bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Practical Problems Involved in a Study of the Industrial Noise Problem
Authors: McGrath Ralph Martin
Published: September 2005

Medical authorities all agree that the noise problem is serious. How serious it is for a given industry can only be ascertained by a properly conducted noise survey which will give data on the noise levels to which its industrial workers are subjected and an audiometric survey which will give data on the hearing acuity of workers subjected to such environments. Noise level meters, filter sets and analyzers, and audiometers are available with which to conduct these surveys. There is need for standardization in the methods by which the two surveys are conducted and interpreted. There is need, also, for data on how the adverse effects of noise upon personnel in turn affect the quality of the product, labor turnover, absenteeism, accidents, and compensation claims. Industry, confronted with a serious problem, cannot wait for elaborate refinement of data but must act with the data available. Fortunately, industries all over the country are acting and the steps being taken are reviewed. More before and after studies are needed to help others tackle their problems. The steps taken at Hawthorne are summarized with a brief review of the fundamental theoretical problems involved in compensation claims. The role that the Acoustical Society of America can play in coordinating the efforts of all organizations interested in assisting industry to solve the noise problem is outlined briefly.
Proposed Acoustic System for Ordnance Research Laboratory Water Tunnel
Authors: Kendig Paul M.
Published: September 2005

A description is given of the acoustic methods and equipment for detecting and locating sources of cavitation on underwater bodies and propellers (under test) in the high speed water tunnel now under construction at the Ordnance Research Laboratory at the Pennsylvania State College. Sound arising inside the tunnel will pass through an acoustically transparent window to an external tank in which is placed a small piezoelectric crystal hydrophone at the focus of an ellipsoidal reflector. The source of sound can thus be located because the hydrophone is most sensitive to sounds originating at the conjugate focus of the ellipsoid which is inside the tunnel. The reflector and hydrophone assembly has three degrees of freedom.
Acoustic Filter for Water Filled Pipes
Authors: Hoover R. M. , Laird D. , Miller L. N.
Published: September 2005

It is anticipated that some of the auxiliary equipment to be used in conjunction with the new water tunnel under construction at the Pennsylvania State College will be particularly noisy in the ultrasonic frequency region where certain low level acoustic measurements are to be made. This potentially noisy equipment includes such items as a deaerator, an energy dissipator, and a pressure control system which are located in a water loop, external to the main tunnel section. To effectively isolate this loop acoustically from the remainder of the tunnel where the acoustic measurements will be made, it has been considered desirable to design an acoustic filter which can be inserted at the junctions of the loop with the tunnel. This filter should serve the multiple function of reducing the sound transmission through the pipe walls and through the water in the pipes while permitting the passage of relatively large volumes of water at small loss of pressure. The problem of isolation in the pipe path is a fairly common one and essentially requires the use of sound attenuating gasket material. However, the isolation of the water path is more complex in that water must be allowed to flow while sound is attenuated. In this case a honey-combed structure of a pressure release material is used. This paper discusses the hydraulic consideration of the problem and presents the results of acoustic transmission measurements on the filter components. The measurements include: 1. The frequency characteristics of the acoustic filter under free field conditions, 2. The transmission properties of the isolating gaskets mounted in the pipe flanges, and 3. The effective response of the filter and isolation gaskets combined.
The Properties of Gaseous Solutions as Revealed by Acoustic Cavitation Measurements
Authors: Blake F. G.
Published: September 2005

That very small gas bubbles can serve as nuclei for the formation of cavities in liquids is well established. That experimental observations on the rupture of liquids can be interpreted only on this basis is perhaps not so obvious but none the less true. In the present series of experiments on acoustic cavitation in water, two distinct types of bubble formation occur. One, the violent formation and collapse of vapor-filled cavities, results from mechanical instability of gas nuclei. The other, relatively quiet gas bubble formation, occurs as a consequence of the slow growth of nuclei by “rectified” diffusion of dissolved gas from the surrounding liquid. Each process has a threshold of excitation by a sound field; which has the lower threshold in any given case depends largely upon the concentration of dissolved gas in the liquid. Measurements of the acoustic cavitation threshold in conventionally “deaerated” water, as a function of temperature and ambient hydrostatic pressure, reveal how the equilibrium size of gas nuclei depends upon these variables. Observations on sonically induced effervescence in saturated solutions provide at least a qualitative explanation for the pulse length and viscosity effects observed elsewhere. Cavitation at the surface of a sound projector apparently is profoundly affected by adsorbed gases. The conclusion that gaseous nuclei exist more or less in equilibrium with solutions not supersaturated with gas is contrary to the conventional theory of gaseous solutions. Stabilization of nuclei in the surface cracks of suspended solid particles is a very plausible but not entirely satisfactory explanation. Revision of the theory is a tempting subject for speculation.
A New High Speed Inkless Recorder
Authors: Niemann A. W. , Reitz L. P.
Published: September 2005

