bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of nonlinear propagation distortion on jet noise
Authors: Blackstock David T.
Published: October 2005

A previous study of intense broad-band noise in a tube [F.M. Pestorius and D.T. Blackstock, “Finite-Amplitude Wave Effects in Fluids,” in Proceedings 1973 Symposium, Copenhagen (IPC Science and Technology, Guildford, England, 1974), pp. 24–29] showed that propagation distortion is significant for plane waves at sound pressure levels encountered in jet noise fields. We have modified our computer program to account for spherical spreading. Using measured noise near actual jets as the input for our program, we have computed the distortion that is expected to occur during subsequent propagation. Computations have been made for noise from a model supersonic jet (data furnished by Lockheed-Georgia Co. in the form of 1/3-octave-band spectra) and from a T38 aircraft (tape-recorded noise provided by NASA Langley). In both cases, the computed waveforms exhibit shocks and other evidence of nonlinear effects at moderate distances. However, our model does not include atmospheric attenuation, ground effects, and distributed source effects. These effects may severely limit the importance of nonlinear propagation distortion. Thus much work remains to be done. [Research supported by DOT and AFOSR.]
Investigation of sonic boom focusing phenomenon through ballistic range experiments
Authors: Sanai M. , Toong T. Y. , Pierce A. D.
Published: October 2005

A two-part investigation of shock focusing as related to sonic booms has been conducted in a ballistic range with the objective of studying the nonlinear effects. In part I, experiments pertaining to propagation of converging shocks are described and the similarity of the observed phenomenon with enhanced sonic booms or superbooms created by accelerating supersonic aircraft is discussed. For weak shocks, a structure resembling that of a folded shock predicted by the geometrical acoustics theory is observed while for stronger shocks, a concave front with enhanced overpressure is recorded. Other results are in general accord with the basic concepts of shock propagation and in conjunction with some theoretical scaling laws indicate that the peak magnification of sonic booms due to aircraft flight acceleration in the real atmosphere should be in the range of 6 to 13. In part II, simulation experiments pertaining to the superbooms generated as a result of atmospheric refraction in threshold Mach-number flights are reported. The flow field observations indicate that the generated shocks are reflected near the sonic cutoff elevation, where the local sound speed equals the projectile speed, provided that such an elevation exists. The incident shock and its reflected portion join to form a Y-shaped configuration near the cutoff region. Enhanced shock overpressures are detected near the “critical altitude” where the flow speed behind the shock becomes sonic. A maximum focus factor of 1.7 has been measured for the leading shock which, with some theoretical assumptions, leads to an estimated value of 1.3 for the constant which appears in the Guiraud-Theory scaling law.
Computer simulation of parabolic acoustic reflectors
Authors: Hunter D. E. , Priestley J. T.
Published: October 2005

Various forms of parabolic reflectors are used in different areas of acoustic research. Computer programs have been developed that allow simulation of the beam pattern produced by an arbitrary parabolic section with an elliptical aperture. The beam pattern in planes other than those containing the major and minor axes of the aperture may also be observed. The location of the acoustic source may be specified, consequently, the effect of off-focus feed elements may be predicted. The results are output in table form as well as in a polar plot. The program's capabilities in the area of simulating beam patterns of acoustic arrays are also covered.
Information measures and performance bounds for array processors
Authors: Scharf L. L. , Moose P. H.
Published: October 2005

Information measures and performance bounds are derived for frequency-domain linear array processors deployed in homogeneous Gaussian random fields. J divergence, a measure of the (net) information rate of an array, is shown to be a useful measure of how effectively detection and estimation functions can be performed in optimum and conventional array processing structures. In a detection context, J divergence becomes a detection index that can be interpreted in terms of array gain and output signal-to-noise ratio. Comparisons between the divergence of optimum and conventional processors indicate, for example, that optimum processing can provide on the order of 13-dB gain over conventional processing when trying to detect a 20-dB signal in the presence of a 20-dB interference located within the Rayleigh limit of the array. In an estimation context, J divergence can be used to derive “critical divergence” and Cramer-Rao bounds on resolution variance. These bounds indicate that approximately 25-dB output signal-to-noise ratio is required to obtain a 10:1 improvement over the classical Rayleigh resolution limit. The Rayleigh limit is argued to have significance only at output signal-to-noise ratios of approximately 10 dB. The argument is based on a new resolution limit termed the critical divergence limit. This limit is shown to give resolution limits approximately three times the Cramer-Rao bound, indicating that the latter bound is an optimistic resolution limit. [Supported by Office of Naval Research, Statistics and Probability Branch, Arlington, VA.]
Role of beam formation in optimum detectors
Authors: Adams S. L.
Published: October 2005

