bluuebunny/crossref_metadata_2025 huggingface dataset:
Model Studies of Effects on Motor Vehicle Noise of Shapes and Arrangements of Buildings along Urban Streets. II. Experimental Findings
Authors: Plane Vern C. , Knudsen Vern O.
Published: October 2005

Descriptions are given of the various models investigated and the acoustical characteristics of the noise sources simulating motor vehicle noise. The models tested correspond to streets of typical widths, faced with buildings of typical heights, having various shapes and orientations (conventional and modified), with and without spacings (alleys), and with the facing surfaces either reflective or absorptive. One series of curves, using the gasoline engine as the noise source (operating at low and also at high speed), shows sound-pressure levels versus the horizontal transverse distance across the model for five wall separations ranging from 10 to 30 ft. The levels agree with predictions. Similar curves show dBA and octave-band levels versus the longitudinal distance along the base of one wall, for both continuous and spaced walls. The curves reveal the anticipated effects of diffraction. Noise reductions of as much as 12 dB were obtained by the use of oblique, flat surfaces at the wall bases. This encouraging result is being followed with tests on models for buildings having appropriate parabolic facings. The findings have predictive value for full-scale constructions.
Further Analysis of Helicopter Noise Experiments in an Urban Environment
Authors: Kinney Wayne A. , Pierce Allan D. , Rickley Edward J.
Published: October 2005

A previous paper by the authors [J. Acoust. Soc. Amer. (in press)] discusses preliminary analysis and interpretation of recent experiments in which recordings were made while a helicopter flew over (1) an array of microphones placed in an open field, and (2) a similary array placed in the center of a city street surrounded by tall buildings. The present paper examines (1) the frequency dependence of the urban enhancement effect, (2) the variation in noise-versus-time profiles with microphone location, and (3) the reproducibility of the helicopter flyover noise data. Third-octave-band spectra of the open field and urban recordings are exhibited and discussed and simultaneously recorded data by microphones in the center and at the side of the street are exhibited. [Research supported by U. S. Department of Transportation.]
Noise from Aerial Bursts of Fireworks
Authors: Maglieri D. J. , Henderson H. R.
Published: October 2005

As part of a broad study relating to sonic-boom exposures and their effects on people and building structures, the opportunity was taken to make measurements of the shock-wave pressure time histories resulting from aerial bursts during a professional fireworks display. The information derived from these tests may be of general interest with regard to community noise criteria. Data were obtained using sonic-boom instrumentation located at two positions on the ground almost directly under the airburst which occurred at about 300-ft altitude. Ground launching mortars varied in size from 4 to 6 in. in diameter and had composition charges of from about 2 to 3 lb. Peak overpressures of up to about 15 psf were observed and the signature durations were about 12 msec as compared to normal sonic-boom signatures having overpressures and durations varying from about 1 to 3 psf and 100 to 300 msec, respectively. Also included is information relating to the signature rise times, frequency spectrum, and impulse.
Acoustic Scaling of Solid Cylindrical Targets
Authors: Ryan William W.
Published: October 2005

Scaling of acoustical targets has been for many years an integral part of the acoustic program of ARL as well as many other laboratories. This paper presents a brief summary of the scaling laws. Also presented are a series of backscattering data for a series of aluminum targets whose scale factors range from 1 to 1/15. These data are compared to the theoretical equations [after J. J. Faran, J. Acoust. Soc. Amer. 23, 405 (1951)] for the backscattered energy. Good agreement between experiment and theory has been obtained. [Work sponsored by Naval Ship Systems Command.]
Three Glottal Features
Authors: Ladefoged Peter
Published: October 2005

Evidence for laryngeal control mechanisms may be obtained from observations of the states of the glottis that can be used to produce linguistic contrasts in the languages of the world. All languages use differences in pitch, which are produced by controlling the glottal tersion. All languages contrast voiced and voiceless sounds. Some languages also have breathy voiced sounds, others also have creaky voiced sounds, others contrast stiff voice and slack voice, etc. But no language contrasts more than three of these phonation types. This constraint on languages can be explained by setting up a single feature, glottal stricture, on which only three distinctions can be made at a time. This feature is controlled primarily by the distance between the arytenoid cartilages, which is smallest in a glottal stop and increases through creaky voice, stiff voice, voice, slack voice, and breathy voice, until it reaches its maximum in voiceless sounds. The third feature, which is used by many languages, is glottal timing, or voice onset time, which distinguishes aspirated from unaspirated sounds.
Comparison of Phonemic and Graphemic Features of Eight English Consonants in Auditory and Visual Modes
Authors: Jeter Irma K. , Singh Sadanand
Published: October 2005