A portable instrument is described for recording level changes or low frequency wave forms on a 2-inch wide strip chart. A novel servo system, employing a power driven stylus, is utilized, giving a greater force-to-mass ratio than has heretofore been possible. Recording speeds in excess of 1000 db per second on a logarithmic db scale are attainable, with a continuously variable stylus-speed control. A novel feed-back loop used in conjunction with antihunt circuits makes possible very rapid stylus movement insuring maximum accuracy and stability. Eight synchronous chart speeds from 1 to 200 mm/sec. are push-button selected for accurate time axis recording. A take-up chart spindle is provided for continuous recording. Especially designed for acoustic reverberation studies, it provides accurate means for investigating low reverberant chambers of 0.1 second, and less, reverberation time.
The Present Status of Piezoelectric Transducer Crystals
Authors: Jaffe Hans
Published: September 2005

The piezoelectric characteristics of transducer crystals may be expressed in terms of electromechanical coupling coefficient, mechanical compliance coefficient, and dielectric constant, all referring to the mode to be applied, and the density. The modes considered are face shear (utilized in the torque “Bimorph”), lateral expansion, thickness expansion, and thickness shear. Properties not readily expressed in circuit terms but of the highest practical importance are dielectric and mechanical strength and permissible temperature rise. Rochelle salt offers a coupling coefficient of 0.5 or more, combined with fairly high mechanical compliance and high dielectric constant for face shear and lateral expansion. Quartz combines a rather low coupling of about 0.1 with low electric compliance; these factors are disadvantageous for most transducer applications but may be outweighed by excellent stability. The newer crystals, ammonium dihydrogen phosphate (ADP) and lithium sulfate monohydrate (LH), combine fair stability against atmospheric conditions with intermediate dielectric constant and couplings about 0.3, the former for face shear and lateral expansion, the latter for thickness and volume expansion. Neutral potassium tartrate (DKT) in face shear or lateral expansion is indicated for transducer uses requiring fairly high coupling, up to 0.25, with a low temperature coefficient of resonant frequency. Polarized barium titanate ceramic takes its place besides the single crystals. It combines low mechanical compliance and very high dielectric constant with coupling of 0.20 for the lateral expansion and 0.45 for the thickness expansion. It may be shaped into curved transducer elements. A comparative table for these and some other substances will be given.
Absorption Measurements in Magnesium Sulfate
Authors: Beyer R. T. , Smith M. C. , Barrett R.
Published: September 2005

Ultrasonic absorption measurements are reported for dilute water solutions of MgSO4. For frequencies in the range 3 to 10 megacycles, the measurements are made by measuring the rectified output of a crystal detector. Measurements proportional to the acoustic intensity are made along the axis of the radiated beam, and the absorption is calculated from formulas which take into account the spreading of the beam and the size of the microphone. In this connection, the necessary measurement of the wave-length of the radiation can be made by use of the spatial modulation of the acoustic signal by the electromagnetic pick-up. Measurements at frequencies in the range 10–30 megacycles are made with a conventional radiation pressure balance. Measurements are reported for various concentrations at the different frequencies. The values obtained indicate an increase in the absorption coefficient which is approximately linear with concentration.
Techniques of Research Used in Quieting Machinery and Appliances
Authors: Hardy H. C.
Published: September 2005

As our age becomes more industrialized, the problems of quieting machinery and appliances—whether they occur in industry, office or home—become more numerous and more difficult. The economy of using improved research methods and competent scientific personnel is emphasized. Determination of qualitative data (source of energy, source of radiation, relative spectral distribution, relative intensity of frequency peaks, etc.) is usually more important than spending excess time obtaining quantitative data (precise sound intensity, exact frequency spectrum, percent harmonic content, etc.). The importance of analysis of sound energy sources, sound radiation sources, and coupling factors between them will be emphasized. A system of analyzing noise problems, by schematic diagrams giving the energy flow between sound energy sources and the surrounding propagating medium, will be outlined and illustrated by actual data from typical research problems.
Method for Quieting Ram Jet Motor Test Stations
Authors: Snow W. B. , Young C. J. T.
Published: September 2005

The Applied Physics Laboratory of Johns Hopkins University, operating under contract with the Bureau of Ordnance of the U. S. Navy, set up during the war a testing laboratory for ram jet motors at Forest Grove, Maryland, a short distance outside of Washington, D. C., in a location surrounded by open country. Postwar building in the neighborhood made it necessary to quiet this installation if operation were to continue at the same location and the Kellex Corporation undertook design of the revisions. Since very large volumes of air and hot gases had to enter and leave the test cells, it was necessary to design a duct system which offered extremely low resistance to gas flow, but high attenuation to sound. This paper gives a brief description of the resulting construction which has allowed the laboratory to continue operation in the midst of a residential community.
Acoustic Absorption Coefficients at High Frequencies
Authors: Cramer William S.
Published: September 2005

