bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of noise from a fan stage for a turbofan engine by use of long-chord acoustically treated sister vanes
Authors: Dittmar J. H. , Scott J. N.
Published: October 2005

A set of acoustically-treated long-chord vanes was designed to replace the stator vanes in an existing fan stage to investigate the noise-reduction possibilities of both increased stator chord length and this different method of incorporating acoustic damping material. The long vanes consisted of a turning section and axial extension pieces that were added downstream of the turning section. Both the turning and extension pieces included acoustic damping material. The stator vanes were tested with the acoustic material both active and inactive. The tests with the inactive acoustic material showed significant broadband noise effects. A noise reduction occurred as a result of the longer chord in the middle to high frequencies, and an increase was observed at low frequencies. No reduction in blade passage was observed but decreases in the blade passage harmonics were observed toward the rear of the fan. The tests with the active acoustic treatment showed large noise reductions over a wide-frequency range.
Two-dimensional finite-element analysis of electroelastic normal modes of ferroelectric disks and shells
Authors: Krile Thomas F. , Sabbagh Harold A.
Published: October 2005

A variational method, using two-dimensional finite elements as the basis functions, is used to calculate the short-circuit and open-circuit electroelastic normal modes of a radially polarized, ferroelectric shell and an axially polarized, ferroelectric disk. A method by which suitable two-dimensional piecewise polynomial finite elements are generated will be described. The relative merits of satisfying boundary conditions by the use of a Lagrange multiplier or a perturbed (“penalty”) Lagrangian is discussed, as will the convergence properties with respect to grid refinement.
Exact solutions for the propagation of electric and acoustic waves in distributed coupling transducers
Authors: Zalesak Joseph F.
Published: October 2005

A distributed coupling transducer consists of an acoustic transmission line continuously and reversibly coupled to an electrical transmission line. In such a device it is possible to transfer almost all of the energy from one of the transmission lines to the other transmission line. In particular if the transmission lines are finite in length it is possible to achieve a high efficiency, nonresonant, broad-band electroacoustic transducer. Some of the salient features of the exact solution are as follows: (1) the distance required to achieve complete energy transfer is significantly less than that predicted by approximate theory when the coupling coefficient is large; (2) the amount of energy transferred depends strongly on the termination impedance at the input end of the nondriven line; and (3) the input impedance of the driven line depends on the coupling coefficient and the termination impedance at the input end of the nondriven line. Some of the differences between a continuously coupled and a discretely coupled transducer are presented. [Work supported by NAVSEA 06H1.]
Underwater Helmholtz resonator transducers
Authors: Woollett R. S.
Published: October 2005

Compact low-frequency sound sources using piezoceramic drivers are feasible if the driver is incorporated into a Helmholtz resonator. The ceramic driver can be in the form of a spherical shell, a stack of rings, or a flexural-mode disk, but the disk is usually the most advantageous. A liquid-filled Helmholtz resonator transducer is capable of operation at unlimited depths. When the depth requirement is only moderate, however, it is advantageous to replace part of the liquid in the compliance chamber by compliant tubes; this substantially reduces the size of the resonator. The radiation resistance of these compact transducers is low and is usually considerably exceeded by the internal-loss resistance of the resonator. For broad-band applications the internal dissipation is not a significant disadvantage, since the resonance even when damped will give a very worthwhile bass boost to the low end of the transmitting response. For narrow-band applications, where efficiency is important, careful consideration must be given to minimizing losses. Then the Q of the resonator may be on the order of 100. The resulting response peak would be too sharp to permit stable operation, but this problem can be overcome by use of acoustoelectrical feedback. The feedback flattens the response without negating the advantages of resonance with respect to efficiency and power. [Work supported by NAVSEA Sonar Technology Division.]
Development of a high-power transducer DUMILOAD
Authors: Miller W. A. , Auyer S. E.
Published: October 2005

DUMILOAD (DUmmy Mechanical Impedance LOAD) devices have been used to test transducers for many years. In concept the DUMILOAD consists of another, specialized, piezoelectric transducer mechanically coupled to the transducer to be tested. By varying the electrical impedance placed across the DUMILOAD's electrical terminals, varying mechanical loads can be presented to the transducer being tested. Drawbacks to this approach have included the need for a cumbersome mechanical coupling device and the limited operating frequency band of the DUMILOAD. This paper describes some of the considerations involved in designing and constructing a DUMILOAD capable of operating at a power level of 1100 W in the frequency band from 3000 to 4000 Hz. Details of a “quick connect/disconnect” mechanical coupling device are also described.
A deep-ocean hydrophone array
Authors: Behrens John A. , Stokes Robert H.
Published: October 2005

A curved face hydrophone array has been designed, constructed, and tested for 20 000-ft depth operations. A basic description of the hydrophone design is presented, where the hydrophone consists of a beamforming array of staves mounted on the circumference of a 20-in.-diameter cylindrical housing. Since conventional pressure release materials cannot be used in the construction, solutions to problems encountered, such as flexural waves generated in the housing wall and improper backing impedances for the individual elements, will be briefly discussed. A presentation of the received frequency response and beam patterns show that the transducer properties are insensitive to hydrostatic pressures up to 1000 psi.
Transmission of sound across dry metallic interfaces
Authors: Karplus H. B. , Tupper M.
Published: October 2005

