bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic Studies of Dispersions of Solids in Electrolytes
Authors: Jackopin L. G. , Yeager Ernest
Published: October 2005

Ultrasonic absorption measurements in dispersions of solids such as colloidal silica in aqueous electrolytes indicate substantial excess absorption beyond that expected in the suspending medium. This excess absorption has been investigated as a function of the type and concentration of the colloidal particles, pH, ionic strength, and frequency. The following processes have been considered as contributing to the excess absorption: (1) shear losses arising from differences in the amplitude and phase of the velocities of the suspended particles and surrounding liquid, (2) relaxation effects arising from the perturbation of the equilibrium between ions adsorbed on the surface of the suspended particles and in the bulk liquid phase, and (3) relaxation effects involving the diffuse ionic layer surrounding each suspended particle (ionic atmosphere). Theory and experiment are compared. [Research supported by the Office of Naval Research.]
Effect of “Click” Location within a Word on Location Errors
Authors: Berry R. C.
Published: October 2005

The effect of “click” location within a word on the direction of the errors in click location was investigated. Twenty-four experimental sentences were randomized three times with 37 padding sentences. The clicks in the experimental sentences were located on the word immediately preceding or following the major syntactic boundary with an equal number occurring in both positions to balance any effect of syntax. The clicks were located either in the middle of the first half of the word, middle of the last half of the word, or in the middle of the word. The exact position within the word was verified by means of the Kay sonograph. Three groups of 18 subjects heard the sentences and clicks dichotically. Group I heard the tape with the clicks center, Group II heard the clicks first half, and Group III heard the clicks last half. Six subjects in each group heard one of the three randomizations for each condition. Subjects were provided with a text of the sentences and were instructed to indicate where the click occurred with a slash mark. Results indicated that click location within a word is an extremely important variable. When the click occurred in the first half of the word, significantly more responses preceded the word than for the click center or click last half condition. This finding was also observed for the click last half, i.e., more responses after the word than in the other two conditions. These findings indicate that a careful control and verification of click location is essential in an investigation where simultaneously presented clicks and speech stimuli are used.
Effectiveness of Work by Divers with and without Voice Communication
Authors: Hollien H. , Rothman H. , Hollien P. , Tolhurst Gilbert C.
Published: October 2005

It has been suggested that one of the factors that hampers effective work by divers is the lack of good communications. To test this notion, we conducted an experiment that alternated matched teams in a complex underwater construction task. Site of the research was TEKTITE-2, U. S. Virgin Islands. Two four-member teams matched in ability but unused to working with each other and unused to using communication systems served as subjects. The work task consisted of assembling a mini-DICORS (132 parts) in 20 ft of low-visibility water. On the first trial, members of Team A wore Aquasonics 420 units; Team B had no communication gear. On the second trial (a day later), the communicators were worn by Team B. Time of assembly and number and type of errors constituted the objective measures. In all cases, the performance of the team without the communication gear was superior. It was concluded that to be aided by communication systems (1) divers must be trained in their use; (2) they must be allowed to develop appropriate communication procedures; and (3) systems with better intelligibility than those currently available must be obtainable.
The Automatic Detection of a Particular Class of Underwater Acoustic Transient
Authors: Levine Mark S. , Nitsche Jude R.
Published: October 2005

The time waveforms of the underwater acoustic transients under consideration may be described as noise-corrupted pulses with varying risetimes and fall times, varying durations, and varying levels. In the past, these transients have been experimentally obtained using omnidirectional hydrophones and recorded on analog magnetic tape. The fact that these transients have been properly recorded is aurally verified before any spectral analysis is commenced. In order to perform the preanalysis detection of the transients at a faster rate and at adverse signal-to-noise ratios, an effort was initiated to develop an automatic system for the detection of this particular class of underwater acoustic transient. The development program consisted of three phases. First, the general class of transient was studied in detail to determine recognizable and repeatable attributes fo the signal. Using these attributes, a mask of the transient was constructed. A cross-correlation detector was developed that used the mask in conjunction with a general prupose computer and a specially designed analog system. Finally, the automated detector was used to locate transients which had previously gone undetected by direct aural means. This paper describes the metamorphosis of the development program. Examples of the detector output are also given. [Work supported by ONR.]
Digital Deresonation of Acoustic Recordings
Authors: Stockham T. G.
Published: October 2005

Recent research into the problem of eliminating blur and reverberation from digital signals has led to the invention of a statistical deconvolution method based on the theory of homomorphic filtering. The application described here involved the removal of recording horn resonances from old acoustic disks. A major distortion in these disks is the convolution of the recording horn impulse response with the voice waveform. This impulse response is estimated by chopping the recorded signal into many 1-sec intervals and averaging logarithms of the corresponding Fourier transforms. After averaging several such segments, the impulse response emerges in the form of its log Fourier transform and is thereafter removed in a digital convolution involving a computed system inverse. The resulting enhanced sound is generally considered far more acceptable and informative than the original although a slight increase in apparent surface noise is induced. A demonstration will be made. [This research was supported in part by the University of Utah Computer Science Division and by the Advanced Research Projects Agency of the Department of Defense, monitored by Rome Air Development Center, Griffiss, AFB, New York 13440, under contract.]
Implications of Fresnel Corrections in a Non-Gaussian Surface Scatter Channel
Authors: McDonald J. F. , Spindel R. C.
Published: October 2005

