bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic invariance for place of articulation in stops and nasals across syllabic contexts
Authors: Blumstein Sheila E. , Stevens Kenneth N.
Published: October 2005

In earlier ASA meetings, we presented theoretical and experimental support for the view that invariant cues for place of articulation in initial voiced stop consonants reside in the gross shape of the short-term spectrum at consonantal release. It is postulated that this concept of invariant spectral shapes is generalizable across phonetic contexts to all stop consonants and nasals. We have examined the spectral shapes for a large number of tokens of initial and final voiced and voiceless stop consonants and nasals spoken in various vowel environments by four male and two female speakers. The spectra obtained were matched to a set of templates or “windows” we developed to test quantitatively for compactness and diffuseness. Between 75% and 80% of the stop consonants were correctly classified by these templates. The failure of the remaining spectra to fit these templates may reflect limitations of the particular spectral analyses as well as the role of secondary context-dependent cues for place of articulation. The application of these procedures to nasals indicates that onsets may need to be defined in terms of changes in spectral amplitude from the nasal murmur to consonantal release. [Work supported in part by NINCDS and the John Simon Guggenheim Foundation.]
Voicing distinction in Polish word-initial stop consonants
Authors: Moslin Barbara J. , Keating Patricia A.
Published: October 2005

Voice onset time measurements were made of word-initial stop consonants produced by native speakers of Polish in order to determine how the values for the Polish voiced and voiceless categories are distributed along the VOT continuum. According to traditional phonetic descriptions, the Polish language utilizes the voicing lead and short-lag categories along the VOT continuum to contrast its voiced and voiceless stops. VOT measurements were made of stops produced in a number of different speaking conditions: minimal pairs read in citation form, words embedded in controlled sentence contexts, and words excised from both formal and informal discourse. Preliminary results indicate that VOT values for productions of the Polish voiced stop are distributed almost exclusively within the “lead” region of the continuum. Values for the voiceless stop, however, in certain conditions do not cluster in the predicted, contiguous short-lag region of the continuum. In certain speaking conditions Polish voiceless stops cluster within the noncontiguous, long-lag region and tend to be aspirated. Acoustic characteristics of stop consonants as a function of speaking style will be discussed, and results of Polish listeners' identification of synthetic CV syllables along a VOT continuum will be provided.
Independent acoustic features in speech perception
Authors: Massaro Dominic W. , Oden Gregg C.
Published: October 2005

Experimental and theoretical procedures are used to investigate how the various acoustic features of a speech signal are integrated into a synthesized percept. Stop consonant-vowel syllables were factorially generated by independently varying acoustic cues for voicing and for place of articulation and were presented to subjects for identification. The identification data for these stimuli were used to test a quantitative model which assumes that (1) the acoustic dues are perceived independently, (2) the feature evaluation stage provides information about the degree to which each quality is present in the speech sound, (3) each phoneme is defined by a prototype in long-term memory, and (4) the speech sound is identified on the basis of the relative degree to which it matches the various alternative prototypes. The present experiments replicate and extend previous work which has found evidence for shifts in the identification boundary of one acoustic dimension as a function of the level of another dimension. These results have been interpreted as evidence for the interaction of the perception of the acoustic features themselves. In contrast, the present model provides a good description of the data, while still maintaining complete noninteraction at the feature evaluation stage of processing.
Linear prediction phase spectrum for formant extraction
Authors: Yegnanarayana B.
Published: October 2005

Extraction formant information from linear prediction phase spectrum is proposed. It is shown that the derivative of phase spectrum gives reliable formant information. Since the phase spectra of several resonators in cascade are additive and also since the resonance peaks are sharper in the derivative of the phase spectrum than in the magnitude spectrum, the problem of identifying merged peaks is very easily solved by this method. Application of the method is illustrated through examples of linear prediction spectra obtained for simulated and actual speech segments.
Single- and multipath transmission fluctuations in random and deterministic media
Authors: Adams S. L. , Clark J. G.
Published: October 2005

In recent years both random and deterministic media have been employed in transmission fluctuation models, and the distinction between single- and multipath propagation shown to be important in determining the character of the fluctuations. In addition to the number of paths, the critical parameters in these models are the characterizations of the path amplitude and the path delay modulations, and the background noise. This paper reviews these models and determines the conditions under which continuous-wave and resolved multipath experiments are useful in relating fluctuations to environmental factors.
Bistatic volume propagation measurements at the Azores Fixed Acoustic Range
Authors: Buehler B. G. , Freese H. A.
Published: October 2005