The beam former and null former appear as components of the optimum array detector for the very special case of a known plane-wave signal from a known direction in a Gaussian noise field whose statistical properties are known. An optimum detection processor exploits any knowledge of the true statistical characteristics of the signal and noise fields. This paper reviews recent research results in optimum detection theory for array processors which incorporate more realistic assumption about the signal and noise fields. Specific cases are identified in which the optimum spatial processor is not a beamformer. If the optimum spatial processor is not a beamformer, then adaptive processors whose structure is constrained a priori to a beam former or a linear spatial filter are necessarily suboptimum. [Research supported by Office of Naval Research, Code 222.]
Preliminary results using inverse filtering of speech for automatic evaluation of laryngeal pathology
Authors: Davis S. B.
Published: October 2005

Inverse filtering of speech by an approximation of the supraglottal transfer characteristic produces a residue signal which appears to be a good indicator of laryngeal pathology [Koike and Markel, Ann. Oto. Rhinol. Laryngol. 84, 117 (1975)]. In the present study, residue signals from isolated occurrences of /a/ for 17 normal and 22 pathologic male and female speakers were used to compute the amplitude of the autocorrelation peak corresponding to the pitch period, the coefficient of excess, the pitch and the amplitude perturbation quotients, and the inverse filter and residue spectral flatness measures. A closed two-choice Bayes maximum likelihood test based on these features resulted in correct identification of 100% of the normal speakers and 95% of the pathologic speakers. Respective discrimination in an open two-choice test, where the speakers were divided into reference and test groups, was 72% and 91%. Results were tabulated for different pathologies, analysis conditions and data base sizes. These findings indicate the feasibility of using statistical methods to automatically discriminate between normal and pathologic voices. [This research supported by the National Institutes of Health under Grant No. NS01877.]
Acoustic characteristics of speech produced with an electronic artificial larynx
Authors: Weiss M. S. , Yeni-Komshian G. H. , Heinz J. M.
Published: October 2005

This study investigated the acoustic characteristics of speech produced with an electronic artificial larynx (electrolarynx). Five normal-speaking adult males were taught to use an electrolarynx, and each talker recorded a set of speech materials in his normal voice and with an electrolarynx. The recordings were subjected to analyses which included: (1) intensity level measurements of speech as well as the direct radiated sound from the electrolarynx; (2) speech-duration measurements; (3) spectral analysis of the radiated masking sound from the electrolarynx; and (4) formant frequency estimates derived from the spectrum of a linear prediction inverse filter. Results indicated that the overall intensity of electrolarynx speech was similar for the five talkers, but that intensity of the radiated noise, and hence speech-to-noise ratios, varied considerably among talkers. In addition, talkers required about 50% more time to produce speech with an electrolarynx, indicating modification of articulatory behavior. Spectral composition of the radiated sound from the electrolarynx varied from talker-to-talker. Formant frequencies for a given talker were similar for the normal voice and the electrolarynx productions, but the intensity relationships between formants was different in the two modes of production. [Research supported by NINCDS and a grant from the Samuel W. Traylor Foundation.]
Brain potentials and speech of stutterers and nonstutterers
Authors: Love Laura R. , Peters Robert W. , Wood Thomas J. , Otto David A.
Published: October 2005

Van Riper [The nature of stuttering (Prentice-Hall, Englewood Cliffs, NJ, 1971), pp. 347–351] in reviewing electroencephalographic studies concluded that atypical EEGs occur beyond chance in stuttering populations. Recently, Zimmerman and Knott [“Slow potentials preceding speech in stutterers and normal speakers,” Electroenceph. Clin. Neurophysiol. 36, 216 (1973)] reported that slow brain potentials, contingent negative variation (CNV) disappear immediately prior to stuttering behavior. The purpose of the present experiment was to explore brain wave potentials at the vertex and at the right and left parietal hemispheres for stutterers and nonstutterers prior to speech tasks. Specific concerns were the comparison of stutterers and nonstutterers and brain potential activity immediately preceding high- and low-expectancy stuttering words. Data were recorded on analog tape using a Hewlett-Packard 3955 system with Beckman Type 9806-A A-C preamplifiers capacitor coupled to provide a 5-sec time constant. Electrophysiological data were digitized in 4-sec epochs at 64 Hz and averaged (20 trials/average) on a PDP-12 computer. Results indicate that the amplitude of the expectancy wave (CNV) precedIng a signal to articulate specified words is greater in control subjects than stutterers. Among stutterers, however, the expectancy wave is smaller preceding frequently stuttered words than never-stuttered words.
The influence of consonant environment on duration of vowels in the speech of normal hearing, moderately hearing impaired, and deaf adults
Authors: Whitehead R. L. , Jones K. O.
Published: October 2005

The present study investigated the effect of consonant environment on the duration of vowels in the speech of ten normal hearing, ten moderately hearing impaired, and ten profoundly deaf adult males. Each subject uttered randomizations of eight CVC nonsense syllables consisting of the vowels /i/ and /α/, and the consonants /p/, /b/, /s/, and /z/. The moderately hearing impaired and deaf subjects all had adequate speech to perform the required verbal tasks. Each CVC sample was recorded on a tape recorder and was then individually played into a Honeywell visicorder which produced an audio wave. The duration of the vowels in the voiced/voiceless and plosive/fricative environments were measured in milliseconds from the oscillographic recordings. Results indicated that for the normal-hearing and moderately hearing impaired subjects, a significant difference in vowel duration occurred between the voiced/voiceless and between the plosive/fricative consonant environments. For the deaf subjects, there was no significant difference in vowel duration for any of the consonant environments.
Dichotic listening in a patient with a presumed lesion in the region of the medial geniculate
Authors: Berlin Charles I. , Cullen John K. , Berlin Harriet L. , Tobey Emily A. , Mouney Daniel F.
Published: October 2005