An investigation is made of the effect of the beam pattern of a source exciting an acoustic surface scatter channel using the Fresnel-corrected geometric-optics approximation. Results are presented for monochromatic and impulsive excitation using both deterministic and random boundaries. In the random case non-Gaussian statistics are permitted for the surface deformations. This study concentrates on the limits of very narrow- and very broad-beam patterns and specular geometry at moderate grazing angles. The results for the broad-beam pattern are found to be simpler than the corresponding ones for narrow- and intermediate-beam patterns. The theory is applied towards the calculation of impulse response convolutions and bifrequency spreading functions. An attempt is made to relate current and past physical results in a nomenclature suitable for application in signal processing and communication theory.
Controlled Response of a Ceramic Microphone
Authors: Nickell R. E. , Strickler D. C.
Published: October 2005

The dynamic response of a piezoelectric ceramic microphone, supported on soft rubber washers, was mathematically modeled at three levels of refinement in order to understand the damping mechanisms that control the voltage output. First, a direct variational procedure was used to identify the parameters that govern the lowest system resonances and the low-frequency sensitivity of the microphone. Then, an exact solution with a lumped-parameter model of the support structure was formulated and compared to the experimentally obtained voltage output, as a function of acoustic driving frequency. Finally, a finite element solution was obtained, with the support configuration modeled precisely, and compared to experimental results. The analyses were hampered, to some extent, by an inadequate thermomechanical characterization of the rubber material. By making reasonable assumptions about the thermorheological behavior of the rubber, however, adequate agreement with experiment was shown. The ramifications of the analyses for using soft rubber supports to control the response of microphones over a wide temperature range are discussed.
Approximation of Natural Frequencies for Membranes of Arbitrary Shape
Authors: Hayes D. E. E. , Torvik P. J.
Published: October 2005

The method employs the nonseparable solutions to the Helmholtz wave equation discovered by D. S. Moseley [Quart. Appl. Math. 27, 451–459 (1970)] as the elements of an expansion for membrane deflection. The boundary conditions for a membrane of any shape are then approximated by selecting the coefficients for the expansion so as to minimize the mean square error over a number of points on the boundary greater than or equal to the number of terms in the series representation. This procedure leads to an eigenvalue problem, and the minima in the eigenvalues lead to approximations of the natural frequencies. The resulting approximate solution satisfies the differential equation exactly and approximates the boundary condition. One advantage of the method is that it furnishes approximations to the frequencies of higher modes, as well as the first. When the method was applied to shapes for which the exact solutions are known, the results showed excellent agreement.
Mechanical Efficiency and Noise Reduction of Segmented Stator Vanes
Authors: Embleton T. F. W. , Thiessen G. J.
Published: October 2005

Model experiments indicating the possibility of several decibels of noise reduction with small change of mechanical efficiency in axial flow compressors using segmented stator vanes have been reported [J. Acoust. Soc. Amer. 47, 111 (A) (1970)]. Compared with straight-edged vanes, the serrated vanes provide 2–5 dB of noise reduction and no change in efficiency at the design conditions. Changing relative numbers of rotor blades and stator vanes gives either improved efficiency and no noise reduction or reduced efficiency and greater noise reduction. Off-design flow angles present a complicated pattern of results, but, in general, the serrated vanes compared with straight-edged vanes are equally efficient and have increased broad-band noise, but less blade-passage-frequency noise. As a noise reduction mechanism for turbine engines, it may be used with most other techniques, and the effects are likely to be additive; however, its maximum benefit is likely to be about 5 dB.
Theory and Measurement of Modal Spectra in Hard-Walled Cylindrical Ducts
Authors: Bolleter U. , Crocker M. J.
Published: October 2005

The propagation and interaction of acoustic modes in ducts is of importance for the measurement and control of sound generated by ducted fans and compressors. A method is presented by which the modal spectra (pressure and power spectral densities) for the first nine cross modes can be determined from pressure cross-spectrum measurements in the duct. The flow noise, a potential source of errors, is suppressed by placing the two microphones sufficiently far apart in the duet. The modal spectra and some of the modal interaction terms (modal correlations) for a number of fans are presented. The method should have many applications in verifying modal propagation, absorption of linings, and scattering of modes as well as in identifying sound sources. [Essential support of this work was given by Air Conditioning and Refrigeration Institute.]
Blade Interaction Noise from Lift Fans
Authors: Krishnappa G.
Published: October 2005

