bluuebunny/crossref_metadata_2025 huggingface dataset:
Pitch: Is it learned
Authors: Hall Joseph W. , Peters Robert W.
Published: October 2005

In an experiment Where the pitch of a high-frequency complex sound was changed and maintained in the direction of a low-frequency complex sound with which it was associated, six observers made pitch matches for the pitch-shift stimulus (1250-1450-1650 Hz) before and after simultaneous presentation of this stimulus with the first through the fifth harmonics of 200 Hz (200-400-600-800-1000 Hz). Data were collected for each observer on five consecutive days and one week following the last day. The experimental phases each day were: ten matches, simultaneous stimuli, ten matches, simultaneous stimuli, and ten matches. Association periods for simultaneous stimuli were 5 min, and a 5-rain rest period followed each association period. For matching, the pitch-shift stimulus and a sine wave were presented alternately to the right and left ears, respectively. The results indicated that the pitch for the pitch-shift stimulus changed significantly each day, one through four, from an initial 210 Hz to about 205 Hz. The post one-week match was significantly lower than the initial pitch.
Pitch of the residue relative to variables for nonsimultaneous harmonics
Authors: Hall Joseph W. , Peters Robert W.
Published: October 2005

We previously reported [J. Acoust. Soc. Am. Suppl. 1 67, S20 (1980)] that for experienced observers, pitch perception for nonsimultaneous harmonics was based on spectral frequency in quiet and fundamental frequency in noise (signal 6 dB above masked threshold). This experiment extends the initial study and examines pitch perception for nonsimultaneous harmonics as a function of intervals between harmonics and signal-to-noise ratios. As in the previous experiment, observers judged for low pitch for the nonsimultaneous harmonics of 200 Hz versus 180 Hz in a 2AFC paradym. The higher fundamental (200 Hz) stimulus had relatively lower frequencies than the lower (180 Hz) stimulus. The results indicated that pitch judgments in noise change from fundamental-based to spectral-based as the temporal separations between harmonics are increased. The perception also shifted from fundamental to spectral as the signal-to-noise ratio was increased. Further, the results indicated that some observers judge pitch by spectral cues in all nonsimultaneous harmonic conditions. Thus, there appears to be a population for which analytic (spectral) perception is dominant.
Pitch processing of nonharmonic tones: A search for an auditory mechanism that recognizes spectral patterns
Authors: Cohen Elizabeth A.
Published: October 2005

Experiments on tone fusion [E. A. Cohen, J. Acoust. Soc. Am. Suppl. 1 65, S123 (1979); 66, 530 (1980); K. T. Marcus, M. V. Mathews, and J. R. Pierce, J. Acoust. Soc. Am. 66, 542 (1980)] suggested that tonal unity (fused pitch) is assured if the necessary and sufficient condition of a systematic overtone structure is met. The series fn′ = KAlog2nf1 was employed to insure the availability of structured harmonic and unharmonic partials. The 2nd partial of this series was deleted and a subject allowed to insert it by means of a tunable oscillator. If we are capable of recognizing nonharmonic systems then subjects should place the missing partial in the position called for by the mathematical order of the partials. Limited evidence for this ability was revealed (within ±5% of harmonic position). The results also show limited evidence for a subjective stretch of the octave when the 2nd partial is determined. It was observed that subjects (all trained musicians) experienced a remarkable, degree of difficulty even for placement of the truly harmonic partials.
Measurements of the spectral envelope of the sound from a cymbal
Authors: Fletcher Harvey , Bassett Irvin G.
Published: October 2005

The average spectral envelope over several blows on an 18-in. French cymbal was determined. The sound was picked up through a 38-in. microphone and analyzed at 13-octave intervals on an Ivie Electronics IE-30A spectrum analyzer. The cymbal was mounted horizontally in an anechoic chamber. The microphone was placed one meter below the outer edge of the disk. Although each blow gave a slightly different spectrum, they all had the same general characteristics. The envelope rises at about 7 dB per octave, to a peak in the 630-Hz region. Another broad peak occurs in the 4-kHz band. From there the falloff is quite steady at 16 dB per octave. The level at 16 kHz is 33 dB below the maximum value.
The acoustics of the harpsichord: A preliminary report
Authors: Kottick Edward L. , Savage William R. , Preece John
Published: October 2005

During the spring of 1980 the first author recorded response curves and modes of vibration of over forty harpsichords. About half of these instruments were newly built, while the others were antiques in museums. Sinusoidal forces of appropriate frequency were transmitted to each bridge pin in turn. Sound pressure levels were measured, and a driving point response curve was plotted for each harpsichord. Chladni patterns were detected by vibrating the glitter-covered soundboard; at certain frequencies of vibration the glitter formed stable patterns which were then photographed. It was found that newer harpsichords tended to respond at higher frequencies than the antique instruments.
Impedance measurement source and microphone proximity effects
Authors: Keefe D. H. , Benade A. H.
Published: October 2005

