bluuebunny/crossref_metadata_2025 huggingface dataset:
Grouping of young deaf children according to progress as a function of training
Authors: Asp C. W. , Nabelek A. K. , Shipley C.
Published: October 2005

Twenty young deaf children received daily auditory training and their speech reception/production was evaluated at four-month intervals with a similarity scale, a phonetic count, and a battery of acoustical measures. There was a significant improvement in similarity score for the group as a function of training. The similarity score was used to assign the children to groups. At the first evaluation, there were two groups: Group 1 had a good similarity score and Group 2 had a poor similarity score. After one year of training, Group 1 improved and had the best score; however, Group 2 split into three subgroups. Subgroup 2a showed fast progress, Group 2b had slow progress after one-year, and Group 2c had no progress. These four groups were also compared graphically for changes in phonetic count, mean F0, contour of F0, syllable match, voice duration, and latency. Groups 1 and 2a did noticeably better than Groups 2b and 2c on most of these measures. Phonetic count, mean F0, the contour of F0, and syllable match displayed differences among these four groups as a function of training.
Interaction between a beam-stiffened plate and an acoustic fluid
Authors: Lin G. F. , Garrelick J. M.
Published: October 2005

The interaction between an acoustic fluid and an infinite, point-excited, beam-stiffened plate is considered. The size, number, and locations of the beams are arbitrary. Results are presented showing the effects of the beam constraints on the plate's vibration pattern and on the associated radiated sound field. The ranges of validity of various asymptotic approximations to the exact Green's function for an elastic plate in an acoustic fluid are discussed. [The work presented here was supported, in part, by the Office of Naval Research Structural Mechanics Branch.]
Another look at the coincidence radiation from plates
Authors: Stuart A. D.
Published: October 2005

The K-wavenumber integral representation of the radiated pressure field is evaluated by means of the method of steepest descent in conjunction with how the location of the poles of the pressure integrand vary with frequency. In such a representation, it can be shown that the coincidence radiation is associated with the occurrence of the so-called leaky wave pole near the saddle point. As such, coincidence radiation can be physically attributed to the energy transfer from a particular type of nearfield pressure distribution that is focused into the farfield in a particular direction. It is found that the radiated power increases at a constant rate with frequency for heavy fluid-loaded plates, but jumps rapidly at the familiar critical coincidence frequency for lightly loaded plates. [Supported by the Naval Ordnance Systems Command.]
Numerical evaluation of the scattering integral for backscattering from the sea surface
Authors: Boyd M. L. , Welton P. J.
Published: October 2005

A general wave expansion of the sea surface scattering integral was given in the companion paper. To obtain valid results from this expansion as the frequency is increased, more and more terms must be retained. When a realistic representation of the sea surface gravity wave autocovariance function is used, the analytic difficulty becomes overwhelming after just a few terms. In order to extend the model's range of applicability, it was necessary to evaluate the scattering integral numerically. The scattering integral, however, is unusually difficult to integrate for the backscattering case using conventional numerical methods, since the integrand is a rapidly oscillating function with a very large dynamic range. The evaluation was carried out in double precision using a quadrature integration routine over each lobe of the integrand (i.e., between adjacent zeros of the integrand) and summing the resultant areas. This backscattering model is limited to frequencies below 10 kHz for two reasons. First, the numerical technique breaks down for large rms wave heights at higher frequencies. Second, the dominant backscattering mechanism shifts at higher frequencies from gravity waves to smaller-scale features (such as capillary waves) which have not been accounted for in the representation of the sea surface used here. Good agreement with existing backscattering data was obtained using this model.
Pulse probing of a rough surface scatter channel
Authors: Zornig J. G. , McDonald J. F.
Published: October 2005

A computer-based signal generation and acquisition system has been developed which is capable of handling broad-band pulses (50 kHz–1.3 MHz). This system has been used to explore the statistical properties of a model rough water surface scatter channel by pulse probing. A preemphasis-equalization scheme is used to compensate for transducer response, giving good signal-to-noise ratios throughout the frequency range. Results have been obtained for the average transfer function at low grazing angles (12°, 16°) which agree in large part with existing theory. Significant, although minor, discrepancies have been detected. The same technique has been used to measure the frequency cross-correlation function for the same physical channel, which has been found to agree with recently published theory.
Field-type acoustic wattmeter
Authors: Olson Harry F.
Published: October 2005

The field-type acoustic wattmeter [Olson, U.S. Patent 1,892,644 (1932)] consists of a velocity microphone responding to the particle velocity in a sound wave, a pressure microphone responding to the sound pressure in a sound wave, and an electronic means for combining the outputs of the microphones so the ultimate output of the system indicates the acoustic energy flow in a sound field. The electronic system is all solid state. The field-type acoustic wattmeter is a useful and powerful tool for measuring the sound power output of loudspeakers, the noise power output of machines in place under operating conditions, the sound absorption of walls, ceilings, and floors, the performance of sound-reproducing systems in rooms, the sound field in rooms, etc.
Mechanical impedance of electret microphones
Authors: Sessler G. M. , French J. C.
Published: October 2005