Use of ultrasonic energy at high temperature, (e.g., in nuclear reactors) precludes conventional liquid coupling. Ultrasonic energy can be transmitted across dry interfaces if the surfaces are sufficiently flat and smooth, and static pressure is applied. Transmission and reflection coefficients were measured for shear waves polarized normal to the plane of incidence across lapped flat steel surfaces as a function of temperature, surface finish, and contact pressure. The transmission increases and reflection decreases monotonically with applied pressure. For example, at 20 °C, a contact pressure of 500 psi (3 MPa) produces 50% transmission across interfacing 304 stainless steel samples having measured surface finishes of 30μ in. (0.7μ m) and 70μ in. (2μ m), respectively. The contact pressure is reduced by using finer surface finishes and interposing soft metallic (e.g., Pt) shims.
Transforming noise to tone and whisper to voice through repetition
Authors: Warren Richard M. , Bashford James A.
Published: October 2005

Short, single bursts of Gaussian noise lasting from 10 to 0.1 msec when recycled by a digital delay line at repetition rates from 100 to 10000 Hz, respectively, sound purely tonal with no noiselike character. Below 100 Hz, this “recycled-noise tone” (RNT) has an increasinly hisslike quality. Different samples of Gaussian noise of the same duration produce RNTs of the same pitch with clearly different qualities, but above about 1000 Hz such quality difference diminish. Some characteristics of RNT can be explained through Fourier analysis into spectral components. Recycling segments from noise having a complex formant structure can preserve this structure while introducing harmonic components, so that recycling an 8-msec segment of a steady-state whispered vowel produces perception of the same vowel sustained and clearly voiced with RNT pitch corresponding to a fundamental frequency of 125 Hz. Whispered discourse can be transformed into an intelligible voiced monotone by reiteration of regularly spaced samples. Demonstrations of the basic phenomena will be presented and implications for theory discussed. [Work supported by NSF and NIH.]
Musical pitch of interrupted white noise
Authors: Wicke Roger W. , Houtsma Adrianus J. M.
Published: October 2005

The pitch of periodically chopped white noise has been the object of several investigations in the literature. Because of the essentially flat spectrum of such a sound, any musical pitch effects are difficult to account for with a place model. Previous investigations, mostly involving pitch matching experiments, have left some doubt whether observed pitch effects were indeed factual or artifactual [Pollack, J. Acoust. Soc. Am. 45, 237 (1969)]. A series of musical interval identification experiments was performed using interrupted gaussian wide-band noise whose interruption rate was given by the notes to be presented. Intensities were 30 dB SPL, the noise on-time fraction was 0.5 and gating frequencies varied between 100 and 300 Hz. In this range, the pitch confusion data are well described by a simple Gaussian decision model whose variances are somewhat larger than the data scatter in previously reported pitch matching experiments. However, pitch identification performance with chopped noise is much worse than the same subjects' identification performance with pure tones or other periodic signals, which seems to indicate that, at least from a musical standpoint, we are dealing with a rather weak effect. [Work supported by the National Institutes of Health, grant 1RO1 NS 11680-01.]
Failure of selective attention in simple recognition tasks: Critical band effects
Authors: Ahroon W. A. , Pastore R. E.
Published: October 2005

In the second in a series of studies examining the ability of human observers to perform two independent dichotic frequency difference limen tasks, the effect of separating the base frequencies was examined. We reported earlier [W.A. Ahroon, R.E. Pastore, and J.P. Wolz, J. Acoust. Soc. Am. 56, 545 (1974)] that trained observers performed no better during dichotic stimulation when attending to one frequency difference limen task than when they attempted to attend to both channels, when the base frequencies were either within the same critical band or separated by only two or three critical bands. The present study examined the effect of widely separating (by nine to ten critical bands) the base frequencies in the two-channel frequency difference limen task. Observers again showed a decrement in performance in the selective attention condition relative to monaural performance. However, this decrement did not seem as great as the decrement for the binaural (shared attention) condition. Selective attention continued to be impaired although not as greatly as when the two tasks involve frequency discriminations in the same critical band. [Work supported by NINDS.]
Application of ambient noise to the study of low-frequency attenuation in the ocean
Authors: Kibblewhite A. C. , Shooter J. A. , Watkins S. L.
Published: October 2005

