bluuebunny/crossref_metadata_2025 huggingface dataset:
The acoustic behavior of dolphins echolocating in the presence of white noise
Authors: Au Whitlow W. L. , Penner Ralph H. , Kadane James
Published: October 2005

An acoustic click detector was used in conjunction with a microprocessor to monitor two dolphins performing a target detection task in the presence of white noise. The psychophysical experiment involved the detection of a 7.62-cm sphere located at a range of 16.5 m from the animals. From the acoustic data, the number of clicks, the click interval and its distribution, the response latency and the total latency as a function of the masking noise level were determined. The average number of clicks emitted per trial increased as the masking noise level increased to 77 dB re 1 μPa/Hz after which the number of clicks decreased with further increases in the noise level. Dolphin E also did not emit any detectable clicks during 10% of the trials at 82 dB and 41% at 87 dB, while dolphin H did not emit any detectable clicks in 14% of the trials at the 87-dB noise level. The response latencies for correct rejections were always greater than for correction detections at all noise levels for both dolphins. The click interval results indicated that the animals seem to have good control of the click intervals used in a click train, and may preprogram a desired click interval even before starting on an echolocation search, based on prior knowledge of the target range.
Directional hearing sensitivity of the bottlenosed dolphin (Tursiops truncatus) in the vertical plane
Authors: Moore Patrick W. B. , Au Whitlow L.
Published: October 2005

The ability of the dolphin to detect pure tone signals presented from directly ahead, with noise presented from various vertical angles was determined behaviorally for pure tone frequencies of 30, 60, and 120 kHz. The animal's position at the centerpoint era 3.5-cm arc was fixed by requiring firm contact on a biteplate. Using a yes-no response procedure, vertical directional sensitivity was examined by varying the noise levels and determining masked thresholds via a tracking method of stimulus presentation. Polar plots of the threshold points for the three frequencies generally showed a narrowing of receiving beam patterns with increased frequency. Maximum sensitivity occurred between five and ten degrees above the midline of the mouth. Sensitivity dropped more sharply with increasing angle above the midline rather than below, as might be expected with an animal that hears via the lower jaw. These receiving beam patterns show close agreement with the echolocation pulse transmitting beam patterns reported by Au, Floyd, and Haun [J. Acoust. Soc. Am. 64, 411–422 (1978)]
The effect of a forward fringr on the Masking-Level Difference
Authors: Yost William A.
Published: October 2005

The Masking-Level Difference (MLD) for a pulsed signal and masker may be less than that obtained with a continuous masker [D. McFadden, J. Acoust. Soc. Am. 40, 1414–1419 (1966)]. A noise fringe presented before the pulsed signal-plus-masker can increase the size of the MLD. In the present study, the signal was a 500-Hz tone presented either in (So) or out (S.) of phase at the ears. The signal and the masker were 17 ms in duration. The masker was a 3000-Hz low-passed filtered, 40-dB spectrum-level noise presented in phase at the ears (No). The interaural parameters, the spectral and temporal characteristics, and the level of the forward fringe were varied to determine what aspects of the fringe are effective in producing large MLDs. In general, the MLD is largest when there is a large difference between the interaural values of the fringe and those of the signal-plus-masker in conjunction with a small difference between the interaural values of the fringe and those of the masker alone. The results will be discussed in terms of the dynamics of binaural processing. [Work supported by NSF.]
Interactions within combinations of click maskers
Authors: Stanny R. R. , Elfner L. F.
Published: October 2005

Under a variety of circumstances, a combination of a forward and a backward masker (or two or three forward maskers) will elevate a probe's threshold intensity more than the sum of the elevations produced by the individual maskers. At least in forward masking, this does not occur when sets of brief maskers are presented with short intermasker silent intervals [Penner, J. Acoust. Soc. Am. 68, 455–457 (1980)]. We carried out an experiment using combinations of 0.1-ms click maskers with onsets placed 2.5, 1.5, and 0.5 ms prior to and after a 0.1-ms probe click's onset. The maskers were equated for effect by finding the level of each that masked an approximately 15-dB SL probe. All subsets of forward and all subsets of backward maskers produced threshold shifts comparable to those produced by single maskers. By contrast, all subsets containing one forward and one backward masker produced masking exceeding the individual maskers' summed effects. Thus for these conditions, forward and backward masking indeed seem to have different sources, and nonadditivities that depend on different mechanisms.
Forward masking with combined sinusoidal and noise maskers
Authors: Neff Donna L. , Jesteadt Walt
Published: October 2005

Masked thresholds as a function of masker level were obtained for three normal listeners using a 400-ms, 1000-Hz sinusoidal masker or a 400-ms, narrowband noise masker (60-Hz centered at 1000 Hz). The signal was a 30-ms, 1000-Hz sinusoid, which followed masker offset by 2 ms. The noise masker consistently yielded a steeper slope of masking than the sinusoid for all listeners. These growth-of-masking data were used to equate the noise and sinusoidal maskers in terms of the amount of forward masking produced. Masker levels expected to produce 10, 20, 30, 40, or 50 dB of forward masking were selected. When the equated noise and sinusoidal maskers were combined in forward masking, no additional masking above that predicted by energy-based detection (3 dB) was found. This contrasts with analogous conditions in simultaneous masking, where considerable additional masking was obtained. [Work supported by NIH and NSF.]
A comparison of psychophysical tuning curves obtained in forward, backward, and combined forward-backward masking
Authors: Dye Raymond H. , Yost William A.
Published: October 2005