The real and imaginary parts of the mechanical impedance of a condenser-microphone diaphragm (including the air load on both sides) are determined from the noise voltage generated by the transducer and from the frequency dependence of the electrical transducer capacitance. Data obtained at reduced ambient pressures furthermore allow separation of the impedance contributions of diaphragm and medium. Noise measurements in the frequency range 0.5–5 kHz on typical electret-condenser microphones (2.5-cm diameter, 25-μm Teflon electret, 25-μm air gap, perforated backplate with cavity, sensitivity 2 mV/μbar) yield an almost frequency-independent noise voltage of about 4 nV/(Hz)1/2 at atmospheric pressure, corresponding to a mechanical resistance of 600 g/sec. In vacuum, the resistance drops by about two orders of magnitude. Capacitance measurements give a stiffness constant of 5 × 107 g/sec2 at atmospheric pressure, and again a much smaller value in vacuum. These results show the impedance at atmospheric pressure to be largely due to losses and restoring forces of the air in the gap, backplate perforations, and backplate cavity. The results are compared with those of analytical studies.
Frequency and amplitude of intermittency in a free jet
Authors: Wehrmann O. H.
Published: October 2005

To analyze the structure of intermittency in the edge region of a jet, a statistical analysis of the fluctuations was used. The four parameters: laminar time, turbulent time, intensity, and “frequency” are presented by distribution functions. These distribution functions show a Rayleigh-type distribution with a maximum and an exponential tail. Also, they are of similar character and indicate a minimum size of the turbulent elements. The “frequency” follows the law τ ⋅U3/2, a result previously obtained for vortex-like structures in jets.
New method for measurement of the total energy density of sound waves
Authors: Cook Richard K.
Published: October 2005

The total energy of a sound field in reverberation chambers is usually sampled by an array of microphones. Each measures the time average of the squared sound pressure at its location. This is equivalent to sampling the time average of the potential energy density of the sound field. It would be advantageous to measure as well the time-averaged squared particle velocity. This would yield the kinetic-energy density, which added to the potential-energy density would then yield the total-energy density. A principal advantage of the total energy density is that its spatial variance is in general appreciably less than the potential variance. We find this from an analysis of the variances for the eigenmodes of rectangular chambers having reflecting (rigid) walls. A microphone for total energy density can be made from a spatial array of four elements arranged at the corners of a tetrahedron. Electret microphones seem to be particularly suitable for the elements. The total energy density can be computed from the sums and differences of the electret outputs, with the help of integrated circuits, and displayed as a running function of time, e.g., as a graphic recording. For a standing-wave tube, only two elements are needed, and the total-energy-density microphone then takes a very simple form.
Direct determination of vocal-tract wall impedance
Authors: Ishizaka K. , French J. C. , Flanagan J. L.
Published: October 2005

The side wall of the human vocal tract yields and vibrates in response to contained sound pressure. This motion influences the acoustic resonances of the vocal tract and the vibratory behavior of the vocal cords. Accurate computer modeling of the cord/tract system therefore requires knowledge of the mechanical impedance of the yielding walls. Heretofore, this factor has only been estimated indirectly from sound wave measurements. We describe here a technique for direct measurement of the wall impedance. We also give a rationale for interpreting the low-frequency impedance in terms of a simple mass-compliance-viscous loss combination. Finally, we give mechanical parameters for the vocal-tract wall which we presently use in computer simulations.
Comparison of high-frequency scattering formulations
Authors: Junger M. C. , Garreliek J. M.
Published: October 2005

For complex scatterer configurations, the cross section is typically dominated by highlights, i.e., specularly backscattered echoes conveniently evaluated by Kirchhoff's approximation. The cross section is obtained as a surface integral over the entire illuminated surface (physical acoustics) or, alternatively, over the Fresnel zone generating the highlight (geometric acoustics). Elementary scatterer configurations are used to compare the error of the simpler geometric acoustics calculation (omission of creeping wave contributions) with the physical acoustics error resulting from overestimating amplitudes and phase velocities of shadow-zone boundary contributions. Finally, the hard sphere provided with a ρc-cap illustrates that both techniques are misleading for scatterers partially coated with anechoic material. [Supported by Office of Naval Research, Acoustics Programs.]
Frequency sensitivity of auditory fibers in the eighth nerve of the spadefoot toad Scaphiopus couchi
Authors: Capranica R. R. , Moffat A. J. M.
Published: October 2005