The time, frequency, and angular spreads imposed on acoustic transmissions by inhomogeneities in the ocean volume have been measured over 1.5- and 18-mile purely refracted paths. The dependence of these spreads on acoustic frequency has been investigated and results over the range of frequencies from 400 to 5000 Hz are presented. Fluctuations in received intensity have also been quantified and results are presented in the form of log variance as a function of range and frequency. The transition from the weak to strong (saturated) regime is clearly visible as range and frequency are increased. The large quantity of available data, the long averaging times used, and the consistency of results over many experiments, together with the availability of detailed simultaneous measurements of oceanographic parameters, make the results especially valuable in the evaluation of acoustic propagation models. [Work supported by NAVSEA, ONR, and ARPA.]
Effect of hemispherectomy on frequency difference limens for the two ears
Authors: Efron R. , Yund E. W. , Divenyi P. L. , Dennis M.
Published: October 2005

Hemispherectomized subjects display a strong ear dominance for the pitch mixture of dichotic chords: The tone presented to the ear ipsilateral to the removed hemisphere is less salient in the dichotic sound image than is the contralateral ear tone [R. Efron, M. Dennis, and J. E. Bogen, J. Acoust. Soc. Am. 60, Suppl. No. 1, 550 (1976)]. Two possible causes for similar ear dominance seen in normal subjects are an asymmetry in the transducer properties of the two ears or an asymmetry in the way two basically symmetrical inputs are combined centrally [E.W. Yund and R. Efron, J. Acoust. Soc. 62, 607–617 (1977)]. Evidence for the former derives from the finding that the dominant ear tends to have a superior frequency resolving capacity [P.L. Divenyi, R. Efron, and E.W. Yund, J. Acoust. Soc. Am. 62 624–632 (1977)]. Evidence for the latter derives from the present experiments which show that, in hemispherectomized subjects, there is no difference between the frequency dl in the two ears. The results suggest the existence of an efferent pathway from the cortex which can influence the way pitch information from the two ears is combined (weighted). [Work supported by the Veterans Administration.]
Measurement of the spatial and temporal stability of the underwater acoustic channel
Authors: Jobst W. , Dominijanni L.
Published: October 2005

Techniques for measuring the spatial and temporal stability of the underwater acoustic channel are discussed. Using acoustic data collected over a 500-km path, comparisons are made between estimates of the channel stability obtained by several algorithms. It is shown that a channel digit response algorithm suggested by T. Birdsall, combined with a phase estimator, allows measurement of single-path propagation distance to within ±0.14 m at 500 km. Time series of the channel digit response are shown. Channel time spread and spatial coherence are estimated.
Error analysis for digital signal processing of impulsive signals
Authors: Holmer Curtis I.
Published: October 2005

Digital signal processing techniques are frequently used to find the energy spectrum of an impulsive signal used as a source in underwater acoustics. Previous error analyses for digital techniques have considered stationary noiselike signals rather than the highly structured transients which occur for explosive sources. In this study, analytic techniques have been used to identify that the discrete Fourier transform, without windowing, can be error free when the signal is adequately anti-alias filtered, and wholly contained in the analysis time window. A unique analytic model of an explosive signal time series was used to generate exact spectra for comparison with digitally analyzed spectra. Errors due to FFT roundoff, aliasing quantization, and registration were studied with the model to verify analytic error expressions or to identify empirical error bounds. Quantization (discrete amplitude representation) was found to introduce systematic errors at low frequencies, when insufficient resolution was provided. Analytic expressions for FFT roundoff and aliasing were found and confirmed. Registration was found to be an insignificant factor. [Work supported by Long Range Acoustic Propagation Program (LRAPP, NORDA 600).]
Strategies for reducing error in machinery noise measurement
Authors: Holmer Curtis I.
Published: October 2005

Error considerations play a significant role in the design of measurement procedures and the performance of acoustic measurements. The types of measurements performed can be broadly classified into sound field evaluations. The types of measurements performed can be broadly classified into sound field evaluations (i.e., to evaluate personnel exposure) and source characterization (i.e., to quantify source emission). The latter will be the subject of this talk. All source characterizations can be interpreted as powerlike measurements, which forms a basis for further analysis. The errors in powerlike measurements can be further categorized as methodological and site determined. The methodological errors are those differences from “truth” which result (on the conceptual level) from an ideal measurement, applying a particular test method to the ensemble of sources for which it is intended. The site-determined errors are those variations in the test results which can occur when a particular method is applied to the ensemble of possible test sites meeting the requirements of a given method. Sources of error in lab and field measurements are reviewed and evaluated in the perspective of this classification. Implications for the test engineer and standards designer are drawn.
Relationship between sound power level and sound pressure level outside of laboratories
Authors: Schultz Theodore J.
Published: October 2005

This brief paper does not try to settle the current dispute over the question whether the sound output of mechanical devices is better expressed in terms of sound power level or sound pressure level. Instead, it considers the relationship between these quantities in spaces which have not been specifically designed to be reverberation rooms, and concludes that, once we have measured the noise of a piece of equipment, no matter whether in terms of the sound power level or the sound pressure level, we had better be cautious in how we use the measured data.
New look at using close in measurements of machine noise in situ
Authors: Angevine O. L.
Published: October 2005

