proportional to the internal friction Q−1. [Supported by the Army Research Office, Durham, North Carolina.]
Numerical procedure for calculating finite-amplitude distortion in a one-dimensional standing wave
Authors: Van Buren A. L.
Published: October 2005

A numerical procedure is developed to calculate the one-dimensional, finite-amplitude standing wave produced between a source vibrating with a given particle-velocity time profile and a boundary of known impedance. The method is based on a theoretical model that stepwise calculates the behavior of a progressive wave under the combined effects of nonlinearity and absorption (with possible dispersion). In addition, two assumptions are made: (1) that oppositely directed waves do not interact, and (2) that reflection from the impedance boundary is a linear process. The resulting standing wave builds up to a stable configuration by multiple transits between the vibrating source and the impedance boundary. Although the present computer program is limited to preshock conditions, use of weak-shock theory to describe propagation when shocks exist may extend the program's range. A comparison test of this procedure is made with a completely different procedure developed by Coppens and Sanders [J. Acoust. Soc. Am. 51, 154(A) (1972)], which accurately predicts the preshock behavior near resonance In a gas-filled, rigid-filled, closed tube. Results are in excellent agreement. [This work was supported by the Naval Ship Systems Command.]
Simple model for describing the interaction of infinitesimal and finite-amplitude waves
Authors: Pridham Roger G.
Published: October 2005

A phenomenological model is given that approximately describes the interaction of infinitesimal and finite-amplitude waves in a viscous medium. The model, which represents the interaction as a modulation process, can treat realistic propagation eases, including spreading and nonlinear attenuation. For the parametric receiver, the model gives the correct expressions for arbitrary pump propagation (including the nearfield of a source) with nearfield and farfield signals. When applied to the problem of sound absorption by sound, the model yields the induced attenuation coefficient given by Westervelt [P.J. Westervelt, J. Acoust. Soc. Am. 53, 384(A) (1973)] for the case of an infinitesimal wave propagating in an intense isotropic noise background.
Measurement of enhanced nonlinear radiation in the presence of microbubbles
Authors: Clynch James R. , Rolleigh Richard L.
Published: October 2005

In a 60 × 15 7-ft tank, microbubbles were produced by acoustic cavitation with a cylindrical transducer. A sound beam from another transducer was focused inside the cavitating region with a lens. This beam contained primary frequencies of 190 and 195 kHz. The difference frequency at 5 kHz was measured at several positions and angles. Near the axis of the primary beam, the 5-kHz signal was 20 dB higher with the bubbles present than with them absent. The secondary radiation appeared to be omnidirectional when the bubbles were present. The maximum source level observed at 5 kHz was 149 dB re 1 μPa at 1 m. This was achieved with primary pressures of 231 and 234 dB re 1 μPa. The bubbles were contained in a volume of 2 cm3. The relative volume in the bubbles was 2 × 10−5. With the 190-kHz pressure constant at 231 dB re 1 μPa, the 5-kHz signal was observed as the 195-kHz pressure was varied. Saturation was observed at the higher pressures. [This work was supported by Naval Coastal Systems Laboratory.]
Lateralization with monaural maskers
Authors: Zurek P.
Published: October 2005

Experiments were performed to determine the effectiveness of several types of masking waveforms in disrupting lateralization performance. Subjects were required to discriminate a change in the interaural phase of a 1000-Hz tone in the presence of a monaural masker. Both the binaural signal and the monaural masker were gated simultaneously together for 500 msec. Psychometric functions relating percent-correct and interaural phase where obtained in a 3AFC procedure. The experimental variables were the frequency and level of the masking tone. The plot of masker level required for a constant interaural phase sensitivity as a function of masker frequency closely resembled the typical monaural masking pattern. Additional experiments were performed using wide-band noise as the masker. In this case, reducing the level of the signal to a few decibels above masked threshold did not increase the interaural phase threshold above that obtained with no masker. Lateralization was also tested with noise of various bandwidths. Only when the bandwidth of the noise was extremely narrow (less than approximately 50 Hz) did lateralization performance deteriorate.
Binaural interaction in cat and man. III. Interaural noise correlation and signal detection
Authors: Langford Ted L. , Geesa Ben H.
Published: October 2005