Spadefoot toads are primitive anurans which possess poorly developed eardrums on each side of their head for detection of airborne sound. Electrophysiological recordings from single fibers in the eighth nerve of Scaphiopus couchi reveal two distinct populations of auditory fibers. One type is maximally excited by low-frequency tones in the range 100–700 Hz. The response of each of these units to an excitatory tone can be totally inhibited by the addition of a second tone of higher frequency. The other population of fibers has its best excitatory frequencies distributed over the range of 900–1500 Hz. These fibers cannot be inhibited by the presence of a second tone. Units in both populations possess thresholds as low as 40 dB SPL (re 0.0002 dyn/cm2), so that the primitive eardrum of these animals provides moderately sensitive detection of airborne sounds. The population of fibers tuned to the higher-frequency range seem specialized for detection of the vocal signals of this species. The low-frequency inhibitable units seem specialized for detection of other types of sounds. A comparison of the response properties of auditory nerve fibers in this primitive toad is contrasted with more modern anuran species. [Supported by NSF Grant GB-18836 and NIH Grant NS-09244.]
Sonic-Boom Propagation in a Random Atmosphere
Authors: Pierce Allan D.
Published: October 2005

A discussion is given of the propagation of a nominally planar N-shaped pressure pulse of time duration T through a random atmosphere characterized by a scale size l and standard deviation Δv of velocity fluctuations. {This extends the author's previous discussion [J. Acoust. Soc. Amer. 44, 1052–1061 (1968)] of a refraction-diffraction mechanism that tentatively explains the anomalous spikes on sonic-boom waveforms.} Effects are classified as (a) gross effects representing distortions in the waveform's central portion and (b) onset effects that produce distortions near the leading and trailing edges. Gross effects are interpreted on the basis of harmonic waves of period 2T. Those caused by inhomogeneities at distances greater than l2/(cT) are generally negligible. To a limited extent, onset effects may be interpreted within the framework of the Keller-Friedlander geometrical acoustics theory of singular wavefronts. Over large distances, ray paths become tangled such that many singular surfaces may pass a given observer point. A discussion is given of the effect of caustics and of the distribution of wavefront arrival times. The estimated expected effective shock rise time is of the order of (r/l)12(Δv)l/c2, where r is propagation distance. Although this is partially offset by nonlinear steepening, it could explain the finite rise times of sonic-boom onsets.
Acquisition of Syntax
Authors: McNeill David
Published: October 2005

The influence of thought on language will be discussed in the context of the acquisition of syntax by children.
Surface Waves on Magnetic Materials
Authors: Matthews H.
Published: October 2005

The surface of a magnetic solid supports magnetostatic as well as elastic surface modes, and magnetostriction permits coupling between them. The magnetoelastic coupling of Rayleigh and Love waves can be compared, and it can be shown that relatively uncomplicated magnetoelastic Love waves exist. The dispersion relations for magnetoelastic Love waves have been calculated on the basis of Tiersten's boundary conditions. The results for a nonmagnetic layer on a magnetic half-space and for a magnetic layer on a nonmagnetic half-space show that the propagation is nonreciprocal. At the present state of the surface-wave art, experimental observation requires magnetic material with small saturation magnetization. Gallium-substituted YIG is suitable, but frequencies of 400 MHz or greater are required. Transducers and propagating structures for uhf Love waves have been developed. and results obtained at 285 MHz are reported. [Research supported in part by an ONR contract.]
Resonant Frequency of a Fluid Loaded Circular Plate Vibrating in the Second Symmetrical Mode
Authors: Gardner S. , Lindemann O.
Published: October 2005

The method used by Peake and Thurston [J. Acoust. Soc. Amer. 26, 166 (1954)] for the fundamental mode, is extended to obtain the resonant frequency of a fluid-loaded circular plate vibrating in the second symmetrical mode. The analytical results show that, for a clamped plate, fluid loading has approximately the same effect on the resonant frequency of the second symmetrical mode as it does on the fundamental. Therefore, for a clamped plate, the ratio of the second symmetrical mode resonant frequency, to the fundamental reasonant frequency is approximately independent of fluid loading. [Work supported by the Office of Naval Research.]
System for the Complex Plane Representation of Mechanical Vibration Response Parameters
Authors: Pallet David S.
Published: October 2005

The use of vector-component analysis techniques is often highly instructive in the investigation of structural vibration phenomena. Conventional systems for the determination of such response parameters as mechanical impedance, admittance, or transmissibilities generally enable separate representation of absolute magnitude and phase data, and vector resolution of real and imaginary components is not readily feasible. A system for the determination of these components has been devised, which utilizes a specially designed variable gain amplifier to modulate constant frequency and amplitude signals generally available within conventional automatic mechanical impedance systems, so that subsequent analysis with vector voltmeter elements effectually accomplishes vector component resolution. This method has the advantage of relative simplicity and can be operated simultaneously with, and as an extension of the analytic capability of, existing conventional systems. The resultant complex plane representations readily enable the application of such analytic procedures as the quadrature separation technique of Kennedy and Pancu.
Hearing in the Bullhead Catfish (Ictalurus nebulosis)
Authors: Weiss Burton A. , Hartig George M. , Strother William F.
Published: October 2005