Dichotic and monotic performance data were obtained from a patient with a lesion involving thalamic and parathalamic structures. Information gained from the patient's neurological examination, arteriograms and ventriculograms suggest the lesion is confined to the area of the medial geniculate and/or the brachium of the inferior colliculus on the right side. Data will be presented showing normal monaural and monotic performance in “target-challenge” speech identification tasks [Berlin et al., IEEE Trans. Audio Electroacoust, AU-21, 189 (1973)], but differential effects in dichotic target-challenge identification tasks, depending on whether the target was presented to the right ear or left ear. [Supported by National institues of Health, USPHS Grant No. NH 11647-02.]
Measurements of the acoustic effectiveness and quality of trained singers' voices
Authors: Winckel Fritz
Published: October 2005

Having collected physiological data on professional singers, we have the basis to propose neural circuits which effectuate highly qualified voices. We can derive a quality test for stage singers and techniques for training, conserving, and treating the voice. Our method consists of the analysis of swell tones on the vowels /a/ and /ɛ/ in the middle range to obtain (1) the spectral component in the area of 3000 Hz as a measure of the penetrating power of the trained voice in large halls and (2) the parametric characteristics of the vibrato. We suspect that the origin of the vibrate is the consequence of an overload of the control circuit resulting in FM in the m. vocalis in connection with the m. cricothyroid—the controller being synapses in the medulla oblongata. This is similar to the tremor—with a frequency of 8–12 Hz, a slightly higher rate than that for vibrato. We have developed a portable electronic device which indicates (1) the plot of the relative intensity of the singing formant of 3000 Hz and (2) the duration of the messa di voce which gives information about vital capacity and dynamic range. From these values one can get insight into the conscious control of the subglottic pressure (“Stützfunktion”) which is remarkably individual among professional singers. The voice-test device will be demonstrated.
Studies of the Marchesi model for female registration
Authors: Large John , Murry Thomas
Published: October 2005

This paper reports a series of studies in which a model for female registration central to the well-documented vocal method of Mathilda Marchesi (1821–1913) and consistent with the views of today's artists Joan Sutherland and Marily Horne was utilized. Marchesi produced more prima donnas (e. g., Nellie Melba, Emma Calvé, Emma Eames) than any other teacher in the history of Western vocal music. Equalized and nonequalized paired tones (same fundamental frequency, sound level—A-weighting, and vowel—/α/) in the areas of register boundaries (upper limit, chest register—varies from E4, 330 Hz, to F4-sharp, 370 Hz; upper limit, medium register—varies from F5, 698 Hz, to F5-sharp, 740 Hz) were recorded (1) on a high-fidelity tape recorder for Sonagraphic analysis, (2) by a pneumotachographic system for measurement of airflow rate, and (3) with photography for analysis of laryngeal movements. Additionally, samples were taken in which “equal effort” was substituted for equal SPL. The results of these investigations suggest the existence of physical correlates for singers' subjective sensations of different registers. These sensations are responsible for the continued use of traditional terms such as “chest” register and “head” register.
Textual communication in singing
Authors: Ralph Appelman D.
Published: October 2005

It is suspected that four factors alter the intelligibility of the word in vocal performance: (1) the singers' sensation of basic vowel resonance centers determined through auditory feedback, (2) frequency, (3) intensity, and (4) the environment of the vowel. To determine the degree of variation in basic vowel concepts among 15 expert singers and teachers selected for their good diction habits, 12 vowels were sung on 12 frequencies by four sopranos, four altos, three tensors, and four basses. Frequency deviations from the Appelman standard of resonance centers for sung vowels were measured on the vowelometer, an electronic formant tracker and phonetic analyzer. Sonograms of each sung vowel were made for verification of the vowelometer readings. Results of this experiment suggest that when singers sing vowels from conceptual origins within a closed servosystem on any frequency or intensity, each singer selects a specific vocal timbre rather than establish a center of resonance for each vowel. As the articulatory structures are altered to satisfy the singers' preferred timbre, the center of resonance for the intended vowel loses its integrity and migrates to the domain of another vowel, resulting in the loss of word identity and textual communication.
Trading relation between intensity and time for intermittent noise exposures
Authors: Ward W. D. , Cushing E. M. , Burns E. M.
Published: October 2005