Psychophysical tuning curves were measured under conditions of forward, backward, and combined forward-backward masking of a probe tone of 1000 Hz presented at 10 dB SL. The duration of the probe was 30 ms and was gated with a 10-ms rise-decay time. The frequency of the masker ranged from 600 to 1200 Hz, and its total duration was 200 ms (for combined forward-backward masking, both the forward and backward maskers were 100 ms). The interval between the probe and the masker was 0.1 ms. The level of the probe was held constant, while the level of the masker yielding 71% correct was estimated by using a two-interval two-up, one-down technique. Comparing the functions across masking conditions showed that those obtained under forward masking tended to be the most sharply tuned, followed by those obtained under combined forward-backward and backward masking. However, extreme caution should be used in interpreting these results because of large inter-subject variability, with one subject (of seven) showing sharpest tuning in combined forward-backward masking and another showing sharpest tuning in backward masking. [Work supported by grants from NSF.]
Intensity discrimination as a function of level and frequency and its relation to high-frequency hearing
Authors: Florentine Mary
Published: October 2005

In the first of two experiments, intensity difference limens (DLs) for pulsed tones were measured as a function of level at 1 and 14 kHz in five normal listeners. In the second experiment, thresholds from 6 to 20 kHz and DLs at 1 kHz were measured in 12 normal listeners. For both experiments, the stimuli were 500 ms with an interstimulus interval of 250 ms. A 2I, 2AFC procedure with feedback was used. The DLs for the 1-kHz tone decrease from about 2.5 dB at 3 dB SL to about 0.5 dB at 93 dB SL, whereas the DLs for the 14-kHz tone stay relatively constant around 2.5 dB at all levels. Moreover, DLs at high levels are correlated (r = −0.69) with the minimum frequency above 6 kHz at which threshold exceeded 80 dB SPL (i.e., the better the high-frequency hearing, the lower the DL). These results are consistent with the multi-band version of the excitation-pattern model for intensity discrimination [Florentine and Buus, J. Acoust. Soc. Am. Suppl. 1 67, S22 (1980)] [Work supported by NIH.]
Combinations of the TOE constants of the fluoroperovskites CsCdF3 and KZnF3 measured as a function of temperature
Authors: Philip Jacob , Breazeale M. A.
Published: October 2005

We have examined the nonlinear behavior of the fluoroperovskites CsCdF3 and KZnF3 which are known to exhibit similar linear elastic behavior. The temperature variation of some combinations of the third-order elastic (TOE) constants have been measured as a function of temperature using the ultrasonic harmonic generation technique. Measurements have been made from room temperature to 77°K. It is observed that the constant C111 shows a higher temperature variation than it does in other cubic crystals such as copper or silicon. Between 300° and 77°C, C111 changes by 8.5% for CsCdF3 and 23.5% for KZnF3. The combination (C112 + 4C166) does not vary much with temperature, whereas the combination (C123 + 6C144 + 8C456) has a very high (negative) value and a peculiar temperature dependence, showing that these compounds are far away from being solids for which a central, nearest-neighbors model would be appropriate. [Research sponsored by the Office of Naval Research.]
Scattering of a cw plane wave by a pulse
Authors: Trivett D. H. , Rogers Peter H.
Published: October 2005

An examination of the scattering of sound by sound indicates that the boundary of the interaction region is very important in determining not only the level of the scattered sound but also the frequency of the scattered sound. In the case of a pulse propagating through a cw plane wave (where the boundary of the interaction region is propagating at the sound speed) the frequency of the farfield scattered radiation at a fixed angle is the cw frequency, Doppler shifted i.e., fs(θ,φ) = fcw[(1-cos θ)/(1-cos φ)], where φ is the angle between the cw wave vector and the pulse wave vector and φ is the observation angle with respect to the pulse wave vector in the interaction plane. The scattered signal has a strong maximum at the Doppler angie φd, where the scattered signal is equal to the sum frequency. The scattered signal at φd observed at a finite distance from the interaction region thus appears as a pulse whose frequency sweeps from a value somewhat above the sum frequency to a value somewhat below the sum frequency. Previous detection of sum frequency in a crossed beam experiment has been attributed by Westervelt [J. Acoust. Soc. Am. 29, 199 (1957)] to “pseudo-sound,” the interaction of the primary beam's side lobes at the face of the transducer. Positive results from a pulse-cw experiment exhibiting the predicted frequency dependence would unambiguously demonstrate the existence of scattering of sound by sound.
Some possible relations between cochlear neural responses and mechanical parameters of the organ of Corti
Authors: Zwislocki Jozef J. , Kletsky Earl J.
Published: October 2005