The input impedance Zin, as normally defined, is the air column pressure response to a unit plane wave flow excitation. The experimental measurement of Zin for an arbitrary air column is affected by the near-field interactions between an excitatory source (capillary, annulus, membrane, etc.) and microphone. In addition to the plane wave component, the source produces a local disturbance (due to the evanescent modes) at the microphone. The net microphone pressure pm can be written in terms of the source strength us, the wave impedance R0 and radius a of the air column entryway, and wavenumber k: pm = usR0[(Zin/R0) + jkaε]. The evanescent mode factor ε is real and independent of frequency for ka < 1. Its value depends on the source and microphone geometry. Measured values agree with detailed calculation. Placement of one transducer along the center axis of the air column, with the other at r = 0.6a from the center eliminates all azimuthal modes coupling (Jm Bessel functions, m > 0), and minimizes the coupling to the lowest order J0 evanescent mode. If neither transducer can be placed at the center, 90° azimuthal separation will eliminate all J1 modes. Placing one or both at r = 0.6a from the center then minimizes J0 effects. These configurations make the ε contribution to pm negligible for Zin(R0 > 2, but experimental study near Zin minima (i.e., input admittance maxima) still poses special problems. [Work supported by NSF.]
Woodwind instrument tone hole impedances
Authors: Keefe D. H.
Published: October 2005

Open or closed tone holes are usually represented as shunt impedances in the air column transmission line equations. Nederveen and van Wulfften Pathe (1963) pointed out that the lumped circuit for a closed tone hole includes a negative inertance in series with the shunt compliance. The open and closed tone hole impedance parameters have been calculated as a function of frequency for various tone hole proportions using variational method, and experimentally confirmed in detail. Large diameter short chimney holes (as on the sax) behave differently from small diameter long chimney holes (e.g., clarinet). Additional viscous and thermal losses near the sax-type open holes lessen their otherwise higher radiation efficiency. A single sax-type open hole at a pressure node radiates as a dipole while clarinet-type holes do not, since the evanescent modes are more weakly generated at the main bore-tone hole junction and more rapidly attenuated in the long chimney. The series impedance for an open hole, like the closed hole, is a negative inertance larger in magnitude than for the closed hole. The behavior of an open hole lattice near its cutoff frequency differs for the two types of holes. Adjacent open or closed sax holes interact within the main bore, while clarinet holes do not. External interaction via radiation from adjacent open holes raises the shunt inertance by a few per cent. Internal and external hole interactions modify overall instrument tuning and radiation efficiency. [Work supported by NSF.]
Numerical calculation of input impedance for brass horn shapes
Authors: Dudley J. Duane , Strong William J.
Published: October 2005

A numerical method for calculating input impedance of an oboe bore, approximating the bore by concatenated cylindrical increments, has recently been described by Plitnik and Strong [J. Acoust. Soc. Am. 65, 816 (1979)]. Assuming plane waves, and taking tube losses and finger-holes into account, the method produced impedance versus frequency curves that agreed well with experiment. This paper extends that approach to bores that have considerable flare, and larger bell openings where approximation formulas for radiation impedance at small values of kɑ do not apply. Calculations are made for the brass horn shapes studied by Jansson and Benade [Acustica 31, 185 (1974)], and compared to their experimental measurements. The results are in close agreement with experiment, and very close to the plane-wave calculations of Jansson and Benade. The radiation impedance, the effect of viscous boundary layers on sound speed, the necessity of using sufficient computer precision to avoid cumulative round-off error, the optimum increment size, and the application of the method to arbitrary bore shapes will be discussed.
Acoustics of the cornetto
Authors: Eliason Lowell J. , Ayers R. Dean
Published: October 2005

The cornetto or zink is a Renaissance cup-mouthpiece instrument of conical bore with tone holes like those on a woodwind instrument. Its useful range includes the true fundamental mode for each fingering, and higher modes are overblown without the assistance of a vent hole. The modes for the completely closed fingering constitute a good harmonic series, while the third and higher modes for all the other fingerings are noticeably flat. There is a distinct difference in tone quality between the fundamental register and the second octave. Alternate fingerings that employ the third mode also sound quite different from the same notes played in the second mode. Four voices of the cornetto family have been subjected to a study that includes measurement of input impedance by the capillary excitation technique and spectral analysis in an anechoic chamber. An electronic system using inexpensive integrated circuits has been used to make the impedance measurements.
Frequency-manipulated speech using a simulated constant-Q filter bank analyzer
Authors: Palmer E. Paul
Published: October 2005