The auditory range of the bullhead catfish was found to be from 100 to 5000 Hz. Peak sensitivity was at 700 Hz at 35 dB below 1 dyn/cm2. The upper limit of sensitivity was much below that found by previous investigators and seems to correspond with hearing functions explained by frequency and volley theory without a place mechanism that is anatomically lacking. [Research supported by NINDB and ONR.]
Computer-Controlled PCM System for Investigation of Dichotic Speech Perception
Authors: Cooper Franklin S. , Matingly Ignatius G.
Published: October 2005

To facilitate study of dichotic speech perception, a computer-controlled PCM system has been devised for preparation of dichotic tests from natural speech. A test is a series of paired utterances, presented one at each ear, simultaneously or with interaural delay. In compiling a test, each of several tape-recorded utterances is digitized at a 8-kHz rate (10 bits/sample) and read into computer memory. The stored utterance is played back, and its waveform simultaneously displayed on a storage oscilloscope. The experimenter defines the exact beginning and end of the utterance and adjusts its intensity. The edited utterance is saved with others on a disk file. According to the experimenter's test order, the two utterances of each pair are retrieved, converted with a specified relative delay, and recorded each on a separate audio tape track. The system is a useful tool for investigation of lateralization and fusion in speech perception. [Support from the Office of Naval Research and the National Institute of Health (NICHD) is acknowledged.]
New Earphone Cushion and Mounting System for a Protective Helmet
Authors: Allen Clayton H.
Published: October 2005

This paper summarizes the development and performance of a friction-spring earphone cushion, designed to provide improved low-frequency noise isolation when used within a hard helmet. The cushion is soft and seals well for a low-static clamping force against the head; but is stiff and provides a relatively rigid support for the earphone enclosure against oscillating forces induced by an external sound field. Also described is a new mounting system for the earphone enclosure that provides excellent vibration isolation and utility.
Detection of Increments in Gaussian Noise by Rhesus Monkeys
Authors: Clopton Ben M.
Published: October 2005

Rhesus monkeys were trained to make a differential response on a given trial depending on the occurrence of a 100-msec increment (10-msec rise-fall), ΔI, in continuous Gaussian noise I. The task is analogous to the YES-NO task for humans. Banana-pellet reinforcement was made contingent on two correct trials in succession. Each incorrect trial resulted in a short period of darkness. Following stabilization of performance during acquisition, data were collected in blocks of 100 trials. Each daily session consisted of six blocks. Generation of ROC's resulted from variation of a priori signal probability. With a priori probability at 0.5, estimates of d′ were collected for different values of I and ΔI. A surface relating d′ to I and ΔI resulted. Although, in general, findings were comparable to those in humans, some differences were noted. Response-latency data were also collected. [This work was supported in part by grants from National Institutes of Health.]
Phase Perception of Transient Signals Having Identical Power Spectra
Authors: Patterson James , Ronken Don A. , Green David M.
Published: October 2005

A model often proposed to account for the detection of signals in noise is a simple energy detector. Such a model consists of a narrow filter followed by a nonlinear device (such as a square-law device) with no memory and some type of integrator. Such devices are, of course, limited in their ability to follow rapid changes in the time waveform and for transient waveforms tend to react to the total energy content regardless of how it is packaged. Can the ear distinguish between brief (duration of 20 msec or less) signals if these signals have identical power spectra? Digital signals were generated via a method suggested by Huffman. The signals have identical power spectra but different phase spectra. Most of the signals we have tested sound very similar but can be discriminated almost perfectly. Many are easily discriminated. Thus, even for very brief stimuli, the ear cannot be treated as a simple energy detector. Some recordings of these signals are presented. [This research was supported by the National Institutes of Health, Public, Health Service, U. S. Department of Health, Education, and Welfare.]
Masking Effects of Interrupted Tonal Stimuli upon Pure Tones
Authors: Urban Beth , Baker Donald J.
Published: October 2005

The purpose of this study was to determine the masking of interrupted tonal stimuli upon pure tones. Using a Békésy audiometer, each of 10 normal-hearing adults traced his threshold while simultaneously hearing a masking tone. For the three frequencies (200, 400, and 800 Hz), there were 10 conditions. First, the signal was presented without interruption. For the other nine conditions, a gating procedure was used that removed specified amounts of the stimulus. Results of this investigation showed that: (1) maximum masking occurred at masker-maskee frequency coincidence; (2) extended masking occurred with all three interrupted masking frequencies; (3) masking effectiveness decreased as the duration of the interruptions increased, and (4) at a Critical Off Time (COT) of 500 msec, masking was reduced to a significant degree. The COT for normals appears similar to that for subjects with an eigth-nerve involvement as reported in the literature.
Ultrasonic Relaxation in Molecules Containing a Six-Membered Ring
Authors: Reddy K. C. , Piercy J. E.
Published: October 2005