The discrete frequency noise radiation from single-stage lifting fan is analytically estimated based on the measured steady and unsteady aerodynamic data on the fan. A lifting fan in fan-in-wing configuration involves a close rotor-stator blade row spacing. Both types of aerodynamic interactions, potential flow interactions and viscous wake interference, are likely to contribute to the generation of discrete tones. Abdelhamid has estimated potential flow interaction noise from the NRC lifting fan in a recent report. The present work is concerned with the estimation of viscous wake interaction noise. The wakes from the rotor blades were measured using a DISA constant temperature anemometer and linearizer. The measured wake profiles were then represented by Fourier series. Unsteady lift acting on the blades at blade-passing frequency and several harmonics were calculated both for transverse and chordwise velocity variations. Discrete tone levels were then estimated using Lowsons expressions. The analytical estimation shows a reasonable agreement with the measured results under controlled conditions. Rotor potential interactions noise and stator noise due to viscous wake interference are important in fans of close rotor-stator spacing.
In-Duct Investigation of Subsonic Fan ‘Rotor Alone’ Tones
Authors: Moore C. J.
Published: October 2005

The production of tones by an isolated rotor interacting with fluctuating and steady flow distortions is first discussed, and a method of separating the steady components is explained. Circumferential, radial, and axial microphone traverses have been made in the duct of a 1-m diam four-bladed subsonic ventilation fan with no stators. The steady components of the rotor tones were measured and phase related to the shaft rotation. The results show that the acoustic field close to the rotor is dominated by its steady force field. At any multiple of rotational frequency, the basic mode is present having a number of lobes equal to the rotational frequency harmonic order. At greater axial distances from the rotor the basic mode decays, leaving only modes of low circumferential order at the intake. The estimated power in these modes is in agreement with the acoustic power measured from farfield traverses. [Paper read by M. J. Crocker.]
Introductory Comments on Stuttering and the Limbic System
Authors: Buxton Lawrence F.
Published: October 2005

The limbic system of the cerebrum, known also as the visceral or nose brain, was proposed by Papez over 30 years ago as a neural circuit of emotion. The purpose of the present paper is to suggest certain relationships between the limbic system and the three main groups of stuttering etiology: “repressed-need,” “anticipatory-struggle,” and “breakdown” theories. Neuroanatomy and neurophysiology of the limbic system will be reviewed with special attention given to possible epileptogenic and psychoanalytic implications to stuttering. Theoretical evidence of the limbic system as a neural servomechanism and its etiologic role in psychosomatic disease will be related to stuttering.
Development of a Continuously Sensitive Line Transducer
Authors: Miller G. K.
Published: October 2005

A coaxial cable with a dielectric of suitable material can be processed so as to produce a voltage at its terminals when mechanically excited at any point along its length. The development of such a transducer has been aided by an analysis and an experimental program aimed at determining desirable physical properties and dimensions for the cable materials as well as the best treatment process. Measurements are compared with the calculated theoretical predictions, and tradeoffs between cable and treatment parameters are discussed.
Two-Tone Loudness Summation and the Spectra of Comparison Sounds
Authors: Chaves John F.
Published: October 2005

The loudness of monaural two-tone complexes centered at 1000 and 2000 Hz was measured as frequency separation varied from 1 to 8 critical bands. Subjects matched these complexes to comparison sounds consisting of (1) a tone at the center frequency of the complex, (2) a two-tone complex whose components were separated by a single critical band, or (3) a tone set at the same frequency as the higher or lower frequency component of the complex. Measurements were made at an over-all SPL of 60 dB. Normal amounts of loudness summation were measured when the comparison sound consisted of either a single tone at the center frequency or the critical band complex. Less loudness summation was measured, especially at the widest frequency separations, when the comparison sound was a single tone set at the same frequency as one of the components of the complex. [Supported by funds from the National Institute of Child Health and Human Development.]
Pure-Tone Equal Loudness Contours for Standard Tones of Different Frequencies
Authors: Molino J. A.
Published: October 2005

Subjects (14 high-school students) made judgments of equal loudness by adjusting the intensity of comparison tones of ten different frequencies. The comparison tones were presented diotically alternately with standard tones (1-sec duration each). Each standard tone remained fixed at one frequency (125, 1000, or 8000 Hz) and one intensity (10, 20, 40, or 70 dB sensation level) while the data were collected for any single equal loudness contour. In this manner, families of equal loudness contours were generated for each of the three standard frequencies. The contours at 1000 Hz were compared with those for 1000 Hz in the literature. The contours for 125 and 8000 Hz, determined by otherwise using the same algorithm, were different in shape from the 1000-Hz set as well as from each other. These differences implied a violation of the transitivity assumption in the loudness calculating algorithm. Tests for transitivity among the three standard frequencies failed in many cases.
Quality Judgments of Spliced Synthetic Telephone Numbers
Authors: Olive Joseph P. , Nakatani Lloyd H.
Published: October 2005