A constant-Q spectrum analyzer was implemented digitally, using the Fourier-Mellon transform, to synthesize spectrally manipulated speech signals for audible and visual display and especially to produce frequency-transposed speech as an aid for the deaf. The work reported here was to assess the quality and intelligibility of sounds consisting of low-pass-filtered speech plus one "sine" wave, representing the high-frequency information, superimposed upon it. One-eighth-octave filters were used for analysis, and the one having the highest output was chosen to be transposed down in frequency. The general problem of synthesis where the high-frequency information comes at a higher rate than the low-frequency information will be discussed. A comparison of the visual patterns produced with linear- and logarithmic-frequency analysis will be shown and inferences drawn as to the extraction of transient speech information. Interference between the transposed second formant and the untransposed first formant will be illustrated. Preliminary tests of the intelligibility of diagnostic rhyming words incorporated in common phrases will be reported.
Hearing acuity and stop-consonant discrimination in aphasic adults
Authors: Kitselman Kurt
Published: October 2005

In an earlier study [K. Kitselman, J. Acoust. Soc. Am. 64, S51 (1978)], greater group differences were found between ten aphasic adults and ten age-matched controls for discrimination of place contrasts signaled by 25-ms formant transitions compared to discrimination of place contrasts signaled by 40-ms transitions. These data were reanalyzed using a Q-factor analysis to assess individual discrimination performance. Subjects with a high positive loading on the dominant factor showed discrimination functions with the expected sharp peaks of discrimination at category boundaries. Subjects with a smaller loading on the dominant factor showed less boundary effect. The correlation between group and loading on the dominant factor was significant within the 25-ms and the 40-ms stimulus conditions. When hearing acuity (mean of threshold levels at 1, 2, and 3 kHz) in the better ear was controlled statistically, the partial correlation between group and loading was significant at the 0.05 level within the 25-ms condition but not within the 40-ms condition. Although all subjects met a strict hearing sensitivity criterion, factoring out hearing acuity reduced group differences on the discrimination tasks to a level that was considered to be minimal. [Supported by Rehabilitation Services Administration.]
Identification of stop consonant voicing and place of articulation by listeners with normal hearing and by listeners with mild, moderate, severe, and profound hearing impairments
Authors: Johnson Deborah , Whaley Patricia , Dorman M. F. , Raphael L. J.
Published: October 2005

Normal hearing and hearing impaired listeners were asked to identify the voicing and place characteristics of synthetic /bdgptk/ in 2, 4, and 6-choice tasks. For each place of articulation, a VOT continuum was constructed. In general, the boundaries along the VOT continua did not differ for the normal hearing listeners and the listeners with mild and moderate losses. Some listeners with severe impairments and most with profound impairments evidenced abnormal boundaries. In the six-choice task, even when phonetic boundaries were normal, the hearing impaired listeners were more variable in their labeling performance. The identification of place varied inversely with the degree of hearing impairment.
The discrimination of formant frequency differences as a function of duration by hearing-impaired listeners
Authors: Millay Kathleen K. , Godfrey John J.
Published: October 2005

Hearing-impaired subjects with high-frequency, noise-induced hearing loss and normal low-frequency sensitivity were compared to normal hearing subjects in two discrimination tasks. These tasks were designed to determine formant frequency discrimination thresholds as a function of stimulus duration in steady-state speech signals. The first task was discrimination of second formant (F2) frequency differences with F2 in the 2200–2840 Hz range, using computer-synthesized vowels varying in duration in logarithmic steps from 24 to 384 ms. The second task was discriminating first formant (F 1) frequency differences in the 200–360 Hz range for the same durations. Hearing-impaired subjects took the tests at 35 dB SL (re:SRT) and showed elevated thresholds for discrimination of F2 frequency differences, when compared with the normal-hearing subjects at both the 35 dB SL and at a 92 dB SPL presentation level. However, these same hearing-impaired subjects performed similarly to the normal hearing listeners in the F1 discrimination task where hearing sensitivity was normal for both groups. Moreover, the effect of shorter signal duration on formant frequency discrimination appears to be more severe for the impaired listeners.
Articulatory adjustments following orthognathic surgery
Authors: Ewan William G. , Gay Thomas
Published: October 2005

Surgical correction of extreme malocclusion involves surgical repositioning of the maxilla and the body of the mandible with reference to the cranial base. The tongue moves passively with the mandible so that the relationship between any point on the tongue surface and any point on the fixed surface of the vocal tract changes. Preoperative and postoperative articulation should show what parts of an articulatory gesture persist and are therefore reprogrammed and which are left free to vary. Lateral x-ray head films were obtained for a number of patients immediately prior to and at least three months following orthognathic surgery during the production of the isolated vowels [i], [a], and [u]. Spectrograms were made of the recorded voice. Superimposed tracings of the vocal tract of preoperative and postoperative x rays were made for each vowel with a cranial reference and then with a mandibular reference. Analysis showed that the point of maximal constriction persisted for the vowel while the rest of the tongue shape changed. Spectrograms showed slight changes in formant frequencies between pre- and postoperative recordings. These results are discussed in terms of strategies of speech motor programming.
Aberrant laryngeal devoicing gestures produced by deaf speakers: Evidence from high speed laryngeal films
Authors: Metz Dale , Whitehead Robert
Published: October 2005