In a direct empirical test of the present OSHA trading relation between level and time (5 dB per halving), young normal listeners were exposed for 6 h to “magenta” noise (OB spectrum falling at 5 dB/octave) under various conditions of regular intermittency ranging from continuous at 90 dBA to an on-fraction of 1/16 at 110 dBA. Three different periods of noise pattern were used: 1.5, 9, and 40 min. In all cases, the TTS 90 min after cessation of intermittent exposure was equal to or less than that after continuous exposure, indicating that for these regular patterns, the OSHA trading relation is sufficiently conservative. In a second series of experiments, the permitted daily exposure of 30 min at 110 dBA was presented in 80 45-sec bursts, and the interburst interval was varied systematically from 0 to 8 min. In this case, when the (recovery) interval was less than about 5 min, the TTS either 2 or 90 min after exposure was higher. The results imply that a rest period will be maximally effective only if its duration is 5 min or longer. [Research supported by the National Institute for Occupational Safety and Health, Public Health Service.]
On judging sets of noises
Authors: Nagel D. C.
Published: October 2005

Subjects were asked to provide category judgments for the annoyance produced by from one to 12 sounds heard during a fixed duration observation period. The sets of sounds were judged in one of three background noise contexts, determined by actual recordings made in typical rural, suburban, and urban/industrial settings. Two algebraic models were tested to account for mean ratings of each of the noise sets as functions of set composition and background noise. One model asserts that subjects form a weighted sum of the individual sound scale values. Such a model leads to a linear relationship between the judgment of the set and the set size. An alternative model proposes that subjects form a weighted average of the individual scale values in arriving at a single judgment for the set. This model predicts a negatively decreasing relationship between set judgment and set size. Model predictions and experimental results are discussed in terms of relevance to community noise response modeling.
Phonological rules influenced by boundaries
Authors: Javkin Hector
Published: October 2005

Coker [J. Acoust. Soc. Am. 55, 476 (1974)] has argued that (1) the indestructibility of speech is due to the large measure of redundancy that speech contains and (2) that an important role of various phonological processes that create redundancy is to mark boundaries. A survey in 13 languages of rules that are conditioned by boundaries does not seem to support claim (2). Although 183 out of 524 rules examined made reference to boundaries, these did not create reliable boundary markers (i. e., features, segments or combinations of same that only and always occurred at boundaries). Furthermore, there were a number of cases in which a language had the opportunity to mark boundaries merely by blocking the application of a rule, but failed to do so. This suggests that phonological processes occurring at boundaries stem from the same phonetic constraints occurring elsewhere. A detailed phonetic examination of these languages might reveal the existence of reliable boundary markers, but the macroscopic view provided by phonelogical rules fails to do so. [This work supported in part by the National Science Foundation, and used the resources of the Stanford Phonology Archive.]
Functional explanation of differences in voice onset time and oral air pressure rise time for stops articulated at different distances from the vocal cords
Authors: Abler William L.
Published: October 2005

It has been known since 1970 (Joseph Greenberg, Int. J. Am. Ling. 36, 123–145) that a positive correlation exists between voice onset time and distance of stop articulation from the vocal cords. Oral air pressure data tentatively support Greenberg's (1970) conjecture that the larger air cavity between the vocal cords and the point of closure in more anterior stops requires a longer time to build elevated air pressures than the cavity associated with more posterior stops: Prevoiced stops are released at comparable air pressure levels, while the number of glottal pulses occurring, and the time elapsing, as the pressure builds vary directly with the distance of the place of closure from the vocal cords. Air pressure rise times in voiceless stops, and in non-prevoiced /b-d-g/, show a pattern of air pressure rise times comparable to that encountered in the prevoiced stops, suggesting that voiced stops and their prevoiced counterparts may be articulated according to the same internal schedule, or that VOT differences functionally induced in pre-voiced stops may invade the internal organization of the speech production system.
Effect of normalization and transformation in the processing of F for analyzing American intonation
Authors: Takefuta Yukio
Published: October 2005

As any researchers who studied intonation know, this speech signal is an extremely difficult signal to analyze scientifically. Everytime they study it they find the necessity of studying more basic facts about it. Having learned this fact, this investigator collected samples of the simplest intonation, those of one word sentences, and examined the effect of normalization and transformation in the digital processing of physically extracted data F0 for the valid analysis and accurate detection of interrogative signals in American intonation. When optimal methods of normalization and transformation (ten methods tested) were applied, all interrogative intonations of ten different sentences (produced by 60 American speakers and validated by five native speakers of English) were perfectly distinguished from noninterrogative intonations. After these methods of normalization and transformation were applied to the physically extracted data, the basic interrogative intonation pattern and its variant for each of the ten one-word sentences were obtained.
Summertime acoustic conditions in Baffin Bay
Authors: Merklinger Harold M.
Published: October 2005

Noise measurements made in Baffin Bay during the summers of 1972 and 1973 indicated that noise levels were generally higher than in the North Atlantic. Two distinct types of ice-related noise were identified. Loud crashes having a roughly RC-shaped spectrum were observed to result from the rolling and breakup of icebergs. A steady, white noise was observed in the presence of ice debris. Attempts to relate steady noises with stable icebergs failed. During both years seismic survey operations contributed significantly to the average noise levels at low frequencies.
Ambient noise vertical directionality—a useful empirical model
Authors: Stockhausen J. H.
Published: October 2005