Low-frequency attenuation measurements in the deep ocean have repeatedly indicated a departure from Thorp's empirical equation at frequencies below 200 Hz. Furthermore, results from the South Pacific in particular have suggested a regional dependence and the existence of a minimum in the vicinity of 50 Hz. In spite of the increasing evidence for these effects, legitimate doubts are still expressed as to whether the experimental and analytical procedures are not responsible for the behavior observed. A recent study of the ambient underwater noise field has provided an opportunity to examine the attenuation at very low frequencies by quite different procedures. Results will be presented which not only confirm the existence of a minimum around 50 Hz, but also provide support for a recent proposal [K.M. Guthrie, R.N. Denham, R.W. Bannister, and D.G. Browning, “Possible effects of velocity profile shape and scattering loss distribution in SOFAR propagation,” J. Acoust. Soc. Am. 55, 545(A) (1974)] that the effects at low frequencies are a consequence of a scattering mechanism occurring within the upper few hundred meters of the ocean. [Supported by the Office of Naval Research.]
Asymptotic theory of scattering by a rough surface progressing over an inhomogeneous ocean
Authors: Labianca F. M. , Harper E. Y.
Published: October 2005

An asymptotic theory of scattering by a rough surface is presented which is appropriate to small ocean surface wave heights and valid for a slowly varying refractive index. The ocean surface is described as a sum of gravity waves of varying frequency progressing in different directions. It is demonstrated that, to a given order of approximation in the asymptotic theory, the average energy associated with the sideband rays is precisely accounted for by a reduction in intensity of the reflected carrier. The theory is shown to be in complete agreement with results obtained by asymptotic analysis of exact integral representations for the case of an isovelocity ocean. Wavenumber diagrams are introduced which are extremely useful for depicting the directions of the incident and scattered rays at the surface, demonstrating the effect of varying surface wave and acoustic frequency and demonstrating the frequency cutoff of the sideband power spectrum. It is shown how the theory can accommodate the effects of energy focusing, both in the carrier and sidebands, through the use of known uniformly valid asymptotic expansions of the field in the presence of caustics. [Research supported by the Office of Naval Research, Code 480.]
Sound transmission through a simulated sea surface
Authors: Barger James E. , Sachs David A.
Published: October 2005

One-hundredth-scale sea surfaces simulating seas up to B Beaufort 6 were generated with a wave maker. The average rms sound pressure transmitted through the surface to a farfield receiver in water was measured routinely, as were, on occasion, narrowband pressure level probability densities. The experiments covered a wide range of (full-scale) parameters: acoustic frequencies from 30 Hz to 1 kHz, receiver depression angles from 2° to 90°, and source heights from 50 to 1200 ft. The sound path was oriented parallel, antiparallel, and perpendicular to the sea direction. For surfaces with rms slopes of 4° or more, transmission gains, relative to smooth surface transmission, of up to 7 dB, were observed for shallow depression angles and all source heights, while relative transmission losses up to 5 dB occurred for moderate depression angles and sources up to 200 ft (full scale). The results can be explained by including a most-probable slope of 3° to 4° in the surface slope probability density.
Tympanic membrane: Effect of dc pressure changes in the middle ear of cats
Authors: Khanna Shyam M. , Tonndorf Juergen
Published: October 2005

A method for determining the shape of the tympanic membrane (TM) by means of Moire topography was described earlier (Khanna and Tonndorf, J. Acoust. Soc. Am. 57, Suppl. 1, S72(A) (1975)]. This technique was employed to study in live cats the changes in TM shape with variations in dc pressure in the middle ear. The Eustachian tube was sealed and the middle ear pressure altered in increments of 5 cm water over a range from −15 to −30 cm. At each point the pressure was held and a silastic cast taken. From these casts, the TM shapes were determined by Moire topography, revealing substanial changes in TM curvature with pressure. Furthermore, in addition to that in cat, the TM shapes at resting pressure were determined in guinea pig, chinchilla, and sheep. Considerable variations were found. [Supported by several NIH grants.]
Response losses in cats with tympanic-membrane perforations: External canal effects
Authors: Kruger B. , Tonndorf J.
Published: October 2005

Response losses due to small tympanic-membrane (TM) perforations were assessed in cats with surgically shortened ear canals (EAM) and four extensions of different lengths, volumes, and leakiness. Changes in input, required for a criterion microphonic response, were recorded, both in terms of voltages across the transducer (loudspeaker and earphone) and SPLs (at the entrance of the EAM and at the TM). At the TM, SPL changes increasingly sloped toward lower frequencies (12 dB/octave). Flat response losses, as seen audiometrically in clinical patients, were found only (1) in the presence of a leaky EAM—low frequencies, (2) when SPLs were measured at the entrance of the EAM—midfrequencies, and (3) when voltages across the transducer (precalibrated SPLs)—mid and high frequencies. Audiometric results, which depend upon precalibrated SPLs, may not adequately measure hearing losses due to changes in middle ear impedance. [Supported by NIH and HEW grants.]
Noise and kanamycin interaction in the guinea pig cochlea
Authors: Hawkins J. E. , Marques D. M. , Clark C. S.
Published: October 2005