Eight English consonants in CV context were presented graphemically and phonemically in visual and auditory modalities for similarity judgments using the ABX method. An interpretation of two 3-dimensional MD-SCAL configurations (Euclidean) of these iudgements revealed the graphemic feature categories of form (vertical-rounded, vertical-crossed, and angular), place (labial and alveolar), and manner (slop and continuant), and the phonemic feature categories of place (labial and alveolar), manner (stop and continuant), and voicing. The visual data had lower “stress,” hence a better fit, than the auditory data. The graphemic features were better predictors of the visual mode than the phonemic features were of the auditory mode. Visual data showed higher multiple R (0.809) than auditory data (0.677) when their MD-SCAL dimensions were correlated with the graphemic and phonemic features, respectively. The commonality of the features place and manner in cuing visual and auditory judgments indicated the coding of these features at a higher cortical level than where these modalities are distinguished.
Mandarin Tones in Selected Sentence Environments: An Acoustic Study
Authors: Ting Aichen
Published: October 2005

This study investigated the acoustic correlates of the four lexical tones of Mandarin Chinese in isolated words and variations in these parameters in relation to sentence environment, syllable vowel, and preceding consonants. A corpus of 476 words contrasting the four tones in selected segmental and grammatical environments was recorded by five Pekinese speakers. Oscillograms were prepared for the tested items. After segmenting the oscillograms, the syllable nuclei of the test items were measured for duration and for fundamental frequency at three points: beginning, mid, and end, plus any inflection points. Intensity values were compared for three selected vowels. Mean values were calculated for duration and fundamental frequency, and compared for the different environments, vowels, and preceding consonants involved. Results show that the acoustic parameters investigated for tones in isolated words are similar to those described in previous studies. Differences associated with the variables of sentence environment, syllable vowel, and preceding consonant indicate that all of these factors affect the realization of the tone, although the four tones maintain their characteristic basic differences. Results of the present study were discussed and compared with some of the previous findings. Some future investigations were suggested.
Errors of Articulation in the Speech of Profoundly Hearing-Impaired Children
Authors: Levitt Harry , Smith Clarissa R.
Published: October 2005

Recordings were made of the speech of forty children at a large school for the deaf. The children were equally divided between male and female and between the age groups 8–10 and 13–15 yr. Each child read a specially constructed set of sentences containing all phonemes occurring more than 0.1% of the time in spoken English. The recordings were analyzed for phonemic errors by a group of skilled phoneticians. Errors were subdivided into four groups: distortion, omission, unrecognizable substitution, and recognizable substitution. Errors involving consonants were markedly dependent on place of articulation. Distortions, omissions, and unrecognizable substitutions increased with place of articulation toward the back of the mouth, whereas recognizable substitutions were greatest with place of articulation toward the center or front of the mouth. Substitutions were primarily voicedvoiceless with a high proportion of errors involving manner. There were relatively few substitutions involving place. Errors with vowels were most frequently recognizable substitutions and these were typically tense-lax confusions or substitutions towards a more central vowel. [This research was supported by National Institutes of Health, Grant No. NS09252.]
Cochlear Dysfunction Associated with Decompression from 300-ft Hyperbaric Chamber Dives
Authors: McCormick J. G. , Higgins T. L. , Daugherty H. S. , Johnson P. E.
Published: October 2005

J. D. Harris has reported [U. S. Naval Submarine Medical Center, Conn., Rep. No. 591 (5 Aug. 1969)] severe neurosensory hearing loss in Navy divers due to decompression sickness. In an attempt to develop an animal model for this condition with verification of cochlear involvement, we compressed guinea pigs at 1 atm/min to 300 ft in air. Time at 300 ft was held constant at 6 min while decompression schedules were shortened from Navy diving tables. Animals were dived with an open bulla to eliminate barotrauma to the ear drum, and cochlear potentials were measured postdive. The general finding was the onset of auditory loss 10–15 min postdive. Severe loss (40–50 dB} was usually present by at least 1 h postdive. The loss remained stable 2–5 h postdive, and became more severe 6 h postdive.
Nonlinear Aspects of Cochlear Microphonics
Authors: Strelioff D. , Honrubia V. , Ward P. H.
Published: October 2005

Using the resting endocochlear potential as a reference level, the amplitudes of the positive and negative peaks of the cochlear microphonics were measured in each of the four turns of the guinea pig scala media during pure tone stimulation. Since the relative stimulus amplitudes at these peak values were known, these peak values were used to determine the transfer characteristic curve for each frequency. After appropriate adjustments for frequency sensitivity, the curves for each turn were nearly identical for a wide range of stimulus frequencies and intensities. Therefore a single nonlinear frequency-independent transfer characteristic curve for each turn was adequate to describe the cochlear potentials. The significance of these curves is that, due to the differences in the shapes of the positive and negative portions of the curves, they can account, not only for the amplitude of the cochlear microphonics, but for the polarity and magnitude of the summating potentials as well. [Research supported by the National Institutes of Health.]
Study of the Spatial Distribution of the Summating Potential by Drug Perfusion
Authors: Stopp Phyllis E. , Deakin Kathleen M.
Published: October 2005