The ultrasonic absorption in a number of liquids whose molecular structure is a six-membered ring has been measured over the frequency range 0.6–45 MHz at temperatures in the range −100 to +150°C. In piperidine and piperazine derivatives, a large relaxation with a low relaxation frequency is found at the higher temperatures of measurement. The activation energy of the relaxation indicates a barrier to inversion of the chair form of the ring of ∼10 kcal/mole. In cyclohexene and cyclohexanone derivatives, a different relaxation is found at the lower temperatures with a high relaxation frequency. Its molecular mechanism is believed to be the interconversion of chair and boat configurations of the ring, and these measurements represent, apparently, the only direct physical measurements of the elusive and important boat form in relatively simple molecules.
Cochlear Damage Resulting from Exposure to High-Intensity “Hard Rock” Music
Authors: Lipscomb David M.
Published: October 2005

A guinea pig was subjected to a total of 88 h of high-intensity music played by a popular contemporary musical aggregation. Histologic surface preparations of the cochlear tissues underwent phase-contrast microscopic inspection. It was discovered that 19% of the total sensory-cell population in a region one and one-half turns from the base of the cochlea was destroyed. In the region two and one-half turns from the base of the cochlea, 25% of the total sensory-cell population suffered irreparable damage. Numerous phase-contrast photomicrographs are used to depict the destruction caused by the sound stimulus. In addition, cochleograms are presented to map the regions of maximal cell destruction. It was found that there is little or no apparent pattern to the damage that obtains in the wake of exposure to this sound stimulus. This leads to the speculation that conventional pure-tone audiometrics may leave a great deal to be desired in evaluating the presence of TTS after exposure to high-intensity sound. An obvious conclusion determined from the results of this experiment is that the sound intensity generated by modern “rock” combos is sufficient to create widespread cochlear damage.
Functional Model of Perception and Its Application to Speech Processing
Authors: Ross Myron J.
Published: October 2005

During recent decades, problems in bandwidth reduction of speech signals have been studied from the point of view of the speech-producing mechanism. However, when the emphasis is placed on perception, parameters that correspond to the stimulus-receiving mechanism assume relatively greater importance. In this paper, a functional model of perception is described in which the magnitude of the frequency distribution of voiced sounds at the basilar membrane are expressed in terms of a linear combination of Hermite base functions. In terms of this model, an attempt is made to study and simulate the weighting performed by the ear on the original speech signal. The method of measuring the pertinent coefficients is given; the nature of the analyzer-synthesizer scheme is described; and experimental results are presented, with implications for speech bandwidth reduction. [This research was supported by a NASA Fellowship and the Electrical Engineering Department at Northeastern University.]
Digital Equivalent Vocoder Analyzer
Authors: Munnich R. F.
Published: October 2005

Various digital algorithms can be used to perform spectral analysis on a sampled speech waveform for operation equivalent to that of a conventional vocoder analyzer. This paper presents an analysis technique based on the discrete Fourier transform that permits economical implementation while preserving performance. An audio tape of a simulated vocoder will be played to demonstrate results. [Work supported by U. S. Army Electronics Command, Fort Monmouth, N. J., under contract.]
Shock-Design Research—Theory or Experiment?
Authors: Belsheim R. O. , Oleson M. W.
Published: October 2005

Development of useful methods for shock-design/test depends upon application of pertinent theory as implemented by measurements and interpretation relating to the particular problem. Many factors affect the relative importance of theory and measurement, as they affect the form of the resultant design/test method. For example, in structural shock-design research, physical experimentation has long been dominated one might almost say inhibited—by measurement and analysis problems that stem from the inherent complexity of real structures, and from their equally complex response to shock environments. Some years ago, attempts to interpret structural shock records in the time domain were minimized in favor of approaches involving the same records transformed into a frequency domain; the complex data included in the available single-parameter records (usually of relative velocity) seriously impeded physically significant interpretation. Recent improvements in shock instrumentation have produced new possibilities for analytical insight. More or less central to the new instrumentation system is an “integrated-accelerometer” concept, in which small, lightweight accelerometer transducers are coupled with electronic circuitry capable of producing the velocity and displacement integrals of a measured absolute acceleration transient. For the experimental researcher, records of shock response in a convenient three-parameter format (acceleration, velocity, and displacement records are transcribed simultaneously) provide new options for the interpretation of structural response under shock. In general, the successive integrals emphasize motions that are common to different proportions of the total structure while maintaining a physically meaningful interrelationship between these motions. Other examples of shock and vibration research are cited to illustrate further the creative interplay between physical experimentation and theoretical ingenuity. These point out the desirability of close contact between the analytical and experimental portions of shock research problems.
Use of Syntax in the Analysis of Connected Speech Utterances
Authors: Vicens P. J.
Published: October 2005