The measurement of the acoustic absorption coefficient by a steady state method was carried out at frequencies of 9, 20, and 30 kc for seven different materials. This involved the construction of a sound chamber with facilities for creating a diffuse sound field and a sample area where materials could be mounted. The average intensity in the chamber was measured with the sample area covered with the material under test and the results compared with similar measurements when the area was covered successively with a material of negligible absorption and when it was open to the air outside. The expression giving the absorption coefficient in terms of these three relative intensity readings is derived.
The First Symmetrical Mode of Vibration of a Conical Shell
Authors: Hardy H. C. , Ramakrishna B. S.
Published: September 2005

An aid in the design of loudspeakers would be a solution of the vibration of a conical shell. The general solution is exceedingly complex, but a partial solution can be obtained for the lowest symmetrical modes, the ones which appear to be most important in loudspeaker performance. The conical shell can be considered to be divided into identical radial lamina. The vibration is thus found to correspond to a beam whose width varies linearly with the distance from the apex, and whose stiffness varies inversely as the square of the distance from the apex. The problem, therefore, reduces to a fourth-order differential equation. Power series solutions of this equation are given in this paper. However, for the truncated cone the necessity of using four boundary conditions leads to very complicated calculations to obtain the eigentones. A more convenient method for obtaining the first symmetrical mode is the Rayleigh-Ritz method. For the free-free vibration, a simple function is found to fit the boundary conditions. This leads easily to the calculation of the resonant frequency. McLachlan has measured the fundamental frequency of such a metallic cone obtaining 4000 c.p.s. for its first symmetrical mode. The calculated frequency, using the method outlined above, is 3700 c.p.s. The first symmetrical mode in loudspeakers occurs at 500 to 900 c.p.s. and is controlled greatly by the boundary conditions at the skiver, spider, and dust cap.
The Absorption and Scattering of Sound Power by a Microphone
Authors: Cook Richard K.
Published: September 2005

Some years ago Lamb determined the maximum power which can be scattered by small non-rigid objects (e.g., resonators, microphones, etc.) located in a plane wave. Recently Foldy has found that an omni-directional microphone located in a plane wave of wave-length λ transmits maximum power equal to (λ2/4π) × the incident plane wave intensity. This result is identical with that for an antenna picking up electromagnetic waves. This paper presents results showing the relation between the sound scattered and absorbed by several types of microphones which are small in comparison with the wave-length. Microphones located in plane waves near reflecting boundaries are included. The design of a microphone small in comparison with the wave-length for transmitting maximum power will be discussed.
The Sonalator, A 29 Channel Visible Speech Translator
Authors: Foster Harry R. , Crump Elmo E.
Published: September 2005

A heterodyne type of visible speech translator has been developed with 29 channels. This unit employs 29 separate crystal filters and a high speed rotary beam commutation tube. The heterodyne feature makes it possible to explore any desired 4000-cycle band, from 100 cycles up to several hundred kilocycles, by changing the local oscillator crystal. The Sonalator also employs a fast-acting avc system and selective high frequency boost of the type found desirable by R. K. Potter and associates at Bell Telephone Laboratories.
Extraction and Portrayal of Pitch in Speech Sounds
Authors: Gruenz O. O. , Schott L. O.
Published: September 2005

An improved method for automatically extracting the pitch information of speech sounds has been devised. It employs a combination of gain control, double detection, voiced sound selection, unvoiced sound exclusion, and a means for counting the fundamental vibrations in the voiced sound intervals. Reliable indications of pitch have been obtained over a range corresponding to frequencies from 100 to 600 cycles for a wide variety of voices. Several visual portrayal means that have been used to show pitch changes are described. One means involves a display of colored light which changes from purple through amber to blue as the pitch increases. Another is in graphical form employing an array of staff-like lines whose spacings widen or narrow in contour fashion to show how the pitch varies with time, permitting a detailed study of the changes.
Electrical Stimulation of the Skin at Audio Frequencies
Authors: Anderson A. B. , Munson W. A.
Published: September 2005

This paper reports the subjective responses of observers to alternating potentials applied directly to the surface of the skin. The curve of threshold of sensitivity was measured for frequencies from 100 to 10,000 cycles. The intensity range that could be used without extreme discomfort was also determined for this same band of frequencies. Intensity and frequency difference limen tests indicated that frequency discrimination is poor in this frequency range but intensity discrimination compares favorably with auditory results.
X-Ray Study of Vibrating Crystal Plates
Authors: White J. E.
Published: September 2005

The ability of a perfect crystal to reflect x-rays is markedly enhanced by vibration, as has been reported by many writers. Measurements on statically bent quartz are given which establish a quantitative relationship between increased reflecting power and radius of bending. Several pictures show quartz plates in various modes of vibration, light nodal lines separating the dark zones of maximum bending. Other types of vibration are discussed.
Dispersion of Compressional Waves in Rods of Rectangular Cross Section
Authors: Morse R. W.
Published: September 2005

