• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

Jun 1985

Volume 77, Issue 6, pp. 1989-2213

Page 1 of 5 Pages Next Page | Jump to Page

Audiovisual materials and microcomputer software for teaching vibration and sound

F. B. Stumpf

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 1989-1990 (1985); (2 pages)

Full Text: | Download PDF

Show Abstract
Currently available films, filmloops, slides, overhead transparencies, and microcomputer software are listed for those who teach courses involving vibration and sound. The topics covered and addresses of the suppliers are given.
Show PACS
43.10.Sv Education in acoustics, tutorial papers of interest to acoustics educators
01.50.F- Audio and visual aids
01.50.ht Instructional computer use

A high‐angle one‐way wave equation for seismic wave propagation along rough and sloping interfaces

Robert R. Greene

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 1991-1998 (1985); (8 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
A model of acoustic propagation in solid media has been derived. It is a one‐way wave equation based on a high‐order approximation, called a Padé approximation, to the square‐root function. The physical properties of the environment are modeled as stratified, thin, homogenous layers. The model can be applied to obtain an approximate solution in range‐dependent environments by allowing the properties of the layers to vary in range. Furthermore, the effects of rough or sloping reflecting interfaces can be approximated using an equivalent reflector, consisting of two thin layers whose properties vary in range.
Show PACS
43.20.Bi Mathematical theory of wave propagation
43.20.Fn Scattering of acoustic waves
91.30.Fn Surface waves and free oscillations

Scattering by a partially illuminated, doubly periodic, doubly infinite surface

Akhlesh Lakhtakia, Vijay K. Varadan, and Vasundara V. Varadan

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 1999-2004 (1985); (6 pages)

Full Text: | Download PDF

Show Abstract
Using the plane‐wave decomposition of the incident field and the T‐matrix method, scattering by a partially illuminated, doubly periodic, doubly infinite surface is investigated. The general expressions thus derived are simplified for the case when the illuminated area is large. Numerical examples illustrating the applicability of the procedure are also given.
Show PACS
43.20.Fn Scattering of acoustic waves
43.20.Bi Mathematical theory of wave propagation

The inverse source problem for an oblique force on an elastic plate

Jennifer E. Michaels and Yih‐Hsing Pao

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2005-2011 (1985); (7 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
A time‐dependent concentrated force applied obliquely on the surface of a plate generates elastic waves in the plate. The determination of the location, orientation, and time history of the force from the transient wave records is referred to as the inverse source problem of elastic waves. This paper presents an iterative method of deconvolution which determines the orientation and time‐dependent amplitude of the force from the transient response of the plate surface at a minimum of two locations, the source location being given. Numerical results are presented for forces with various orientations and time histories, and for synthetic data both with and without noise.
Show PACS
43.20.Fn Scattering of acoustic waves

Radiation from a point source and scattering theory in a fluid‐saturated porous solid

Andrew N. Norris

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2012-2023 (1985); (12 pages) | Cited 18 times

Full Text: | Download PDF

Show Abstract
The time harmonic Green function for a point load in an unbounded fluid‐saturated porous solid is derived in the context of Biot’s theory. The solution contains the two compressional waves and one transverse wave that are predicted by the theory and have been observed in experiments. At low frequency, the slow compressional wave is diffusive and only the fast compressional and transverse waves radiate energy. At high frequency, the slow wave radiates, but with a decay radius which is on the order of cm in rocks. The general problem of scattering by an obstacle is considered. The point load solution may be used to obtain scattered fields in terms of the fields on the obstacle. Explicit expressions are presented for the scattering amplitudes of the three waves. Simple reciprocity relations between the scattering amplitudes for plane‐wave incidence are also given. These hold under the interchange of incident and observation directions and are completely general results. Finally, the point source solution is Fourier transformed to get the solution for a load which is a delta function in time as well as space. We obtain a closed form expression when there is no damping. The three waves radiate from the source as distinct delta function pulses. With damping present, asymptotic approximations show the slow wave to be purely diffusive. The fast and transverse waves propagate as pulses. The pulses are Gaussian‐shaped, which broaden with increasing time or radial distance.
Show PACS
43.20.Fn Scattering of acoustic waves
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Bi Mathematical theory of wave propagation

Solution of the fundamental problem of transient acoustic propagation in a borehole with the hybrid method

Leung Tsang

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2024-2032 (1985); (9 pages)