The summating potential in response to an 8-kHz tone has an opposite polarity in the basal and apical tums of scala tympani of the guinea pig against a reference electrode in the mouth. This “reversed” apical potential could arise from a generator spatially distinct from that giving rise to the basal potential, or the differences could arise from the geometry of passive electrical conduction acting on a single source. Attempts have been made to perfuse restricted regions of scala tympani with the ototoxic drug, ethacrynic acid, and with other substances. It is found that perfusion of the basal turn destroys both the basal and apical summating potential responses to 8-kHz stimulation, while similar perfusion of the apical half of the cochlea leaves both responses unchanged. Similar experiments at other stimulus frequencies yield results consistent with the hypothesis that the summating potential is generated in a single region.
Combination “Tones” from Cutaneous Mechanoreceptor Single Units
Authors: Hahn J. F. , Lopater S.
Published: October 2005

Single-unit recordings were made from first-order afferents serving Pincus touch corpuscles in hairy skin of anesthetized cat. The stimuli were two sinusoidal frequencies, within the range 10–100 Hz, mixed and presented through a single stimulator. Under conditions specifiable in terms of the single units single-frequency rate-intensity functions, interspike intervals corresponding to combination frequencies could be obtained. [Partially supported by grants from National Science Foundation and U. S. Public Health Service.]
Focusing Properties of Solid Multielement Acoustic Lenses
Authors: Folds D. L.
Published: October 2005

The sound velocity, thermal coeffecient of sound velocity, and attenuation coefficients of 20 common plastics were measured and used as a basis for the design of several lenses. Materials selected were polyethylene, nylon, polystyrene, polyphenylene oxide, and a low sound velocity silicone rubber compound. Using common geometrical optics techniques, lenses were designed to minimize off-axis aberrations for focal length to aperture ratios ranging from 1 to 3 and aperture-to-wavelength ratios up to 150. Using methods analogous to chromatic aberration correction in optics, lenses were designed for constant focal length over the temperature range 0–30°C. Two and four element lens systems with apertures up to 30 cm were fabricated from the selected materials. Measurements were made in the frequency range 300 kHz–1.2 MHz, and good agreement with theoretical predictions of focal length and directional response was observed. The effects of shear waves were not evident. The theoretical model used to evaluate lens performance was based on the numerical evaluation of the Fresnel-Kirchhoff diffraction integral. This work shows that it is possible, using established optical design methods and commonly available solid materials, to fabricate athermal acoustic lenses with good performance characteristics at aperture-to-wavelength ratios up to 150.
Indian Ocean Deep Sound Speed Channel
Authors: Smothers L. A.
Published: October 2005

During a study of the Indian Ocean sound speed structure, a deep sharply focused sound channel was discovered. The study covered the water mass from the surface to 4000 m in depth. The channel axis depth was found to be approximately 1200 m. The channel exists for a distance of approximately 4800 km (2600 nautical miles) in an East-West direction, centered along the 32°S latitude. The channel width is approximately 1100 km (600 NM). The sound speed at the axis is typically 1486 m/sec. This sound speed channel thus established in space, time, and structure is an important oceanographic feature of the Indian Ocean.
Determination of Acoustic Parameters Using Normal Mode Theory
Authors: Kanabis W. G. , Arens H. J.
Published: October 2005

A computer-oriented procedure based on normal-mode theory was used to determine values of acoustic parameters. Short pulses were used to determine the relative strength of the modes composing the sound field. The measured vertical amplitude distribution of the sound field was used to determine CB, the velocity of sound in the bottom. The measured propagation loss as a function of range and depth was used to determine bottom loss. Also considered were the effect of seasonal variations in velocity profile upon bottom loss and the effects of different bottom types and discontinuities in channel stratification upon propagation.
Origins and Mechanisms of Earthquakes
Authors: Bolt B. A.
Published: October 2005

The elastic rebound theory of earthquake generation is weighed against recent objections and experimental results. The role of water in the fault rupture process is discussed. Fault rupture in a series of epsiodes is supported by seismological recording of a number of earthquakes. Strong ground motion accelerometers provide key data for faulting dynamics which in turn yield the essential engineering parameters of peak acceleration and duration. The type of earthquake mechanism is significant for ground motion estimation. Dislocation theory is helpful in modeling the mechanisms.
Computer-Assisted Reading of Spectrograms
Authors: Makhoul John
Published: October 2005

A simple user-oriented computer language has been developed (using LISP) to be used as an aid in reading spectrograms of sentences containing words from a fixed vocabulary. The lexicon is stored in the computer in terms of phonetic segments and features. Questions such as “Give me all two-word combinations that contain the following sequence of phonetic segments or features….” are easily translatable into simple and concise commands in this language. All commands are expressed in terms of phonetic segments or features which the user deduces from the spectrogram. In cases where segmentation is not obvious, a feature may be specified over a variable number of segments. It has been found that the use of such a language in conjunction with the reading of spectrograms provides insight into the kinds of acoustic analysis that are necessary in developing strategies for the machine recognition of connected speech. The language and some implications of its usage, based on experience with a 200-word vocabulary, will be discussed.
Formant Extraction from a Digital Inverse Filter Formulation
Authors: Markel J. D.
Published: October 2005