This is the third in a series of studies designed to determine similarities and differences in binaural processing at the psychophysical level, between cat and man. The present experiment is concerned with the detectability of a 500-Hz signal, in phase at the two ears, masked by a wide-band noise. The interaural noise correlation was varied by changing the relative contributions of three independent noise sources—one led to the right ear, one to the left ear, and one common to both. The stimuli were presented to the cats via small transducers mounted in leather helmets (Robinson and Wakeford, 1973) and to the human subjects via the same transducers mounted in headsets. The data show a smaller binaural release from masking in cat than in man. Data at each value of correlation are compared with those obtained by another method of varying noise correlation (Langford and Hoppe, 1973). [Supported in part by the National Science Foundation.]
Evidence for binaural representation in the dorsal medullary nucleus of the bullfrog (Rana catesbeiana)
Authors: Feng A. S. , Capranica R. R.
Published: October 2005

Metal microelectrodes were used to record the activity of single cells in the dorsal medullary nucleus of the bullfrog (Rana catesbeiana) in response to acoustic stimulation of each ear independently. Electrode tracks were identified histologically. Among the 124 units that were isolated, 56% of them were responsive to stimulation from one ear alone. The majority of these monaural cells could be excited only by ipsilateral stimuli. The binaural cells consisted of two types. One type, comprising about 20% of the binaural units, could be excited by either ear. The neural latency was approximately the same for the two ears. The remaining 80% of the binaural units comprised the second type, which could be excited by one ear and inhibited by the other ear; the majority of these units were excited by the contralateral ear. The frequency to which a binaural unit was most sensitive (excitation or inhibition) was almost identical for the two ears. Cells that could be driven by the contralateral ear were generally found in the ventral part of the dorsal nucleus, whereas cells driven by the ipsilateral ear were usually located in the dorsal part of the nucleus. [Supported by NIH Grant NS-09244.]
Binaural interaction in single units of the chinchilla auditory cortex
Authors: Benson D. A. , Teas D. C.
Published: October 2005

The relative strengths of contralateral and ipsilateral acoustic stimulation on the discharge rate of single units in the chinchilla auditory cortex were systematically compared for various monaural and binaural stimulus conditions. Recordings were obtained from 133 single units in chinchillas immobilized by gallamine triethiodide. Although all units could be shown to be affected by both contralateral and ipsilateral stimulation, unit thresholds for contralateral stimulation were lower and more discharges were elicited than for ipsilateral stimulation over a range of intensities from unit threshold intensity to 80 dB SPL. Binaural stimuli presented over a range of interaural intensity and phase differences also revealed the predominance of contralateral influence on unit responsiveness. A greater number of discharges was elicited for stimuli more intense at the contralateral than ipsilateral ear (62% of the units) or that were leading in phase at the contralateral ear (61% of the units). For all units responsive to click stimuli, the strongest discharge occurred for contralateral-leading stimuli. The predominance of contralateral input for cortical single units is consistent with results obtained from studies of the cortical evoked response and of auditory performance following unilateral cortical ablations.
Muscular control of incoming acoustic signals in the auditory system of bats
Authors: Suga N. , Jen P. H.
Published: October 2005