Recent acoustic, aerodynamic, and glottographic data (R. Whitehead and D. Metz, following abstract, this meeting) suggest that deaf speakers may produce aberrant abductory and adductory devoicing gestures associated with the /h/ segment in /ihi/ syllables. These aberrant devoicing gestures apparently interact with respiratory and upper airway dynamics to such a degree that the normal temporal contiguity of the syllable is disturbed. To gain a more precise understanding of the physiological nature of these gestures, high speed laryngeal films were obtained from four deaf speakers. The films illustrate that aberrant abductory devoicing is characterized by an excessively wide separation of the vocal folds during the production of /h/, while aberrant adductory devoicing is characterized by glottal constriction during /h/ production. In some instances, the glottis is constricted by both the true vocal folds and the ventricular folds which prohibits normal reinitiation of vocal fold vibration for the adjacent /i/ segment. Photographic sequences of individual frames excised at 50-ms intervals from films exposed at 4000 frames/s will be shown to illustrate these aberrant laryngeal gestures. [Work supported by U.S. Department of Education.]
Hearing aid for selecting voice sounds automatically using noisy environment
Authors: Ono Hiroshi , Saito Shigegi , Kanzaki Jin , Fukuda Hiroyuki , Mizoi Kazutoshi
Published: October 2005

It is well known that one of the major complaints of a patient with a conventional hearing aid is low speech intelligibility due to the masking of speech by environmental noise. Consequently, a new hearing aid with selective amplification in the voice frequency band was developed using a compression amplifier which automatically compresses the lower frequency range as a function of the level and spectrum of the environment noise. This hearing aid consists of two filters and a compression amplifier. Sound signals from a microphone are divided by a low pass filter (LPF) and high pass filter (HPF). Only the sound signal passing through LPF is compressed with a compression amplifier and then mixed with the sound signal passing through HPF. In 40 dB ambient noise levels, this hearing aid shows flat frequency response. On the other hand, in environmental noises of more than 60 dB, the voice sounds become clearer and the S/N ratio of the voice sound is improved by selective compression of the lower frequency sounds. Use of this hearing aid on five hearing impaired patients, showed that the environmental noise is decreased and the voice sounds became clearer and more audible.
Vibration analysis of laminated composites
Authors: Dökmeci M. C.
Published: October 2005

This study presents a macromechanical analysis of vibration of laminated composites within the concept of the effective stiffnesses of composites. The laminated composite may possess arbitrary number of matrix and reinforcing layers, each with a distinct but uniform thickness, curvature, and mechanical properties. Starting with a linearized displacement field for each constituent layer and using an unconstrained, dynamic variational principle due to the author [J. Ship Res. 23, 115–122 (1979)], the set of two-dimensional governing equations of the prestressed laminated composite is systematically and consistently established. The continuity of tractions and displacements at the interfaces is maintained, and all the effects of transverse shear and normal strains and the rotary inertia of layers are included. The governing equations accommodate all the types of small incremental motions as well as those of initial finite motions of the laminated composite. Further, special cases of interest are pointed out, and in particular, the linearized version of the governing equations is considered. Then a theorem which enumerates the sufficient conditions for its solutions is constructed by means of the logarithmic convexity arguments. [Supported by AEK Tek: 2940-3-77.]
Flow induced vibrations of long, flexible cylinders
Authors: DeMetz F. C.
Published: October 2005

The mechanisms of flow-induced vibrations in long, flexible cylinders are reviewed. The excitation mechanisms include vortex shedding, turbulent pressure field, fluctuating shear stress, and static and oscillatory instability. The relative amplitudes of the transverse and longitudinal cylinder vibrations are discussed in terms of some elementary models of the forcing functions and the mechanical properties of the cylinder.
Phonetic boundaries and judgmental central tendency
Authors: Espinoza-Varas Blas
Published: October 2005

What determines that phonetic boundaries be placed at some specific loci of speech stimulus continua? According to one view, boundaries would be determined by relatively stable, built-in properties such as psychophysical thresholds, selectively tuned feature detectors, or articulatory constrains. Alternative views, e.g., central tendency in psychological judgments [R. S. Woodworth, Experimental Psychology (Holt, New York, 1938), pp. 445], and adaptation-level theory [H. Helson, Psych. Rev. 55, 297–313 (1948)], suggest that category boundaries are learned psychological standards that subjects develop when classifying stimuli along a dimension. These psychological standards tend to match some central tendency measure of the stimulus distribution. This paper re-evaluates the adequacy of these alternative views with existing labelling data for speech continua of VOT, duration of stop closure, and onset and duration of formant transitions. For most of these data, the observed values of the phonetic boundaries approximated well the arithmetic mean of the stimulus distribution. In addition, changes in the phonetic boundary appeared to follow changes in the arithmetic mean that resulted from varying the range or shape of the stimulus distribution. The contribution of judgmental central tendency to the development of phonetic boundaries will be discussed. [Supported in part by NRC Postdoctoral Fellowship to the author.]
The current status of national and international standardization work in damping technology
Authors: Drake M. L. , Henderson J. P. , Jones D. I. G.
Published: October 2005