Full Text: | Download PDF

Show Abstract
The fundamental acoustic logging problem of a pulsed point source surrounded by both vertical and horizontal boundaries is solved with the hybrid method. The hybrid method yields the complete synthetic waveform including the head wave and the normal mode arrivals. The essence of the hybrid method consists in converting the head wave branch‐cut contribution into discrete modes which, together with the normal modes, form a complete basis for the solution in each region. Boundary conditions at the horizontal bed boundary then couple the modes between different regions and enable the solution to be expressed in terms of reflection and transmission matrices of modes. Numerical results are illustrated as a function of the formation parameters. Transmission coefficients of head waves are calculated. The advantages of the hybrid method are also discussed.
Show PACS
43.20.Px Transient radiation and scattering
43.20.Mv Waveguides, wave propagation in tubes and ducts

On the acoustic power radiated by line forces on elastic beams

R. F. Keltie and H. Peng

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2033-2038 (1985); (6 pages)

Full Text: | Download PDF

Show Abstract
The importance of the spatial extent of applied forces in the topic of structural radiation is studied through formulation of the sound power radiated by a line force acting on an infinite elastic beam. The expression for sound power is integrated numerically and the results examined as a function of kL, the acoustic length of the force, and the wavenumber ratio. Below coincidence the power was found to be generally proportional to (kL)−2. Near and at coincidence, sufficiently large force scales have a significant effect on the power produced. In particular, when the length of the force is an integral multiple of the critical wavelength, the coincidence peak is completely suppressed. Above coincidence, minima in the second power occur when the force length is a multiple of the wavelength of the free bending wave. These minimal values of power are shown to be nearly equal to the power radiated far below coincidence. These results are discussed in terms of the coupled structural/acoustic wavenumber response function and the wavenumber spectrum of the applied force. In addition the relative effects of light fluid loading on the radiation at coincidence are presented.
Show PACS
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.40.Cw Vibrations of strings, rods, and beams

Acoustic impedance of small, circular orifices in thin plates

Michael R. Stinson and E. A. G. Shaw

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2039-2042 (1985); (4 pages) | Cited 10 times

Full Text: | Download PDF

Show Abstract
Measurements of acoustic impedance have been made on a series of small, circular orifices (0.1–0.3 mm radius) in thin plates (0.038 and 0.38 mm thickness). Both real and imaginary components, over the frequency range 0.6–3 kHz, were obtained using an impedance tube technique. The zero frequency limit of resistance was measured with a flow resistance device. Only small amplitude acoustic signals were considered. For the range of orifice radii and frequencies selected the boundary layer thickness is comparable to the radius, and the usual high‐frequency expressions for orifice impedance do not apply. Within the limits of experimental error (approximately 12% for resistance and 6% for reactance) the measured values are in reasonable agreement with Thurston’s general but approximate theory [G. B. Thurston, J. Acoust. Soc. Am. 24, 653–656 (1952)]. The measurements support the simple idea that both real and imaginary components of orifice impedance can be calculated assuming an effective total end correction 16a/3π, where a is the orifice radius.
Show PACS
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.58.Bh Acoustic impedance measurement

Observations of sound propagation during a southern Alberta chinook

David A. Bohlender, Patrick J. Irwin, and Titus Mathews

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2043-2049 (1985); (7 pages)

Full Text: | Download PDF

Show Abstract
An experimental investigation of the propagation of sound in the presence of an elevated temperature inversion has been conducted on a farm site in southern Alberta. The refractive focusing of sound in the inversion layer was observed to cause shadow zones and regions of sound enhancement in which sound levels were up to 20 dB lower and 20 dB higher, respectively, than during normal afternoon conditions. Fluctuations of 35 dB in the sound intensities at microphones 1730 and 2180 m from the source have been witnessed as the location of the focusing region changed. Ray tracing analysis for meteorolgical data acquired predicts excess attenuations of sound consistent with those recorded. The use of a monostatic acoustic sounder proved useful in correlating anomalous sound levels with the appearance of temperature inversions.
Show PACS
43.28.Fp Outdoor sound propagation through a stationary atmosphere, meteorological factors
92.60.Gn Winds and their effects

Generalized Burgers equation for plane waves

David T. Blackstock

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2050-2053 (1985); (4 pages) | Cited 15 times