Intense sounds which most frequently stimulate an animal's ears are self-vocalized signals, so that the animal should have mechanisms for attenuation of self-stimulation. With Myotis lucifugus having highly developed middle-ear muscles (MEMs), we studied the MEM activity synchronized with vocalization and the acoustic MEM reflex and found the following. (1) Both the stapedius (SM) and tensor tympani (TM) muscles discharged action potentials at least 6.1 and 4.2 msec prior to vocalization, respectively. The MEMs thus started to contract at least 4 msec prior to vocalization and reached the maximum contraction during vocalization. The amount of attenuation was more than 20 dB at 20 kHz. The complete relaxation occurred between 2 and 8 msec after vocalization. Since the shortest contraction time observed was 6.8 msec, the MEMs can theoretically contract at rate of 150/sec without fusion. The critical rate for the complete tetanus of the SM was 250/sec. (2) In terms of the EMGs, the shortest latency of the MEM reflex was 3.6 msec for the SM and 4.2 msec for the TM. Its minimum threshold was 20 dB SPL for both the muscles. All tuning curves of single SM fibers were very broad. (3) In terms of muscle contraction, the shortest latency of the MEM reflex was 5. 8 msec. [Supported by NSF Grant GB-40018.]
Ontogeny of bat sonar: paired FM signalling
Authors: Woolf Nigel Keith
Published: October 2005

Throughout the animal's life, starting as early as age three days, the big brown bat (Eptesicus fuscus) produces pairs of tonal, frequency-modulated (FM) vocalizationS. The interpulse interval (i.e., the interval from the beginning of one signal to the beginning of the next signal) within pairs is on the order of 20–40 msec. Depending on the age of the infant, the two signals of the pair differ in duration, initial frequency, terminal frequency, degree of FM, and harmonic content. Both communication and echolocation FM signals exhibit the same paired temporal pattern. When used in echolocation, the paired signals occur during the approach phase. The transition from the approach phase to the terminal phase of echolocation is indicated by the production of FM signals with interpulse intervals shorter than those within pairs. This vocal transition supports the view that the inferior colliculus, in which a very significant number of neural units have slow recovery times of the order of the interpulse interval within pairs, is primarily responsible for information processing during the approach phase of echolocation, but not during the terminal phase, when presumably lower auditory centers process information.
Recognition of synthetic vowels with altered formant frequencies
Authors: Ahumada A. , Kaiwi J.
Published: October 2005

Vowels were synthesized with all three formants either shifted up by a factor of 9/8 or down by a factor of 7/8. For the seven vowels /i/, /a/, /æ/, /e/, /ɛ/, /u/, and /U/, these eight variants and the original were synthesized and the 63 sounds taped in two random orders. Thirty introductory psychology students listened to each sound and checked one of seven categories—“ay,” “ee,” “ah,” “aa,” “eh,” “oo,” or “uh.” The original sounds /i/, /a/, /u/, /U/, and /ɛ/ were recognized accurately, as in a previous study involving only the original sounds, but in the presence of all the variants both the /e/ and /æ/ sound were called “eh.” We expected that the variants in which all three formants went up and all three went down would be the variants classified most like the original vowels, since the ratios of the formants would be left unchanged. The results showed that the variant in which all formants were increased was the most like the original, but that the variants in which all of the formants were decreased were rated less like the original than any of the other variants.
Test of differentiation of phonemic feature contrasts
Authors: Mitchell Patricia D.
Published: October 2005

A new CVC multiple-choice articulation test was developed for use in phoneme and feature confusion analyses. The phoneme differentiation test consists of 200 test items: four tokens each of 22 initial consonant contrasts, 13 final consonant contrasts, and 15 syllable nucleus contrasts. The major difference between the phoneme differentiation test and previous closed-response tests is that for each stimulus word the alternatives were designed to provide contrasts in only one phonemic feature at a time. Thus the set of contrasts for each stimulus is different from the set of contrasts for every other stimulus. Voicing, nasality, manner, and place are contrasted for consonant stimuli. Place, openness, and intrinsic duration are contrasted for vowel stimuli. The test was given to a sample of hypacusic listeners, and was applied in low-pass filtering experiments with normal-hearing listeners. The findings for both clinical and experimental groups are in general agreement with those of previous studies. Several findings in the present study support the theory that phonemes are confused one feature at a time. Applications of this test and the minimal-contrast technique it employs are suggested.
Human versus monkey discrimination of the /ba/ /da/ continuum using three-step paired comparisons
Authors: Sinnott J. M.
Published: October 2005