During the last decade a number of acousticians have investigated the user of close in measurements of the noise of large machines to determine total sound power. This paper reviews the theoretical justification for such procedures and quotes some comparison of results obtained with those found by classical methods. New investigations offer improved methods of better accuracy [J.D. Vrito, Ph.D thesis (Massachusetts Institute of Technology, October 1976) and J.T. Rainey, C.E. Ebbing, and F. Kushner (to be published).]
General theory of the spreading and scattering of finite acoustic beams
Authors: Gaunaurd G. C. , Überall H.
Published: October 2005

We consider the most general acoustic beam possible, finite in 2D, emerging from an arbitrarily shaped collimating aperture, at an arbitrary angle, and with an arbitrary amplitude profile. We derive the analytical expressions for such a beam, and for the cases of a Gaussian and of a flat-topped square amplitude profiles, we study the propagation of the beams and express their spreading in terms of three ratios (i.e., the ratios of aperture size to wavelength, to axial distance from the the aperture plane, or to radial distance from the beam axis). As a particular application of this general theory we analyze the scattering of a finite beam incident on a sphere larger than the beam in an exact fashion. The analysis can be extended to elastic or viscoelastic spheres, but for simplicity we have developed it for a rigid sphere. Expressions for the cross sections are obtained as partial wave series with coefficients given in integral form. The integrals are evaluated by saddlepoint or other techniques, and the plots for the bistatic cross section compare to and extend the results we found earlier [G. Gaunaurd, J. Acoust. Soc. Am. 61, 1121–1132 (1977)] by means of the approximate Kirchhoff method. [One of us (H.Ü.) was partially supported by ONR, Code 421.]
Measurements and analysis of farfield scattering from a prolate spheroid
Authors: Bayliss A. , Maestrello L.
Published: October 2005

The farfield acoustic scattering by a prolate spheroid with axial point sources near the tip of the body was measured. Data were taken for ka between 10–160 where (a) is the semi-major axis of the spheroidal. Comparisons were made with numerical results obtained by an integral equation based on the simple source method with appropriate coordinate stretching introduced to permit high-frequency solutions with a minimal number of grid points. Theory and experiment agree within experimental error except for the highest frequencies in the shadow region where very rapid changes in pressure make precise measurements difficult.
Matched Asymptotic Expansion (MAE) technique applied to acoustic radiation from vibrating surfaces
Authors: Pierucci Mauro
Published: October 2005

The MAE technique has been used in the field of fluid mechanics for many years. Only recently has this technique been applied to acoustic problems, where it has been found to be an excellent and powerful tool in analyzing either scattering and diffraction or radiation from moving rigid objects (propellers). In this paper it is shown how the MAE technique can be utilized to solve acoustic radiation problems from flexible surfaces. The technique is then applied to the following force driven systems: (1) circular piston in infinite rigid baffle, (2) two concentric pistons in infinite modes. For each of problem analyzed, the structural wavelength a is assumed to be small compared to the fluid wavelength (i.e., ka ≪ 1). The inner region close to the vibrating structure (acoustic boundary layer) is governed by the Laplace's equation while the outer solution is governed by the Helmholtz equation. The inner and outer solution is governed by the Helmholtz equation. The inner and outer solutions are solved independently and are then joined together by the MAE matching procedure. A composite solution is then obtained from a combination of the inner and the outer solution. Agreements with the exact theory for the radiated pressure, surface resistance, and reactance are shown to be excellent.
Directivity study of the radiated sound from ducts by using the uncertainty principle
Authors: Cho Y. C.
Published: October 2005

The uncertainty principle is used for the calculation of the directional distribution of the radiated sound from a uniform duct. The result is in the agreement with the one obtained by using a more complicated wave theory for the fundamental mode. The prediction for the radiation of higher-order modes by the existing theories has yet to be confirmed experimentally. The present calculation also includes the radiation of higher-order modes. The present analysis is simple in comparison with any other existing methods, and it helps one gain a physical insight of some characteristics of the sound radiation from ducts. In addition, the analysis provides with the heuristic distinction between the fundamental mode of a hard-walled duct and the plane wave. The latter is frequently misused in the place of the former.
Farfield multimodal acoustic radiation directivity
Authors: Saule A. V. , Rice E. J.
Published: October 2005

Recently, approximate equations [E.J. Rice, AIAA Paper No. 777–1281 (1977)] for the farfield acoustic radiation pattern in the forward quadrant from a flanged circular duct were presented for both single and multimodal excitation. The single mode radiation equation showed that modal identification could be suppressed and that the resulting approximate equation could be expressed as a function of mode cutoff ratio only. In this paper, several exact radiation patterns for modes with similar cutoff ratios will be compared to the approximate equation to check its range of validity. The multimodal approximate equation consisted only of a simple function of directivity angle and an acoustic power biasing function, and was checked in the above reference for the equal acoustic power per mode case. Several cases of exact calculations other than equal acoustic power per mode will be presented here to test the validity of the multimodal approximate equation. A discussion of significant modal participation in a multimodal radiation pattern will be included.
Experimental investigation of acoustic radiation from a source inside a large turbulent free jet
Authors: Ozkul A. , Yu J. C.
Published: October 2005