An inverse filter formulation is applied to the problem of formant extraction from continuous voiced speech. Although the basic analysis equations can be derived from a multitude of different formulations, the inverse filter is believed most appropriate because of the insight it lends to the problem as a frequency domain formulation. Starting from the basis analysis equations, a new algorithm is described for automatically extracting a set of raw data from which the first three formant trajectories can generally be defined by inspection. The raw data set is obtained by simple peak-picking of the reciprocal of the resulting inverse filter spectrum for each analysis frame. Although an automatic formant extraction algorithm is not considered here, for over 90% of the raw data, automatic extraction is trivial, namely F1(k) − F3(k) for frame k equal the first three raw data samples in increasing order of frequency. Examples illustrate the fact that the inverse filter algorithm is capable of correctly extracting closely spaced formant structure and fast transitions. Each analysis frame requires computation roughly equivalent to a single 256-point complex radix-2 FFT algorithm. The complete analysis procedure has been implemented on a small PDP-8 computer with 4 K of core. A more detailed discussion along with computer programs will be presented [SCRL monograph No. 7 (to be published)].
Morph Lexicon for Speech Synthesis by Rule
Authors: Allen Jonathan
Published: October 2005

This paper reports the results of representing the 1 000 000-word Brown Corpus by a set of morphs and their underlying morphemes. The detailed procedure, including practical considerations for handling such a large data base, is discussed, and the algorithm which decomposes words into morphs is presented. It was found that many words decompose into morphs ambiguously, so that a set of selectional rules is needed to indicate the correct morph sequence. Thus affixation is generally preferred over compounding in English. The data base for obtaining these rules is discussed. Some statistics for the resulting lexicon are also presented. Finally, a procedure for merging the morph lexicon (spellings) with the Merriam Pocket Dictionary to obtain pronunciations and parts of speech is presented, together with a description of the resulting dictionary. [This work was supported in part by the National Institutes of Health.]
Aural Harmonics: A Comparison of Two Models for the Tone-on-Tone Masking Paradigm
Authors: Erdreich J. , Clack T. D.
Published: October 2005

Aural Harmonic estimates derived from the tone-on-tone masking paradigm have been described with the simplified model Ar = Aa + Ai sin(α). (1) This is an approximation of the true model Ar2 = Aa2 + Ai2 − 2AaAi cos(α) (2) [Schubert, J. Acoust. Soc. Amer. 45, 790–791 (1969)]. The use of Eq. 1 has received criticism on the basis that if Ai is used to calculate the aural harmonic, Ai should be computed from Eq. 2. Estimates derived from the fit of the simplified model and the fit of the true function show close agreement. Equation 2 gives a better fit, further supporting the concept of vectorial summation of aural and acoustic harmonic. In light of the wide range of applications for the least-squares fit t.o a circle (Eq. 2) the algorithm for the solution is presented.
Frequency-Modulated Tone Thresholds in Normal Subjects
Authors: Young I. M.
Published: October 2005

Descending Békésy thresholds were obtained for frequency-modulated tones in normal-hearing subjects. Measurements were made at a fundamental frequency of 1000 Hz by using combinations of eight modulated rates and eight frequency deviations. Starting intensity level was 100 dB re 0.0002 μbar. Attenuation rate of Békésy-type recording attenuator was 1 dB/sec. Results indicated that for a given modulation rate, the threshold improved with increasing frequency deviation. For a given frequency deviation, as modulation rate increased the thresholds became worse. Combinations of slow-modulatlon rate and wide-frequency deviation resulted in the best threshold. For a given modulation index (the ratio of frequency deviation to modulation rate) better thresholds were obtained by smaller frequency deviations.
Time-Amplitude Forced-Choice Equivalence
Authors: Pollack Irwin
Published: October 2005

Over a wide range of sound levels, there exists a series of trading relations between time (t) and intensity (I) for equal-loudness for bursts of white noise [Miller, J. Acoust. Soc. Amer. 20, 160–70 (1948)]. Despite this trading relation, a listener may well be able to discriminate between different I⋅t combinations, to which he assigns equal loudness. In a four-interval forced-choice test, three auditory pulse trains were presented at one I⋅n (number) combination; one train consisted of a different I⋅n combination. Three equivalent relations were studied as the n1:n2 ratio was varied: I1 = I2; I1n1 = I2n2; and I1n12 = I2n22. The range for time-intensity forced-choice equivalence is considerably smaller than that reported for the time-intensity interaction for equal loudness.
Threshold Perception of Periodically Phase-Reversed Sinusoids
Authors: Burnett Edwin D. , Corliss Edith L. R.
Published: October 2005

In connection with a direct study of the integration time of the ear, we generated a test signal by introducing a phase reversal at integral numbers of zero crossings of a sinusoidal signal. When the number of periods between reversal is large, auditory threshold is found at the same level as for a steady-state pure tone. Subjectively, the phase reversal is sensed as a faint click. In the range 1000–4000 Hz, the threshold is elevated by about 3 dB when the number of periods between reversals is reduced to less than about 50. This is direct evidence of “backward masking.” Ultimately at still shorter intervals between reversals, the sideband components introduced by the interruption are sensed at lower levels than is the central frequency itself, but the central tone is sensed momentarily when an attenuator step is switched, evidently unbalancing the interference.
Pitch of Tone-Doublets
Authors: Nabelek I. V. , Nabelek A. K.
Published: October 2005