An earlier paper [J. Acous. Soc. Am. 20, 833 (1948)] reported measurements of the phase velocity of compressional waves as a function of frequency in rectangular rods where the cross-sectional dimensions are of comparable magnitude. Two modes of propagation were observed each being determined by one of the lateral dimensions, there being a discontinuity in the dispersion curve determined by the larger side. The present paper is an attempt to explain the behavior of these curves using the general methods of the theory of elasticity applied to the symmetrical vibrations of an infinitely long isotropic rod. Harmonic wave solutions of the displacement equations of motion are constructed which satisfy the free-surface boundary conditions for certain wave-length regions in the general case and for all wave-lengths in certain limiting configurations. Dispersion curves are calculated and compared with the observed ones. The frequencies at which the experimental discontinuities were found to occur are closely predicted and the theoretical curves are in good general agreement with the measured values.
Oblique Reflection and Refraction of Plane Shear Waves in Viscoelastic Media
Authors: O'Neil H. T.
Published: September 2005

At sufficiently high frequencies, liquids exhibit both viscous and elastic effects in shear. A recently developed method of measuring the shear elasticity and viscosity of liquids involves ultrasonic plane shear waves, generated in a fused quartz rod and reflected obliquely from a plane interface of the quartz and the liquid. Comparing the effects observed in the presence and absence of the liquid, the change of amplitude and phase of the reflected wave can be correlated with the shear wave parameters of the liquid. The method has been described in two recently published papers. This discussion will be concerned with some of the characteristics of the waves in the two media, which affect the theoretical relations involved in the reduction of the data. The waves in the quartz and in the liquid are of different types; the refracted wave in the liquid has non-uniform amplitudes over the wave fronts.
Improved Devices for the Concentration of Ultrasonic Energy
Authors: Ernst Paul J.
Published: September 2005

The efficiency of all existing devices for the concentration of ultrasonic energy is considerably lowered by the losses cause by reflection, absorption, and diffraction. These losses, though generally unavoidable, can be minimized in various ways. The choice of suitable materials, use of “matching coatings,” design of “stepped lenses,” and development of “acceleration plates” will be discussed, samples of the improved devices shown and numerical and experimental data given.
Some Determinants of Interaural Phase Effects
Authors: Hirsh I. J. , Webster F. A.
Published: September 2005

Recently the binaural masked threshold has been shown to depend upon the phase angle between the two ears for both the masked signal and the masking signal. These interaural phase effects are particularly clear for pure tones of fairly low frequency (100–800 c.p.s.) that are masked by white noise. It has been shown that a pure tone, in-phase at the two ears, that is presented against a background of white noise is more easily heard when the noise is out-of-phase than when the noise is in-phase at the ears. The converse is also true, namely, that if the tone is out-of-phase it is more easily heard when the noise is in-phase. The masked threshold of a 250-cycle tone presented against a background of noise (100 db SPL in a 7000-cycle low pass band) is approximately 15 db lower under antiphasic (tone-in, noise-out or tone-out, noise-in) than under homophasic (tone-in, noise-in or tone-out, noise-out) conditions. When the same tone is masked by another tone whose frequency is fairly close but not close enough to produce beats, no such differences appear. These two masking signals represent the extremes of a continuum of complexity along which the necessary characteristics of the adequate stimulus for these differences should appear. The present experiment constitutes an attempt to find these characteristics. A pure tone at 250 c.p.s. was used as the signal to be masked throughout the experiment. Four different kinds of masking signals were used: pure tones; ‘regular’ pulses (125 p.p.s.), ‘random’ pulses (average 125 p.p.s.) and random noise. The signals were presented in frequency-bands which were varied in respect of band-width and center frequency. The results indicate that a regular, periodic masking signal will not produce these interaural phase effects. A necessary condition is randomness or irregularity with respect to time but not necessarily with respect to amplitude. Frequency spectrum does not enter on any such all-or-none basis but rather contributes to the magnitude of the response. The nearer a frequency-band is to the frequency of the masked tone, the greater are the differences between the homophasic and antiphasic conditions. There is no substantial difference between the interaural phase effects produced by a narrow versus a wide band, provided that both bands contain the frequency of the masked tone.
Distortion of Acoustic Beam Patterns by Echoes and Electric Pick-Up
Authors: Williams A. O. , Keck W. , Smith M. C.
Published: September 2005

When the acoustic intensity is measured, in water, along the axis of a diverging ultrasonic beam, with a very small piezoelectric microphone as a receiver, the results plotted vs. distance from the source follow only approximately the beam pattern predicted by theory. On the steadily falling plot is superimposed a spatial variation repeating at half-wave-length intervals relatively near the source. Another variation shows full wave-length intervals farther away, and there is a transition region between. These variations are found with either CW or pulsed beams, if an averaging detector is used. The full wave-length variation is due to electric pick-up and has previously been used to locate acoustic wave fronts. The other variation cannot be a standing wave between source and microphone, because successively reflected waves are too much weakened by divergence, nor can it be due to standing waves in the whole tank. It seems to be the effect of the first echo returning to the microphone, compounding with the main acoustic and electric signals, and falling off much more rapidly than the electric pickup effect. Measurements and calculations in the 1–3-mc region agree with this explanation, and suggest how to identify the correct beam pattern from the data. Without such corrections the determination of wave fronts at intermediate distances might be markedly affected.
The influence of baffle fairings on the acoustic performance of rectangular splitter silencers
Authors: Kirby Ray
Published: October 2005