Experiments were conducted in an anechoic flow facility to assess the effects of mean flow and shear on the sound radiation from an acoustic source placed in the potential core region of a turbulent free jet. Two different types of source were used; one was a compact source with nearly uniform directivity, the other was a noncompact source with highly directional directivity. A 1.22 m-diam nozzle was used to generate the jet flow on exit Mach number 0.1. The acoustic source was driven by 13-octave band white noise over a range of center frequencies. The ratio of the shear layer thickness to the sound wavelength, an important parameter in assessing the sound refraction by mean shear, was much higher than that obtainable in a previous study [Atvars et al., NASA CR-494 (1966)]. The effects of mean flow convection and mean shear refraction on the sound directivity were determined from measurements made inside the potential core of the jet flow and outside the jet flow in the acoustic farfield. Favorable comparisons were obtained between the measurements and the analytical predictions [Amiet, AIAA paper 77–54 (1977)] for both types of source.
Investigation of the experimental applicability of the Kirchhoff formulation for sound radiation from an oscillating airfoil
Authors: Brooks T. F.
Published: October 2005

The Kirchhoff integral formulation, which is often applied in aeroacoustic problems involving radiation from surfaces, is quantitatively compared to experimental results for the case of an oscillating airfoil. A rigid symmetrical airfoil section was oscillated at small amplitude in a stationary medium (no airflow) to produce the sound field. This pure-tone acoustic source was noncompact in that the compressible frequency parameter kb where k is the wave number and b (22.9 cm) is the semichord, was 1.6 and 2.6, respectively, for the cases considered. Simultaneous amplitude and phase measurements were made of surface velocity and pressure distributions and the acoustic free field. The theory is applied using measured surface pressure and motion, taking into account airfoil thickness and contour. The result of the investigation was that theory overpredicted the sound pressure level by 2–5 dB, depending on direction. Differences were also noted in the sound field phase behavior.
Methodological aspects for the study of cochlear blood vessels
Authors: Axelsson A. , Vertes D.
Published: October 2005

The cochlear blood supply has been evaluated with respect to different vascular parameters, some of which include the density of red blood cells in the lumen, the manner in which the blood corpuscles pass the lumen, and so on. Studies in which specific aspects of the cochlear blood vessel histology are studied in all cochlear vessels have not previously been accomplished. Usually conclusions about the condition of the blood supply are drawn on gross vascular changes occurring in a few isolated vessels. It is suggested that the systematic study of these or similar vascular parameters in all the regularly occurring cochlear vessels is necessary in order to specify the condition of the blood supply following noise or ototoxic drug treatment. The adaptation of morphometric and computerized techniques to the study of the cochlear vasculature is suggested.
Importance of the waveform of the impulse in formulating an Impulse Noise Damage Risk Criteria
Authors: Henderson D. , Hynson K. , Hamernik R. P.
Published: October 2005

Two experiments show the importance of the microstructure of the impulse in producing cochlear lesions and hearing loss. One group of chinchillas was exposed to 50,155 dB, 1-msec A-duration waves and another group was exposed to nominally the same impulse except that the rarefaction phase of the impulse was increased from 2.5 to 4 msec. The animals exposed to the larger duration waves developed 45 dB TTS (X̄,1,2,2.8 kHz) while the animals exposed to the shorter duration impulses developed less than 20 dB TTS. In a second experiment, two groups of five chinchillas were exposed to 50,158 dB, 40-msec A-duration impulses or the same wave with two low level reflected components. The animals exposed to the “clean” impulses had no PTS and only slight hair cell loss, while the animals exposed to the impulse with reflections developed 20–30 dB PTS (X̄2,4,8 kHz) and corresponding lesions in the base of the cochlea. These results point out the pitfalls of establishing a Damage Risk Criteria for Impulse Noise on the basis of only the amplitude and duration of the impulse. [Work partially supported by National Institute for Occupational Safety and Health, Public Health Services, Department of Health, Education and Welfare, Grant No. 1-R01-OH-00364.]
Interaction of sinusoidal vibration and impulse noise: Effects on hearing
Authors: Coling D. E. , Hamernik R. P. , Henderson D.
Published: October 2005

Combinations of whole body vibration and impulse noise exposures can lead to a severe potentiating effect. Three groups, each consisting of five monaural chinchillas, were exposed to (1) 1-h of sinusoidal, 30-Hz vibration at 1 g rms, (2) 50 noise impulses at 155-dB, 1-msec A duration, at the rate of 1/min and (3) a combination of the above vibration and impulse noise. For each group of animals hearing thresholds were estimated before and after exposure at seven frequencies between 0.5 and 8 kHz using evoked response audiometry. Thirty days after the exposure all animals were sacrificed for cochlear histology. Chinchillas exposed to the vibration alone showed no temporary or permanent change of hearing threshold. The group exposed to impulse noise alone sustained a maximum median TTS from 35 dB at 0.5 kHz to 70 dB at 2 kHz. Losses at 30 days showed a maximum of approximately 20 dB at 1.4 kHz with little (<10 dB) or no loss at the other test frequencies. The combination group at all times and test frequencies showed a greater TTS (as much as 25 dB) and a PTS of from 20 to 33 dB at frequencies between 0.5 and 4 kHz. Cochleagrams will be presented with the detailed audiometric data. [Work partially supported by National Institute of Environmental Health Science, Grant NO. 2-R01-ES-00969]
Mechanical tuning of the basilar papilla of the alligator lizard
Authors: Seto W. W.
Published: October 2005