Speech synthesis parameters (f0, f1, f2, f3, amplitude) of digits spoken in isolation and of telephone numbers were extracted. The parameters of the isolated digit were spliced together and resynthesized to generate the same telephone numbers as those analyzed. The parameters of the spliced numbers were manipulated in the following manner. (1) Timing: the duration of the spliced digits were equated to the duration of the corresponding digit in the natural number by a linear compression; (2) Pitch: the over-all pitch contour of the natural number was copied; (3) Formants: the formants of the spliced digits number were replaced by the formants of the natural number. These manipulations were done in all possible combinations, and the different versions were judged in three different tests. The listeners ordered the different versions of each number according to preference and comprehensibility, and rated their naturalness. A multidimensional scaling analysis revealed that (1) pitch was the dominant variable, and timing was negligible; (2) preference and comprehensibility were not equivalent; (3) naturalness depended primarily on pitch; (4) copied formants can detract from the quality of the speech; and (5) although results differed for different numbers, the trend was similar.
Standard Error Measurement in Speech Discrimination Testing
Authors: Bode D. L.
Published: October 2005

Speech discrimination data obtained by sequential testing with 12 normal-hearing listeners were described by Bode and Carhart at the 80th Meeting of the Society in Houston [J. Acoust. Soc. Amer. 49, 95(A) (1971)]. Group results showed that sequential testing provided discrimination functions essentially identical to those measured by conventional constant stimulus methods. Test-retest effects were small and quantifiable. We now have analyzed our results in terms of individual performance and will report these data for scores obtained both within and between test sessions. Of particular interest to us is the fact that a standard error (SE) can be calculated for individuals with sequential testing, even using only one test. Such a determination is not possible with orthodox discrimination test procedures. There are many circumstances, particularly in clinical audiology, in which an investigator or clinician would like to have both a rapid efficient estimate of the SE associated with his measure and one which can be calculated for an individual during a single test administration. Such a calculation would allow the examiner to reach conclusions, for any given obtained score, regarding the probable limits of corresponding true scores. These estimates for individuals, together with those based on group performance, will be described and contrasted. [Research supported by National Institute of Neurological Diseases and Stroke.]
An Acoustic Comparison of Cleft Palate and Normal Baby Cries
Authors: Greene R. A. , Royster L. R.
Published: October 2005

A 13-oct band analysis was used to compare cries occurring in cleft palate and normal babies. Sound-pressure levels on the linear scale, re 0.0002 μbar, were also observed. Cries from twenty-one normal and seven unrepaired cleft palate subjects ranging in ages from 112 to 24 months were recorded in the study. SPLs of the loudest cries averaged 96.7 dB for the normals and 97.5 dB for the cleft subjects. Frequency band means were used for graphically comparing the normal males versus females and the cleft palates versus normals. Results indicate that neither the SPL nor the 13-oct band spectrum of the cry can be used to identify a subject's age, sex, or palatal condition.
The Role of Format Transitions in the Voice-Voiceless Distinction for Stops
Authors: Stevens K. N. , Klatt D. H.
Published: October 2005

Research at the Haskins Laboratories has shown that an acoustic correlate of the distinction between syllable-initial voiced and voiceless stop consonants in English is the onset time of voicing relative to the time of release of the consonant. The present study examines the hypothesis that this critical time on voicing onset is determined by the time when the first formant (and possibly also higher formants) has completed its transition rather than by some fixed absolute time interval of aspiration. A synthesizer was used to generate a series of consonant-vowel stimuli in which (1) the absolute interval between consonantal release and voicing onset, and (2) the duration of the formant transitions, could be manipulated independently. Responses to these stimuli indicate support for the hypothesis. Acoustic analysis of natural consonant-vowel syllables also are consistent with the hypothesis. These findings suggest that the perception of [t] as opposed to [d] in English (for example) is influenced strongly by the presence or absence of a specific acoustic attribute—rapid change in spectrum after voicing onset—and does not require the detection of an absolute voice-onset time from a continuum of values. This attribute may underlie the acquisition of the so-called voice-voiceless distinction by children. [Supported by NIH and by the U. S. Air Force.]
Sound Localization in the Barn Owl
Authors: Konishi M.
Published: October 2005

Barn owls (Tyto alba) can use sound to catch prey in total darkness. Two barn owls were trained to strike protected loudspeakers emitting various artificial sounds. The accuracy of localization depended on the frequency, bandwidth, and temporal pattern of the test sound. Continuous pure tones of frequencies below 6 kHz and above 9 kHz were hard to localize. The accuracy improved as the frequency increased from 6 to 9 kHz. Within this range continuous sounds containing two frequencies were more accurately localized than either frequency alone. Sustained wide-band noises always assured precise localization. The owls localized tone bursts more accurately than continuous tones. Whatever signals were used, accurate localization was largely due to the owls' ability to use the sounds for guiding the flight direction. The midcourse correction could occur during a flight lasting as short as 1 sec. When the signal was switched from one speaker to another after takeoff, the birds could strike the second speaker.
Sonic Booms near the Cusps of Caustics
Authors: Pierce Allan D. , Kuo Frederick
Published: October 2005