A numerical model based on the finite element method is developed for a finite length, HVAC splitter silencer. The model includes an arbitrary number of bulk-reacting splitters separated from the airway by a thin perforated metal sheet and accommodates higher-order modes in the incident sound field. Each perforated sheet is joined to rigid, impervious, metallic fairing situated at either end of a splitter. The transmission loss for the silencer is quantified by application of the point collocation technique, and predictions are compared to experimental measurements reported in the literature. The splitter fairing is shown to significantly affect silencer performance, especially when higher-order incident modes are present. It is concluded that laboratory measurements, and theoretical predictions, that are based on a predominantly plane wave sound source are unlikely to reflect accurately the true performance of an HVAC silencer in a real ducting system.
Measurement of absorption with a p-u sound intensity probe in an impedance tube
Authors: Liu Yang , Jacobsen Finn
Published: October 2005

An alternative method of measuring the normal-incidence sound absorption of a sample of material in an impedance tube is examined. The method is based on measurement of the sound pressure and the normal component of the particle velocity using a “p-u” sound intensity probe. This technique is compared with the traditional, well-established “transfer function method” based on two pressure microphones. The results suggest that the new method can be as accurate as the established method, but whereas the influence of transducer mismatch on the transfer function method can be eliminated using a simple “sensor-switching technique,” the method based on a p-u intensity probe relies on accurate calibration of the probe.
Perceptual interaction between carrier periodicity and amplitude modulation in broadband stimuli: A comparison of the autocorrelation and modulation-filterbank model
Authors: Stein Alexandra , Ewert Stephan D. , Wiegrebe Lutz
Published: October 2005

Recent temporal models of pitch and amplitude modulation perception converge on a relatively realistic implementation of cochlear processing followed by a temporal analysis of periodicity. However, for modulation perception, a modulation filterbank is applied whereas for pitch perception, autocorrelation is applied. Considering the large overlap in pitch and modulation perception, this is not parsimonious. Two experiments are presented to investigate the interaction between carrier periodicity, which produces strong pitch sensations, and envelope periodicity using broadband stimuli. Results show that in the presence of carrier periodicity, detection of amplitude modulation is impaired throughout the tested range (8–1000 Hz). On the contrary, detection of carrier periodicity in the presence of an additional amplitude modulation is impaired only for very low frequencies below the pitch range (<33Hz). Predictions of a generic implementation of a modulation-filterbank model and an autocorrelation model are compared to the data. Both models were too insensitive to high-frequency envelope or carrier periodicity and to infra-pitch carrier periodicity. Additionally, both models simulated modulation detection quite well but underestimated the detrimental effect of carrier periodicity on modulation detection. It is suggested that a hybrid model consisting of bandpass envelope filters with a ripple in their passband may provide a functionally successful and physiologically plausible basis for a unified model of auditory periodicity extraction.
Using digital signal processors for real-time synthesis of acoustic signals
Authors: Olive J. P.
Published: October 2005

Digital computers have been used to process and generate various acoustic signals during the past two decades. Because of needs for real-time interaction with computers, we first introduced the use of hybrid systems, where the computer controlled analog sound generating equipment. More recently, a great deal of special purpose hardware has been built to generate sounds digitally in real-time. Recent advances in VLSI design have brought a new generation of components called the Digital Signal Processor Chips. These chips are relatively inexpensive, and are capable of doing many of the complex operations required for the synthesis of signals such as speech, tones, and music. This paper will desribe a method for using such DSP chips in a real-time scheme. Such a scheme is presently used in speech analysis and synthesis systems, and could be adapted for music and tone-signaling applications.
Computer synthesis of a piano tone
Authors: Garber Mindy L. , Allen Jont B.
Published: October 2005

Attempts to simulate piano tones by summing sine waves of inharmonic frequenices have not been totally successful in the past. The physical understanding of what happens to a string inside a piano has never been fully modeled in all detail. A program has been developed to synthesize a piano sound by creating a model of vibrating string. The model is formed by using a differential equation to describe the motion of the string. The terms in the equation account for both the inharmonicity due to the string's stiffness and the decay rates for each harmonic due to the string's internal damping. The model is obtained by solving the differential equation in discrete time steps using fast Fourier transforms in the spatial domain. The waveform of the string is then determined and can be sampled at each step in time.
Real time in computer music. Incidence on the choice of the basic models
Authors: Cadoz C. , Luciani A. , Berberyan T.
Published: October 2005