The pitch of short tone bursts interrupted by a short pause (so called tone-doublets) was investigated. Tone-doublets consisted of two parts separated by a pause. Each part was formed by m whole cycles of the carrier frequency starting and ending at zero crossings. The frequency of both parts was the same. According to the Fourier transform, the energy spectrum of such tone doublets can have the main maximum at the carrier frequency, below or above it, or it can have a minimum at the carrier frequency. The relative position of the maxima and the carrier is determined by both the value of the carrier frequency and the pause duration. A method of pitch matching was used to determine: (1) if the spectrum or the periodicity of the carrier is more important for the pitch perception and (2) if a short pause causes the two tones in a doublet to be processed by hearing as two separate events.
Signal Detection as a Function of Interaural Intensity
Authors: Yost W. A. , Penner M. J. , Feth L. L.
Published: October 2005

Detection of a masked signal at one ear was measured while a sinusoid of the same frequency and a noise were presented to the contralateral ear. The contralateral sinusoid (500 Hz) was gated on for 100 msec in both intervals of the two interval forced-choice experiment. The signal was gated on for 100 msec with equal probability in either the first or second observation interval. The interaural phase between the signal and contralateral sinusoid was either 0° or 180°. The interaural phase between the broad band continuous noise at the ears was 0°. The spectrum level of the noise at the signal ear was 40 dB. The contralateral sinusoid-to-masker ratio was varied by changing either the level of the sinusoid or the spectrum level of the masker. As the contralateral sinusoid-to-masker ratio increased from −10 to 60 dB, the signal-to-masker ratio required for detection increased from −10 to 25 dB. These results show that contralateral stimulation can either enhance or degrade detection of a monaural signal. In addition, the data indicate that a crucial variable linking studies of the masking level difference (MLD), central masking (CM), and monaural detection with contralateral cue (MDCC) is the interaural intensive difference. [The research was supported by the National Institutes of Health, and by National Science Foundation Post-doctoral Fellowships while the authors were at the University of California, San Diego.]
Criteria for Control of Hearing Loss from Industrial Noise
Authors: Jones Herbert H.
Published: October 2005

There has been much misunderstanding and confusion about the risk criteria for hearing impairment as they have been used in the development of limits of noise exposure for hearing conservation. In order to reduce some of this confusion a discussion of the methodology used in the development of the risk tables will be presented.
W. K. B. Mode Approximation Applied to SOFAR Propagation in the Arctic Ocean
Authors: Kutschale Henry W.
Published: October 2005

A rapid method is presented for computing the approximate pressure signature at long ranges from explosive sources in the Arctic SOFAR Channel. The solution of the wave equation in terms of normal modes for the layered medium bounded above by a rough ice sheet is computed by the W. K. B. approximation. A comparison of these computations with those made by the exact normal-mode solution for the layered medium shows agreement of phasevelocity dispersion to better than four significant figures. Errors in group-velocity dispersion may be somewhat greater, but they appear generally to be small enough to give a satisfactory fit with field data. Agreement between computations by both methods of the variation of pressure and particle motion with depth for each mode is excellent except near the turning point of the ray, where the W. K. B. approximation breaks down. Particle motion is retrograde elliptical at the surface and prograde at the bottom of the ice similar to particle motion of flexural waves. Pressure amplitudes from explosive sources computed by the W. K. B. approximation agree with those computed by the exact solution to better than 7 dB in peak pressure level. The formulas for dispersion and wave amplitudes are incorporated in a ray-tracing computer program.
Source Levels for Shallow sus Charges
Authors: Christian Ermine A. , Shuler Verna K. , Gaspin Joel B.
Published: October 2005

Idealized source levels have been computed for sus charges (1.8 lb TNT) detonated at “standard” depths of 60, 300, and 800 ft. Spectral energy distributions were obtained by transforming quasitheoretical time functions representing the initial shock wave and first three bubble pulse phases of the explosion pressure waves. For the most part these new source level values agree well with results previously published by Weston and Christian; occasional differences of more than 5 dB occur, however, for certain frequency bands and charge configurations. One-third octave band levels have also been examined for charges detonated over the range of depths typically found in practice when the above nominal depth settings are used. This comparison shows that if the analysis bandwidth is narrow compared to the explosion spectrum pattern of peaks and nulls—and this is the case at the low-frequency end of the spectrum for these charges—such variations in depth can introduce scatter of up to 6 dB in the band level.
Role of Virtual Modes in Surface-Duct Leakage
Authors: Labianca F. M.
Published: October 2005