Descriptions of the noise vertical directionality which transform into simple spatial correlation functions are particularly useful because directionality measurements are conveniently made in the spatial correlation domain. A useful model for the horizontally concentrated distant shipping noise is the function exp[−(cosθ/2ζ)2], where θ is the angle with the vertical and ζ is a parameter-controlling beamwidth. For typical beamwidths this expression transforms with negligible error to exp[−(ζkd)2] for the spatial correlation function. Depression or elevation respect to the horizontal can be handled with simple elaboration. Several authors have described the directionality of the noise deriving from surface agitation in terms of cosθ and cos°θ (isotropic), both of which have closed-form transforms In kd space. These three expressions are used in combination to characterize the noise field in the Labrador Sea as measured in three different wind conditions, from frequencies at which shipping noise dominates through the transition region to frequencies at which surface noise is the major factor.
Ambient noise vertical directionality—a numerical model
Authors: Stockhausen J. H.
Published: October 2005

An interactive computer model for generating vertical noise directionality has been developed as an extension of Talham's method to allow unbottomed sensors. Essential features are: a sound speed profile consisting of three linear gradient segments, a selection of bottom types, and provision for volume attenuation and surface reflection loss. The noise directionality is first computed and then numerically transformed into the spatial correlation function applicable to a vertical array. A uniform surface distribution of sources is used, radiating power as cos2θ, where θ is the angle of incidence. It is shown that propagation conditions account for as much variation in noise directionality as there is between the fields resulting from cos2θ and cosθ sources in a much simpler propagation model.
Ambient noise in the surface duct
Authors: Urick R. J.
Published: October 2005

On a number of occasions, and with a variety of instrumentation, the ambient noise level in an area north of St. Croix, VI, has been found to be higher, by amounts up to 8 dB, than at depths below the duct. The difference occurs at the frequencies greater than a few hundred hertz that are trapped in a 120–180-ft duct. Other data in the form of time-delay correlograms obtained with a vertical string of hydrophones indicate that the excess noise arrives at a receiver from near-horizontal directions. It follows that a vertical array used in the surface duct would have a higher noise background and a lower array gain than when placed below the duct. A likely hypothesis is that the excess noise in the duct represents noise from distant near-surface sources trapped by, and traveling within, the duct. This occurrence of duct noise may merely represent some peculiarity of the area where it was observed; on the other hand, it may well be a phenomen of widespread, though apparently hitherto unreported, occurrence wherever a well-developed surface duct exists.
The contribution of the sea urchin to ambient sea noise
Authors: Castle M. J. , Kibblewhite A. C.
Published: October 2005

An unusual component of the ambient sea noise field of coastal New Zealand waters has been recognized for some years. The phenomenon involves an increase in noise level at sunset and sunrise, predominantly in the range of 1 to 2 kHz, with seasonal trends varying the pattern. The effect was reported first in 1962 and tentatively attributed to the seaurchin Evechinus chloroticus Valenciennes (1846). A continuous study in the shallow waters of the Hauraki Gulf throughout 1973 has confirmed this hypothesis. The results of this study will be presented and the characteristics of the effect reviewed.
World shipping distributions
Authors: Ross Donald , Mahler John , Solomon Louis
Published: October 2005

Ocean noise in the lower frequencies (25–250 Hz) is due principally to surface shipping. In the absence of extremely close sources, this is due to many distant ships scattered throughout the acoustic basin. Merchant and fishing vessel distribution is presented for the North Atlantic and North Pacific Ocean between the equator and 70 °N. The information is presented for 5° squares with method for achieving distribution in 1° squares. The distribution applies to the time period 1972–1973 but may also be used for periods within two to three years of these dates, requiring only scaling of the total numbers. The shipping distribution presented herein is a coordinated product of three independent studies and represents the most current information available.
Detection of underwater signals by a California sea lion: Variation in reinforcement schedules
Authors: Schusterman R. J.
Published: October 2005

A sea lion (Zalophus californianus) was trained to report the presence of a pure tone in a yes-no psychophysical procedure. Reinforcement schedules were varied by changing the probability of fish reinforcement [P(SR)] contingent on two classes of response—hits and correct rejections. The P(SR|Hit) and the P(SR|CR) were 1.00, 0.75, 0.50, and 0.25. In baseline, both P(SR|CR) were 1.00. In each of the other schedules, P(SR) was held constant at unity for one response and varied for the other response. Thus seven different reinforcement schedules were used. The sea lion showed rapid acquisition of a stable response bias as a function of systematic variation of reinforcement schedules. These results demonstrate that varying reinforcement schedules is as effective as varying the payoff matrix in the control of response bias in underwater signal detection experiments with sea lions [see H.J. Schusterman. B. Barrett, and P. Moore, J. Acoust. Soc. Am. 57, 1526–1532 (1975)]. [Work supported by ONR.]
Psychophysical tuning curves in the parakeet (Melopsittacus undulatus)
Authors: Bock G. R. , Saunders J. C.
Published: October 2005