Full Text: | Download PDF

Show Abstract
Burgers’ equation, an equation for plane waves of finite amplitude in thermoviscous fluids, is generalized by replacing the thermoviscous term Aut′t′ (A is the thermoviscous coefficient, u particle velocity, and t′ retarded time) with an operator L(u). This operator represents the effect of attenuation and dispersion, even if known only empirically. Specific forms of L(u) are given for thermoviscous fluids, relaxing fluids, and fluids for which viscous and thermal boundary layers are important. A method for specifying L(u) when the attenuation and dispersion properties are known only empirically is described. A perturbation solution of the generalized Burgers equation is carried out to third order. An example is discussed for the case α2=2α1, where α1 and α2 are the small‐signal attenuation coefficients at the fundamental and second‐harmonic frequencies, respectively. The growth/decay curve of the second harmonic component is given both with and without the inclusion of dispersion. Dispersion causes a small reduction of the component. The extension of the generalized Burgers equation to cover nonplanar one‐dimensional waves is given.
Show PACS
43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves

Nonlinear sound waves from a uniformly moving point source

B. O. Enflo

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2054-2060 (1985); (7 pages)

Full Text: | Download PDF

Show Abstract
Nonlinear sound waves from a uniformly moving source with dimensions smaller than the wavelength of the emitted sound are investigated. They are described by spherical Burgers’ equations with parameters depending on the source velocity V and the direction angle θ from the source to the point of observation. It is seen that for certain V and θ values, both for V less than and greater than the sound velocity in the medium, shock waves occur, which do not occur in nonlinear waves from a fixed sound source.
Show PACS
43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves

Bubble interaction effects on waves in bubbly liquids

Jacob Rubinstein

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2061-2066 (1985); (6 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
We derive effective equations for wave propagation in bubbly liquids which include bubbles interactions effect. We homogenize both the linear and the nonlinear versions of the microscopic equations by two methods. The interaction between the pressure fields is found to increase the speed of sound relative to the Foldy approximation.
Show PACS
43.25.Yw Nonlinear acoustics of bubbly liquids

A shallow water experiment to determine the source spectrum level of wind‐generated noise

W. A. Kuperman and M. C. Ferla

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2067-2073 (1985); (7 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
An experiment was conducted in a shallow water region of the Mediterranean Sea to study wind‐generated noise. In addition to measuring the noise field, propagation‐loss data were collected and used in a detailed modeling of the environment. The environmental information was then used as input to a noise model based on wave theory that computes the noise field in the water column for a given (unknown) source strength. By comparing model predictions with data, the influence of the environment on recorded noise levels could be removed and a measure of the noise source spectrum levels obtained as a function of wind speed. It was found that noise levels correlate better with wind speed than with wave height. In addition it was found that the nearfield contribution dominates the noise level, with the result of producing virtually constant noise intensity over depth from moderate to high wind speeds and frequencies above 200 Hz.
Show PACS
43.30.Hw Rough interface scattering
43.30.Lz Underwater applications of nonlinear acoustics; explosions
43.30.Nb Noise in water; generation mechanisms and characteristics of the field

An assessment of second‐order perturbation theory for scattering of sound by hard, statistically rough surfaces

A. Tolstoy, D. Berman, O. Diachok, and I. Tolstoy

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2074-2080 (1985); (7 pages)

Full Text: | Download PDF

Show Abstract
Perturbation theory and boss models for rough surface scattering are compared for the case of a surface bossed with oblate hemispheroids (height a≤radius b). In particular, the surface consists of identical, hard, hemispheroidal bosses sparsely and independently distributed on a hard plane by means of a uniform probability law. To apply perturbation theory we compute the surface correlation function, operate on that function, and compute an effective boundary admittance. Finally, we compare that admittance with (farfield) near‐exact results for hemispherical bosses and for oblate hemispheroidal bosses. Calculations of the magnitude of the reflection coefficient ‖R‖ are presented showing that for low frequencies, i.e., kb=0.1, the discrepancy is approximately 70% for a=b but less than 10% for a/b=0.1. In general, the error decreases as grazing angle increases and decreases as a→0. Thus, at low frequencies perturbation theory is shown to give excellent results for ‖R‖ when a/b≪1, despite the discontinuous and infinite slope in the surface where the bosses meet the base plane. We also examine the effects of increasing frequency for hemispherically bossed surfaces, and in particular, we see errors as large as 3 dB for sparse, hemispherical bosses with a=b=5 m and frequencies less than 60 Hz. We conclude that perturbation theory is excellent in the case of oblate hemispheroids, shows significant percentage errors for hemispheres and should not be used for prolate hemispheroids.
Show PACS
43.30.Hw Rough interface scattering
43.20.Bi Mathematical theory of wave propagation
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties

Resonance response of submerged, acoustically excited thick and thin shells

G. C. Gaunaurd and M. F. Werby

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2081-2093 (1985); (13 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
We study the elastodynamic spectral response of thick and thin shells in water when they undergo resonance scattering caused by the incidence of sound waves that impinge upon them at selected aspects. All the shells considered are elastic, air‐filled, and of cylindrical and prolate spheroidal shapes. Their thickness is intentionally varied three orders of magnitude from very thick (i.e., h≡1−b/a=90%) to very thin (i.e., h=0.1%), so that the effects of shell stiffness on their scattering behavior can be quantitatively analyzed and understood. The quantities a and b are the outer and inner shell radii, respectively. Material composition effects are studied by comparing various metals such as steel and aluminum. The shell motions are described by the exact equations of elastodynamics in all cases, so that comparisons may be drawn concerning the regions of applicability of pertinent shell theories. For the spheroidal shells no exact solution is possible, thus, we have presented results based on an extended T‐matrix method that still makes use of the exact 3‐D equations of elastodynamics to describe the shell vibrations.
For a wide range of shell thicknesses and compositions, we have computed the positions of the poles of the scattering amplitudes, in the complex frequency plane x1. Here, x1 is k1a, where k1=ω/c1, ω is the angular frequency of the incident wave, c1 is the sound speed in the outer medium, and a is the shell’s outer radius. These poles group themselves in certain families and give rise to surface waves that circumnavigate the shell, either in the water side (Franz or SEM‐type poles or waves) or inside the shell metal (Rayleigh/whispering gallery waves for solid bodies, or Lamb momentless and flexural waves for shells). This latter set of waves is the least attenuated and the most dominant. We have shown how the pole families affect the spectral shape of the form function, and that of it’s partial waves, with their interacting modal backgrounds and resonances. As the shells become thinner, only one‐pole family is shown to remain within the displayed boundary of the complex x1 plane. This single‐pole family becomes responsible for the generation of the first‐order set of symmetric/antisymmetric Lamb waves in the shell. All these concepts are illustrated with many examples which show the crucial importance of the pole‐position diagrams to understand the spectral behavior of the form function, and the way it reveals information about the shell and the types of waves it supports on its surfaces. A transition from the rigid to the soft background is observed as the shells become very thin, and it is used to properly isolate the resonances of very thin shells. Extensions of these spectral results to the time domain are forthcoming.
Show PACS
43.40.Ey Vibrations of shells
43.40.At Experimental and theoretical studies of vibrating systems
43.20.Ks Standing waves, resonance, normal modes

Sound transmission loss: Comparison of conventional techniques with sound intensity techniques

R. E. Halliwell and A. C. C. Warnock

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2094-2103 (1985); (10 pages) | Cited 7 times

Full Text: | Download PDF

Show Abstract
Sound transmission losses for a single layer wall are measured in a reverberation room facility using conventional methods (ASTM E90) and the more recently introduced sound intensity method. The specimen is placed in five positions in the tunnel between the two reverberation rooms and measurements are made for four different absorptive conditions in the smaller room. Significant differences between the two measurement techniques are found at low frequencies and at high frequencies. Low‐frequency differences are attributed partly to the increase in sound energy close to the surfaces of the receiving room (the Waterhouse effect) and the lack of any consideration of this in standard test methods. Inclusion of the Waterhouse term in the conventional transmission loss formula improves the agreement between the conventional and the sound intensity measurement technique at low frequencies. High‐frequency differences are not explained.
Show PACS
43.55.Rg Sound transmission through walls and through ducts: theory and measurement

Introduction of mass conservation law to improve the tomographic estimation of flow‐velocity distribution from differential time‐of‐flight data

Takuso Sato, Hisayuki Aoki, and Osamu Ikeda

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2104-2106 (1985); (3 pages)

Full Text: | Download PDF

Show Abstract
The mass conservation law is combined as one of the utilizable physical constraints with differential time‐of‐flight data to improve the tomographic estimation of flow‐velocity distribution by means of inverse operation of the matrix. The formulation and computer simulation are described.
Show PACS
43.60.Gk Space-time signal processing, other than matched field processing

Asymptotic analysis of a viscous cochlear model

Joseph B. Keller and John C. Neu

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2107-2110 (1985); (4 pages)

Full Text: | Download PDF

Show Abstract
A model of cochlear macromechanics, involving a viscous cochlear fluid, is analyzed asymptotically for slowly varying membranes. The results exhibit the effect of viscosity on the amplitude, wavelength, and damping rate, and confirm the conclusion that viscosity is not important. However the method can be used on other models, such as those of cochlear micromechanics, where viscosity is more important.
Show PACS
43.64.Bt Models and theories of the auditory system
43.64.Kc Cochlear mechanics