A three-layer surface-duct model is considered. In the top layer the sound velocity increases linearly (slope g1) from a value C(0) at the surface to C(b) at the bottom of the duct. In the second layer the sound speed decreases linearly from C(b) at depth b to C0 at depth d (slope |g2| > g1). At depths greater than d the sound speed is constant and equal to C0. For typical ocean conditions C(0)>C0. By employing a theorem of Titchmarsh [Eigenfunction Expansions (Oxford University Press, London, 1962), Pt. I] it is shown that only a continuous spectrum of modes exists. This result, so contrary to widely held beliefs, is shown to hold for a broad class of surface duct models including that of M. A. Pedersen and D. F. Gordon [J. Acoust. Soc. Amer. 37, 108–118 (1965)]. Most of the continuum functions correspond to a situation where little energy is contained in the duct. However, under certain conditions, continuum functions exist which represent a strong concentration of energy within the duct. These are called virtual modes in analogy with the virtual states of atomic and nuclear physics. The conditions for the existence of virtual modes and their rate of leakage are derived. [Work supported by the Office of Naval Research under contract.]
Biomedical Studies Using Ultrasonic Holography
Authors: Sikov M. R. , Reich F. R. , Deichman J. L. , Brenden B.
Published: October 2005

Ultrasonic pulse-echo techniques for medical diagnosis are finding increased acceptance. The results we have obtained using liquid-surface ultrasonic holography suggests that it has advantages over the pulse-echo method for certain applications. The formation of the hologram is analogous to the optical process [Brenden, in Acoustical Holography (Plenum Press, New York, 1969), Vol. I]. A reference and an object beam of ultrasonic energy interact at a liquid-gas interface to form a ripple pattern which serves as the hologram. The images are reconstructed in real-time by reflection and diffraction of a beam of coherent light from this liquid surface. Images may be viewed or photographed directly or recorded on video tape. A motion picture prepared from edited tape recordings will be used to illustrate our results. These include studies with experimental animals such as a live fish swimming in the holographic tank, the urogenital system of the rat, and stimulated contraction and motion of the valves of the heart. The instrument also has been used for in vivo and in vitro studies in the human: contraction of the uterus and uterofetal relationships in surgical specimens, and muscle and tendon motion in the hand.
Comparison of the Masking Functions of Speech-Modulated and White Noise
Authors: Berrv R. C. , Nerbonne G. P.
Published: October 2005

The relation between the masking functions for white noise (WN) and speech-modulated noise (SMN) for vowels and words were compared. Three randomizations containing three examples of each of the nine pure vowels in an h_d context (27 vowels/list) and four CID, W-1, word lists served as stimuli. Two matched groups of 20 subjects heard the vowel and word lists at four (−12, −8, −4, 0) S/N ratios. The order of presentation of the lists and S/N ratios were randomized across subjects. One group heard the stimuli in the presence of WN, the other group in the presence of SMN. The SMN was generated in such a manner that the envelope of the masking noise for each stimulus closely approximated the envelope of that stimulus. Subject's performance was consistently better for the vowels than the W-1 words. However, performance on both words and vowels was consistently better under WN masking than under SMN masking. This finding is in direct opposition to previous authors.
Some Parameters Affecting the Differentiation of Modal-Falsetto Voice Quality
Authors: Colton Raymond H.
Published: October 2005

Previously [R. Colton and H. Hollien, J. Acoust. Soc. Amer. 47, 105(A), (1970)] it was reported that observers could distinguish modal and falsetto voice quality when the phonations from the two registers were presented at the same fundamental frequency and intensity. Other data [R. Colton, (unpublished)] demonstrates that modal phonations exhibit more energy in the higher harmonics than do falsetto phonations; suggesting that frequency bandwidth is an important cue for the differentiation of modal and falsetto voice quality. Phonations produced in the two vocal registers were low-pass filtered to equate the bandwidth of modal phonations to falsetto phonations. The filtered phonations were presented in a paired comparison paradigm to observers who judged the similarity or dissimilarity of voice quality of each stimulus pair. The proportion of correct responses was 0.71; a decrease of 20% when compared with the responses obtained for these phonations in an unfiltered condition. These results indicate that stimulus bandwidth is an important acoustic parameter for the differentiation of the modal and falsetto registers. However, an analysis of individual phonations suggest other acoustic differences may aid in the distinction of modal and falsetto voice quality.
Speaking Fundamental Frequency of Eight-Year-Old Girls—Revisted
Authors: McGlone R. E. , McGlone J.
Published: October 2005

Several recent studies have suggested that average speaking fundamental frequency levels are lower now compared to speaking levels several decades ago. Indeed, the present investigators found that a group of 6-yr-old girls when identifying pictures of objects used fundamentals lower than those previously reported for teenage girls. To use a method that permitted comparison with similar studies of young girls, many of the above subjects were recorded two years later reading a standard passage. A graphic display was made of this recording and the fundamental frequency of each speaker was determined from wavelength measurements. The results showed a group mean fundamental frequency within l0 Hz of the group level reported previously for girls of the same age. The differences found by the present investigators for the two age groups appear to be related more to the speech sample than other developmental features of the subjects.
Detection, Lateralization, and the Phase Angle, α: 1000 Hz
Authors: Jeffress Lloyd A. , McFadden Dennis
Published: October 2005