Guinea pigs were exposed to octave band (0.1, 2, or 8 kHz) or broad-band noise at 90, 100, and 106 dB SPL, eight hours daily for seven days, while receiving kanamycin 100 mg/kg daily s. c. Controls were subjected to noise exposure or kanamycin injection only. Cochlear injuries were assessed electrophysiologically in terms of reduction in microphonic (CM) and neural (N1) potentials, and histopathologically in terms of the location and extent of hair cell loss seen in surface preparations of Corti's organ and recorded in cytocochleograms. Potentiation between noise and kanamycin was seen only after exposures at 100 dB or more, and then not in all animals. With 0.5-kHz exposures even at 112 dB, affecting mainly turn 3, there was no indication of enhancement of the injury by kanamycin, which has its major site of action in the basal turn. It appears that for potentiation to occur the noise and the antibiotic must act on the same region of the cochlea. [Supported by NIH-NIEHS contract No. 1-ES-2-2110 and NM Program Project Grant 05785.]
Aminooxyacetic acid protects against noise-induced cochlear hair cell loss
Authors: Bobbin R. P. , Guth M. S. , Mines A. B.
Published: October 2005

Aminooxyacetic acid (AOAA) has been shown to reversibly reduce the endocochlear potential [R.P. Bobbin and M.I. Gondra, Ann. Otol. Rhinol. Laryngol. 84, 192 (1975)]. In this study, guinea pigs were pretreated with AOAA (20 mg/kg, s. c.) or saline 50 min prior to exposure to a 30-min, 4-kHz, 126 dB SPL tone. The animals were sacrified 21 days after exposure and hair cell counts conducted by means of the surface preparation. Animals pretreated with AOAA prior to intense tone exposure demonstrated a significant reduction in the number of destroyed hair cells. We speculate that the endocochlear potential plays a role in noise-induced hair cell destruction. [Supported by National Institutes of Health, USPHS Grant Nos. NH-11647-01 and NS-10463-01.]
Vestibular changes following impulse noise exposure
Authors: Barlow J. , Hamernik R. P. , Henderson D.
Published: October 2005

The results of a pilot study designed to evaluate the nonauditory vestibular effects of exposure to high-intensity impulse noise will be presented. Ten chinchilla were exposed to one of the following impulse noise paradigms: Group I animals: 155-dB peak SPL reverberant impulses (∼200 msec-“B” duration) presented 1/min for 50 min. Group II animals; 140–1333 peak SPL reverberant impulses, for 8 h at a rate of either 1/min or 1/sec Ampullar function was studied pre- and postexposure by comparing serial, bithermal caloric responses recorded using electronystagmography. All animals were sacrified for cochlear and vestibular histology. Postexposure caloric testing revealed that the Group I animals had a 6%–10% increased excitability to the exposed ear, which persisted for the 32-day recovery period. Group II animals showed either little change or a slightly reduced excitability throughout the postexposure period. Neither group showed any significant behavioral abnormalities or positional nystagmus. Gross examination of the vestibular system revealed no abnormalities of the endolymphatic membranes or a disruption of otoconia. Across all animals, the status of the cochlear hair cells varied from relatively small losses to nearly total degeneration of the sensory epithelium. [Work supported by NOSH and NIEHS.]
Sound attenuation in a liquid-filled, acoustically lined tube
Authors: Ho L. T. , Heiner L. F. , Ko S. H.
Published: October 2005

A study has been made on the energy attenuation in sound waves propagating inside a liquid-filled tube lined internally with acoustic materials. In this study, the derivation of the eigenvalue equation was based on the matching of the acoustic impedances at the interface between the fluid and the tube walls. The sound energy expression derived elsewhere [S.H. Ko, J. Sound Vib. 22, 193–210 (1972)] was used for the present study. The wall impedances as a continuous function of frequency were determined experimentally, for a given lining material, by an impedance measuring technique described previously [L.T. Ho, L.F. Heiner, and J.M. Shrader, J. Acoust. Soc. Am. 56, Suppl. No. 1 (1974)]. With the wall impedances as input data, a computer program was developed to solve for the eigenvalues, and to obtain the modal attenuation of sound waves through a section of acoustic liner. Reasonably good agreement was observed between theoretical and experimental results. Some conclusions are drawn from the present analysis and presented in this paper.
Low-frequency vibration modes of a flexible tubing filled with liquid
Authors: Shajenko Peter
Published: October 2005

Holographic investigations of the vibration modes of an oil-filled viscoelastic tubing of 1-in. diameter and 1/8 in. wall thickness and the relation between pressure variation within the tubing and the vibration modes, in the frequency range from 25 to 470 Hz, are presented. At a given frequency, the oil-filled tubing vibrates in many modes simultaneously, creating a complex modal structure. The problem is made more complicated because of the temperature and frequency dependencies as well as the inhomogeneity of the viscoelastic material properties and the dimensional variation of the tubing. Because holography provides visual presentation of the resultant modal structure and permits discrimination between vibration modes, the various vibration modes can be selected and their effect on the variation in the internal pressure can be studied. From the modal resonances, the elastic modulus and its frequency and temperature dependencies can be deduced. [Work supported by Naval Material Command.]
Intense sound generation by unsteady discharges
Authors: Dwyer H. A. , Karnopp D. , Margolis D.
Published: October 2005