There are two national standard committees currently conducting studies on standards that will directly effect all those working in the vibration damping field. The ASTM E33.03M committee has developed a standard damping material characterization test based on the resonant vibrating cantilever beam test procedure. In a cooperative effort the American National Standards Committee on Mechanical Shock and Vibration S2-73 is working on a standard damping material data display method. This data display is based on an extension of the reduced frequency plot and is called the reduced temperature nomogram. The basics of each proposed standard and their current status will be reported. There are two international committees, TC63 and TC103, which are working similar standards. The direction and current status of the international committees will also be discussed.
Complex modulus measurement of a damping polymer at very low strain levels
Authors: Jones D. I. G. , Lagnese T. J.
Published: October 2005

Damping techniques which incorporate polymeric materials with high energy dissipation properties have been studied and applied for years. As a precursor to correct design and application the designer needs to know the damping properties (loss factor, complex Young's modulus) of the viscoelastic material within the environmental conditions of each application. It is considered within this work that for some applications, such as large spacecraft structures, polymeric materials should not only be tested at temperature and frequency but at very low strain levels. This paper will address measurement techniques, difficulties associated with low strain level measurements, and discuss some preliminary results.
Glass coatings for high temperature vibration damping in turbine engines
Authors: Kumar B. , Graves G.
Published: October 2005

A discussion of the various selection criteria to determine suitability of glass composition for a given high temperature vibration damping application will be presented. The criteria to be discussed are: the damping temperature, size and shape of the damping peak, the stability of the glass composition at operational temperatures, possible glass to metal interactions and their consequences, glass to metal thermal expansion match, the slope of the viscosity temperature curve, and the compatibility of the glass to a protective coating. These criteria will be considered with respect to phenomenon as devitrification, phase separation, selective volatilization, and chemical reactivity with the engine environment. The possible interaction of the glass with the metal substrate and its effect on the substrate mechanical properties, e.g., low cycle fatigue and stress corrosion, will also be discussed.
Some results on the effect of interface friction damping on turbomachinery blade dynamics
Authors: Jones D. I. G. , Muszynska A.
Published: October 2005

The presentation will review problems of damping in turbomachinery blades and bladed disks. The blade-disk and blade-to-blade interface effects represent an important source of damping controlling vibration and stress levels. These effects are substantially nonlinear and depend on different factors (physical, micro, and macro-geometrical, kinematical). Their magnitude, however, exceeds the magnitude of damping brought to the system by internal (material) and external (fluid flow) dissipation of energy. A nonlinear discrete modelization based on modal analysis of forced response to periodic excitation of a single blade and bladed disk and the model identification based on experimental results will be discussed. The mathematical model of the system is being analyzed numerically. Some results of the calculations will be presented: the effects of phase differences between excitation forces at each blade, mistuning of blades, magnitude of excitation forces, magnitude of interblade and blade-disk friction forces, viscoelastic coupling between blades. The investigation throws light on blade-to-blade coupling effects and blade-root interaction. The results may be of interest to turbomachinery blade designers, who are concerned with development of frictional vibration control configurations.
Damped aircraft structure design for fatigue control
Authors: Kluesener F. , Drake M. L.
Published: October 2005

In this paper emphasis is placed on incorporating visco-elastic damping materials into typical aircraft panel structures to reduce resonant stress and displacement of the structure induced by extremely high sound pressure levels. The increased modal damping, by reducing the resonant stress, extends the fatigue life of the component. It is shown that a damping treatment can be used on a standard thickness panel to reduce stress and extend the fatigue life over that of the standard panel, or the damping treatment can be used on a thinner panel to obtain the same stress and fatigue life as in the standard undamped panel, but realizing a weight savings. Constrained layer damping treatments and fraying surface damping treatments are analyzed by the finite element method and compared for their effectiveness and weight savings.
A practical application of constrained layer viscoelastic damping on a ground power turbine engine
Authors: Drake M. L. , Ruddell M. J.
Published: October 2005