A method to analyze connected speech utterances using a finite-state grammar acting on a restricted vocabulary is proposed. The sentences are commands to a computer-controlled HAND-EYE system able to find blocks and stack them. Audio input to the system is provided through an analog speech preprocessor producing six parameters every 10 msec. Using these parameters, a computer procedure segments the whole utterance and generates a sound description. The decoding of the commands is done by scanning the speech-utterance description forward and backward looking for “known” (previously learned) words. The vocabulary is chosen so that the word boundaries are always at a minimum of amplitude or at a fricative-type segment. The word recognition is done on a best-match-type comparison scheme acting on prelearned word representations. At any step, feedback from the grammar is used to eliminate from the matching process the syntactically incorrect word representation. The program “understands” the key words of an utterance like: “PICK UP EVERY MEDIUM BLOCK STARTING AT THE BOTTOM RIGHT CORNER” in about 10 sec.
On Velocity and Gradient Hydrophones
Authors: Parvulescu Antares
Published: October 2005

Hydrophones sensitive to particle velocity or pressure gradient are not yet available as off-the-shelf devices, although they have been studied quite thoroughly in the past. A new look at their possible application to underwater-acoustic research shows that they hold promise in applications where low sensitivity can be tolerated, since reproducible performance can be bought at the expense of sensitivity. Nearfield studies of radiators can, for instance, make use of extremely insensitive transducers. The noise performance of the devices in the presence of turbulent flow is, on the other hand, a very severe restriction to their use in a free field.
Automatic Audiometer Coupled to a Data-Acquisition System for Animal Use
Authors: Wilpizeski C. , Taylor F. , Kay L. , Ramshaw W.
Published: October 2005

A simple, programmed shock-avoidance procedure is described for conditioning squirrel monkeys to track MAF or MAP thresholds. The method requires the animal to press a lever within 3 sec of tone onset to avoid mild shock punishment. Successful or unsuccessful responses control the increase or decrease step of a recording attenuator. Analog-to-digital conversion of recorder pen position is made with an add-subtract stepper in parallel with the recording attenuator. Coding is done through a diode matrix, and the value on each trial is punched into eight-channel paper tape. Arithmetic means and standard deviations are computed off line. The method permits test sessions up to 8 h in duration and is unaffected by appetitive variables associated with food or water rewards. Examples are given of tracked thresholds under normal and selected experimental conditions. [Work supported in part by National Institutes of Health.]
Noise Control of Aircraft Iron-Core Electrical Components
Authors: Reed David H.
Published: October 2005

Low-noise-level electrical components are needed for use in passenger and crew cabins of commercial aircraft. Iron-core electrical components are particularly offensive because of pure-tone noise at the magnetostrictive frequency of 800 Hz and its harmonics. This paper describes Boeing's energetic campaign to have equipment manufacturers design and produce electrical components that are satisfactory for aircraft cabin installation. A general description is given of Boeing's approach to noise control and of noise-reducing design features for this type of equipment. Noise-reduction programs for some equipment items are discussed in detail, and some outstanding results are presented.
Underlying Physiological Mechanisms of Syllable Stress
Authors: Netsell R.
Published: October 2005

Three adult male subjects spoke sentences and varied the placement and degree of stress on selected test syllables. Simultaneous recordings of the following were obtained from the subjects as they spoke: (1) muscle action potentials of the cricothyroid muscle; (2) volume velocity of airflow; (3) intraoral air pressure; (4) subglottal air pressure; (5) fundamental frequency of vocal fold vibration; and (6) the speech audio signal. Sound spectrograms were analyzed as were derived functions of articulatory and glottal resistance to airflow. A listener panel assigned the various degrees of stress to the test syllables. The results were interpreted as evidence that minimal stress contrasts are effected by the laryngeal system and more than minimal contrasts incorporate active participation of the sub- and supralaryngeal systems. The data are also supportive of Öhman's “energy pulse” hypothesis in that it is speculated that the entire speech musculature is energized for stress and that this energy is manifested differentially in the sublaryngeal, laryngeal, and supralaryngeal systems as a function of the degree of stress.
Influence of the Tongue on Oral and Nasal Sound Pressure Levels: A Preliminary Investigation
Authors: Massen-Gill Raymond
Published: October 2005

In this study, a comparison is made between oral and nasal sound-pressure levels for subjects with different degrees of the tongue missing. The importance of the tongue in dividing the oral and nasal cavities and the impact of the tongue on oral and nasal sound-pressure ratios before and after removal of the tongue is discussed. Brüel and Kjær equipment was used exclusively throughout this study for the sound-pressure measurements, and a Philips cinefluorographic unit was used for the physiological portion of the investigation. Anatomical drawings projected on slides and cinefluorographic film are utilized to review the study.
Fundamental-Frequency Measures and Ratings of the Speech of Patients with Cancer of the Vocal Folds
Authors: Hecker Michael H. L. , Kreul E. James
Published: October 2005