At recent meetings of the Society we reported experiments in which the same narrow band of noise (50-Hz bandwidth) served as both masker and signal. The signal was added to the masker at various values of the phase angle, α. Both detection and lateralization performance were measured at center frequencies of 250 and 500 Hz. By controlling the value of α, by means of a phase shifter between the masker and signal channels, it is possible to control the relative contributions of interaural time differences and level differences. The present experiment is essentially a replication of the others except that the center frequency of the 50-Hz band of noise was 1000 Hz. Data were obtained by the single-interval, forced-choice procedure, YES-NO for detection, and RIGHT-LEFT for lateralization. As in the previous experiments, some subjects performed best at α = 90° where level difference was the only cue, and other subjects performed best at α = 90° where the only cue was an interaural time difference. [This research was supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education and Welfare.]
Suprathreshold Loudness Adaptation
Authors: Morgan D. E. , Dirks D. D.
Published: October 2005

Loudness adaptation at 500 Hz (70 dB SPL) was measured over a 7-min stimulation period using the tracking method. The duration of a simultaneous, contralaterally presented comparison stimulus (400 Hz) was either 250 or 3000 msec. Duty cycle of the two comparison stimuli was identical (3313%), however, use of the tracking method (8 dB/sec attenuation rate) necessitated one important difference between the two test conditions. The comparison stimuli were either (1) a 3000-msec pulse presented once each 9 sec, or (2) a train of six short pulses (250 msec on, 500 msec off) presented each 9 sec. During the on-time of the comparison stimulus the subject was required to balance the loudness of the comparison tone (400 Hz) to the loudness of the contralateral, continuous stimulus (500 Hz). No loudness adaptation in the 500-Hz stimulus was observed throughout the 7-min period when a 3000-msec comparison stimulus was employed. An apparent immediate enhancement of loudness which was maintained throughout the 7-min period was observed with the 250-msec comparison tone. The results of a subsequent study have delineated the durational conditions under which the “enhancement” of loudness can be observed.
Perstimulatory Loudness Adaptation as a Function of Comparison Signal Duration
Authors: Stokinger T. E. , Cooper W. A. , Resnick S. B.
Published: October 2005

The present study was conducted as part of a continuing investigation of the influence of control ear stimulation on the amount of loudness adaptation. Perstimuiatory loudness adaptation at 1000 Hz was assessed for six normal-hearing subjects via single simultaneous dichotic loudness balances using the method of constant stimulus differences. The amount of adaptation was determined as a function of the duration of the comparison signal for two levels (50 and 80 dB SPL) and two durations (8 and 12 sec) of the adapting signal. The duration of the comparison signal ranged from 0.2 to either 6 or 8 sec. An apparent increase in the amount of adaptation occurred as the duration of the comparison signal was increased. The magnitude of this increase and the shape of the function relating the amount of adaptation to comparison signal duration differed for the two adapting durations employed, but was relatively independent of the intensity level of the adapting signal. [This research was supported by the Oklahoma City Veterans Administration Hospital, Project No. 9-70.]
Air-to-Ground Sound Propagation—Some Practical Considerations
Authors: Sutherland Louis C.
Published: October 2005

Recent improvements in theoretical methods for predicting air-to-ground sound propagation are briefly reviewed and predictions compared with field observations previously reported in the literature. The remaining problems in theoretical methods are considered and preliminary models outlined for making practical engineering predictions of air to ground propagation loss. Representative noise source spectra are used to illustrate the expected trend in attenuation versus distance for various types of single number noise scales under a variety of atmospheric conditions. [This research has been sponsored, in part, by the Army Research Office.]
Airport Noise Monitoring
Authors: Eldred K. McK.
Published: October 2005

This report describes the monitoring requirements of the proposed noise regulations for California airports. The requirements include measuring the noise of each aircraft under the takeoff and approach paths at points which are analogous to those of the Federal Aviation Regulation for aircraft certification. Additionally, they require monitoring of community noise exposure on a contour of equal community noise equivalent level, which is analogous to a contour constructed in accordance with federal noise exposure forecast methods. The paper also discusses the rationale of the quantities to be monitored and their relationship to quantities used by the federal government for certification and land use planning. [This work was supported by the Department of Aeronautics of the State of California.]
Automatic Speaker Verification Using Phoneme Spectra
Authors: Hair G. D. , Rekieta T. W.
Published: October 2005

A technique, amenable to completely automatic real-time application, for verifying the identity of a cooperative speaker has been demonstrated and evaluated. Wide-band digital recordings of 10 isolated words were made on each of 9 weeks for 230 speakers. Segments of selected phonemes were automatically edited and power-density spectra computed over a 7.5-kHz bandwidth. A preliminary analysis of 40 randomly selected speakers has been performed. Phoneme spectra for five repetitions were averaged to produce speaker standard pattern vectors with the remaining four repetitions used for error-rate estimation. Pattern vectors of dimension 180 (smoothed spectra of six phonemes), 26 (features derived from the spectra), and 206 (combination of spectra and features) were used for technique evaluation. Combined error rates of 2, 5, and 1%, respectively, were obtained using a simple hypersphere decision rule. It is concluded that reliable real-time speaker verification can be achieved with completely automatic digital processing techniques and modest pattern storage requirements.
Preferred Waveform Criterion for Sonar
Authors: Rowlands Richard O.
Published: October 2005