A turbine engine was incurring vibration related fatigue failures in the cast aluminum inlet guide vane case. A field applicable damping wrap was designed with a temperature range of −50°F to +150°F. A single blade test item was used for laboratory testing. Results of tests showed high stresses and relatively low modal damping in the second bending and torsional modes. A computer prediction program was used to determine which damping materials should be effective over the temperature range. Empirical testing of predicted materials in different configurations determined which configuration was optimum for this application. Laboratory results indicated a maximum dynamic response reduction of 86%. An engine test as conducted to measure the dynamic stresses in the vanes with and without the damping application. The test results showed a 76% to 90% dynamic stress reduction due to the addition of the damping treatment.
The national voluntary laboratory accreditation program
Authors: Forman Howard I.
Published: October 2005

Formally established in 1976 by the U.S. Department of Commerce, the National Voluntary Laboratory Accreditation Program (NVLAP) is designed to examine the professional and technical competence of private and public testing laboratories at their request. The Department will grant or deny accreditation to testing laboratories based on its assessment of their competence. Actions undertaken in NVLAP are based on established standards and test methods in specific product area. NVLAP benefits consumers and manufacturers by assuring more consistent product testing. It benefits government agencies and industry associations by providing procedures for accrediting laboratories which could be used as part of their product certification programs. Additionally, NVLAP benefits laboratories by providing a focus for increased professionalism and by minimizing the number of bodies whose approvals the laboratory may find it necessary to obtain. The first accreditations were granted on 12 October 1979 to 30 laboratories that test thermal insulation materials. The Department currently has programs for three product areas: thermal insulations materials, freshly mixed field concrete, and carpet. Laboratories applying under these three programs are currently being assessed. New programs for accrediting laboratories that test other products are being considered.
Biot's second compressional wave: measurement and theory
Authors: Plona T. J. , Johnson R. K.
Published: October 2005

Recently, Plona reported the experimental observation of Biot's second compressional wave in a fluid-saturated porous medium composed of water and sintered glass beads at frequencies near 1 MHz [T. J. Plona, Appl. Phys. Lett. 36, 259–261 (1980)]. Favorable agreement between the Biot theory and the measured second wave speed (as well as the fast compressional and shear) have been shown by Berryman (to be published to Appl. Phys. Lett.). For these calculations, the moduli of the porous frame were theoretically determined using various existing composite media models together with the moduli and density of the constituent glass and water. In this paper, estimates of the frame moduli are experimentally determined based on ultrasonically measured shear and compressional wave speeds in the air-saturated porous frame. Thus the Biot theory predictions of wave speeds in the water-saturated porous structure are calculated using primarily measured data. Experimental and theoretical results will be shown for a suite of sintered glass bead samples ranging in porosity from 0% to 35%. The validity of using dry velocity measurements as input to the Biot theory will be discussed as well as the dependence of the second wave speed on porosity and permeability.
Transient streaming potential measurement on fluid-saturated porous rocks: an experimental verification of Biot's slow wave in the quasi-static limit
Authors: Chandler Richard
Published: October 2005

The time behavior of the streaming potential is identical to that of differential pressure when local laminar flow is maintained and electromagnetic relaxation is not important. The time evolution of the streaming potential waveform resulting from the application of a pressure pulse to one face of a cylindrical water-saturated core is found to depend on the elastic properties of the fluid and rock frame and on the porosity and permeability of the core. The analysis of this quasi-static flow based on Biot's soil consolidation work (1941) is completely equivalent to that obtained from Biot's slow wave model (1956) in the limit of zero frequency. Both analyses result in a homogeneous diffusion equation in pore pressure (and streaming potential) where the diffusivity is expressed in terms of the bulk moduli of the fluid and solid constituents, bulk and shear moduli of the solid frame, fluid viscosity, porosity, and permeability. The predicted streaming potential transient response is in excellent agreement with experimental observations, permitting, for example, the extraction of core permeability. Models assuming an incompressible frame are shown to be grossly inadequate in describing the temporal features of quasi-static flow.
Transition noise—The role of fluctuating displacement thickness
Authors: Lauchle Gerald C.
Published: October 2005

The role of the fluctuating wall shear stress on the noise generated by incompressible boundary-layer transition was recently analyzed [G. C. Lauchle, J. Acoust. Soc. Am. 67, 158–168 (1980)]. The solutions of that analysis suggest that the shear stress mechanism generates hydrodynamic sound weakly in comparison say to the sound generated by a fully developed turbulent boundary layer flow. Because boundary-layer transition is a very unstable and nonsteady flow, we might expect that other acoustic mechanisms exist. In this paper, we examine one other; namely, that of the fluctuating boundary layer displacement thickness which is expected to occur as turbulence bursts are created and convected over the surface. The analysis shows that a weak monopole sound source occurs, and at low subsonic flow velocities, this source generates significant acoustic energy. Comparisons of the theoretical predictions with available experimental data support this conclusion. [Work supported by NAVSEA.]
Acoustic properties of fluid filled porous rocks
Authors: Odé H. , Dutta N. C.
Published: October 2005