At the recent ASA Second Sonic Boom Symposium, Wanner described French field tests that document the extremely high magnifications of boom overpressures that may be expected at a super focus, i.e., the cusp of a caustic or an arête. In the present paper, the theory of sonic booms near such cusps is developed, with emphasis on the estimate of the peak overpressure that may be expected in given circumstances. The parameters of importance in the analysis are (1) the minimum radius of curvature R of the shock front some time before it reaches the cusp, (2) the second derivative R″ of the curvature radius with respect to transverse distance along the front, (3) the peak overpressure Δp0 at the point where R and R″ are measured, and (4) the risetime τ. The linear theory predicts that the maximum overpressure at the cusp is of the order of (Δp) (R/cτ)12, which, for realistic values, predicts magnifications much larger than observed. A similitude theory incorporating nonlinear effects, similar to that previously used by Hayes (NASA SP-180), gives (Δp)max as equal to p0F(ξ), where F(ξ) is a universal function of the parameter ξ, given by (Δp/p0)/[RR″]12. Exploratory experiments to measure F(ξ) are described which suggest that F(ξ) may be approximated by 20ξ.
Supersonic Turns without Superbooms
Authors: Ribner H. S.
Published: October 2005

Maneuvers in supersonic flight, unless very gentle, will, in general, lead to superbooms: sonic booms much intensified by focusing. The superbooms normally occur on the inside of a turn. It is proposed that the focusing can be suppressed by the simple expedient of slowing down the aircraft. The correct deceleration will eliminate the local curvature of the wavefront (Mach “cone”) responsible for the focusing. The curvature (concave outward) is proportional to the component of resultant acceleration resolved along the normal to the wavefront. In this proposed scheme the tangential deceleration component is adjusted to cancel out the centripetal acceleration component. [The attractive companion notion of combining a turn (pullup) with the transonic acceleration apparently will not eliminate the transonic superboom: the centripetal acceleration vector is perpendicular to the effective direction.] [Work supported by Air Force Office of Scientific Research.]
An Experimental Acoustic Homing System Operating in Air
Authors: Horwath T. G.
Published: October 2005

An experimental gravitationally propelled acoustic homing system operating in the fluid medium of the atmosphere is presented. A four-element array of porous pipe sensors receives the acoustic signal emanating from the target, and also serves the purpose of axial flow noise refection. Phase detection signal processing is used to determine the direction of the target. Criteria for selecting the guidance scheme and the characteristics of the airframe are discussed from the standpoint of compatibility with the acoustic homing concept. The construction of experimental models is presented in detail together with performance data in the form of typical results obtained from flight tests. [This work was conducted at the Systems Development Office of the U. S. Army MERDC, Fort Belvoir, Virginia 22060.]
Radiation of Acoustic Energy from a Long Rod into a Semi-Infinite Liquid Medium
Authors: Maxwell G. G. , Hixson E. L.
Published: October 2005

The solution of the problem of the semi-infinite cylindrical ideal rod set in an infinite baffle and radiating into a semi-infinite ideal liquid is the subject of this paper. An approximation method is utilized. The axisymmetric stress fields in the rod are expressed as infinite sums over eigenvalues which are solutions of the dispersion equation. The dispersion equation is obtained by satisfying the appropriate boundry conditions for the rod. The pressure in the liquid is derived using the Green's functions technique. An infinite series of integrals is the result, since the velocity of the rod must be inserted in the integral expression for pressure. In order to solve the problem numerically these infinite sums are truncated. By matching the boundary conditions across the interface, the velocity profile is obtained which can then be used to construct the farfield radiation patterns in the liquid. Power, radiation impedance, beamwidth, directivity factor, and the directivity index are calculated from the fields. The computer results obtained over a limited frequency range for the aluminum-water case validate the approximation method. The technique provides a general method for calculating the velocity profile at the boundary between a vibrating cylindrical rod and a semi-infinite medium.
On the Multi-Terminal Extensions of the Thevenin and Norton Theorems and Their Application in Vibration Problems
Authors: Sykes Alan O.
Published: October 2005

Generalizations of the Thevenin and Norton theorems are as useful in solving multi-terminal mechanical network problems as their original forms are for solving lumped and four-pole problems; however, care must be used in applying them in that different forms of the theorems must be used depending on the nature of the sources being considered. Two forms of both the Thevenin and Norton theorems are presented, and limitations in applying them are discussed.
Auditory Temporal Order Judgments Perturbed by Tactile Stimuli
Authors: Sherrick Carl E.
Published: October 2005

Hirsh and Sherrick [J. Exp. Psychol. 62, 423–432 (1961)] determined that the limen for perception of temporal order for two stimuli is about the same (ca. 20 msec) for vision, audition, and touch. They suggested that a central processing system must be responsible for the uniformity of results. The present experiments test the hypothesis that the same system processes all modality inputs and that judgments of order in one modality can be perturbed if signals to a second modality are simultaneously present. Observers were presented with successive bursts of noise or tones dichotically, simultaneously with mechanical taps to each index fingertip. When the succession of auditory stimuli was the same as for the tactile, e.g., left-right, detection of order was unperturbed. When the succession for one modality opposed that of the other, e.g., auditory left-right, tactile right-left, detection was seriously degraded. Several parameters of stimuli that diminish or augment these effects have been studied and will be discussed. [Research supported by the National Institutes of Health, Department of Health, Education, and Welfare.]
Temporal Order and Perceptual Classes
Authors: Thomas Ian B. , Fitzgibbons Peter J.
Published: October 2005

