bluuebunny/crossref_metadata_2025 huggingface dataset:
On a Dynamical Mechanical Model of a Bat's Middle Ear
Authors: Fleischer Gerald
Published: October 2005

An enlarged model of a bat's middle ear (diameter of the ear drum is 20 cm) was made out of steel, lead, and aluminum. The model allows the variation of the tension of the tympanic membrane, the fixation of the malleus, the stiffness of both articulations of the ossicular chain, and the rigidity of annular ligament. Furthermore insertion and force of both middle-ear muscles can be altered, as well as size and location of the orbicular apophyse. (The latter is an additional bulky mass of bone at the malleus, present in bats, in some insectivores, and in some rodents.) Frequency characteristic and the mode of vibration of the ossicular chain will be shown after stimulation with sound as well as with a punctually applied mechanical movement. Measuring transducers are piezoelectric elements. The influence of some of the above mentioned parameters on the transmission of vibration will be demonstrated. Finally the model will be stimulated with music and speech by means of an acoustical and a punctually applied mechanical analog signal. The recording from the base of the stirrup will be presented to the auditorium as playback of a tape recording.
The Temporal Relationship Between Motion of the Basilar Membrane and Initiation of Nerve Impulses in the Auditory Nerve Fibers
Authors: Konishi T. , Nielsen D. W.
Published: October 2005

It has been suggested that the initiation of nerve impulses in the auditory nerve fibers is associated with the deformation of the basilar membrane toward the scala vestibuli. In order to verify this possibility, the temporal patterns of nerve impulses of the auditory nerve fibers were examined in the guinea pig, when the basilar membrane was statistically displaced. This displacement was produced by driving the round window membrane with an electromechanical transducer, after the helicotrema had been plugged with bone wax. The electrical signal to the transducer was a trapezoid wave. The hair-cell responses to this trapezoid motion, recorded from the scala media, demonstrated a unidirectional displacement of the basilar membrane. Our results indicate that the displacement of the basilar membrane toward the scala tympani causes the tonic excitation in about 45% of the primary neurons and the tonic inhibition in 3%. Displacement in opposite direction shows the reverse effects. About 20% of our total data showed responses during rising and/or falling period of the trapezoid stimuli. These responses were observed in about 50% of the fibers with middle or low best frequencies. [Supported by NINDS Grant.]
Placement of Electrodes for Activation of VIIIth Nerve
Authors: Cowden David , Walloch Richard
Published: October 2005

The goal of this study is to supplement recent attempts to use electrical stimulation as a hearing prosthesis in cases of sensorineural hearing loss by examining various placements for the stimulating electrodes. In the basal turn of an anesthetized guinea pig, two electrodes were placed in scala tympani and two were placed in scala vestibuli. A fifth electrode was placed in a neck muscle. These electrodes were used five times in each possible pairing to deliver bipolar pulses with a 0.5-msec duration. The order of use was random. The threshold in microamperes for an evoked potential recorded from the contralateral auditory cortex and the threshold for a twitch in the facial muscles were obtained in a double blind manner. When two stimulating electrodes in the cochlea were employed, the threshold for an evoked potential was 156 μA and 3610 μA were needed before a muscle twitch could be detected. Different placements of the two electrodes within the cochlea did not significantly affect their performance. When a single intracochlear electrode and a muscle electrode were used for stimulation, 92 μA were needed to evoke a cortical potential and 557 μA caused a muscle of the face to contract. Because of the larger range, bipolar is preferable to monopolar stimulation of the auditory system. [Supported in part by the Deafness Research Foundation and the National Institute of Neurological Diseases and Stroke.]
Changes in the Auditory Nerve Evoked Potential after Intense Sound Stimulation
Authors: Mitchell Curt , Brummett Robert , Vernon Jack
Published: October 2005

Intense sounds were found to produce a decrement in the nerve evoked potential (NEP) at a lower sound pressure level than that which produced a decrement in the ac cochlear potential. Both types of potentials were recorded from the round window of guinea pigs. Guinea pigs were exposed to pure tones of 3, 4, 6, and 12 kHz, at 95–115 dB SPL (5 dB below the maximum cochlear potential output), for 15–30 min. These intensities produced no noticeable effect on the cochlear potential but produced a marked decrement (up to 30 dB) in the NEP. The greatest loss in the NEP wa at 12 oct above the stimulating frequency. These findings correspond to the reported shifts in hearing thresholds.
Discrimination of Spectrally Weighted Speech by Hearing-Impaired Subjects
Authors: Thomas Ian B. , Pfannebecker G. Barry
Published: October 2005