Previous work has shown that parakeets differ from mammals with respect to several measures of auditory masking (eg., critical ratios and tone-on-tone masking.) This research was extended in the present study by the use of Zwicker's “psychophysical tuning curve” procedure. Parakeets were trained to respond to a probe tone of fixed frequency (630, 1600, or 2500 Hz) and intensity (10 dB SL) in the presence of a continuous masking tone of variable frequency and intensity. The intensity of the masker was adjusted at each frequency to obtain a threshold for masking of the probe tone. The resulting frequency-threshold curves for the three probe frequencies exhibit broader tuning than that observed in human subjects under similar conditions. This contrasts with comparisons of other forms of masking in parakeet and man, and raises important questions concerning cochlear mechanisms in birds. [Work supported by NSF.]
Auditory sensitivity of red-winged blackbirds
Authors: Hienz R. D. , Sinnott J. , Sachs M. B.
Published: October 2005

The auditory sensitivity of red-winged blackbirds (Agelaius phoeniceus) has been measured with two behavioral techniques. The first was a two-alternative forced-choice procedure in which a bird initiated a trial by pecking a center key; a tone was presented with 50% probability on each trial. The bird was rewarded with food for pecking a right or left key, depending on whether a tone was present or not. In the second technique, a bird pecked the center key continuously until a 2-sec tone sounded; reinforcement then occurred for pecking the right key during the tone. The method of constant stimuli was employed to determine thresholds in the frequency range of 125 Hz to 10 kHz. The two procedures produced similar audiograms. The lowest threshold were 5–15 dB SPL in the 2–4-kHz range. At lower frequencies, thresholds rise gradually to 65 SPL at 125 Hz. At higher frequencies thresholds rise sharply above 6 kHz; at 10-kHz thresholds were 70–75 dB SPL. Both procedures are also being used to obtain frequency- and intensity-discrimination thresholds by substituting a train of tone bursts for the normally silent periods in the threshold procedures. Blackbirds are then trained to detect alternations in tone-burst frequency (or intensity). Frequency DLs at 1.5 kHz are about 15 Hz, and intensity DLs at 1 and 2 kHz are 2.5–3.0 dB. [Research supported by NIH Grant No. R01 NS12112.]
Comparison of audiograms and song spectra in two blackbird (Icterid) species
Authors: Sinnott J.
Published: October 2005

Dooling [J. Acoust. Soc. Am. 50, 706 (1971)] has hypothesized that avian songs, which are broadcast signals adapted to distant communication, should fall in the frequency region for which a songbird has maximum auditory sensitivity. Using operant conditioning procedures, we have compared behavioral audiograms in two blackbird species belonging to the same family (Icteridae) with significantly different song spectra: The redwing blackbird (Agelaius phoeniceus), whose song energy is concentrated in the 2–4-kHz region, and the brown-headed cowbird (Molothrus ater), whose song consists of unusually high frequencies in the 6–10-kHz region. Results revealed maximum auditory sensitivity for both species to be at 2–4 kHz, with no tendency for the cowbird to be more sensitive than the redwing in the region of its own song (6–10 kHz). Therefore the cowbird, unlike the redwing, does not show the predicted match between song spectrum and region of maximum auditory sensitivity. One factor contributing to this mismatch may be that the cowbird, a brood parasite who lays its eggs in the nests of smaller species such as sparrows and warblers, imitates the high frequencies in the sounds of these birds. [Research supported by NIH Grant No. R01 NS12112.]
Evidence for turtle auditory localization
Authors: Lenhardt M. L.
Published: October 2005

Evidence is presented that the semiaquatic turtle Pseudemys scripta and the terrestial turtle Terrapene carolina major can detect the direction of a tone within their sensitive area of hearing. The stimulus was a 5% modulated 500-Hz tone generated in a Y maze with speakers at a 45° angle. The SPL at the discrimination area of the maze was 82 dB. Only one turtle of each species met the criteria of either ten consectuve correct responses or an overall 75% correct response level. However, all other animals responded above chance. Lastly, evidence is presented suggesting that the turtle can use its limited hearing in a problem solving situation.
Existence of the acoustic cricothyroid response in the rat
Authors: Yonovitz A. , Lozar Joseph , Mitchell C. W.
Published: October 2005

A recent investigation by P. H-S. Jen et al. [J. Acoust. Soc. Am. 57, S42 (A) (1975)] has shown that during acoustic stimulation the cricothyroid musclc (CTM) responds in echolocating bats. Previous studies have shown that the rat emits ultrasonic cries which can be used to echolocate. Our study attempts to determine the existence of the acoustic CTM response in this species. Electromyography of the CTM was obtained in ten rats. Rats were stimulated with pure tones between 5 and 60 kHz. During acoustic stimulation the rate of the action potential response was obtained using varying intensities and frequencies. Interspike interval histograms were also obtained during spontaneous activity from the CTM. Latencies from the CTM response were found to be within the range of 8 to 30 msec. Data are presented which support the acoustic CTM response in the rat.
Floating slab design in the control of transit train noise and vibration
Authors: Lee Peter Y. N. , Wilson George Paul
Published: October 2005