The problem of unsteady discharge from a vessel with an exhaust system has been approached with a new technique. The technique consisted of solving the nonlinear equations of motion with the shock capturing finite difference schemes, which are capable of describing shock formation, shocks, contact surfaces, varying area, friction, and heat transfer effects. The physical problem that the method was demonstrated on was discharge from a two-stroke engine with an expansion chamber connected to it. Flow simulations were carried out with an without simple mufflers attached to the expansion chamber. Considerable wave steepening was observed both in the expansion chamber and the muffler sections, and some nonlinear high-frequency resonances were observed in the muffler. The influence of wall fraction was generally very weak; however, such phenomenon as high-frequency damping, Fanno Line effects, and damping of low-frequency resonances were observed. The sound levels which were predicted by a simple source far from the exit agree well with the few experimental results which are available.
Stop voicing production and perception: Natural outputs and synthesized inputs
Authors: Lisker L.
Published: October 2005

In recent years the initial stop consonants of English have been subjected to the relentless attention of speech researchers concerned with the basis for their division into the two categories /p, t, k/ and /b, d, g/. The data which suggest the several hypotheses currently entertained have two main sources: natural productions of “normal” speakers of the language operating in “normal” fashion and the responses of persons of like description to synthesized speech stimuli designed to measure the effect of systematic variation of selected acoustic features. The responses required of subjects in tests of synthetic speech can hardly be considered representative of their behavior in responses to natural speech; what the testing of synthetic speech demonstrates is the capability of the perceptual system to deal with the features selected for study, not that this capability is exploited in the perception of speech. Two kinds of information of relevance to the question of speech cues have not been collected: (1) the extent to which features having potential cue value show variations in natural speech matching the magnitudes tested in synthesis and (2) the extent to which features for which distinctive function is claimed may be subjected to experimental manipulation by skilled speakers without significantly reducing intelligibility. Experimental and other data are presented to indicate that certain acoustic features affecting the perception of stop voicing are of marginal importance or less in the perception of natural speech.
Prosodic signals of sentence structure: Their syntactic distribution
Authors: Harris M. O.
Published: October 2005

We have previously reported a technique for the use of perception tests to identify boundary signals in continuous reading. The distribution of boundary locations between words was described generally in terms of simple parsing state changes, or lack of change. Now we are beginning to analyze the classification of boundary placement in considerable syntactic detail. Computer storage of the data has made it possible to search quickly for various sets of information about syntax and perception. The present data base for this continuing study includes the responses of three listeners to three speakers, each reading the same 1870-word text. Because of the sequential nature of the speech stream in time, boundary signals can be imposed on the words and sentence segments only successively, as they occur. But additional analysis suggests the way in which this sequential system realizes the multidimensional combination of sentence segments. At each boundary, there exists a limited range of possibilities for the succeeding segment, with different probabilities of occurrence or different degrees of functional relatedness attached to each. The least familiar will be most highly marked. The set of possibilities at each kind of boundary may be stated in syntactic terms.
Neuromuscular control systems in singing
Authors: Wyke Barry
Published: October 2005

The neuromuscular control systems involved in the performance of trained singers operate in the following triple temporal sequence: (1) Prephonatory tuning. This consists (after each voluntary interphrase inspiration) of voluntarily initiated adjustments of motor unit activity in the abdominal, intercostal, laryngeal, and orofacial musculature that precede (by between 50 and 500 msec) the onset of the expiratory air flow. The process is operated from the frontal lobes of the brain in terms of a learned vocalizing program that is stored in the temporal lobes. (2) Intraphomatory reflex modulation. This involves rapid, reflex (i.e., unconscious) readjustments of the present muscular activity during actual phonation. These reflexes operate through the spinal cord and lower brain stem, and are triggered and controlled by the activity of mechanoreceptors located in the lungs, chest wall, larynx, pharynx, oral cavity, orofacial musculature, and temporomandibular joints. These processes cannot be learned, but their operational efficiency may be increased by vocal training programmes. (3) Postphonatory acoustic automonitoring operates in response to cochlear self-stimulation by the singer's ongoing vocal output, and imposes still further readjustments on the activity of the respiratory, laryngeal and articulatory musculature. These adjustments are effected voluntarily to a small extent (in response to acoustic perception of the vocal output and/or of reverberations generated thereby), but mainly reflexly through acoustic reflex pathways in the brain stem.
Effect of voice training on lung volumes in singers and the possible relationship to the damping factor of Pressman
Authors: Gould Wilbur J.
Published: October 2005

In an attempt to document the presumed relationship between vocal efficiency and respiratory efficiency in singers, and the effects of vocal training on both, vital capacity (VC), total lung capacity (TLC), residual volume (RV), inspiratory capacity (IC), expiratory reserve volume (ERV) and functional residual volume (FRV) were compared in professionally trained singers, students of voice and in subjects with no vocal training. The results showed that many of the professional singers had a markedly low RV/TLC ratio, while the ratio in students of voice was intermediate between that of the professional and those without voice training, who had the highest RV/TLC ratios. There appeared to be a correlation between length of vocal training and improvement in vocal ability, as reflected by the RV/TLC values. All of the students whose RV/TLC ratios were within two standard deviations of the predicted value had received five years or less of training, while the professional singers, with RV/TLC ratios substantially lower than predicted values, had an average of 14 years of training. It seems clear, therefore, that there is a specific correlation between increased breathing capacity, as reflected by a reduction in RV/TLC and long-term vocal training and further that the professional singer attains an increased capacity in effect by expanding the proportion of VC within TLC. The results also suggest that the increased breathing capacity may be a crucial factor augmenting the damping factor described by Pressman in the production of the high tones of the head voice.
Function of the laryngeal muscles in singing
Authors: Hirano Minoru
Published: October 2005