Human versus monkey discrimination along an eight-step synthetic /ba/ /da/ continuum was tested, using a procedure in which the subject was required to release a response key in the presence of a stimulus change from a repetitive /ba/ towards /da/, or vice versa. Probability of response data indicated that humans were better discriminators of three-step pairs than the monkeys. This measure, however, did not indicate “categorical perception” in humans, since intraphonemic pairs were sometimes equal in discriminability to interphonemic pairs. Latency was a better indication of “categorical perception” in humans, since interphonemic pairs were always more quickly reacted to than intraphonemic pairs. Latency data furthermore indicated that the phoneme boundary shifted for the humans, depending upon whether a particular stimulus pair had been preceded by repetitive /ba/ or /da/: the shift was in the direction of the preceding stimulus. After the shift had occurred, a comparison of human and monkey latencies revealed that monkeys were relatively faster than humans in discriminating within the phoneme category, but relatively equal to humans in discriminating across the phoneme boundary. These interspecies comparisons lead us to believe that categorical perception for humans is reflected in this procedure not by the loss of the ability to discriminate in the phoneme category, but by a delay necessary to effect the discrimination. [Research supported by grants from NIH and the University of Michigan.]
Sweep-tone vocal-tract spectra driven by an internal source
Authors: Wood C. A.
Published: October 2005

This paper was a one subject replication of the Fujimura and Lindquist study [J. Acoust. Soc. Am. 49, 541–556 (1971)] that measured vocal-tract transfer characteristics, except that instead of a transcutaneous external source, an internal source placed near the vocal folds was used. This internal artificial signal was generated using a locally modified Brüel & Kjaer model 4219 Artificial Voice. This transducer is encased in a container supplied with a conical throat connected to a 5-mm-diameter, 20-cm-long nasal catheter. This catheter was inserted through the nasal cavity to a point just above the glottis. An amplitude compressed and compensated sweep tone from 100 to 5000 Hz was used. The resulting articulated output was analyzed as a function of frequency using a high-speed pen recorder. Most of the articulations, as well as open and closed glottal conditions, studied by Fujimura and Lindquist were used in the present study and are compared and discussed.
Terminal analog synthesis of French
Authors: Tzeutschler H. S.
Published: October 2005

Tables for the synthesis of French segmental phonemes were successfully created using the Mattingly-Holmes algorithm. While some of the phonemes, such as the fricatives, were borrowings from the General American Tables (developed by I.G. Mattingly, G. Kuhn, and others), with Might modifications, most other phonemes represent considerable modifications. A combination of spectrographic data and data from the literature on acoustic correlates to spoken French was used. Among the interesting facts which surfaced were two. The French /r/, traditionally classified as a liquid, sounded most natural if synthesized similarly to a velar fricative. The synthesis of nasal vowels, hindered by the absence of nasal formant generators, was made effective by a cutback of first ferment amplitude and considerable modifications in the second and third formant frequencies relative to their so-called “hemorganic” counterparts.
Speech synthesis of Finnish by rule
Authors: Nearey Terrence M.
Published: October 2005

The Holmes-Mattingly algorithm (as modified by Kuhn) has proved to be adequate for the synthesis of intelligible speech in several languages besides English. The synthesis of Finnish by rule has been accomplished by means of relatively straight-forward modifications of the user-supplied rules tables previously developed for English. Accepting as input a character string that is essentially isomorphic with Finnish orthography, the system produces synthetic speech of acceptable quality on the University of Connecticut's Glace-Holmes parallel resonance synthesizer. Certain general properties of the system are explained and strategies adopted in the solution of specific problems in the synthesis of Finnish are discussed. Prominent among the latter are total ferment assimilation of [h] and recursive synthesis of trilled apical [r]. A brief demonstration tape will be played.
Surface-duct propagation loss versus frequency and depth
Authors: Cummins James
Published: October 2005