At preceding meetings we showed that a model of cochlear mechanics, which includes a resonance of the hair-cell stereocilia loaded with the tectorial membrane, can simultaneously account for the observed typical response characteristics of the basilar membrane and of the cochlear-nerve fibers. In this paper we demonstrate that the low-frequency radial displacement magnitude of the tectorial membrane relative to that of the reticular lamina at the location of the inner hair cells can not only determine the phase of the low-frequency fiber responses but also the shape of the neural tuning curves. Specifically, the shape of tuning curves encountered in Mongolian gerbils is associated with a scala-tympani excitatory response phase, in agreement with experimental evidence. A few tuning curves of cat fibers suggest an opposite polarity. This seems to be more generally true after kanamycin treatment. Effects of stereocilia and tectorial membrane damping are also investigated.
Modulation of the evoked response in primary auditory neurons by low-frequency tones
Authors: Patuzzi Robert , Sellick Peter , Johnstone Brian M.
Published: October 2005

Period histograms of the evoked activity from the cells of the guinea pig spiral ganglion were collected in response to a 40-Hz sinusoid plus a high-frequency tone corresponding to the characteristic frequency (CF) of the cells (13–16 kHz). Period histograms were synchronized to the 40-Hz tone. Phase of the 40-Hz motion of the basilar membrane was inferred from cochlear microphonic. At moderate intensities of the 40-Hz tone (80–90 dB SPL), suppression of the CF response was observed for basilar-membrane displacements towards scala tympani and potentiation towards scala vestibuli. For higher 40-Hz intensities (90–100 dB SPL), suppression of the CF response was observed for displacements of the basilar membrane towards scala tympani and also for maximum displacements towards scala vestibuli. Potentiation was still observed for moderate displacements towards scala vestibuli. For even higher intensities of the 40-Hz tone, the neural response to the 40-Hz tone predominated. Such modulation is observable for high-frequency tones of frequency greater than 1 octave below CF. For frequencies lower than this, no modulation was observed. [Work supported by the National Health and Medical Research Council.]
Sound absorption in a 0.02 M MgSO4 solution and in a 0.02 M MgSO4-0.6 M NaCl mixture at 25°C and pressures up to 307 arm
Authors: Hsu C. C. , Fisher F. H.
Published: October 2005

Sound absorption from 30 to 300 kHz in a 0.02 M MgSO4 aqueous solution and in a 0.02 M MgSO4−0.6 M NaCl aqueous mixture were measured at pressures of 1 and 307 atm and 25°C with a 100-liter titanium spherical resonator. Assuming a single relaxation process for both solutions, measured data were analyzed for the values of the maximum absorption per wavelength, (αλ)m, and of the relaxation frequency, fr. The fr values are 149 kHz for the pure solution and 162 kHz for the mixture. Slight decreases of fr values with pressure were shown in both solutions. (αλ)m values decrease linearly with pressure according to the equation of (αλ)m(P) + (αλ)m(o)(1-aP), where P is in atmg and a = 6.4 × 10−4/atmg for pure solution and 6.5 × 10−4/atmg for mixture. These pressure coefficients are nearly the same as that in the sound absorption-equation for seawater for Schulkin and Marsh [J. Acoust. Soc. Am. 34, 864 (1962)] but 21% smaller than that measured in Lyman and Fleming seawater [Hsu and Fisher, J. Acoust. Soc. Am. Suppl. 1 69, S48(1981)] and 38% smaller than that in 0.5 M magnesium sulfate solution [Fisher and Simmons, J. Acoust. Soc. Am. 62, 558 (1977)]. [This research was supported by ONR, NSF and ARPA.]
Structural characteristics of the Shuttle Orbiter ceramic Thermal Protection System
Authors: Cooper P. A.
Published: October 2005

The ceramic Thermal Protection System (TPS) consists of ceramic tiles bonded to felt pads which are in turn bonded to the Orbiter substructure to protect the aluminum substructure from the heat of reentry. The successful certification of the TPS for first flight required the joint effort of several NASA centers, the prime contractor, and university consultants led by the TPS system managers from the NASA Johnson Space Center. This paper describes the TPS and addresses the results of some of the experimental work including dynamic response studies performed at the NASA Langley Research Center in support of the efforts to certify the TPS for flight.
Unsteady environments and responses of the Shuttle combined loads Orbiter test
Authors: Schuetz P. H. , Pinson L. D. , Thornton H. T.
Published: October 2005

Separate and combined wind tunnel and vibration shaker tests were conducted on two structural panels representative of the Shuttle Orbiter in the NASA/LaRC 8 ft Transonic Pressure Tunnel to determine the effects of combined loads on the Thermal Protection System (TPS). Objectives of this test were to provide a combined full scale load environment and realistic time history of the dynamic pressures and responses and Mach numbers (through transonic) to these panels. Panels were selected from locations where interactive load sources such as aerodynamic shock waves, turbulent boundary layers, strut-induced vorticity, and substrate deformation combined to provide high bonding loads between the TPS and the Orbiter structure. Test panels were instrumented with static and dynamic pressure gauges, accelerometers, deflectometers, strain gauges, schlieren and high speed photography, and instrumentation necessary to determine SIP/structure interface loads. Two test specimens of each Orbiter panel were utilized. The first panel for each test was utilized to calibrate the tunnel and shaker system and gather data for applied static and dynamic loads. The second panel or each test was subjected to flight time exposures only so that TPS characteristics as a function flight mission exposure could be determined.
Cetacean middle and inner ear morphology
Authors: Norris Jeffrey C.
Published: October 2005