On the basis of electromyographic investigations the following conclusions appear justified: (1) The cricothyroid muscle stretches and elongates the vocal cord. When it is activated the vocal cord is located along the line between the anterior commissure and the posterior cricoarytenoid ligament. The cricothyroid muscle is primarily a fundamental pitch agent although it influences vocal register significantly. (2) The vocalis muscle tenses, shortens, and adducts the vocal cord. It participates in regulating fundamental pitch, intensity, register and onset of voice significantly. (3) The lateral cricoarytenoid muscle adducts, slightly elongates, and slightly lowers the vocal cord. It participates in regulating fundamental pitch, intensity, register, and onset of voice. (4) The interarytenoid muscle adducts the vocal cord chiefly at its posterior portion. Its participation in regulating acoustic parameters of voice is less significant than that of the former three muscles. (5) The posterior cricoarytenoid muscle abducts the vocal cord and is usually inactivated during phonation. However, it contracts to some extent for high tones in heavy register to brace the arytenoid cartilage against the anterior pull.
Survey of light vehicle operations
Authors: Gray R. F.
Published: October 2005

Current exterior noise test methods for automobiles and light are based only on full throttle acceleration. To discover how representative of normal vehicle operation such test methods are, a survey has been made of the driving patterns of randomly selected drivers throughout the U.S.A. Chase cars were used to monitor approximately 2500 drivers and 11 000 miles of driving in 12 regions. Speed, turns, brake applications, a second-by-second description of the type of roads and the environment in which the vehicle was operating, and description of the vehicle and its occupants were recorded. Driving has been separated into idle, cruise, acceleration, and deceleration modes, and distributions of time and distance in speed and acceleration bands have been calculated. Average acceleration versus profiles have been calculated, and the amount of time spent under full throttle acceleration versus speed profiles have been calculated, and the amount of time spent under full throttle acceleration has been estimated. The effects of vehicle type, road type, traffic density, and population density on driving patterns were examined, and those factors which are significant identified.
Motor vehicle noise emission while accelerating up a hill
Authors: Hellweg Robert D , Nechvatal Michael F.
Published: October 2005

A noise survey was performed in 1975 to determine motor vehicle noise emissions while accelerating up a grade. A-weighted sound levels were measured at locations 50 ft from urban streets with grades carrying between 4.3% and 9.6%. The recorded sound level data are presented as a function of grade for five classes of vechicles: passenger cars, light trucks (GVW: under 8000 lb), light-medium trucks (GVW: 8–14 000 lb), medium trucks (GVW: 14–24 000 lb), and heavy trucks (GVW: over 24 000 lb). Statistical distributions of the recorded sound level data are presented for each class of vehicle and compared to level street acceleration data measured in 1974 [Michael F. Nechvatal and Robert D. Hellweg Jr., J. Acoust. Soc. Am. 56, S34(A) (1974)].
Auditory responses from the cortex of the anaesthetized tree shrew
Authors: Manley Judy
Published: October 2005

Species-specific vocalizations, pure tones, and white noise were used to elicit responses in the primary auditory cortex of tree shrews (Tupaia) anaesthetized with urethane. Action potentials were recorded with 25 μ platinum iridium wire from small clusters of neurons. Almost all the cell groups responded to white noise and pure tones over a wide range of frequencies, and fewer responded to vocalizations. In contrast, studies on awake, unrestrained tree shrews using the same type of electrodes [J. A. Manley and P. M. Milner, J. Acoust. Soc. Am. 57, S54(A) (1975)] showed that almost all cell groups respond to vocalizations and considerably fewer to tones and noise. In both studies the cell groups responding to vocalizations responded to all or several calls and no real specificity was seen. Response patterns in the anaesthetized animal consisted mainly of phasic “onset,” “on-off,” or “off” although sustained responses also occurred, whereas the awake animals gave almost entirely sustained responses. A shorter latency and less intertrial variability were seen in the anaesthetized preparation. Occasional cell groups exhibited reverberating bursts of activity. [Supported by a National Research Council of Canada grant to P. M. Miller.]
Attentional factors in simultaneous two-channel auditory signal detection
Authors: Puleo J. S. , Pastore R. E.
Published: October 2005