Continuing our work on temporal order perception, we have measured the duration of four equal segments in a continuously repeated sequence of four pure tones necessary for correct perception of their temporal order. When all four tones were within a musical fourth (critical band?) the segment duration necessary for correct order perception was 125 msec—the same as we obtained earlier for natural vowels. However, when the tones were more widely spaced in frequency, the duration of each segment necessary for correct order perception was considerably greater (up to 500 msec) depending on the specific distribution of pure tones. Likewise, for a mixture of “different” stimuli (e.g., pure tones, white noise, etc.) segment durations again were considerably greater than 125 msec for correct order perception. It appears from these tests that much of the segment time in excess of 125 msec necessary for correct order perception results from the need to shift attention among “different” classes of stimuli. [Work supported by NIH.]
An Auditory Phi Phenomenon?
Authors: Divenyi P. L. , Hirsh I. J.
Published: October 2005

A possible auditory analogy of the visual phi phenomenon is a perceptual similarity, between sudden and continuous frequency transitions. Listeners heard 300-msec tone bursts, each comprised of three parts: the first and third were steady frequencies, f1 and f2, and the second or middle part was either a 20-msec glide or a silent gap of variable duration. Both the method of adjustment and the 2AFC paradigm were used to establish what gap duration yielded no or minimal discrimination between the two types of burst. Although perceptual identity is rarely reported, the jump-versus-glide discrimination is poorest when a 20-msec glide is paired with a gap of 1–2 msec. The gap duration corresponding to such “similarity” decreases as the frequency difference between f1 f2 decreases. [Supported by PHS grant by NINDS.]
Lateralization of Filtered Clicks
Authors: Wightman Frederick L. , Yost William A. , Green David M.
Published: October 2005

Lateralization of brief clicks was studied while the frequency content of the clicks was altered by filtering. The subject was asked to discriminate a centered image, a pair of identical clicks that arrived simultaneously at the two headphones, from a displaced image, a pair of identical clicks in which the click to the left ear was slightly delayed. The discrimination deteriorated as the high-pass cutoffs of the clicks increase beyond 1000 Hz and was largely unaffected by low-pass filtering. Masking with high- and low-pass noise showed that low-pass noise severely disrupted the lateralization of the high-passed clicks, but the high-pass noise produced no disruption of the lateralization of the low-passed clicks. Thus, our results showed that the information crucial for lateralization occurred in the frequency range below 1000 Hz. [Research was supported by the National Institutes of Health, Publich Health Service, U. S. Department of Health, Education, and Welfare.]
Validation of Holographic Observations on the Displacement of the Tympanic Membrane in Cats
Authors: Tonndorf Juergen , Khanna Shyam M.
Published: October 2005

Previous experiments, using time-averaged holography [J. Acoust. Soc. Amer. 47, 60 (1970); 48, 112 (1970)], had strongly suggested that the displacement of the tympanic membrane, at least in fresh cadavers, obeys the “curved-string” principle of Helmholtz rather than the “stiff-plate” concept of von Békésy. These unexpected findings required further evaluation of the experimental procedure. (1) The tympanic membrane had been widely exteriorized for holographic purposes: Round-window cochlear microphonic recordings provided correcting factors for the SPLs measured at the membrane. (2) The membrane had been coated for proper reflectance: Further microphonic experiments demonstrated no measurable effects upon middle-ear transmission. (3) Fresh cadaver specimens had provided maximal holographic resolution by minimizing thermal agitation and minute movement: Additional obsevations in living cats altered the resolution, but not the results. These and other, earlier, evidence argue emphatically the validity of the holographic observations. [Supported by several NIH grants.]
Acetylcholine Mimicks Crossed Olivocochlear Bundle Stimulation
Authors: Bobbin R. P. , Konishi T.
Published: October 2005

The methods used to record the cochlear potentials, stimulate the crossed olivo-cochlear bundle (COCB), and perfuse the scala tympani in guinea pigs were those described by Konishi [J. Acoust. Soc. Amer. 47, 1055–1062 (1970)]. Acetylcholine chloride (247 μM) and eserine sulfate (10 μM) when combined produced an inhibition of the action potential and an augmentation of the cochlear microphonics. The action potential and cochlear microphonics became insensitive to the continued presence of the drug combination. A second perfusion with the acetylcholine (247 μM)-eserine (10 μM) combination following a perfusion with artificial perilymph reproduced the “mimicking” response. A perfusion with curare (50 μM) together with acetylcholine (247 μM)-eserine (10 μM) following a perfusion with curare (50 μM) did not demonstrate a “mimicking” response. These data are consistent with hypotheses that the COCB is cholinergic. [Supported by a Public Health Service grant and an NIH fellowship from NDS.]
Experimental Demonstration of a Viscoelastic “Crossover” Effect
Authors: Moffett Mark B. , Kolsky Herbert
Published: October 2005