Cochlear nucleus, inferior colliculus, and medial geniculate responses during the behavioral detection of threshold‐level auditory stimuli in the rabbit

Ronald E. Kettner and Richard F. Thompson

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2111-2127 (1985); (17 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
Rabbits were conditioned to respond behaviorally to auditory stimuli by pairing a white‐noise conditioned stimulus (CS) with a corneal airpuff unconditioned stimulus (US). The conditioned response (CR) was movement of the nictitating membrane (NM). After the subjects were responding at better than the 90% correct level, the intensity of the auditory stimulus was reduced to behavioral threshold using a staircase procedure. Simultaneous measurements of neural unit activity and behavioral NM responses were then made in rabbits performing at behavioral threshold. After the experiment was completed neural unit responses during behavioral detection trials were compared to neural responses made during nondetection trials. Neural unit responses to a constant intensity, white‐noise stimulus at behavioral threshold were well defined and essentially identical on behavioral detection and nondetection trials in the ventral cochlear nucleus, the ventrolateral division of the central nucleus of the inferior colliculus, and the ventral division of the medial geniculate body. This suggests that an auditory stimulus can be neuronally ‘‘detected’’ without being behaviorally detected, and that the neural ‘‘decision’’ to respond behaviorally is not made in these nuclei. Responses recorded from the dorsomedial division of the central nucleus of the inferior colliculus, the pericentral nucleus of the inferior colliculus, and less commonly in the medial division of the medial geniculate body were also clearly present and nearly identical during the onset of the auditory stimulus, but were sometimes consistently different for detection and nondetection conditions during the latter part of the auditory stimulus. These brain regions appear to receive both auditory and nonauditory inputs, and show responses which are more highly correlated with detection behavior.
Show PACS
43.64.Qh Electrophysiology of the auditory central nervous system
43.66.Gf Detection and discrimination of sound by animals

A power‐law transformation predicting masking by sounds with complex spectra

Robert A. Lutfi

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2128-2136 (1985); (9 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
In a previous paper [R. Lutfi, J. Acoust. Soc. Am. 73, 262–267 (1983)], the following rule was proposed for predicting masking by pairs of simultaneous maskers; Xab =[XPa+XPb]1/P, where in units of power, Xa and Xb are the individual masking effects of the maskers, Xab is the combined effect, and 0.20≤p≤0.33. In this paper, the rule is used to predict the results of studies in the literature that have measured masking by sounds with various other complex spectra. In most of these studies, the individual maskers comprising the complex have nominally nonoverlapping power spectra. A single value of p=0.33 yields predictions in good agreement with the data of these studies. For a study in which the component maskers overlap more appreciably, a larger value of p=0.50 produces equally accurate predictions. The rule also predicts some general features of the results of studies in which the individual effects of the maskers in the complex are not known but can be estimated. It is suggested that the general applicability of the rule reflects a conjoint analysis by the auditory system of two or more waveform statistics.
Show PACS
43.66.Ba Models and theories of auditory processes
43.66.Dc Masking

The danger of using narrow‐band noise maskers to measure ‘‘suppression’’

Brian C. J. Moore and Brian R. Glasberg

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2137-2141 (1985); (5 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
These experiments investigated whether perceptual cueing plays a role in the ‘‘unmasking’’ effects which have been observed in forward masking for narrow‐band noise maskers and brief signals. The forward masking produced by a 100‐Hz‐wide noise masker at a level of 60 dB SPL was measured for a 1‐kHz sinusoidal signal with a raised‐cosine envelope and a duration of 10 ms at the 6‐dB‐down points, both for the masker alone, and with various components added to the masker (and gated synchronously with the masker). Unmasking was found to occur even for components which were extremely unlikely to produce a significant supression of the masker: these included a 75‐dB SPL 4‐kHz sinusoid, a 50‐dB SPL 1.4‐kHz sinusoid, a noise low‐pass filtered at 4 kHz with a spectrum level of 0 dB, and a noise low‐pass filtered at 4 kHz with a spectrum level of 20 dB presented in the opposite ear to the masker‐plus‐signal. It is concluded that perceptual cueing can play a significant role in producing unmasking for brief signals following narrow‐band noise maskers, and that it is unwise to interpret the unmasking solely in terms of suppression.
Show PACS
43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.66.Lj Perceptual effects of sound