Musical activity is multifarious. From instrument making to instrument playing and compositional conception, machines and man/machine relations are quite different. It is nevertheless exclusively in the instrument playing, more generally in instrument experiments that the man/machine relation corresponds to and needs the true real-time situation as defined in computer context. So, instrumental experience is a fundamental reference to conceive the basic functions of systems in real-time digital synthesis. Accordingly, algorithmic models appear as intermediary between instrumentist gesture and musical sound. Then their functions are: (1) to permit and guide the gestual action, (2) to pick up the pertinent information from it, and (3) to create an acoustical signal combining this temporal information with an atemporal or structural one. The latter may be considered as instrument definition or representation. By its mechanical nature, the gesture implies a mechanical modelization, at least at a first step. We shall present a digital sound synthesis system, the CORDIS system, entirely founded on a mechanical modelization of musical instruments. The latter are analyzed and reconstructed from elementary mechanical components. One of our goals is to give a way of understanding certain elementary components of musical languages by correlating them with concrete elementary experiments of acoustical source objects.
Coarticulatory effects of stop voicing on F0 from voicing onset to vowel target
Authors: Ohde Ralph N.
Published: October 2005

Fundamental frequency perturbations due to stop voicing were measured using a computer waveform editing program for the first five pitch periods and vowel target. Five adult males recorded five repetitions each of voiceless aspirated /ph, th, kh/, voiceless unaspirated /sp, st, sk/ and voiced /b, d, g/ stops in combination with the vowels /i, e, u, o, a/. Voice onset time (VOT) was determined for each utterance. Mean differences in VOT between voiceless unaspirated and voiced stops collapsed across vowels were only 3, 6, and 4 Hz for bilabial, alveolar, and velar places of articulation, respectively, whereas comparable differences between voiceless unaspirated and voiceless aspirated stops were 42, 56, and 47 Hz. In general, F0 fell from the first pitch period to the second pitch period for all voicing conditions. The average magnitude of this fall was greatest for voiceless unaspirated stops and least for voiced stops. Slight changes in F0 occurred from the second pitch period to the vowel target. Moreover, the average absolute differences in F0 between voiceless unaspirated and voiceless aspirated stops for the second pitch period to vowel target never exceeded 3 Hz compared to at least a 9-Hz differential between voiceless unaspirated and voiced stops. The results indicate the importance of F0 change at voicing onset as a property that distinguishes not only voiceless aspirated from voiced stops but also voiceless unaspirated from voiced stops. [Work supported in part by NINCDS.]
Voicing cues for tense/tens versus tensing/tenzing
Authors: Fourakis Marios , Port Robert
Published: October 2005

To determine possible effects of resyllabification of a post-nasal word-final consonant on the durations of the preceding vowel and nasal, American English productions (by ten speakers) of words containing VnC (where the C = [s, z, č, j, t, d]) were examined in two syllabic conditions: VnC♯ and VnCing (e.g., lunch-lunching). The vowel and nasal intervals were measured from spectrograms. Results showed that the voicing of the post-nasal consonant in final position had the expected effect on the vowel and nasal durations. The effect was weaker, but still present; when the final consonant was pronounced as part of the -ing syllable. The ratio of the sum V + N before voiceless Cs to voiced Cs was 0.6 in word-final position and 0.8 when followed by -ing. Although auditory judgments and VOT measurements suggest that resyllabification generally occurred, the temporal characteristics of syllable-final position remained in attenuated form, implying that English consonants may simultaneously exhibit syllable-final and syllable-initial voicing cues. [Research supported by NIH, HD12511.]
Coarticulation of intervocalic /s/
Authors: McCasland George P.
Published: October 2005

A set of 12 pairs of CVCV /sɪsi,sɪsɑ/ tokens spoken by one male were subjected to PCM editing to prepare five modified sets having the residual shapes: CV_V, V_V, _V, V_, CV_. In a perceptual identification test, 11 subjects judged the consonant represented by the blank to be either /p-b/ or /t-d/. For /ɪ_/, /_i/ or /ɪ_i/, the votes were 50% labial /p-b/. For /_i/ or /ɪ_i/ with acoustical energy restricted to the range of the first 3 vowel formants by LP filtering, the % labial /p-b/ votes rose to 90% indicating a strong labial formant transition cue. The test items of the type /_ɑ/ or /ɪ_ɑ/ resulted in 92% /t-d/ votes, indicating a strong alveolar formant transition cue for an /ɑ/ final vowel. The perceptual differences between the /i/ and /ɑ/ final vowels are highly significant, statistically. Clearly, an unexpected coarticulation effect is present for /s/ in the high vowel context. A corresponding spectrographic analysis of the onset transition of the second formant of /i/ supports the perceptual results. Please see the pilot study [J. Acoust. Soc. Am. Suppl. 1 63, S21 (1978)]. [Haskins Laboratories provided valuable assistance in preparing the speech samples on NICHD Contract No. NIH-71-2420.]
Do midfrequency hearing thresholds in listeners having high-frequency sensorineural hearing loss provide an accurate picture of the underlying lesion?
Authors: Humes Larry E.
Published: October 2005