Speech samples of five patients with laryngeal cancer involving the vocal folds and five matched normal speakers were analyzed with respect to: (1) distribution of fundamental frequency; (2) perturbations in successive glottal periods; (3) maximum rate of change of fundamental frequency; and (4) perturbations in fundamental frequency occurring during the production of specific consonants (vocal-tract constrictions). The pathological speakers exhibited a more restricted distribution of fundamental frequency than the normal speakers. However, the other measures did not appear to differentiate the two groups of speakers. The results of listening tests, in which the same speech samples were rated with respect to hoarseness, harshness, and breathiness, are also discussed.
Threshold of Cavitation at Elevated Pressure
Authors: Angona F. A.
Published: October 2005

The threshold of cavitation has been measured in distilled water at ambient pressures from 1 to 15 atm. A focusing acoustic system was used to obtain the acoustic pressure required to produce cavitation at these pressures. The measured thresholds for degassed water agree with those predicted by Blake [Tech. ♯ 12, Harvard University, Cambridge, Mass., 1949] and Akulichev [Soviet Phys.—Acoust. 12, 199 (1966)] up to 8 atm. As the ambient pressure is further increased, the threshold diverges from the theoretical curves to lower values.
Nucleation of Cavitation by Alpha Irradiation of Liquid Helium
Authors: Shadley J. R. , Finch R. D.
Published: October 2005

It has been shown that the presence of an alpha particle emitter, a 1 mCi Po210 sealed source, causes a lowering of the ultrasonic cavitation noise threshold in helium II by as much as 50%, the sound field being generated by a cylindrical PZT 4 transducer resonant at 57 kHz. The lowest temperature investigated was 1.80°K. Thresholds corresponding to various specific sound-level increments were determined from graphic records. There is no discernable effect on the threshold in helium I, so that the nucleation mechanism cannot be the formation of microbubbles at hot spots as in Seitz's theory [Phys. Fluids 1, 2–13 (1968)]. Neither the presence of a 13 mCi tritiated titanium beta source nor electric fields affected the nucleation, so that ions, per se, are also ruled out as a nucleating mechanism. However, several similarities to the behavior of the threshold in the presence of a rotating shaft and bucket were observed. Evidence was obtained indicating that the cavitation noise was localized in the vicinity of the alpha source. It is concluded that the nucleation occurs on vortex filaments created by the alpha particles.
Intrusive Noise and the Ambient Noise Environment
Authors: Sawley R. J. , Gordon C. G.
Published: October 2005

The extent to which an intruding noise source penetrates the general ambient noise environment in a community, serves as a useful indicator of the likely reaction of the community to that noise source. Available techniques using this approach generally provide a measure of community response based upon the absolute difference in level between the intruding and the ambient noise. Such techniques rarely take account of the percentage time for which the intruding noise is audible within the ambient—a question of importance in determining the possible onset of complaints. The major difficulty in obtaining this information concerns the usual need for sophisticated equipment in establishing the appropriate statistical description of the ambient. This paper looks at a simple method based upon a concept of time and position interchangeability whereby it would appear that the required ambient-noise-level picture may be readily obtained with a sound level meter alone. Tentative guidelines for the interpretation of community response to intrusive noise in terms of the developed statistical picture are put forward.
Effect of Absorbing Surfaces on the Statistics of Diffuse Sound Fields
Authors: Embleton T. F. W.
Published: October 2005

The random-incidence absorption coefficient of a sound absorbing surface, calculated from the difference of decay rates of the sound field in a reverberation room, invariably exceeds the random-incidence absorption coefficient computed from the acoustic admittance. The excess at high frequencies is too large to be explained by diffraction due to the finite size of the absorbing sample. The increase can be related to the anisotropy of the sound field in the immediate vicinity of every surface. When surfaces have different absorption coefficients (and hence at least some differ from the average), the total absorption is always greater than the product of the total surface area times the average absorption coefficient. This theory, to a first approximation, provides a qualitative explanation of the difference in absorption coefficients calculated from reverberation room and impedance tube measurements. It also shows that the coefficients measured for an absorbing patch in a reverberation room should increase slightly either as the size of the patch decreases or as the total surface area in the room increases—in qualitative agreement with previous experimental observations [e.g., Kosten, Acustica 10, 400–411 (1960)].
Experimental Evaluation of Microphone Traverses in a Reverberant Room
Authors: Ebbing C. , Ingalls D. J.
Published: October 2005

Accurate measurements of sound power using the reverberant room technique are dependent upon sensing the mean of the squared pressure throughout the volume of the room. The present ASHRAE Standard 36-62 specified the use of a linear or circular microphone traverse for spatial sampling. The proposed revision of the ASHRAE Standard extends the sampling techniques to include the use of arrays of multiple microphones. Theoretical investigations of others have compared various forms of spatial sampling and the results indicate that there is some merit to planar and volumetric microphone traverses. Measurements of the effects of linear, planar, and volumetric microphone traverses in a 300-m3 reverberant room (T60 = 13.3 sec at 500 Hz) on the indicated mean of the squared pressure are presented.
Anechoic Duct Termination Development Using Scale Model Theory
Authors: Myers G. H.
Published: October 2005