During 1941–62, Biot laid the foundation of a comprehensive theory concerning the mechanics of deformation and acoustic wave propagation in fluid-filled porous solids. The theory describes the motion of the solid matrix and the pore fluids by coupled differential equations and predicts the existence of three body waves: a single shear wave, a fast compressional wave and a slow compressional wave. The latter propagates in the manner of a diffusion process. In this paper we will review the fundamental aspects of Biot's theory and present some theoretical results for the attenuation and dispersion of seismic waves in a partially gas saturated porous rock. The importance of this problem for seismic exploration was first pointed out by White [Geophysics 40, 224–232 (1975)], and later reformulated by Odé and Dutta [Geophysics 44, 1777– 1788 (1979)]. Further we will illustrate the correspondence of the mathematical description of Biot's theory with the theory of heat conduction. Finally we will provide an explanation based on Biot's theory of a recently observed “slow” bulk compressional wave in fluid-filled porous solids at ultrasonic frequencies.
Auditory brainstem evoked responses in young hearing impaired individuals with and without amplification (hearing aids)
Authors: McPherson David L.
Published: October 2005

The relation between the auditory brainstem response and the psychological responses to acoustic clicks in an aided condition was studied. These results were compared to the KEMAR responses using the same acoustic stimulus as for the auditory brainstem response measures. Results indicate that the hearing aid is the primary limiting factor in using the auditory brainstem responses for amplification selection. Measures of gain, maximum power output, output limiting, and dynamic range may be estimated using the auditory brainstem response measure. There is a casual relationship of these measures to behavioral thresholds, most comfortable listening levels, and the loudness discomfort level. It was found that click rates of less than 5 per second must be utilized due to the processing characteristics of the hearing aid.
Interior noise and vibration environment of propeller aircraft
Authors: Shepherd Kevin P. , Dempsey Thomas K. , Mayes William H.
Published: October 2005

A series of laboratory and field studies are being conducted to provide design information that maximizes passenger comfort for proposed propfan aircraft. Particular emphasis in these studies is being placed on the predicted interior noise and vibration environment and the resultant passenger acceptability. Due to inadequate information about the noise/vibration of such vehicles, the present field investigation provided data of this nature. Previous ride quality research at NASA Langley has indicated that vibrations of sufficient intensity to produce whole-body movements (at frequencies less than 80 Hz) cause human discomfort. Further, within complex interior vehicle environments, this type of vibration interacts additively with noise to produce discomfort. However, recent questions have arisen concerning the frequency of vibration aboard propeller/propfan aircraft and the manner in which the noise and vibration combine to produce passenger discomfort. To examine this issue, noise and vibration data were taken on board a Shorts 330. Microphones were placed at forward, aft, and center positions in the cabin and accelerometers were placed on the floor, sidewall, window and armrest. Data were collected for various flight conditions, including takeoff, landing, and cruise. There is a clear similarity between the noise and vibration spectra suggesting a forced vibration response. More important, the Shorts 330 data indicate the existence of high-frequency vibration in the range of 80 to 1000 Hz. This type of vibration is clearly perceptible through a tactile (touch) sensation, but does not independently produce passenger discomfort. The question as to whether or not the noise and this higher frequency vibration interact to aggravate the noise environment will be studied in future passenger simulation tests.
Vibration and noise relationships: Some simple rules for the machinery design engineer
Authors: Feit David , Cox Spruce M. , Richards E. J.
Published: October 2005

In a world in which the expert is king, countries become very small and communication between them becomes very difficult. This is so in the world of acoustics; symposia are divided into specialist sections, and experts only want to hear from greater experts than themselves. Unfortunately new technologies develop across such separations, and from time to time it is necessary to try to bridge the gaps in a manner which is simple enough to persuade each group to interest itself more widely. Such a technology is that of trying to design industrial machinery which, while increasing productivity, reduces its noise and minimizes deafness. Machinery noise emanates from heavy impacts between parts. The vibration which results from this is the flow of vibration into parts that can radiate efficiently; the noise radiated depends upon the magnitude and the wave form of this vibration, upon its frequency and upon the balance between the rate of radiation and the rate of absorption in the machine. The seriousness of the noise, and the methods of reduction must depend upon the form of the units by which it is measured. This paper goes back to first principles in trying to provide the basic physical insights which will permit an approach to machinery noise which can both be used by the design engineer looking for simple design rules, while also tempting the expert acoustician, vibration engineer and psychoacoustician to extend his interests into what must surely become a new branch of acoustic technology.
Novel technique being explored to warn of impending failures of operational systems
Authors: Yang J. C. S. , Dagalakis N.
Published: October 2005