The mixed surface layer of the ocean forms a duct for propagation of underwater sound. Recent unique measurements are used for the first time to present a comprehensive concept of surface-duct propagation loss, with novel comparisons between theory and experiment at frequencies from 0.4 to 10.0 kHz. For a sound source in the mixed layer, surface-duct propagation loss is described versus acoustical frequency and receiver depth, at various horizontal ranges. Similar to a bandpass filter, the surface duct has a low-frequency cutoff due to leakage out of the duct, a high-frequency rolloff caused by surface scattering and attenuation, and characteristics that vary with receiver depth. The cutoff frequency is primarily a function of the mixed-layer depth and the in-layer sound-speed gradient. Versus receiver depth, propagation loss is minimum usually well within the mixed layer, with greater loss near the ocean surface and the themocline, but the prominent features shift with frequency. Background information was given at the 84th and 85th Meetings [Papers W4, W5, and B4, J. Acoust. Soc. Am. 53, 332(A) (1973); 54, 269(A) (1973), respectively].
Convergence zone propagation in the North American Basin
Authors: Shaffer J. D. , Guthrie A. N. , Fitzgerald R. M. , Nutile D. A.
Published: October 2005

The long-range propagation of explosive signals and of 14- and 111-Hz CW signals were studied experimentally. The tow ran from a point near Antigua to the Grand Banks, a distance of about 2800 km. The detonations were shallow and nearly equispaced. The CW sources were towed at shallow depths and operated without significant interruptions. The signals were received on a sound channel hydrophone near Antigua. Graphic records of the explosive signatures were aligned to produce a three-dimensional plot of the rectified acoustic pressure as a function of range and time. This arrangement of successive recordings shows the arrival patterns in an easily identifiable form, The pattern produced by the highest peak pressure, the RSR arrivals, repeats at convergence zone intervals and persists over the entire range. Analysis of the 14-Hz signal envelope shows well-defined convergence zones out to 2800 km, while the 111-Hz signal envelope shows them to only 2000 km. The locations of convergence zones are different for the two frequencies.
Fluctuations of waves propagating in a random medium
Authors: Wenzel Alan R.
Published: October 2005

A theoretical analysis of wave propagation in a one-dimensional random medium is presented. A two-variable perturbation method is used to study the incoherent (or randomly fluctuating) component of the wave field. Approximate expressions are obtained for both the correlation function of the incoherent wave and the variance of the wave field. It is shown that the two-variable method avoids the secular terms which appear in corresponding expressions obtained using standard perturbation methods, such as the Born approximation.
Single-scattering limit of the stochastic ray theory result
Authors: Neubert J. A.
Published: October 2005

The stochastic Helmholtz equation is expressed by an outer expansion of its rms refractive variation. The two-term outer expansion is shown to be the conventional Born or single-scattering approximation. This Eulerian sound propagation relation is systematically analyzed from a physical point of view to provide a basis for comparison with the stochastic ray theory result. Single scattering is then imposed on the comparable ray theory result, which reduces its Lagrangian form to the Eulerian form of the other result. Since the free-space Green's function then appears, the volume integral gives the (Eulerian) Born approximation as the single-scattering limit of the stochastic ray theory pressure relation.
Ray diffusion in a randomly inhomogeneous ocean
Authors: Weinberg H. , Mellen R. H.
Published: October 2005

Sound channel attenuation measurements reveal a component of loss that is independent of frequency and apparently caused by volume scattering. Diffusion constants calculated from ray diffusion theory show order-of-magnitude agreement with values estimated from perturbation in sound-speed profiles. A random-walk ray program based on ray diffusion theory has been devised to study the interaction between regular and random variations in index of refraction. Several illustrative examples of random ray tracing and intensity calculations are presented.
Coherence function for cylindrically spreading waves in a random medium
Authors: Fitelson M. M.
Published: October 2005