Operational experience with underground or subway rapid transit systems has shown that vibration and noise from trains can and does create intrusion in buildings located close to the underground facilities. This intrusion is usually in the form of a low-frequency (31.5–125-Hz range) noise or rumble generated by the ground-borne vibration from the subway trains. The use of floating slab trackbed supported on resilient elements intended to vibration-isolate the slab from the subway structure has been determined to be effective in reducing the transmission of vibration and noise to the surrounding ground and nearby buildings. This paper presents information on the two types of floating slab trackbed, the continuous floating slab track support system and the discontinuous slab system, which have been designed and are under construction at the Washington Metropolitan Area Transit Authority (WMATA) and Toronto Transit Commission systems and are proposed for use by the Metropolitan Atlanta Rapid Transit Authority system. Some sections of continuous floating slab trackbed are already in service at WMATA and measurements of the reduction of noise and vibration achieved at the adjacent buildings are presented.
Scattering from large plane gratings composed of compliant tubes
Authors: Brigham G. A. , Libuha J. J. , Radlinski R. P.
Published: October 2005

A two-dimensional, structural-acoustical model of planewave scattering from an infinite, uniform plane grating of elliptical, cylindrical shells is developed to study transmission through compliant tube arrays. At low frequencies, an individual compliant tube is described by an elliptical shell that deforms in flexure. The unknown scattering coefficients are determined from the boumdary conditions by the use of an addition theorem for elliptical harmonic wave functions from which the elliptical Schlömilch series are generated. The scattered pressure is then rewritten in terms of propagating and evanescent plane waves. Calculations from the model are shown to be in agreement with measurements from the compliant tube arrays. Effects of tube orientations and spacing on array resonance and bandwidth are discussed. The use of multilayered gratings is shown to widen the insertion loss bandwidth. [Work supported by NAVSEA Sonar Technology Division.]
Some effects of speech materials on vocoder quality evaluations
Authors: Huggins A. W. F. , Nickerson Raymond S.
Published: October 2005

A set of six sentences was composed, of which the first contained only vowels and /r, w, y/. Besides vowels, the next three sentences contained only nasals, only fricatives, and only stops and affricates, respectively. The final two sentences contained between them almost all the consonants of English. The sentences were recorded by three male and three female talkers, and the recordings were passed through a set of 12 simulated LPC vocoders, whose bit rates were equalized at about 2600 bits/sec (nonoptimal coding). The processed sentences were used in a quality rating task (each talker x system x sentence presented once), and also in a rank-ordering task, in which a subject ranked all systems for each talker x sentence combination. The same subjects served in both experiments. The responses were subjected to multidimensional scaling analysis. The results show that the relative quality of a pair of systems can be strongly affected both by the speech material and by the talker. Implications for quality evaluation are discussed.
Effect of early echoes and reverberation on the subjective evaluation of speech
Authors: Patterson B. R. , Esteves Irene , Sessler G. M. , West J. E.
Published: October 2005

Using a male and a female speaker, test sentences were created having 25 combinations of early echoes (EEs), i.e., echoes arriving within 10 msec of the direct sound, and four values of reverberation time (RT). These test stimuli were bandlimited from 0.5 to 3.3 kHz and evaluated by subjects in an anchored rating test according to the subject's preference for use in telephony. Analysis of the data by a multidimensional scaling technique showed that preference decreases slightly with increasing RT up to 0.25 sec and more strongly for RTs from 0.25 to 0.5 sec. Addition of six EEs distributed over 7 msec decreases preference three times more than an RT of 0.25 sec and somewhat less than an increase in RT from 0.25 to 0.5 sec. Periodically spaced EEs subjectively degrade speech more than an equal number of irregularly-spaced ones. Four bunched EEs spread over 0.6 msec are preferred to four EEs distributed over a 4-msec interval.
Reduction of long-time reverberation by center clipping
Authors: Mitchell O. M. M. , Yates G. H. , Bateman T. B.
Published: October 2005

We have investigated use of center clipping to reduce effects of long-time reverberation of speech. Center clipping in contiguous bands allows harmonic distortion to be avoided at the output. Previous studies used six 23-octave bands with fixed clipping levels [O.M.M. Mitchell and D.A. Berkley, J. Acoust. Soc. Am. 47, 84 (A) (1970)]. We have obtained improved performance by the use of a simpler center clipping system that adapts to varying input speech levels. This system has been realized both in digital simulation and in real-time analog circuitry. Output tapes showing the effect of processing speech recorded in an auditorium and a small office will be played.
Subjective and objective correlates of digital signal distortions
Authors: Goodman David J. , McDermott Barbara J. , Nakatani Lloyd H.
Published: October 2005