Eighteen adults ranging in age from 25 to 55 years and having a high-frequency sensorineural hearing loss presumably due to noise exposure served as subjects in this study. Despite normal hearing thresholds (0–10 dB HL) from 500 through 2000 Hz in all subjects, some subjects in this study reliably exhibited abnormal performance on masking patterns obtained in the region of normal hearing (eg., 1000 Hz masker at 85 dB SPL). This same subgroup of subjects exhibited considerably poorer performance on word-recognition tests administered in quiet and in noise. Measurement of hearing thresholds in the transition region of the hearing loss in the presence of low-level low-pass noise in some of the subjects in this subgroup suggests that the observed abnormality of masking patterns may be an indication of invalid hearing thresholds rather than abnormal “upward spread of masking.” [Work supported by the National Institute of Occupational Safety and Health.]
Effect of temporal lobectomy on binaural integration of dichotic tones
Authors: Efron Robert , Crandall Paul H.
Published: October 2005

Recent studies of the phenomenon of ear dominance for pitch have shown that 66%–75% of normal-hearing subjects exhibit a left-ear dominance when tested with dichotic tone pairs of 1650–1750 Hz. Since a previous report [Efron et al., Brain and Language 4, 537–549 (1977)] indicated that ear dominance might be related to an (asymmetrical) function of the cerebral cortex, the present experiments measured the direction and magnitude of a subject's ear dominance before and after an anterior temporal lobectomy (for chronic epilepsy). In all nine subjects tested, the lobectomy decreased the contribution of the pitch signal in the ear contralateral to the side of the lobectomy. Thus, depending on the subject's pre-operative ear dominance and the side of the lobectomy, his post-operative ear dominance was expected to either increase or decrease in magnitude. The specific prediction for each of the nine subjects was confirmed. The results demonstrate an important role played by temporal neocortex on the binaural integration of pure tone dichotic stimulation.
Frequency discrimination by infants and adults
Authors: Olsho Lynne Werner
Published: October 2005

Frequency difference thresholds were estimated for infants (5 to 8 months old) using the visually reinforced head-turn procedure. Stimuli were 500-ms tone bursts at six frequencies ranging from 250 to 8000 Hz presented monaurally via a TDH-49 earphone. Tone bursts were presented at 70 dB above adult absolute threshold. An adaptive threshold estimation procedure with a variable step size was used. An adult group was run using the same protocol. The relative difference threshold (Δf/f) was a nonmonotonic function of frequency with a minimum around 1000 Hz for both age groups. However, infants had higher thresholds than adults at frequencies from 250 to 2000 Hz (approximately 2% for infants versus 1% for adults). No age difference in threshold was observed at 4000 or 8000 Hz. Age differences in absolute sensitivity at low frequencies [Trehub et al., J. Exp. Child Psychol. 21, 219–225] are not great enough to account for the rather large difference in discrimination performance in the low-frequency range. It is suggested that these findings reflect continuing development of the analytic capacity of the auditory system during the first year of life. [Work supported by Virginia Commonwealth University Faculty Grants-in-Aid.]
Automated digital system for measuring the complex sensitivity and directivity of hydrophone arrays
Authors: Luker L. Dwight , Zalesak Joseph F. , Brown Craig K. , Scott Richard E.
Published: October 2005

This paper describes a computerized benchtop system for calibrating long hydrophone arrays, such as sonobuoy arrays, with individually accessible elements. The system uses USRD type G19 calibrators to insonify the array elements. The individual drive signals for the G19's originate in digital form in a minicomputer, are multiplexed through D/A converters, and amplified by high-power operational amplifiers. Before applying the final drive signals, the computer first generates a system calibration signal for each of the G19's. The resulting sound fields are monitored by calibrated hydrophones located within the G19's. The hydrophone signals are amplified, digitized, and analyzed using a DFT to calculate the amplitudes and relative phases of the sound fields within the G19's. The computer then uses these results to determine the G19 drive signals required to simulate a sound wave incident on the array at any desired direction of incidence. The system operates over the frequency range from 50 to 1000 Hz. With this system one can determine both the array receiving sensitivity and farfield patterns by simulating sound fields which exist over hundreds of feet in the ocean.
A model for predicting hearing-aid performance
Authors: Karzon R. Gottlieb , Niemoeller Arthur F.
Published: October 2005

A major problem in selecting a hearing aid is the inability to determine output speech and noise levels quickly and accurately as a function of frequency and aid-control positions. Exploring a solution to this problem, we developed a computer-based quantitative model of a commercial hearing aid. In this paper the required measurements of performance and the schematic and mathematical models of this aid are presented. After entry of the positions of the hearing-aid controls, the talker's voice levels, and the noise levels at the aid's microphone, the computer prints these and calculates, prints, and graphs the levels of speech and noise at the aid's output. The validity of the model is demonstrated by comparing measured values of hearing-aid gains, maximum output levels, and noise levels with the corresponding data from the model. [Supported by NINCDS Grant NS03856.]
Auditory-perceptual approaches to phonetic perception
Authors: Miller James D.
Published: October 2005