This study explores the possible mechanical processes that are taking place inside the peripheral auditory organ of the alligator lizard. Of primary concern is the frequency tuning capability in the lizard cochlea. Mechanical models are posed for the basilar membrane, the papillary bar, the ciliary tufts, and the hair cells. The mechanical frequencies of vibration and responses are determined and compared with existing data for the neural and receptor cell electrical activity. Hair cell motion is the only mechanical process that can explain in part the first stage mechanical tuning of the basilar papilla of the alligator lizard.
Dynamic methods in speech processing
Authors: Neuburg Edward P.
Published: October 2005

Many experiments in phonetics and other areas of speech science depend on new speech-processing techniques for extracting parameters to be used in the experiments. An example is LPC analysis, and resynthesis with changed duration, pitch, or some other parameter. Parameters are usually estimated in a static, context-free manner; in some cases dynamic methods lead to improvement and/or simplification of the process. Some examples include: (a) Making an automatic voiced-unvoiced decision (as an aid in doing phonetic marking) based on context; (b) finding “pitch pulses” (points of glottal closure) with a simple form of Dynamic Programming (sometimes called Viterbi's algorithm); and (c) time-aligning two LPC-resynthesized tokens of an utterance (warping one to fit the other) using Bridle's algorithm, another form of Dynamic Program. These and other examples will be discussed and illustrated.
Application of linear prediction to the spectral analysis of speech
Authors: Makhoul John
Published: October 2005

Linear prediction has become one of the most popular tools for speech analysis. In this paper we review the properties of linear prediction when applied to spectral analysis. Time and frequency domain approaches will be examined. The method is seen chiefly as a spectral parametric-modeling method where the model spectrum is all pole. Comparisons will be made with other noniterative but nonparametric methods such as cepstral smoothing and filter bank representation. Of particular importance in these comparisions is the extraction of formants, the analysis of high-pitched voices, and the performance under noisy conditions.
From sound to articulation
Authors: Atal Bishnu S.
Published: October 2005

Methods for determining the shape of the vocal tract directly from acoustic information in the speech signal are of considerable importance in speech research. This paper will review the nature of the articulatory-to-acoustic transformation in the vocal tract and will discuss the present status of research on methods for inverting this transformation. The discussion will include techniques such as analysis-by-synthesis, nonlinear regression, computer-sorting and table look-up procedures. The problem of ambiguous mappings, in which different vocal tract shapes have identical acoustics, will also be discussed. Mathematical procedures for systematically studying the ambiguities will be presented. It will be shown that the acoustic-to-articulatory relationship is multivalued for many cases of interest. For example, the frequencies and amplitudes of the first three formants do not determine the vocal tract shape uniquely; a knowledge of additional articulatory constraints on the vocal tract shape is needed to resolve the ambiguities.
On the estimation of vocal-tract shapes from acoustic analysis of speech sounds
Authors: Wakita Hisashi
Published: October 2005

One of the interesting topics in recent speech analysis techniques is the possibility of estimating vocal-tract shapes and hopefully extracting some articulatory parameters from speech sounds. Estimation of vocal-tract shapes either from acoustic data or directly from acoustic speech waveforms has been investigated on the basis of the linear prediction model of speech analysis (LPC model). Although the precise reconstruction of the original smooth shapes from the bandlimited speech signal is known to be theoretically impossible, it is expected that fairly reasonable estimation of the shapes is possible in terms of discrete acoustic tubes under certain assumptions and constraints. Uncertainty due to individual voice source characteristics can be avoided to a large extent by estimating the formant frequencies and bandwidths during the glottis-closed portion of speech waveforms. The differences between the LPC model and the actual speech production mechanism can be adjusted by modifying the measured formant frequencies and bandwidths by use of a realistic speech production model. Merits and technical problems involved in the method will be discussed, and some analysis examples will be given.
Ocean ambient noise measurements near Lanai: A quiet location
Authors: Armogida F. P. , Stixrud T. E.
Published: October 2005