Observations were made of the longitudinal stress pulses reflected from an interface between two viscoelastic rods. The incident medium (polystyrene) was nearly elastic, while the reflecting medium (unplasticized polyvinyl chloride) was fairly lossy, having a frequency-dependent complex extensional-wave impedance. The frequency at which the impedances of the two materials are equal in magnitude is termed the “crossover” frequency and is temperature dependent. Fourier components well above the crossover frequency are reflected substantially in phase, while those well below this frequency are reflected nearly out of phase. By varying the temperature, and hence the crossover frequency, the reflected pulses were made to vary from essentially positive at room temperature to essentially negative at 55°C. At an intermediate temperature, the reflected pulse had a minimum amplitude and a shape significantly different from that of the incident pulse. (This case is the viscoelastic analog of impedance matching for elastic media.) The experimental results serve to demonstrate the viscoelastic-crossover effect predicted by Kolsky and Lee [Div. of Appl. Math., Brown Univ., Tech. Rep. No. 5, 562(30)/5 (May, 1962)].
Comparison of Slip and Slide Damping for a Friction-Clamped Beam Excited by Sinusoidal Vibration at Resonance
Authors: Himelblau H.
Published: October 2005

Mentel and Ungar have each shown that the damping of friction-clamped beams is proportional to the coefficient of friction and clamping pressure when sliding friction between the structure and its supports is assumed. Metherell and Diller have shown that the damping of a lap joint is inversely proportional to these parameters when slip is assumed. A direct comparison is made of these seemingly contradictory results when the structure is a single span beam which is friction clamped at each end to rigid supports. Clamped-clamped and hinged hinged boundary conditions are utilized. The implications of these results on the understanding of friction damping of more complex structures are discussed.
Sound Isolation Criteria for Music Activities
Authors: Geerdes Harold , Watters Bill G. , Hirtle Parker W.
Published: October 2005

Laboratory demonstrations and tests have been conducted by the authors to establish maximum allowable intrusive music levels for music teaching spaces. Calibrated tape recordings of a music education class, band, orchestra, and choir practice were reproduced through a spectrum shaping filter network and a high-quality sound reproduction system. Subjective responses of test subjects were recorded for various levels of intrusive noise in a controlled acoustical environment. Variations in the background noise levels during the tests confirm the importance of the signal-to-noise ratio in music privacy. The test procedures are described, sound-isolating constructions are evaluated, and tentative sound-isolation criteria are presented.
Basilar Membrane Tuning
Authors: Johnstone B. M. , Yates G. K.
Published: October 2005

Georg von Békésy's visual observation of the basilar-membrane travelling wave showed a broad mechanical tuning, quite at variance with the sharp tuning from neural recordings. A few years ago, Johnstone and Boyle applied the Mössbauer technique to the basilar membrane and showed the tuning to be much sharper than previously thought. Our latest results show high-frequency cutoffs of up to 340 dB per octave. Using a special Mössbauer source with an isomer shift to eliminate the 180° ambiguity of previous work, the phase shift has been shown to asymptote to π/2 lead at low frequencies, rotating approximately linearly with increasing frequency and finally asymptoting sharply to 3π lag at the tuning-curve cutoff. The low-frequency slope of about 12 to 24 dB/oct is apparently much less than the neural curves. However, the Mössbauer technique requires a higher sound level than used for neural threshold curve, and if neural curves are constructed with constant firing rates as a parameter, e.g., 50 impulses per second, so that comparable sound pressures are used, then they show a low-frequency scope of around 36 dB/oct—not too different from the mechanical figure. Hence, taking into account a basilar membrane nonlinearity of the type found by Rhode, the neural and mechanical curves may be reconciled.
Evidence for Nonlinear Vibrations in the Cochlea from Mössbauer Experiments
Authors: Rhode W. S. , Robles L.
Published: October 2005

The Mössbauer technique has been applied to the measurement of vibration of the basilar membrane in the squirrel monkey's cochlea. Both steady-state and transient responses have been recorded in the 7–8 kHz range of the cochlea. The steady-state response indicates that the basilar membrane vibrates nonlinearly from frequencies of stimulation near or greater than the characteristic frequency. The nonlinearity can be observed at the lowest levels of stimulation, 70–80 dB SPL, for which measurements could be made. The nonlinearity extends to lower frequencies and the baslar-membrane transfer function tends to broaden as SPL is increased. Rapid post-mortem changes occur in the cochlea. The amplitude of the transfer ratio (basilar membrane/malleus) decreases 10–15 dB over a period of several hours, with a downward shift of 1.5–3 kHz in the characteristic frequency of the basilar membrane at a given location. The low-frequency slope of the transfer ratio settles to 6 dB/oct by six hours after death. The slope of the phase of the transfer function increases as the characteristic frequency decreases. The transient response was studied using acoustic clicks of approximately 150 μsec in duration, presented in sequences of 100 000 to 400 000. The transient response has an early component which has a fast decay and a second component which has an extremely slow rate of decay and displays nonlinear behavior.
Cochlear Mechanics, Nonlinearities and Cochlear Potentials
Authors: Dallos Peter , Cheatham Mary Ann
Published: October 2005