It is shown that a signal whose frequency spectrum is symmetrical in amplitude but not necessarily in phase, about the midband frequency has a narrower autocorrelation function than one whose amplitude spectrum is asymmetric.
Energy Beam Pattern for Baffled Pistons under Pulsed Operation
Authors: Stepanishen P. R.
Published: October 2005

This paper presents an extension of an approach which was previously developed by the author [J. Acoust. Soc. Amer. 49, 629–638 (1971)] to investigate the pressures at spatial points in the field resulting from a specified pulsed velocity notion of a baffled piston. In the present paper an investigation of the farfield pressures radiated from baffled pistons and the characteristics of the time-dependent energy beam pattern are presented. The earlier approach is shown to reduce to simple expressions relating the time history of the farfield pressures to the time history of the piston motion. It is noted that the pressure at points in the field resulting from a pulsed velocity can consist of a multipulse structure. In different regions of the field, the pulses can be proportional to the piston displacement, velocity, or acceleration. As a result it is shown the pressure pulses may have nonzero average values for a pulsed sinusoidal velocity. For nonsinusoidal pressure fields the energy pattern of an array is defined and expressions are developed for the energy pattern in both the frequency and time domain. Numerical results are presented comparing the beam and energy pattern of a pulsed array. Several generalizations are noted.
Dynamics of Ambient Sea Noise
Authors: Parkins B. E.
Published: October 2005

Previous measurements of low-frequency ambient sea noise have shown that there exist slow changes in the noise power of the ocean which cause the modulation of observed frequency spectra. These slow changes have been studied by measuring the variation and covariation of the fluctuations occurring within bands of deep-sea noise in the region from 100 to 800 Hz. This was done by measuring the spectra, the coherencies, and also the cross-correlations of the changes in the intensities of band-limited noise signals and in the wind speed that occurred over a period of 1112 days off Bermuda in winter. Slow changes with frequencies lower than 1 cycle/day were seen in the spectra of all noise channels and the wind channel. These slow changes for frequency bands from 200 to 800 Hz were strongly covarying among themselves and with the fluctuations in the wind speed. A much lower covariation was observed between the changes in the noise bands at and near 100 Hz and those at 400 and 800 Hz and the wind channel. There was, however, appreciable covariation between the changes in level at 100 and 200 Hz which is taken to be the effect of shipping. [Work supported by the U. S. Navy Electronic Systems Command.]
Pitch Change in Trills and Vibratos
Authors: Divenyi P. L. , Hirsh I. J.
Published: October 2005

Musically trained subjects adjusted the absolute frequency change in a vibrato, ΔfVibr, to match the pitch change in a trill having a constant frequency separation, ΔfTrill, between its upper and lower tones. The form of frequency modulation of the sinusoidal signals was a square wave for the trill, and, for the vibrato, either a triangular or a 50% steady-state trapezoidal wave. Both trill and vibrato had identical center frequencies, fc, and duration (750 msec). Within the range tested (4–12 Hz), the modulation frequency had no effect on ΔfVibr. However, the adjusted ΔfVibr were consistently higher for the triangular modulation of the vibratos. The function relating ΔfVibr to ΔfTrill was monotonic with an average slope of 1.72 for the triangular vibrato and 1.07 for the trapezoidal vibrato. No difference could be observed as an effect of two different center frequencies (fc = 705 or 2330 Hz) when frequency ratios ΔfTrill/fc and ΔfVibr/fc were considered. The width of the observers' internal filter was estimated from the data. [Supported by NINDS Grant No. NS03856.]
Schlieren Techniques for Showing Ultrasonic Wave Propagation
Authors: Posakony G. J.
Published: October 2005

A 19-min color movie which describes high-frequency sound-wave propagation and reflection is presented.
Compatible Tests on Earcap and Ear-Insert-Type Earphones
Authors: Bryant H. W.
Published: October 2005

This paper covers the use of the 6- and 2-cm3 ASA (Standard Z 24.9-1949) couplers employed to measure the response of earcap and ear-insert-type earphones, respectively. The investigation revealed that in order to compare the subjective loudness of the two types of earphones at any given frequency, a correlating adjustment had to be applied because the couplers measure the sound pressure developed at opposite ends of the auditory canal. In addition, to avoid a 3-dB error, the basic 2-cm3 volume had to be reduced to 1.3 cm3, coinciding with the unoccupied coupler volume. An experimental 6-cm3 coupler is described which measures the pressure developed at the tympanum end of the canal, and direct comparisons with data taken on the 1.3-cm3 coupler are presented. The necessary correlating information was obtained with ear probes projecting into the canal.