Ambient noise measurements were conducted off the south-west coast of Lanai in the Hawaiian Islands. Recordings were made for approximately 8 h periods on both a SSQ-57A sonobuoy with the hydrophone at 300 ft and with a special VLF buoy with the hydrophone at 850 ft. Temperature profiles were taken throughout the 24 h period on location and local ship traffic observed. Spectrum levels recorded at 850 ft with no ship traffic present were essentially flat at approximately 68 dB re 1 μ Pa from 25 to 200 Hz. Ambient noise at 300 ft ranged from 74 dB re 1 μ Pa at 25 Hz to 65 dB at 200 Hz.
Vertical directionality of low-frequency ambient noise in the ocean
Authors: Morris G. B.
Published: October 2005

Using a 532-m-long vertical array suspended near the sound channel axis, the vertical directionality of ambient noise in the 10–50-Hz frequency band was measured at a location about 200 miles southwest of San Diego. The outputs from 20 hydrophones, configured as a nonuniform spaced array, were digitized for later beamforming. The frequency domain beamforming produced beam noise level versus direction for 200 discrete frequencies, separated by about 0.2 Hz, covering the band from about 10–50 Hz. At times when there were no ships in the immediate vicinity of the array, the noise in the 20–50-Hz interval was concentrated in a near horizontal direction with most of the noise included in the angular segment from −14° to +14° with respect to the horizontal. Below about 20 Hz this strong, near-horizontal lobe of high noise appears to diminish with decreasing frequency. In many instances in the 10–15-Hz band, the noise no longer shows the strong concentration near the horizontal but instead appears to be almost isotropic. [Work supported by ONR.]
Standard deviation of ambient noise in the South Pacific Ocean
Authors: Bannister R. W. , Denham R. N. , Guthrie K. M. , Browning D. G.
Published: October 2005

Ambient noise data collected during Project SPAN 3 in the South Fiji Basin, an area of relatively low shipping density, have been analyzed to investigate the standard deviation of the time series. In general it has been found that the standard deviation decreases with frequency from about 6 dB at 10 Hz to 1 dB at frequencies above 200 Hz. This is consistent with a transition from distantly generated sound sources at low frequencies to local sources such as wind-generated wave action at higher frequencies. This interpretation is supported by data samples which are separately dominated by weather noise under different wind conditions and by identified local shipping noise. A comparison is made with other published results. [Work supported by NUSC and DSE.]
Temporal world shipping distributions: Introduction
Authors: Solomon L. P. , Barnes A. E. , Lunsford C. R.
Published: October 2005

Shipping distributions serve as primary inputs to ambient noise models. The variation of ambient noise with season is in part caused by the nonstationarity of ship distribution throughout the world for time scales of approximately three months. The distributions vary primarily due to two factors: (1) changing routes due to weather, and (2) variation in port traffic caused by economic and other reasons. The determination of temporal distributions demands both factors be known. The seasonal route envelopes were generated by reported positions at sea for a 24-month period. The port traffic is available from various sources. Both routes and port traffic are functions of ship type. [Supported by ONR.]
Temporal world shipping distributions: Techniques
Authors: Solomon L. P. , Barnes A. E. , Lunsford C. R.
Published: October 2005

Ship distributions are a function of route envelopes and port traffic levels. Data for seasonal envelopes and pert traffic was available. Lloyds lists 2425 ports, this allows approximately 3 000 000 possible routes. Canonical ports and routes were generated: 50 ports and 75 routes. Modeling of the routes for commercial traffic between any two points, subject to constraints (land avoidance, strait passages) based upon economic reality results in generally simply connected envelopes on a sphere. Multiply connected routes may be analyzed though the union of a set of simply connected envelopes. The use of the real data coupled with the mathematical formulation consisting of a series of bilateral one to one mapping functions is presented.
Interpolation and smoothing of periodic data: Applied to shipping fields
Authors: Barnes A. E. , Hill V. J. , Solomon L. P.
Published: October 2005

Shipping fields are being generated on seasonal and monthly bases, in addition to the standard yearly averages. These fields are necessary for computer ambient noise models. However, to use only the set of discrete fields would result in discontinuous behavior of the noise model results as the computer code proceeds from one time interval to the next. To preclude this, an interpolation of the discrete data sets must be done in the time domain. A number of interpolatory functions are considered for either seasonal (4 data points) or monthly (12 data points) periodic fields. Linear, quadratic, and cubic splines were actively investigated. The linear spline does not model seasonal fluctuations in the data well; cubic splines do, and are easy to compute. Linear splines are wholly adequate for monthly fluctuations. [Work supported by ONR.]
Effects of quasistationary noise on the detection of quasistationary signals
Authors: Heine J. C. , Nitsche J. R.
Published: October 2005

Receiver operator characteristics derived for post detection integration receivers are significantly perturbed if the signal power fluctuates with a characteristic time roughly two or more times the receiver integration time. In this paper, the effects on detection performance of slow fluctuations in both signal power and in noise power, such as occur in the 10–200-Hz region due to merchant shipping, are explicitly considered and are compared to results for signal fluctuations alone. Further degradation in detection performance in the region of PD ⩾ 0.5 is shown to occur and the sensitivity of the degradation to the characteristic times of the fluctuations and to the statistics of the noise power fluctuations is demonstrated. The effects of the noise statistics on experimental determination of sonar system performance is discussed.
Point sensor for vertical directional noise environments
Authors: Friedman A. J. , Hyams E. H. , Jaarsma D.
Published: October 2005