This study investigated attentional factors involved in two-channel auditory signal detection. The brief 50 msec sinusoidal signals, masked by binaurally uncorrelated, band-limited noise, were presented simultaneously to two separate earphone channels each with an independent probability of 0.5. The two-channel detection tasks required observers to monitor one (selective attention condition) or both (divided attention condition) of the earphone channels. Compared to the single channel condition, observers showed a slight (1–3 dB), but consistent, decrement in detection performance in both the selective and divided attention conditions with signals separated in frequency by less than one critical band (Δf=65 Hz). With signals separated in frequency by more than one critical band (Δf=1565 Hz), observers again showed a slight performance decrement when dividing their attention between two earphone channels, but could effectively monitor one channel while attempting to ignore the other. [This work was supported by a grant from NINDS.]
Interaural time discrimination of clicks: Dependence on interaural time and intensity differences
Authors: Shepard N. T. , Colburn H. S.
Published: October 2005

The dependence of the just-noticeable difference (jnd) in interaural time delay on interaural amplitude difference and interaural time delay was measured for a 100-μsec click stimulus using a symmetric, two-interval, two-alternative-forced-choice plus feedback paradigm. Results are similar to those obtained for 500-Hz tone bursts [R. H. Domnitz, J. Acoust. Soc. Am. 53, 1549–1552 (1973)]. As in the tonal data, the most interesting aspect of the data is the asymmetric (about 0 μsec) dependence on interaural time delay when the interaural amplitude ratio is large. The jnd was measured for amplitude ratios of 0. 6. 12. and 20 dB. Results for amplitude ratios less than 20 dB are very consistent, whereas results for 20 dB are more variable. [Work supported by NIH.]
Vocal tract normalization for /s/ and /š/
Authors: May Janet
Published: October 2005

The acoustic cue separating /s/ and /š/ was studied, using synthetic speech stimuli, in the context of two different following [ae]'s: one appropriate for a large vocal tract and one for a small vocal tract. For each vocal tract size, the center frequency of the frictional portion of the stimuli was varied in ten steps from 2974 to 4455 Hz. In preliminary experiments, it was found that listeners have a reasonably consistent boundary along this scale at which they stop hearing /š/ and start hearing /s/. It was hypothesized that a listener's boundary would be higher for the small-vocal-tract stimuli than for the large-vocal-tract stimuli. Nineteen subjects who were asked to identify 40 tokens of each stimulus showed an upward boundary shift of varying magnitude for the small-vocal-tract stimuli as compared with the large-vocal-tract stimuli. This result suggests the /s/-/š/ cue is dependent on vocal tract size.
Three models of perceptual adaptation to speech
Authors: Cole R. A. , Cooper W. E.
Published: October 2005

Experiments were conducted to test the merits of three competing models of speech adaptation. Two models were sensory based and concerned (a) a shift and/or decline in the sensitivity peak of a speech analyzer following repeated listening to an adapting stimulus or (b) a narrowing of the stimulus range to which an analyzer is sensitive following repeated listening. A third model was response based, representing a bias effect of contrast. Three selective adaptation experiments were conducted using series of test syllables ranging from [ǰa] to [da], produced by variations in the duration of frication. In Experiments I and II, listeners were asked to identify by number each of seven test stimuli before and after adaptation with the [ǰa] endpoint member of the test series or after adaptation with either [ǰi] or [di]. A signal detectability analysis revealed highly systematic shifts in the peaks of sensitivity, as measured by values of d′ for adjacent stimuli. No systematic effects of response bias were obtained. In Experiment III, listeners were asked to identify nine test stimuli by consonant category [ǰ] or [d] before adaptation and after adaptation with either a single adapter (as in previous experiments) or with an adapting sequence that included the first six members of the test series. The average duration of frication of the six adapters was equal to the frication duration of the single adapter. The two adaptation tests produced nearly identical effects, suggesting that repeated listening to the single adapter did not reduce an analyzer's sensitivity range. The results provided support for a model in which the sensitivity peak of a speech analyzer is shifted by adaptation.
Noise-source location for large machines from measurements of surface acoustic intensity
Authors: Hodgson T. H.
Published: October 2005

Noise source strength measurement and location for the case of large machines in situ can be difficult with conventional methods. This is due, in part, to the complicated motion of the large surface areas as well as the variable acoustical conditions around the machine in a typical workspace. A noise-source identification technique based on the well known results for the sound power W= ∫IdS, where I is the surface acoustic intensity and where the integral is taken over the component surface S, is described. The method avoids all of the problems of the contamination of the pressure field around the machine caused by surface reflections, proximity, and reverberant effects. An example of the method applied to a large centrifugal chiller is described. It is shown that the sound power spectra of the two major radiating components could be obtained. These were found to be in good agreement with sound pressure spectra measured at the AR1575 standard positions. The need for further development of the method is discussed.
Measurements of frequency selectivity in listeners with sensorineural hearing loss
Authors: Leshowitz B. , Lindstrom R. , Zurek P.
Published: October 2005