Middle and inner ear structure and function of seven Odontoceti; Tursiops truncatus, Delphinus delphis, Grampus griseus, Globicephela sp., Orcinus orca, Phocoena phocoena, Phocoenoides dalli, and four Mysticeti; Balaenoptera physalus, B. acutorostrata, Balaeana glacialis, and B. mysticetus were investigated. Measured parameters of middle ear morphology include ossicular mass, density, morphology, and lever ratios, tympanic membrane area, and calculations of middle ear impedances. The inner ear structures described and measured include cochlear morphology, basilar membrane length, width, and thickness, and spiral laminae morphology. Correlations are made between basilar membrane length, width, thickness and thickness/width. Greenwood's equations [D. D. Greenwood, J. Acoust. Soc. Am. 33, 1344–1356 (1961)] are used to estimate auditory thresholds using basilar membrane length and elasticity. Verification of this procedure's accuracy is presented. Inner ear examinations were made using surface preparations, cross sectioning, and scanning electron microscopy. These investigations are designed to complement previous studies in other marine mammals and bats. Results are discussed in light of currently accepted cetacean auditory theory with special attention given to low-frequency auditory adaptations in Mysticeti, high-frequency hearing in phocoenids, and ossicular chain function.
Frequency representation and discharge properties of single units in the inferior colliculus of the mustache bat, Pteronotus parnellii
Authors: Pollak G. D. , Bodenhamer R. , Zook J.
Published: October 2005

The biosonar signals of the mustache bat are characterized by a relatively long duration constant frequency (CF) component having a frequency of about 61 kHz, and a brief, downward sweeping frequency modulated portion. In this study we monitored the activity of neurons in the bat's inferior colliculus (IC), directing special attention to the distribution of best frequencies (BF), and the manner in which different BFs are organized within the nucleus. Remarkably, over 50% of the neurons in each bat's IC had almost identical FBs, the variation being only ±150–250 Hz. The frequency that these neurons were tuned to was about 61 kHz, and was the same frequency as that to which the individual bat's cochlear microphonic audiogram was also tuned. Neurons in this over-represented frequency band were distinguished by their very sharp tuning curves, in which the average Q10 dB value was 122, and by the ability to respond to sinusoidally frequency modulated signals with spike trains in tight registry with the phase of the modulating waveform. The sinusoidally frequency modulated signals were designed to mimic the frequency modulations imposed upon the echo CF component by the beating wings of a small insect. These over-represented neurons, having common BFs, common tuning properties, and sharing the ability to phase lock to frequency modulated signals, were found only in the posterior division of the IC, a region that is topographically and cytoarchitecturally segregated from the other divisions of the central nucleus of the bat's IC. [Supported by NIH Grants NS 13276 and NS 00367.]
The role of spectral distribution and decay time in the auditory perception of duration in speech and nonspeech stimuli
Authors: Heuven Vincent J. van , Broecke Marcel P. R. van den
Published: October 2005

In two experiments subjects reproduced the steady state duration (varying between 100 and 450 ms) of various signal types (sine, white noise, sawtooth, synthesized vowel /a/) with abrupt (10 ms) or gradual (50 ms) decay portions. Results indicate that (1)jnd ranges from 20% for short reference durations to less than 10% for longer reference values, (2) jnd is smaller for gradually decaying signals, (3) the duration of abruptly terminating signals is perceived as somewhat longer than that of signals with smooth decays, (4) narrow-band signals are perceived as shorter than wideband signals, and (5) the time order error is a function of both spectral distribution and signal decay characteristic. Implications of this study are that (1) duration discrimination for speechlike signals is more accurate than has hitherto been assumed, and (2) the temporal organization of the acoustic cues to the fortis-lenis contrast in postvocalic obstruents is optimally suited to counteract forward masking effects of the vowel on the following noise burst.
Effects of glottal waveform on the perception of talker sex
Authors: Carrell Thomas D.
Published: October 2005

Glottal volume velocities produced by male and female talkers have been shown to differ from one another in a systematic fashion [R. B. Monsen and A.M. Engebretson, J. Acoust. Soc. Am. 62, 981–993 (1977)] due, primarily, to the relative sizes of the vocal folds. The present study examined the perceptual importance of these differences with an identification task. Subjects were presented with continua of synthetic vowel stimuli, each ranging from male to female in terms of their formant characteristics (based on Fant's k factor) [G. A. Fant, Speech Sounds and Features, 84–93 (1973)]. Half of the stimuli were synthesized with a relatively symmetric source waveform, similar to that of the glottal volume velocity of a female, and the other half were synthesized with a more asymmetric source waveform, similar to that of a male. The subjects' task was simply to indicate for each stimulus whether it sounded as if it were produced by a male or a female talker. The perceptual crossover from male to female along the k-factor continuum occurred at lower values for the stimuli synthesized with femalelike voicing and at higher values for stimuli with malelike voicing. These results demonstrate that glottal source information plays an important role in the perception of the talkers sex. Moreover, the findings open the possibility that the glottal waveform may be an important factor in vowel normalization as well. [Supported by NINCDS grant NS-12179.]
An interactive activation model of speech perception
Authors: Elman Jeffrey L. , McClelland James L.
Published: October 2005