A new point-sensor concept is defined, evaluated, and shown to have enhanced performance, relative to other simple configurations, in ocean environments which exhibit noise vertical directivity. This property is characteristic of deep ocean areas at low frequencies, and the successful exploitation of the acoustics of such an environment imply special sensor and processing design factors. The concept treated in this paper involves three orthogonal, directional elements and a single omnidirectional element, with all elements colocated. The receiver utilizes cross correlation between one directional element, oriented along the vertical, and the other elements as well as individual element power spectra. The outputs are suitably combined to produce log-likelihood statistics and maximize detection probability for weak signals arriving along angles at or near the noise peak. Analytical results are presented for detection performance of this concept relative to other concepts in representative signal and noise environments. [Work supported by Naval Electronics Systems Command, Code 320.]
Sound transmission loss of gypsum wallboard wall partitions
Authors: Green David W. , Sherry C. W.
Published: October 2005

Using the data bank of the acoustic laboratory of Domtar Research, statistical equations based on frequency and surface density were derived for predicting sound transmission loss (STL) and sound transmission class (STC) of double leaf wall partitions constructed using gypsum wallboard and either steel or wood studs. The equations show close agreement with experimental data for all frequency bands except those near the coincidence dip. Results predicted using these equations also agree closely with experimental results published by other laboratories. Using these equations the effect of frequency, surface density and cavity filler on STL and STC is easily seen. However, the study also revealed some unexpected results: (1) Whether or not a partition was “Balanced” as to board placement did not significantly affect the STC of either steel or wood stud partitions. (2) For multilayer wood stud partitions attaching the second layer of board to the first with screws, rather than using glue, dramatically reduced the STL at higher frequencies. For higher surface density partitions this decrease may negate any benefits to be derived from adding fiberglass to the cavity space.
Use of computers in the study of room acoustics
Authors: Berkovitz Robert , Schultz Theodore J.
Published: October 2005

A number of attempts have been made to apply the enormous calculating capabilities of digital computers to the solution of problems in the acoustical design of large rooms, such as concert halls. We believe that it is premature to rely on computer studies for concert hall design purposes, but point out the great advantage that computer programs can provide by promoting a useful intuitive grasp of the elements of such acoustics problems. Some examples will be presented.
Use of quantitative criteria for optimum design of concert halls
Authors: Baxa D. E. , Seireg A.
Published: October 2005

This paper describes a set of eight quantitative merit criteria for the design of concert halls which are used in a developed automated computer optimization procedure based on the ray-tracing method. Idealized optimum hall configurations and surface absorption coefficients are determined based on each criteria for illustration. The acoustical merits of the optimum designs for a hall with given floor and stage areas are evaluated and compared to those of an existing hall with acclaimed acoustical quality. They are also compared to those calculated when the total sum of all the eight merit criteria is used as the optimizing objective function. The study represents a first attempt at optimizing acoustic space based on quantitative figures of merit. The developed technique can be invaluable in giving insight into the effect of improving a particular design objective on the configuration and absorption coefficients as well as how the improvement of one merit criterion can affect the other criteria.
Effect of a moving reflector on the power output of a source
Authors: Waterhouse R. V. , Brooks J. E.
Published: October 2005

A source radiates a pure tone in a reverberation chamber which contains a reflector large compared to the wavelength of sound in air. When the reflector is stationary, the signal picked up by a microphone in the sound field is a simple harmonic signal. When the reflector is rotated about a fixed axis, experiment has shown that the signal picked up by the microphone resembles a frequency-modulated signal. The energy spectrum contains sidebands, equally spaced along the frequency axis, the frequency difference between any two adjacent sidebands being equal to the frequency of rotation of the reflector. We give here an analysis of a simplified model of this situation, where the reflector is a rigid flat plat which reciprocates sinusoidally. Results are given for the energy spectrum of the resultant sound field which are in general agreement with the experimental results cited.
Experimental investigation of outdoor propagation of finite-amplitude noise
Authors: Webster Don A. , Alexander Douglas E. , Blackstock David T.
Published: October 2005

Propagation measurements of intense noise were made outdoors. A ground-mounted electroacoustic source transmitted broadband, octave band, or 13-octave band noise in the frequency range 2–10 kHz. Band levels (100-Hz bands) at the peak of the source spectrum were as high as 133 dB (re 20 μ Pa at 1 m). A microphone mounted on a boom extended from the elevator of an 85-m tall radio tower was used to measure power spectra as a function of propagation distance. Nonlinear propagation distortion caused substantial growth with distance of the high-frequency end of the noise spectrum, even at low source levels. For example, when the source band level peaked at 113 dB at 4 kHz, at a distance of 77 m the band at 20 kHz was 23 dB higher than would be predicted using linear theory. Preliminary calculations based on nonlinear acoustical theory show that observed spectral distortion is in line with that predicted for a homogeneous medium, even though winds with ground speeds as high as 25 km/h were present. [Work supported by NASA, ONR, AFOSR, and NOAA.]
Studies of wind effects on propagation of automobile sounds
Authors: Hillquist Ralph K.
Published: October 2005