Recent work by Martin, Osberger, and Pickett [J. Acoust. Soc. Amer. 52, 184(A) (1972)] shows that for both normal and hearing-impaired subjects, F1 causes considerable masking of F2 transitions at the higher intensity levels typically necessary for the hearing impaired. Accordingly, we have processed normal speech to alter the relative intensities of F1 and F2 over a considerable range and presented this processed speech to hearing-impaired listeners. We have also presented normal (unweighted) speech to the same listeners at the same true rms level as a comparison. Spectral weighting was achieved by altering the attenuation slope of a high-pass filter having a cutoff frequency of 1600 Hz. Slopes of 6, 12, 18, and 24 dB/oct were considered. Intensities of weighted and unweighted speech were 20, 30, 40 dB above the speech reception threshold for unweighted speech. Results show that weighting usually increases discrimination for a given intensity level, but the most desirable attenuation slope changes as a function of intensity level. Discrimination gains are typically small (<20%) and best in the marginal hearing conditions (20 and 30 dB SL). [Work supported by NIH.]
Evaluating Communication Systems with Respect to Both Speech Intelligibility and Speaker Identification
Authors: Williams C. E. , Mosko J. D.
Published: October 2005

Communication systems which involve extensive speech processing may yield high intelligibility and yet fail to transmit characteristics associated with the talker (identity, vocal effort, expressive state, etc.). Some exploratory studies have been conducted to determine if the modified rhyme test (MRT) can be utilized to evaluate both the capability of communication systems to transmit intelligible speech and the features of talkers' voices that enable listeners to identify them. Tape recordings were made of each of five selected speakers reading different randomizations of MRT word lists. Single-speaker lists (50 words by a given speaker) and multiple-speaker lists (10 words by each of the five speakers, in random order) were constructed for presentation to listeners. Training tapes were also constructed to familiarize listeners with the speakers' voices. The training tapes and test tapes were processed through two vocoders and the output tapes, along with the unprocessed tapes, were presented to groups of listeners. Intelligibility scores obtained for the single-speaker and multiple-speaker lists and speaker identification scores will be presented and discussed.
Interference Test Evaluations of Telephone Speech, Quality
Authors: Nakatani L. H. , Dukes K. D.
Published: October 2005

The interference test for speech quality evaluation was investigated for sensitivity and validity with various types of telephone speech. Three components of the telephone system (microphone, transmission channel, and earphone), each with two alternatives (high fidelity or telephone), were used in all possible combinations to obtain eight types of telephone speech. The interference test was sensitive enough to measure the amount by which each telephone component degraded speech, even though all the speech types were highly intelligible according to articulation tests. Consistent and systematic relationships were observed between the interference test results, articulation test scores, and subjective evaluations of the same speech types, indicating that the interference test is a valid procedure for measuring speech quality. Moreover, by simply adding up the interference test measures associated with the telephone components, the measure for a speech type with any combination of the components could be accurately predicted. The results confirm that the interference test yields sensitive, valid, and additive measures of speech quality.
Speech Reconstituted from Spectra of Reduced Dimensionality: A Study of Intelligibility
Authors: Li K. P. , Hughes G. W. , House A. S.
Published: October 2005

In this preliminary study, we attempt to relate the space defined by a statistical [principal component] analysis of speech spectra to perceptual space represented by intelligibility scores. Speech spectra were represented in terms of a varying number of dimensions [3, 5, 7, 10, 15, and 35], each corresponding to a different degree of statistical accuracy, and the waveform was reconstituted from the reduced spectral data by means of inverse FFT computation [K.-P. Li, G. W. Hughes, and A. S. House, J. Acoust. Soc. Amer. 49, 134(A) (1971)]. Consonantal intelligibility scores for isolated monosyllabic utterances by one talker were determined from the responses of 12 listeners to a total of 553 test items. The average score increases monotonically from 47% to 75% as the spectral dimensionality varies from 3 to 35. Along with the number of dimensions, manner and place of consonant articulation and the effects of the details of the reconstitution process enter into the relationship between statistical accuracy and intelligibility.
Acoustic Radiation Pressure and its Use in Power and Intensity Determinations
Authors: Rooney J. A.
Published: October 2005