An up-to-date description of the relationships among stimulus-related cochlear potentials and various mechanical events in the inner ear is presented. Of special interest is to consider (1) how well the mechanical tuning characteristics (amplitude and phase) of the basilar membrane are represented in cochlear microphonics and summating potentials, (2) what these potentials reveal about the mode of excitation of the two groups of sensory cells of the cochlea, and (3) how nonlinearities are reflected in the recorded electrical responses.
A Study of the Effect of Bottom Topology on Long-Range Sound Propagation in the South Pacific
Authors: Bannister R. W. , Denham R. N. , Browning D. G. , Thorp W. H.
Published: October 2005

Previous experiments in the South Pacific have shown that bottom features have a significant effect on sound channel propagation when observed at a bottom-mounted hydrophone A comparison is made of a similar bottom-mounted system with a hydrophone suspended at the sound channel axis in mid water using data obtained during the KIWI ONE Experiment along a 6000-NM track from New Zealand to South America. The effect of the East Pacific Rise and the Louisville Ridge on the observed propagation loss from shots detonated at the sound channel axis is discussed.
Influence of the Subsurface Sound Channel on Long-Range Propagation Paths and Travel Times
Authors: Shaffer J. D.
Published: October 2005

Explosive sources were detonated at shallow depths in two long-range deep ocean experiments. Signals were recorded from a shallow hydrophone in one experiment and from a SOFAR channel hydrophone in the other. The propagation was strongly influenced by subsurface sound channels. The shot arrival patterns determine the convergence zone locations and the sound velocity of the subsurface channel. Energy was detected which traveled more than 800 km through the subsurface channel.
Surface Duct Propagation Loss Measurements Using Explosive Sources
Authors: Keir D. L. , Townsen R. W.
Published: October 2005

In a recent ocean experiment, explosive sound sources at a depth of 18 m were used to measure surface duct propagation loss at frequencies from 0.4 to 20.0 kHz, ranges from 1 to 32 kyd, and hydrophone depths from 6 to 180 m concurrently with detailed environmental sampling. These measurements were part of the experiment described in papers W4 and W5 at the 84th Meeting [J. Acoust. Soc. Amer. 53, 332(A) (1973)]. The investigation covered the low-frequency cutoff due to leakage out of the duct and the high-frequency rolloff due to surface scattering and attenuation. The explosive signals were recorded broad band and the surface duct arrivals were analyzed through 13-oct filters. Three sets of these measurements using explosive sources were made alternately with four sets of similar measurements using towed projectors. Comparisons between the two types of measurements showed an overall agreement. Explosive sources in addition to towed projectors were used to partially alleviate the encountered dynamic effects of the mixed surface layer on underwater sound propagation loss. Results indicate that certain frequencies and hydrophone depths for each of the data sets gave less propagation loss than for other cases.
Application of Normal Mode Theory to an Ocean Stratified in Depth and Range
Authors: Kanabis W. G. , DiNapoli F. R.
Published: October 2005

In both deep and shallow water the stratification of the medium quite often varies significantly with range as well as depth and thus affects the nature of acoustic transmission. In these cases a model of acoustic propagation should be able to accommodate the effect of such changes in the stratification of the ocean. A computer-oriented procedure with its foundations in normal mode theory has been developed for problems of this type. Arbitrary changes in velocity profile, water depth, and bottom composition with range can be accommodated. The effect of mode conversion is included in the analysis. The theoretical procedure is discussed and the results are compared to values obtained from a deep-water low-frequency experiment for which the velocity profile changed significantly with range. [This work was supported by the Naval Ship Systems Command.]
Sound Propagation in an Epstein-Type Under-Ocean Duct
Authors: Nomady V. G. , Überall H.
Published: October 2005

We investigate the sound propagation in a deep ocean channel with an Epstein-type velocity profile using the normal-mode approach. Our treatment includes the effects of earth curvature, and the propagation of pulsed signals. The modes are obtained as the residues in a pole series arising from the Watson transformation. Intensity versus range curves over a curved earth are given both for phased and random modal sums. Dispersion curves for phase and group velocities of the modes are obtained. Arrival times in terms of the group velocities are shown to be inverted (the lowest-order, closest-to-axis mode arrives last) in agreement with experiment, but in contrast to the predictions of a parabolic profile [P. Hirsch, J. Acoust. Soc. Amer. 38, 1018 (1965)]. Our Epstein parameters were chosen to reproduce an equivalent profile that applied to the long-range propagation experiment in the southern ocean [A. C. Kibblewhite, R. N. Denham, and P. H. Barker, J. Acoust. Soc. Amer. 38, 629 (1965)]. [Supported in part by the Office of Naval Research.]