We describe a model of speech perception [based on the Interactive Activation Model of Visual Word Perception (cf. McClelland and Rumelhart, in press; Rumelhart and McClelland, in press)] in which excitatory and inhibitory interactions among nodes for phonetic features, phonemes, and words are used to account for aspects of the interaction of bottom-up and top-down processes in perception of speech. Results from a working computer simulation of this model are presented. Input to the program consists of specifications of distinctive features of speech as they unfold in time. Features, phonemes, and words consistent with the input are activated, missing specifications may be filled in, and slight errors may be corrected so that the “percept” formed by the simulation exhibits such phenomena as phonemic restoration and related perceptual effects. [Work supported by NSF.]
Some acoustical correlates of speech-rate perception
Authors: Bond Ronald N. , Feldstein Stanley
Published: October 2005

A previous study by the authors found that vocal frequency and intensity both influenced the perception of speech rate, and proposed three alternative explanations of the results. They argued that the findings were a function of: a methodological limitation; the exception that if one speech characteristic changes, the others change in a similar direction; or experience with producing and hearing covariation among pitch, loudness, and speech rate in ordinary speech. The present study tested the hypothesis that such covariation does occur in the perception of speech, and assessed the plausibility of the three explanations. Three levels of frequency and intensity were factorially varied within each of three different speech rates, using a 20-s speech segment played backwards to produce the stimuli. Each stimulus was compared with a standard stimulus in terms of four scales—perceived speech rate, pitch, loudness, and duration—by 21 males and 40 females. ANOVAs indicated that frequency and intensity positively influenced the perception of speech rate, pitch, and loudness, and that frequency negatively affected the perception of duration. The results suggest the third explanation above as the most viable.
Speeded classification of natural and synthetic speech in a lexical decision task
Authors: Pisoni D. B.
Published: October 2005

How fast can human observers recognize isolated words? How is the process of word recognition affected by the quality of the initial acoustic-phonetic input in the speech signal? In this paper we report the results of a lexical decision experiment which examined the response times for classification of natural and synthetic word and nonword stimuli. The results showed an overall increase in response time of 145 ms for synthetic stimuli compared to natural speech. In addition, words were recognized 140 ms faster than matched nonword controls. However, there was no interaction between signal type (natural versus synthetic) and classification response (word versus nonword). These results suggest that differences in perception between natural and synthetic speech lie at early stages of perceptual analysis in which the initial phonetic or segmental representation of the input signal is developed rather than at later stages of lexical access and search where these representations are examined or compared prior to execution of the observer's classification response. The findings will be discussed in terms of the extensive use of synthetic speech stimuli in perceptual experiments and its application in voice response systems used in applied settings. [Supported by NINCDS grant NS-12179.]
Capacity demands in short-term memory for synthetic and natural word lists
Authors: Feustel T. C. , Luce P. A. , Pisoni D. B.
Published: October 2005

Two experiments comparing recall for synthetic and natural lists of monosyllabic words were conducted to determine the locus of previously demonstrated perceptual difficulties for synthetic speech produced by rule [D. B. Pisoni and S. Hunnicutt, ICASSP, 572–575 (1980)]. If the perception of synthetic speech demands increased processing capacity in early encoding stages, recall differences between synthetic and natural speech should arise when short-term memory is differentially stressed. In the first experiment three presentation rates (1, 2, and 5 s per word) were used to manipulate the demands placed on short-term memory. Although recall was consistently poorer for the synthetic lists at all presentation rates, the decrement for synthetic stimuli did not increase with faster rates. A similar pattern of results was obtained in the second experiment in which strings of digits of varying length (0, 3, and 6 digits) were presented visually for retention prior to each spoken word list. However, the recall of the digits was considerably worse for the 6-digit list relative to the 3-digit list when the following word lists were synthetic. These results indicate that at least some of the difficulties observed in the perception and comprehension of continuous synthetic speech are due to increased processing demands in short-term memory. [Supported by grants from NIMH and NINCDS.]
Two-tone suppression boundaries of cochlear-nerve fibers in gerbil
Authors: Schmiedt Richard A.
Published: October 2005

The algorithm developed by Kiang and Moxon [J. Acoust. Soc. Am. 55, 620–630 (1974)] to track the isorate response of a single fiber with respect to frequency (tuning curve) was modified to track the lower threshold boundary of two-tone rate suppression (TTRS). In this study automated tuning curves were first determined, after which a continuous tone at the fiber's characteristic frequency (CF) was placed 10 to 15 dB above threshold. Results indicate that suppression boundaries, especially those below CF, are often remarkably similar in absolute threshold for fiber CFs between about 0.6 to 12.0 kHz. Further, the absolute level of the suppression boundary is largely independent of that of the tuning curve and its tail. For example, fibers of similar CFs can have tail thresholds differing by as much as 30 dB yet have essentially the same TTRS contours. These data suggest that the tuning curve is a locally determined phenomenon along the cochlear duct, whereas TTRS is determined more globally and is to a large extent independent of the tuning curve. [Work supported in part by an SC Biomedical Research Grant.]
Temporal representation of CV syllables in populations of auditory-nerve fibers
Authors: Miller Michael I. , Sachs Murray B.
Published: October 2005