A 10 000 cfm aerodynamic and acoustic fan test facility required development of an anechoic section to facilitate in-duct sound testing. The resulting design incorporates sound absorbing material to reduce the plane-wave resonance effects within the test duct while permitting efficient air flow passage in either axial direction. This anechoic section is located between the end of the test duct and a 180° full radius elbow. The aerodynamic measuring section and auxiliary exhaust supply are connected to the elbow and physically located above the test duct. Using a one-to-four scale ratio, the 18-in. diam test duct was simulated by a 4.5-in. diam pipe. Conical, exponential, and catenoidal horn flaring geometries were reviewed as possible candidates for the termination's external configuration. The design value for the ratio of the maximum to minimum sound pressure occurring in the model test section as a result of the standing wave formed by incident and reflected plane waves was specified as 1.5 bB for the model frequency range of 240–1600 Hz. Results of the model test study indicate that an anechoic section having a catenoidal horn profile will provide satisfactory performance. The optimum acoustical performance (minimum SWR) was obtained with a sound absorbing material filling the termination cavity except for an aerodynamic passage through the center of the horn. Performance of a full scale design is compared with the model.
Influence of Flow and High Sound Levels on the Attenuation in a Lined Duct
Authors: Kurze U.
Published: October 2005

The attenuation of the fundamental mode in a lined duct can be calculated as a function of the frequency and the impedance of the lining with a finite difference approximation of the differential equations. A recently developed formula is extended to the influence of flow with and without shear. Theoretical results are compared with measured data in a narrow duct of 1-in. square open area for a turbulent flow with Mach numbers −0.5 ⩽M⩽0.5. The influence of the flow on the wavelength of the sound in the duct, which decreases the attenuation for positive Mach numbers and increases the attenuation for negative Mach numbers, dominates the influence of the turbulent-flow profile, which has the opposite effect. The impedance of the duct lining, consisting of a fiber metal or a perforated plate in front of a honeycomb structure, varies at high sound-pressure levels, when the flow resistance of the fiber metal or the perforated plate becomes nonlinear. The nonlinear attenuation of sound with levels up to 160 dB is measured and compared with the biasing effect of a turbulent flow in the duct. [Research supported by Brunswick Corporation, Needham, Massachusetts.]
Vibrations of Elastic Surface Systems Carrying Dynamic Elements
Authors: Jacquot R. G. , Soedel W.
Published: October 2005

The set of problems where shells, plates, or membranes carry discrete dynamic systems at discrete points on their surface is treated in a general manner. Interaction of each discrete dynamic system with the surface system is assumed to be in direction of the normal to the surface only. General solution equations are given. To apply these general equations to a specific problem, the eigenfunctions and eigenvalues of the surface system alone and the displacement inpedances of the discrete dynamic systems at their point of attachment are required. The eigenfunction and eigenvalue equations of a system consisting of a circular cylindrical shell carrying a dynamic absorber, which is also connected with a second spring to ground, are obtained as specific examples.
Intelligibility of Speech Produced in Compressed Air
Authors: Sergeant R. L.
Published: October 2005

Recordings of three Navy divers reading aloud word lists of the modified rhyme test within an air mixture were made under ambient pressure conditions that varied from 14.7 psia, which is normal atmospheric pressure, to 127 psia, which is roughly equivalent to pressures found 250 ft underwater. The recordings were presented to listening panels consisting of 25–30 sailors each. Analyses were made of the responses by the panels to sounds in the initial and final positions of test words, and phonemic matrices were constructed. Correct responses dropped progressively from 95% at 14.7 psia to below 75% at 127 psia. Sounds in the final position of words consistently were less easily recognized than those in the intial position, for all pressures studied. Sounds most seriuosly effected by increased pressures, except for /b/, are the lingual dentals /t∫, t, d/ and /z/, and the least effected sounds, except for /∫/ are the semivowels /r,l/ and /w/. Sounds for which intelligibility was low under normal pressure conditions of 14.7 psia were either very slightly or not changed at all by increasing pressure to 127 psia. Results of this study can be applied to construction of special vocabularies for use in deep-submergence diving operations.
Dichotic Detection of Correlation between Pulsed and Continuous White Noise
Authors: Creelman C. Douglas , Twining Bruce E.
Published: October 2005

Human observers were presented trains of noise pulses in one earphone while continuous white noise was presented to the contralateral ear. Signals were varied in frequency, duration, and duty cycle. Contralateral continuous noise was drawn either from the same white-noise generator that provided the pulse trains, or from a separate independent generator. In a two-alternative temporal forced-choice experiment, the observers discriminated between correlated and independent continuous noise. Discrimination improved with increases in pulse frequency and pulse-train duration. Under most conditions, discrimination was possible with pulse durations of less than 1 msec. Implications of the data for models of binaural cross correlation are considered.