Studies of large groups of automobile exterior sound level tests were conducted with gross wind speed and direction at the test site as distinct parameters. The effects of wind on test data are slight but not negligible, and certainly not quantifiable. The range of variability of test data is found to be sensitive to wind direction, but not to wind speed (up to 12 mph).
Studies of metric patterns
Authors: Liberman M. Y. , Olive J. P. , Zukofsky Paul
Published: October 2005

Traditional metrical notation specifies at least two kinds of information — (1) nominal point of occurrence for each note and (2) a grouping of notes with implication for their relative stress, often in several levels of subdivisions. These two kinds of information are not the same; for example, the same set of six numerically equidistant time points can be grouped as 2 threes or 3 twos. For performance, the nominal duration of a note is presumably obvious (e.g., a 16th note at d=60 MM is, in principle, 250 msec). The objective interpretation of the metric grouping of notes is not at all obvious (e.g., how do we distinguish 2 threes from 3 twos?). We have studied this question both by analysis of live production and by computer synthesis, concentrating on patterns in which the same sequence of nominal durations is subject to different metrical groupings. Listening to synthetic patterns reveals that even small differences in onset-to-onset duration, articulative space, on time, timbre, or attack can strongly affect the way we group notes perceptually. We will discuss the use of such differences in live performance, giving examples.
The application of semiconductor devices in voicing
Authors: Walker James R.
Published: October 2005

Designers of electronic organs intended for the production of serious music strive to imitate the sounds produced by the pipe organ. This report describes progress towards producing certain organ pipe voices by the employment of diodes and transistors together with conventional electronics components. The advantages are more authentic sound and reduced cost. Spectrographic analyses of the electronic voices are compared with those of organ pipes.
Hair cells as biological amplifiers?
Authors: Khanna S. M. , Tonndorf J. , Sherrick C. E.
Published: October 2005

Many sense organs possess specialized receptor cells. In some mechanical sense organs, e.g., the vestibular organs and the organ of Corti, hair cells play this role. Some other mechanical receptors, e.g., the touch receptors (Pacinian corpuscles and the hairs of the skin), lack such specialized cells. The threshold sensitivity of the two types of mechanoreceptors, in terms of power input, is strikingly different. The sensitivity of the touch receptors is generally estimated to be on the order of 10−6 W; in contrast, that of the organ of Corti (cat) is 10−18 W in the frequency range of 100–8000 Hz [S.M. Khanna and J. Tonndorf, J. Acoust. Soc. Am. 61, S1(A) (1977)] and that of the vestibular organ (man) is at least 10−16 W or better. These large differences suggest that the hair cells act as biological amplifiers. [Supported by NIH grants.]
Lateral line microphonics: Evidence for multiple dc components
Authors: Boston J. Robert
Published: October 2005

The microphonic potential recorded from the lateral line organs of fish appears to be produced by a quadratic nonlinearity in the sensory hair cells, resulting in an electrical response to a sinusoidal stimulus consisting of a second harmonic and a dc component. Results presented here show that the dc component does not behave as would be expected from a simple quadratic nonlinearity. Specifically, the dc component increases with stimulus frequency, while the second harmonic decreases, and the dc component does not grow with stimulus intensity in the same manner as the second harmonic. A parametric model of hair cell function, incorporating capacitive effects, can explain the decrease in the second harmonic with increasing stimulus frequency, but it cannot explain the increase in the dc component with frequency nor the differential growth of the two components with intensity. These results are interpreted to suggest that an additional mechanism contributes to the dc component. Similarities with the cochlear summating potential are discussed. [Supported by grants from NSF and the Deafness Research Foundation.]
Single auditory nerve responses to acoustic and electric stimuli
Authors: Strelioff D. , Maceri D. , Paull D. , Honrubia V.
Published: October 2005

The characteristics of single auditory nerve fiber responses to low frequency acoustic stimuli and sinusoidal electric current injected in the scala media were investigated in guinea pigs. A glass microelectrode in the scala media of the second turn was used to measure cochlear microphonics or to inject sinusoidal electrical currents up to 8μA p-p. At 40 Hz, the phase lag between the maximum of the neural response and the positive peak of the voltage change inside the scala media was −3±65° for acoustic stimuli and 127±47° for electrical stimuli. Thresholds were as low as 0.5μA p-p for electrical stimuli and the degree of phase-locking increased proportionally (slope=0.94) with stimulus amplitude. These data, together with the finding that electrical stimuli modulate neural responses to acoustic stimulation, suggest that these electric stimuli act upon hair cells rather than directly upon the nerve fibers. [Research supported by NIH Grant NS 08193 and the Deafness Research Foundation.]