Representations of the syllables [ba] and [da] based on the temporal response properties of populations of auditory-nerve fibers were studied. Post-stimulus time histograms and interval histograms were computed from 20-ms segments of fiber spike trains occurring in response to each stimulus. Discrete Fourier transforms with a resolution of 50 Hz were computed from each histogram. As a measure of the response of the population of fibers to each harmonic of the 50-Hz resolution frequency, the magnitude of the response to that frequency was averaged across all fibers whose characteristic frequencies were within one-fourth octave of that harmonic. We have previously called this measure the average localized synchronized rate (ALSR). Response profiles for the 20-ms segments of the stimulus were generated by plotting the ALSR versus stimulus frequency. Time-varying spectral features of the stimulus are well preserved by such profiles. For example, the onset spectra and formant transitions of the stop consonants are well represented. Furthermore, the fine structure in the speech spectrum related to the pitch of the excitation source is maintained in the response profiles derived from PST histograms. [Supported by NIH Grant No. 12112.]
Modes and resonances of finite elastic structures under heavy fluid loading
Authors: Crighton D. G. , Innes D.
Published: October 2005

An asymptotic low-frequency theory is applied to a number of problems involving coupled fluid: structure interactions in finite elastic-plates under heavy fluid loading. Typical problems involve circular or rectangular plates, with a variety of edge conditions and either freely suspended or mounted in a rigid baffle, and excited by concentrated (point force) mechanical drive. It is shown that—with full account taken of fluid loading—such structures have very sharp resonances, whose frequencies and Q can be predicted in simple analytical form. Correspondingly, over most of the plate (i.e., except near the drive point and the plate edges) the motion can be described in terms of modes, whose shapes are slight distortions of the vacuum mode shapes. The drive admittance is studied; it is purely imaginary if small radiation damping is ignored, but may be either masslike or stiffnesslike, may vanish or become infinite depending upon the values of plate and fluid parameters. [Work supported by ONR, Code 222.]
Better acoustic model of the vocal tract
Authors: Maeda Shinji
Published: October 2005

Speech signals were synthesized by assuming plane wave propagations and nonrigid vocal-tract walls. The tract is excited by specifying the time function of the glottal area. A constant air pressure source is assumed. The quality of 11 different French vowels synthesized was excellent in terms of naturalness as well as of intelligibility. It seems that this high quality is primarily due to a better realization of the source-tract interaction, especially the time-varying characteristics of the clottat impedance within each fundamental period. Interestingly the quality of nasal vowels or nasals was not satisfactory. We suspect that a simple acoustic tube is a rather poor representation of the nasal tract. Our theoretical analygig and also experiments by Lindqvist-Gauffin and Sundberg [“Acoustic Properties of the Nasal Tract,” Phonetica 33, 161–168 (1976)], suggests that the sinus shunt cavities within the nasal tract may play an important role in shaping appropriate nasal spectra. Results of simulation experiments will be demonstrated.
Musical pitch of two-tone complexes and predictions by modern pitch theories
Authors: Houtsma A. J. M.
Published: October 2005

Most studies of the musical pitch of harmonic tone complexes have utilized signals comprising two or more successive harmonics. The present study provides systematic data on melodic interval recognition by three musically experienced subjects with sounds whose missing fundamentals were represented by two nonsuccessive harmonics nf0,(n+m) f0, delivered to separate ears. Data were obtained in the ranges 1?n?9, 2?m?4, and 200 Hz ?f0?1000 Hz. The data are interpreted in the light of three theories, the ’’optimum processor theory,’’ the ’’virtual pitch theory,’’ and the ’’pattern transformation theory.’’ For each theory, a constraint on performance is proposed based on interference between the ’’analytic’’ and ’’synthetic’’ pitch perception modes. The former is obtained with large spacings between harmonics, where listeners are more likely to perceive harmonics as individual tones, each having their own pitch. This degrades the listener’s ability to hear the fundamental pitch.
Cochlear macromechanics: Time domain solutions
Authors: Allen J. B. , Sondhi M. M.
Published: October 2005

In this paper we report on a new method of solving a previous derived, two-dimensional model, integral equation for basilar membrane (BM) motion. The method uses a recursive algorithm for the solution of an initial-value problem in the time domain, combined with a fast Fourier transform (FFT) convolution in the space domain at each time step. Thus, the method capitalizes on the high speed and accuracy of the FFT yet allows the BM to have nonlinear mechanical properties. Using the new method we compute (linear) solutions for various choices of model parameters and compare the results to the experimental measurements of Rhode. [J. Acoust. Soc. Am. 49, 1218–1231 (1971)]. We also demonstrate the effect of including longitudinal stiffness along the BM and conclude that it is useful in matching the high-frequency slope as measured by Rhode.
Signature information in the song of the humpback whale
Authors: Hafner Gordon W. , Hamilton C. Lee , Steiner William W. , Thompson Thomas J. , Winn Howard E.
Published: October 2005