Acoustical aspects of contrastive stress in question–answer contexts

William E. Cooper, Stephen J. Eady, and Pamela R. Mueller

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2142-2156 (1985); (15 pages) | Cited 11 times

Full Text: | Download PDF

Show Abstract
A series of experiments was conducted to examine the influence of contrastive stress on intonational patterns of duration and fundamental voice frequency (F0). In a preliminary study, intonational patterns in spontaneous speech were compared with the patterns in oral reading of the transcribed spontaneous material. In both circumstances, a general declination of F0 peaks throughout the course of a sentence was not regularly observed, contrary to earlier findings with oral reading of isolated sentences. Two experiments were then conducted to examine the possibility that the general absence of declination observed here might be due to the influence of sentence focus, following previous results from Swedish showing that declination was not observed consistently in isolated sentences until after the site of focus. In experiment 1, we found no evidence of this restriction on declination in the oral reading of English declaratives. Declination was observed both before and after the focused item in a sentence. Furthermore, our analyses revealed that focus (as manifested by contrastive stress) is generally accompanied by an increase in duration on the focused word and by a sharp drop in F0 following the focused item. In experiment 2, these effects were replicated and extended using longer sentences. In both experiments, the influence of focus was strictly localized to the site of focus in the case of duration, but not F0. The results for both duration and F0 indicate that the influence of focus assignment on these attributes varies systematically as a function of the focus location in the sentence. Finally, the combined elongation effects for focus and utterance‐final lengthening were less than would be predicted by an additive model, suggesting the operation of an expandability constraint on segmental lengthening in speech production.
Show PACS
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Intonation in text‐to‐speech synthesis: Evaluation of algorithms

Glenn Akers and Matthew Lennig

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2157-2165 (1985); (9 pages)

Full Text: | Download PDF

Show Abstract
Two algorithms, termed schematic and naturalistic, for generating intonation contours in an English text‐to‐speech system are compared by eliciting preference judgments from a total of 21 subjects. The major problem for both algorithms, but especially for the schematic algorithm, has to do with accent assignment and with the determination of the intonation phrase rather than with the phonetic realization of accent through manipulation of F0. Due to parser errors, phrase boundaries are incorrectly identified in 30% of the sentences used in the three experiments. Moreover, the naturalistic algorithm uses a grammatical part‐of‐speech hierarchy which ranks nouns higher than verbs. Therefore, incorrect classification of verbs as nouns (the major classification error) results in an unintended accent. The results indicate that accent assignment and phrase determination are the primary areas requiring improvement in order to further increase the naturalness of synthetic speech intonation.
Show PACS
43.72.Ja Speech synthesis and synthesis techniques

Numerical calculation of flute impedances and standing waves

William J. Strong, Neville H. Fletcher, and Ron K. Silk

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2166-2172 (1985); (7 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
The purpose of this study was to investigate a numerical method for calculating impedances and standing wave patterns of flute structures. To this end, the physical dimensions of flute joints and tone holes were used to compute impedance and standing waves as a function of frequency for several different fingerings. Numerically computed resonance frequencies for head joint, middle and foot joints, and complete flute are compared to experimentally measured values. Computed pressure standing wave patterns for two fingerings of A6 are compared to experimental values. Reasons for the observed discrepancies between the predicted and experimental frequencies are discussed.
Show PACS
43.75.Ef Woodwinds
43.20.Mv Waveguides, wave propagation in tubes and ducts

An open tube technique for the measurement of acoustic parameters of porous absorbing materials

John I. Dunlop

J. Acoust. Soc. Am. Volume 77, Issue 6, pp. 2173-2178 (1985); (6 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
A new method of measuring the acoustic parameters of porous materials is described. The method is based on the measurement of radiation impedance at the end of an open flanged pipe placed against a sample. Five samples of polystyrene foam of differing porosities have been used to assess the usefulness of the method. The acoustic characteristics of the samples were first determined using a conventional acoustic impedance tube with rigid end cap. Estimates of the acoustic parameters of the samples—sound speed and attenuation constant—were then obtained by applying various acoustic models to match the measured characteristics. Open tube measurements were then made on the samples and these impedance characteristics compared with those predicted by application of acoustic models. Moderately good agreement was obtained between measured and predicted impedance although the values of acoustic parameters derived deviated from those obtained from the closed tube measurements. The results confirm the potential of the method to be developed into an alternative method of measurement of acoustic absorptivity.
Show PACS
43.58.Bh Acoustic impedance measurement
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
Page 1 of 5 Pages Next Page | Jump to Page
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close