An experiment has been performed to investigate the subjective quality of digitally coded speech. The aims were to find objective measurements that could be used to predict subjective evaluations and to provide information that would be useful in the design of coding equipment. We identified three distortions that arise in pulse-code modulation: peak clipping (C), bandlimiting (B), and quantizing (Q). The experiment included 208 encoders with various combinations of four quantizer ranges (related to C), four sampling rates (B), seven step sizes (Q), and three logarithmic compression laws (also related to Q). Forty-eight subjects used for ten-point opinion scale to rate each coder. They heard a phonetically balanced set of ten sentences spoken by two females and two males. The results indicate that the ratings depend strongly on C and Q but are relatively insensitive to B. A useful objective measure of C is percentage of samples clipped P, rather than the clipping noise pewer. On the other hand, the signal-to-noise pewer ratio S, measured in decibels, does reflect the effect of Q. The ratings R are reliably predicted by the regression formula R = aP + bS + c.
Acoustics of chimes
Authors: Culver Randall , Rossing Thomas D.
Published: October 2005

The sound spectrum of tubular bells or orchestra chimes have been studied by means of a real-time spectrum analyzer. The frequencies of the various modes of vibration are found to agree favorably with those calculated according to the methods of Rayleigh and others. The strike tone appears to result from a combination of modes whose frequencies are nearly harmonic, since there is no mode of vibration at the frequency of the strike tone itself. Attempts to synthesize chime sounds by combining several of the spectral components will be described.
Further studies in musical interval perception
Authors: Burns E. M. , Ward W. D.
Published: October 2005

In previous papers we have presented evidence that, when using experimental paradigms comparable to those used in categorical perception experiments in speech, musicians exhibit categorical perception for melodic musical intervals. In this paper, the effects of varying the parameters of stimulus duration and interstimulus interval on the degree of categorical perception were studied. In addition, the effect of discrimination training on within-category discrimination was examined. The results of these investigations are compared with those from speech perception experiments, with regard to the question of whether there is a basic difference in the perception of certain consonants and the perception of vowels and nonspeech stimuli.
Structure of the vocal cord as a vibrator
Authors: Hirano M. , Koike Y. , Mihashi S. , Kasuya T. , Okada M.
Published: October 2005

The vocal cord is not uniform in its structure. From a histological point of view, there are five layers in the vocal cord at and near the edge: the epithelial layer, the superficial, intermediate and deep layers of the lamina propria; and the muscle layer. From a physical point of view, the vocal cord has three layers, i.e., the “cover” which consists of the epithelium and the superficial layer of the lamina propria, the “transition” which consists of the intermediate and deep layers of the lamina propria, and the “body” which is the vocalis muscle. The blood vessels are clearly separated between the transition and the body. The elasticity is the greatest in the body and the smallest in the cover when no laryngeal muscles are activated.
Human tolerance research and advanced anthropomorphic dummy development
Authors: Eppinger R. H.
Published: October 2005

The promulgation of Federal Motor Vehicle Safety Standards in the area of occupant protection requires a reliable methodology for assessing the human injury hazard in the automotive crash environment. This methodology is utilized not only by the Government as a compliance technique for determining if a particular safety system is providing the protection level sought, but also by the industry as a research tool in the actual development of their safety systems. In our present view the most feasible technique for accomplishing this task is to develop a physical human surrogate in the form of an anthropomorphic dummy which, when placed in the actual crash environment, can assess the human injury hazard. Discussed will be specific research programs and how they combine into the NHTSA's comprehensive overall program to develop this anthropomorphic test dummy. Emphasis will be on how the two fundamental, yet contradictory, design requirements necessary for the development of a viable test device, sophistication for biofidelity, and simplicity for repeatability will be combined into a single set of realistic design specifications.
Standards for noise measurement
Authors: Heymann R. W. , Sachs F. Z.
Published: October 2005

The thrust toward a quieter environment at work and at play has spurred many manufacturer's and trade associations to consider standardizing methods and procedures for the measurement of noise within their respective industries. Because the general methods and detailed procedures applicable to noise measurements are very much dependent on the intended end use of the noise information, there can be no single universally applicable noise measurement standard even if there was complete scientific consensus. The various factors comprising the makeup of a noise measurement standard are discussed and the applicability of the available alternatives to the different types of end use situations is illustrated. Among the more important factors discussed are sound pressure versus power measurement, single number rating versus rating by frequency bands, type and control of acoustical environment during measurement, measurement location, instrumentation precision, and statistical accuracy. A compendium of some of the recent noise measurement standards is presented and comparisons of the standards are made according to approaches taken in the above factors. The discussion and focusing of the various approaches should provide some assistance in the drafting of standards.
Piping noise: causes and cures
Authors: Nelson J. L. , Hillquist D. R.
Published: October 2005

Piping is often the major source of noise within a chemical plant or refinery. Seldom, however, does piping generate the noise. The noise is generated mostly by valves, ejectors, and high-speed rotating machinery and is broadcast by the attached piping. Only rarely, contrary to popular belief, is the noise generated by high-velocity flows in the piping. A review will be made of parameters that can be used to predict and treat pipeline noise problems. Presented also will be the evaluation of silencers and certain problems with the use of acoustic insulation.