This report tests the hypothesis that individual humpback whales (Megaptera novaeangliae) can be recognized and discriminated from other individuals on the basis of the ’’cry’’ vocalization. Multivariate discriminant analyses, based on six measurable variables, were used to examine intra- and interindividual differences in the ’’cries’’ from several individuals. Cries between themes of one song are very different, whereas those between songs of one individual are similar. Results show a high degree of discriminating power between individual animals. Thus, signature information is potentially available from ’’cries’’ within songs, despite common song formats for all calling animals on a given bank. The statistical techniques used will be of great value in animal vocalization studies.
Effects of small room reverberation upon the recognition of some consonant features
Authors: Gelfand Stanley A. , Silman Shlomo
Published: October 2005

The effects of small room reverberation (T=0.8 s) upon phoneme recognition was studied for normal listeners. Recognition performance was significantly poorer under reverberation than in quiet, and poorer in the final position of words than initially. Relative information transmission under reverberation was poorest for place of articulation, and for stop and frication consonants; whereas sibilance, duration, and semivowel information were barely affected. The findings suggest that small room reverberation affects phoneme recognition in much the same way as a speech-shaped masking noise. In some cases, the error distributions reflect the limited response alternatives imposed by the real word recognition test.
Loss of auditory sensitivity following exposure to spectrally narrow impulses
Authors: Price G. Richard
Published: October 2005

Damage-risk criteria (DRC) for impulse noise do not presently take the spectrum of an impulse into direct account; yet it is clear that the ear is spectrally tuned. In order to establish the sensitivity of various sections of the cochlear duct to trauma from impulses, ears were exposed to 100 spectrally narrow impulses (1.0, 5.0, or 10.0 kHz) delivered in 10 min. Changes in auditory sensitivity were measured by an electrocochleographic technique in 43 cat ears and a threshold of loss established for each type of impulse. Expressed in SPL at the ear drum, the loss threshold rose at 3.2 dB/octave between 1.0 and 10.0 kHz. Expressed in stapes displacements, the loss threshold fell at 5.4 dB/octave in the same region. This curve was used to establish a tentative shape for a DRC for the human ear for impulse noise. The patterns of loss, rates of loss, lack of recovery, and loss thresholds are discussed with respect to their probable physiological basis with the conclusion that mechanical displacement rather than metabolic exhaustion is the most reasonable causative factor.
Encoding of steady-state vowels in the auditory nerve: Representation in terms of discharge rate
Authors: Sachs Murray B. , Young Eric D.
Published: October 2005

Responses of large populations of auditory-nerve fibers to synthesized steady-state vowels were recorded in anesthetized cats. Driven discharge rate to vowels, normalized by dividing by saturation rate (estimated from the driven rate to CF tones 50 dB above threshold), was plotted versus fiber CF for a number of vowel levels. For the vowels /I/ and /ε/, such rate profiles showed a peak in the region of the first formant and another in the region of the second and third formants, for sound levels below about 70 dB SPL. For /a/ at levels below about 40 dB SPL there are peaks in the region of the first and second formants. At higher levels these peaks disappear for all the vowels because of a combination of rate saturation and two-tone suppression. This must be qualified by saying that rate profiles plotted separately for units with spontaneous rates less than one spike per second may retain peaks at higher levels. Rate versus level functions for units with CFs above the first formant can saturate at rates less than the saturation rate to CF tones or they can be nonmonotonic; these effects are most likely produced by the same mechanism as that involved in two-tone suppression.
Reply to ’’Shading of acoustic and antenna arrays’’ [J. Acoust. Soc. Am. 66, 916–917 (1979)]
Authors: Sullivan E. J.
Published: October 2005

Comments are made regarding the ability of the Lagrange multiplier method of shading arrays to control individual side lobes. Also, the method is compared to the linear programming approach to shading.
Exploring azimuth effects with an anthropometric manikin
Authors: Dirks Donald D. , Gilman Samuel
Published: October 2005

In these experiments, the effects of sound direction on the eardrum response of an anthropometric manikin (the KEMAR manikin) were investigated. Pure tones and pink noise (analyzed in 1/3-octave bandwidths) over a wide frequency range were used as signals as the manikin rotated 360° with respect to a point source in a anechoic chamber. The simulated eardrum SPL was compared with the averaged human field-to-eardrum data reported by Shaw [J. Acoust. Soc. Am. 56, 1848–1861 (1974)]. It was concluded that the KEMAR manikin can be used up to frequencies of ?8.0 kHz, with (1) 1/3-octave pink noise signals to measure a response equivalent to that obtained by averaging over a number of humans, and (2) pure-tone signals to measure the response equivalent to that of a single human having average head and ear dimensions.
Evidence for direction-specific channels in the processing of frequency modulation
Authors: Gardner R. B. , Wilson J. P.
Published: October 2005