When you hear a mysterious new sound when driving your car you know that it usually means trouble. Now such signals can be translated into a “signature” which identifies the problem by a technique called “Random Decrement”. First the vibrations have to be picked up by a sensor, like the pickup in a record player. Then these signals which appear meaningless in their original form are sorted, and a characteristic signature is established which engineers can relate to the mechanical properties of the system. If a flaw such as a fatigue crack develops, the signature changes, thus warning the operator of impending failure. The “Random Decrement” technique is particularly well suited to the class of problems in which characteristics are desired of an in-service structure subjected to unknown random excitation such as wind, earthquakes, waves, sound, traffic loads, etc. Analysis requires only the measurement of the dynamic response of a structure, and not the excitation. Continuous automatic monitoring is possible. The method has been applied in flight flutter testing of the F-16 aircraft, in monitoring the seals during operation of a wind tunnel, in detecting cracks, and measuring damping in structures such as ships, bridges, pipes, and machinery. More recently it is being used in a joint ONR-USGS research program for remote detection of underwater structural failures in ocean platforms.
A statistical model of the rotating diffuser acoustic modulation process in a reverberant sound field
Authors: Elko Gary W. , Tichy Jiri
Published: October 2005

The rotating diffuser (RD) acoustic modulation spectrum in the reverberant sound field for pure tone excitation, is known to be narrowband and discrete. This is due to the relatively long geometric periodicity of the RD's position in the chamber. A statistical model of this process is formulated on the assumption that the discrete frequencies are added in random phase. Experimental and theoretical results for the probability distributions or the instantaneous pressure and pressure envelope were investigated. The AM, FM, and total spectra generated by the RD for the various rotational speeds were measured for both discrete positions and the spatial average. These results indicate that a significant amount of the RD spectral energy is FM. The experimentally measured data were used to calculate the normalized pressure-squared variance, the envelope variability, time averaging requirements, and the calculation of the expected probability distribution. A closed form approach to the calculation of the confidence levels for the measured sample variance is derived. The results show that even with a large number of measured degrees of freedom, the measured variance spread is large. Some interesting new results on the RD phenomenon will be discussed.
Sampling statistics of reverberant sound field in rectangular rooms—pure tone excitation
Authors: Chu W. T.
Published: October 2005

The sampling statistics of reverberant sound field proposed by Schroeder, Waterhouse, and Lubman were derived from the freewave model under several simplified assumptions. A corresponding analysis using the eigenmode approach reveals, however, that these assumptions might not be met in actual rooms. An important parameter to be considered is the absorption characteristics of the walls. Even under relatively ideal situations, the standard deviations of the normalized mean-square pressure and the sound pressure level can deviate significantly from 1 and 5.57 dB respectively, depending on the wall absorption characteristics. For the limiting case of perfectly reflecting boundaries, the former approaches (2)1/2 while the latter can reach as high as 9.65 dB.
Modulated reverberation with an absolute sound power source
Authors: Cook Richard K.
Published: October 2005

The basic idea of the relatively new method of modulated reverberation is to amplitude modulate, at a low infrasonic frequency, the sound power radiated by an audiofrequency source. There will be a corresponding amplitude modulation of the total acoustical energy in the sound field, but reduced in amplitude and lagging in phase due to the absorption in the reverberation chamber. Measurement of the phase angle yields the “instantaneous” time rate of exponential decay. The new method is applied with an absolute sound power source. Its output is absolutely determined, as a running function of time while it is radiating acoustically, through electroacoustical measurements conducted directly on the source. The analysis then shows that the new method will yield (a) an absolutely measured total energy, potential and kinetic, of the reverberant sound field, and (b) the “instantaneous” time rate of energy absorption. The basic analysis is applicable to the use of such sources in three-dimensional reverberation chambers. A more detailed analysis will be given for a simple “thought” experiment; the modulated reverberation of the sound field in a standing-wave tube. This will show quantitatively the precise relationships between the kinetic and potential energies, and the “instantaneous” time rate of energy absorption.
Scale models in room acoustics—What accuracy is needed
Authors: Kihlman Tor , Kleiner Mendel
Published: October 2005

Modeling costs depend to a great extent on the degree of accuracy specified. This influences the room model impulse response, especially the early part. Results from full scale and model experiments will be discussed, as well as the degree of accuracy needed.
Multipurpose hall design—a new direction
Authors: Long Marshall
Published: October 2005

In Beraneks evaluation of concert halls, he attributed 40% of the rating to his own discovery initial time delay gap, 30% to factors associated with reverberation time, and 16% to factors associated with loudness. Multipurpose halls following this design philosophy have emphasized the use of clouds to provide early reflections and moveable curtains behind partially open panels to vary the reverberation time at the expense of loudness, side reflections, and bass. Recent listener preference space sludies have attributed 47% of hall preference to factors associated with sound force, and 28% to factors associated with sensation definition and clearness (i.e., side and front reflections). The direction of this research points overwhelmingly to a return to smaller volume halls with strong side reflections even for multipurpose uses.