The coherence function for a cylindrically spreading wave in a random medium is obtained as the exact solution of an equation derived from the wave equation when forward scattering is dominant. The region of validity for this equation is obtained under the assumption that the index of refraction is a Gaussian field. It is shown that the region of validity for this equation extends far beyond the region where the random effects just begin to become significant, where one expects a Rytov or perturbation solution to become invalid. The coherence function for cylindrically spreading waves is compared with the corresponding solution for the plane wave case. Both the cylindrical and plane wave solutions are shown to have essentially the same range of validity.
Amplitude fluctuations of the sound from a low-frequency moving source in the deep sea
Authors: Urick R. J. , Tulko T. J.
Published: October 2005

The sound from a steady source in the sea fluctuates in amplitude on reaching a distant receiver. One way to express the fluctuation is by means of its power spectrum, normalized to the mean level of the carrier frequency. Such spectra have been obtained for 3-min samples of the signals from 142- and 275-Hz CW sources towed together in range as far as the first convergence zone from Sonobuoy hydrophones at 90 and 300 ft. At all ranges and at both depths, the spectra in the band 0.01− 0.5 Hz (periods 2−100 sec) show a broad peak near 0.1 Hz. The integral under the spectrum, equaling the square of the modulation coefficient, ranges from less than 1% to about 50%, with a strong dependence on carrier level. That is the fluctuation is low when the mean level is high, and vice versa, so that the fluctuation power tends to be constant. The results indicate that the observed fluctuation with primarily bottom-bounce propagation is the result of multipath interference effects of ocean waves, along with, at longer periods, sub-bottom penetration of the sound from the moving source.
Low-frequency acoustic coherence in the deep ocean
Authors: Fitzgerald R. M. , Guthrie A. N. , Shaffer J. D. , Nutile D. A.
Published: October 2005

Measurements made at long ranges of CW signal coherence in the direction of propagation are presented. The observed range dependence is explained using wave model calculations. Predictions of coherence in the vertical coordinate, depth, are also presented. Implications are made concerning spatial coherence in the coordinate transverse to the propagation direction.
Use of nonuniform liners as sound suppressors
Authors: Vaidya P. G. , Ridd J.
Published: October 2005

It is desirable in many practical situations to design a liner for a duct while maintaining the shape of its cross section intact. When these cross-sectional areas are large, a lot of the acoustical energy could stay unaffected by the wall treatment. Experimental results are presented which indicate that this problem might be remedied by means of an axially nonuniform treatment of the duct. In the case of an exponentially lined duct, some evidence that sound energy would flow away from the center of the duct is obtained. Also included in this paper is a theoretical discussion supporting the possibility of the modal conversion in presence of nonuniform liners. [Work partly supported by NASA Lewis.]
Design of an experimental facility for sound propagation studies
Authors: Vaidya P. O. , Sullivan J. , Shashaani R.
Published: October 2005

A multipurpose sound propagation analysis facility has been built at the Herrick Laboratories of Purdue University. The main purpose of this facility is to carry out basic studies related to the area of multiple pure-tone sound radiation from supersonic rotors. Spinning modes are generated by use of eight speakers, whose input is monitored to obtain a desirable phase relationship. Sound transmission, with or without flow, can be analyzed in the case of a hollow cylinder or various annular cylinders. The case of conversion from an annular to a hollow cylinder could also be studied. An anechoic termination simulates the very long duct case and it could be removed to study the finite-length case. Radial and axial traverses are used and correlation technique is used to obtain circumferential information. The test section could be lined with various absorbents. The paper also discusses possibilities of future modifications of the facility. [Work supported by NASA Lewis under Grant No. NAS 3-18010.]