Evidence is provided for the existence of at least three feature-specific channels in the auditory system. Thresholds for the detection of small repetitive or nonrepetitive frequency changes were measured following various adapting stimuli using a 2IFC procedure in two subjects at 1 kHz. Thresholds for single linear upward frequency sweeps (up sweeps) were increased by a factor of 2 to 3 following exposure to repetitive (8 Hz) up sweeps but not following exposure to down sweeps or tone bursts; correspondingly, thresholds for down-sweep stimuli were increased only by down sweeps. Sinusoidal FM test stimulus thresholds were elevated by both up-sweeps and down-sweeps and to a lesser extent by tone bursts. These results suggest the existence in the auditory system of channels specific to upward FM, downward FM, and probably repetition rate.
An experimental investigation of swimbladder resonance in fishes
Authors: Lo/vik Arne , Hovem Jens M.
Published: October 2005

An investigation of the resonant behavior of the swimbladder for different species and sizes has been performed. Most measurements have been done using the ring-hydrophone method, but also a few normal echo measurements have been done. The results show the resonance frequency to increase with depth, but also to depend on what degree the fish is adapted to the depth. After a sudden transfer to new depth, the resonance frequency will first oscillate and then gradually adjust to a new resonance frequency given by the necessary swimbladder volume to retain neutral buoyancy. The time required to adapt to a deeper depth is longer than for a transfer in the opposite direction suggesting that gas production takes longer time than letting out gas. The observed Q values are also dependent on adaption, but appears to increase almost linearly with the resonance frequency at least for low Q values. The measured values are compared with a model for scattering from swimbladder fish and values for the swimbladder tension and viscosity of the fish tissue are calculated.
A ray theory model of acoustic interaction with the ocean bottom
Authors: Mitchell S. K. , Lemmon J. J.
Published: October 2005

A ray theory model of bottom interaction has been constructed, motivated by observations of ’’refracted arrivals’’ reported by Christiansen, Frank, Geddes, and others. Plane wave reflection coefficients have been computed using ray theory to trace the ray paths in the bottom from an incident plane wave, and then applying the necessary boundary conditions at interfaces by treating each ray locally as a plane wave at the interfaces. In addition to a simple, intuitive picture of bottom interaction, the model affords fast, efficient computations of bottom loss (as a function of frequency and/or grazing angle) and can be used for signal simulation in the time domain. The primary conclusion of this study is that this ’’local plane wave’’ approach works well for realistic models of the ocean bottom down to frequencies of the order of several Hertz. Example results from the model are presented: bottom loss, 1/3-octave band averaged bottom loss, and the plane wave impulse response (Fourier transform of the plane wave reflection coefficient). The bottom loss results are compared to the results of exact (wave theory) approaches.
A path-integral approach to the parabolic approximation. I
Authors: Palmer D. R.
Published: October 2005

We use Feynman’s theory of path integrals to study the parabolic approximation. With the aid of path-integral representations for the solutions to the parabolic equation and the Helmholtz equation, we show the parabolic approximation, for either the two-dimensional or the three-dimensional parabolic equation, may be decomposed into two, simpler approximations: a type of geometric optics or eikonal approximation and a stationary-phase approximation. We then relax the geometric optics approximation by assuming, instead, a variant of the Rytov approximation. This development leads to a two-dimensional parabolic equation which models a three-dimensional ocean. Finally we discuss the validity of the stationary-phase approximation.
Compact parametric hydrophone using nonlinear interaction within a cylindrical rubber waveguide
Authors: Corsaro R. D. , Jarzynski J.
Published: October 2005

This paper investigates the effects of placing a rubber cylinder between the pump and receiving transducers in an otherwise conventional parametric receiver. The use of this rubber cylinder is experimentally found to increase parametric conversion gain by 20 to 24 dB, while simultaneously reducing beam width by a factor of two to three. These improvements are relative to the same pump-receiver separation distance (0.23 m) in water alone, over the experimental frequency range of 4.8 to 23 kHz. A theoretical model of this configuration is developed, using the numerical solution of the system of equations obtained by coupling the interior surface Helmholtz equation to the integral equation for the exterior of the cylinder. The resulting calculated beam patterns and efficiency levels are found to be in very good agreemnt with the data collected. Using this model, the observed efficincy improvement is found to be largely due to the slow speed of sound in this rubber (1018 m/s) as compared to water, while the directivity improvement is , to a significant extent, due to the acoustic slow-waveguide effect.
Masking of filtered noise bursts by synthetic vowels
Authors: Resnick Steffi B. , Weiss Michael S. , Heinz John M.
Published: October 2005

The present investigation assessed the simultaneous and temporal masking produced by computer-generated synthetic vowels. The durations (100 and 200 ms) of each of four vowel-like maskers were employed. The masker was presented at 70 dB SPL. The probe signals were three filtered noise bursts whose spectral distributions corresponded to regions of high spectral energy in three English stop consonants. Quiet and masked thresholds were determined using the method of adjustment. Data are reported for two experienced listeners who participated in all the listening conditions. The results were generally in accord with the results of masking experiments using nonspeech signals in that both the frequency specificity of masking and temporal masking effects were demonstrated.