For listeners with hearing loss due to cochlear damage, we have shown that in frequency regions displaying threshold elevation, there is a marked alteration in the psychophysical tuning curve [J. Acoust. Soc. Am. 58, S71 (A) (1975)]. Of major importance was the observation of a complete disappearance of the low-threshold finely tuned segment in regions of cochlea damage. In the vicinity of the probe, in contrast to the normal tuning curve, the effectiveness of the masker was sharply diminished. The “notch” in the tuning curve has now been confirmed with several listeners having various types of cochlear pathology. Follow-up investigations of the frequency-selective properties of sensorineural listeners were also carried out. In general, the results of experiments examining frequency discrimination and additivity-of-masking are in good agreement with the unusual frequency response revealed by tuning-curve measurements. For example, in regions of threshold elevation, as much as a 10-fold decrease in frequency discrimination was observed. Additivity-of-masking effects also revealed a close correspondence between musket effectiveness and region of cochlear damage. These findings are being used to build a profile of the auditory capacities of listeners with sensorineural hearing loss.
Measurements of acoustic input impedance of the cochlea in cats
Authors: Lynch T. J. , Nedzelnitsky V. , Peake W. T.
Published: October 2005

Although the middle ear is often called an impedance matching device, published measurements of the load impedance presented by the cochlea are not extensive. In the experiments reported here, sound stimuli were applied directly to the stapes in anesthetized cats in which the malleus and incus had been removed. Measurements were made of sound pressures at the stapes (Ps) and in the vestibule (Pc) with calibrated probe-tube transducers. Stapes velocity Vs was determined with the Mössbauer technique. Magnitude and phase of the total acoustic impedance Zf = Ps/(AfpVs) and the cochlear impedance Zc = Pc/(AfpVs) were obtained at frequencies between 10 and 104 Hz (Afp = footplate area). Zt is approximately characterized by a series circuit with compliance of 3 × 10−10 cm5/dyne, resistance of 1 × 106 dyne-sec/cm5, and mass of 3 × 10 g/cm4 .Zc is approximately equal to Zt from 500 to 5000 Hz, hence for this frequency range force applied to the stapes is all transmitted to the cochlear fluid. At lower frequencies the annular ligament absorbs most of the applied force. [Supported by grants from NIH and the Research Fund of the American Otological Society.]
Frequency response of bone vibrators
Authors: Brinkmann K. , Richter U.
Published: October 2005

The frequency response curves of four different types of bone vibrators used in audiometry were determined both on human foreheads and a Brüel and Kjaer artificial mastoid. Subjective measurements were carried out by means of a loudness comparison with a free sound field. All vibrators used had a plane area of contact of 1.75 cm2 and were applied with a static force of 5.4 N as recommended by the IEC. As could be expected, the two response curves of each vibrator were quite different from one another, but their disparity proved to be independent of the special type of vibrator to within ± 2 dB in the frequency range 125 to 4000 Hz. This verifies the fact, established earlier by direct measurements of mechanical impedances, that bone vibrators are loaded by the artificial mastoid in the same way as by human foreheads. Contrary to air conduction audiometry, the normal threshold of hearing for bone conduction therefore could be standardized by only one set of figures valid for every type of bone vibrator, as is in agreement with IEC recommendations.
Force as definition of bone conduction input
Authors: Queller J. E. , Khanna S. M. , Tonndorf J.
Published: October 2005

Previous studies [J. Acoust. Soc. Am. 55, S62(A) (1974), EE 8; 56, S4(A) (1974), B8] showed acceleration to be a poor indicator of bone conduction (BC) responses. Using the same magnetostrictive vibrator, unoccluded BC thresholds were measured in terms of acceleration at the input (forehead) and force for frequencies between 100 and 10 000 Hz and for four different-size contact areas. In terms of force, thresholds were independent of the contact area or its place, while in terms of acceleration they varied considerably. Békésy (1939) had already monitored force at the input, realizing this to be the only quantity defining cochlear input, measurable outside the skull. Being the equivalent of electrical current, it is constant throughout a series circuit: i.e., skin, bone, skull content, cochlea. A second vibrator (Radio-Ear B 70 A), calibrated in terms of force, was also employed. Results, when compared with those obtained with the magnetostrictive vibrator, for a comparable contact area, varied by as much as 20 dB. Reasons for these discrepancies will be discussed. [Supported by NIH grants.]
The acoustic pressure field alongside KEMAR's head with a view towards in situ hearing aid tests
Authors: Burnett E. D. , Kuhn G. F.
Published: October 2005

To simulate actual usage conditions, it is expected that the frequency response of heating aids will be measured on the head of the KEMAR manikin over the frequency range of 0.2 to 8 kHz. The acoustic pressure around the head can vary rapidly with both the frequency and the location. In order to compare and interpret the hearing aid response at various frequencies and locations on the head, it is necessary to precisely know the pressure variations. The amplitude and phase of the acoustic pressure were measured in increments ranging from 2 to 5 mm alongside KEMAR's head with frontal sound incidence. The acoustic driver was located in front of EMAR at a distance of 1.0 and ∼ 3.5 m from the ear canal axis. The test frequencies were the octave band center frequencies from 0.5 to 4.0 kHz and the third octave band center frequencies from 4.0 to 8.0 kHz. It will also be shown that pink noise of 6% and 29% at 6.3 and 8.0 kHz has a smoothing effect on the acoustic pressure variation with location.