While acknowledging the important role of “top-down” processing in perceiving and understanding the speech of others, it is argued that an auditory-perceptual system which is modifiable by early experience and which is highly sensitive to spectral-temporal relations within speech sounds may eventually account for many of the facts of phonetic perception. Evidence pointing in this direction can be found in the perception of human speech by animals and human infants; in data pointing toward invariant, relational acoustic cues for phones whether consonant or vowels, and in comparison of the identification, discrimination, and adaptation of speech and nonspeech. The major shortcoming of auditory-perceptual interpretations has been the failure to provide a sensible approach to phenomena such as talker and rate normalization, cross-language differences, effects of “spectral trajectories,” and phoneme boundary shifts based on spectral-temporal alterations of synthetic syllables. Suggestions for new approaches to these matters are offered. [Supported by NINCDS Grant NS 03856.]
The mass law for a finite panel
Authors: Leehey Patrick
Published: October 2005

It is a classical result that the sound power per area transmitted by a limp infinite panel decreases by 6 dB per frequency or panel mass doubling. Several years ago, Sledjeski and I demonstrated that a plane wave transmitted normally through a baffled rectangular membrane yielded a transmitted sound pressure level which asymptoted at high frequency to a constant at any fixed on-axis position. It is shown that this results from the summed effect of all those panel modes that are driven sufficiently above their resonance freqencies that their responses are masslike and the modes themselves are acoustically fast. The panel then acts as a rigid piston with directivity which increases by 6 dB per frequency doubling. The last statement is verified experimentally. [Work sponsored by ONR Sensor Technology Program.]
Pulse-number distribution for the neural discharge in the cat's auditory nerve
Authors: Teich Malvin Carl , Khanna Shyam M.
Published: October 2005

Pulse-number distributions (PND) were recorded from primary afferent fibers in the auditory nerve of the cat, using standard microelectrode techniques. Pure-tone and broadband-noise stimuli were used. The number of neural spikes (pulses) n was measured in a set of contiguous intervals, each of duration T seconds. The quantity n varies from one interval to another. These data were then used to determine the PND, which is the probability p(n, T) of occurrence of n spikes in the time T, versus the number n. The estimated mean and variance of p(n, T) were obtained; these quantities are generally slowly increasing functions of the stimulus intensity I. For many units, the mean-to-variance ratio (MVR) is broadly peaked, reaching a maximum value of about 2 at stimulus levels in the vicinity of 10–20 dB re frequency-tuning-curve threshold. The MVR will be compared with the synchronization index as a measure of phase locking for units of various characteristic frequencies. [Work supported by NIH Grant 5 R01 NS 03654.]
A neural-counting model incorporating refractoriness and spread of excitation: Role of the peripheral auditory system in intensity discrimination and loudness estimation
Authors: Teich Malvin Carl , Lachs Gerard , Saia Rosalie A.
Published: October 2005

An energy-based, neural-counting model incorporating refractoriness and spread of excitation, has been successfully used to predict the outcome of a number of psychophysical experiments [M. C. Teich and G. Lachs, J. Acoust. Soc. Am. 66, 1738–1749 (1979); 69, 774–782 (1981); J. Acoust. Soc. Am. Suppl. 1. 69, S104 (1981)]. We have extended this model to include the effects of receptor saturation, and spontaneous neural activity in the primary afferent fibers (G. Lachs, R. A. Saia, and M. C. Teich, J. Acoust. Soc. Am., preceding abstract). We demonstrate that this extended theoretical system effectively predicts the outcome of loudness-estimation and intensity-discrimination experiments, both for pure-tone and variable-bandwidth noise stimuli. Parameter values required for the model to provide a good fit to the data are in reasonable accord with accepted values. We discuss the role of middle-ear transmission, critical bands, and fiber-density distribution in the context of these psychophysical tasks. [Work supported by NSF.]
Speaker-independent isolated word recognition using a new matching method
Authors: Nose I. , Mizuno K. , Yamada K.
Published: October 2005

This paper describes a speaker-independent isolated word recognition system which accepts telephone line speech. A recognition method is named selective weighted matching (SWM) which uses a weighted distance measure. The input speech signal is frequency-analyzed every 10 ms by a filter bank. The individual glottal characteristic is normalized frame by frame using a least-square-fit line of the speech spectrum. Each reference pattern has a specific region in the time-frequency domain. In the matching process of that region, the weighted distance computation is carried out under the predetermined condition. In the computer simulation of telephone line speech, we got the recognition accuracy greater than 96% with 12 words (digits and two command words in Japanese) spoken by 130 talkers. The same result was also obtained in the recognition test of the prototype machine.