The radiation force upon an object placed in a sound field can be used to determine the acoustic power or intensity. Two types of test objects have been extensively used as targets in radiation pressure determinations. The first is either an absorbing or reflecting target which intercepts the entire sound beam. For the case of a traveling plane wave in an open vessel impinging on an absorbing target, the radiation force F equals the acoustic power divided by the velocity of sound c even when nonlinearities of the propagation medium are taken into account. The second type of test object used for calibration is a sphere. For an elastic sphere of radius a surrounded by a nonviscous fluid in a traveling plane wave F = Yπa2I/c. Here I is the local intensity and Y is the acoustic radiation force function. Experimentally the forces on targets have been determined by observations of deflections for pendulum arrangements, measurement of change in target weight using analytical balances, measurement of change in displacement of targets attached to floats, and determination of the force necessary to maintain the target in equilibrium. For measurements of low acoustic powers, it is necessary to minimize fluctuations associated with building vibration, convection currents, and interfacial effects. [Work supported by HAS project at the University of Vermont and by the National Institutes of Health.]
Acoustic Results Obtained with an Upper-Surface-Blowing Lift-Augmentation System
Authors: von Glahn U. , Reshotko M. , Dorsch R.
Published: October 2005

The noise caused by the interaction of the exhaust jet and the wing was measured under static conditions for several versions of a small-scale STOL engine-over-the-wing configuration. Three basic nozzles were tested: a circular nozzle with deflector, a 5:1 slot nozzle with and without deflector, and a 10:1 slot nozzle. The wing included a flap lift-augmentation system with flap deflection angles of 20° for a takeoff condition and 60° for an approach condition. Far-field noise data are presented for nominal jet pressure ratios of 1.25 to 1.7 for the flyover mode. The data are discussed in terms of SPLs and normalized sound pressure spectra: comparisons with nozzle-only data are also made. The model OASPL near 90°—measured from an engine inlet—follow a 6th–7th power relationship with jet velocity compared to an 8th–9th power law for the jet alone. Only minor acoustic differences were obtained between the two flap deflection positions. The most significant noise reduction was achieved with the 10:1 slot nozzle. Implications of extending the small-scale model acoustic data to a full-scale aircraft are discussed and indicate a sizable noise attenuation may be achieved owing to wing shielding.
Sound Propagation in a Surface Duct with a Rough Surface
Authors: Bucker H. P. , Thompson J. L.
Published: October 2005

Sound propagating in a surface duct is partially scattered by surface reflections. This can be accounted for in propagation models by first using a surface reflection coefficient with modulus less than one and then by adding a ray theory correction representing sound scattered directly from the surface to the receiver. An outline of the theory is presented, and calculated propagation loss curves are compared to experimental values taken during recent sea observations.
Amplitude Fluctuations in Shallow Water Acoustics
Authors: Barakos P. A.
Published: October 2005

Large amplitude and phase fluctuations in underwater acoustic wave fields occur and are primarily due to the temporal and spatial variability of the water and its boundaries. The amplitude part of this phenomenon is investigated by obtaining, simultaneously, time and space series of environmental and acoustic data from sensor arrays fixed in space, in shallow coastal water off southern Califormia. The signal output from a nuclear powered ultrasonic source, mounted on a tripod 3 m above the bottom is monitored continuously by a hydrophone 150 m away. The source radiates three CW pulses every 3 sec, sequentially at 30, 45, and 60 kHz. A sampling interval of 3 sec was used. Time series of temperature from a vertical thermistor array, surface waveheight, and the two horizontal components of water motion from an EM current meter are obtained. Two dominant frequencies, one associated with the surface swell and the other with the internal waves in this area, are found in both the acoustic and the environmental data. Statistical and deterministic techniques are employed to clarify the interaction between acoustic and environmental wave fields.
Sound Speed Perturbations Due to Internal Tides
Authors: Mooers Christopher N. K.
Published: October 2005

Internal tides are perhaps the most prevalent, and largest amplitude, internal gravity waves in the ocean. They are commonly generated by the scattering of surface tidal energy into internal modes when the surface tides propagate on to continental shelves. A portion of the internal tidal energy propagates into the deep ocean. One of the effects of internal tides on underwater acoustic propagation is to perturb the temperature and salinity versus depth profiles, and, thus, the sound speed versus depth profile. Starting with temperature and salinity versus depth profiles from near Eleuthera Island, the internal tide eigenfunctions, as well as the sound speed profile, have been computed for a water depth of 4500 m. Assuming a value for the vertical displacement amplitude of a first vertical mode internal tide, the perturbed temperature and salinity profiles have been computed. From these perturbed profiles, the consequent perturbed sound speed profiles have been computed for cases of maximum up and down internal tide displacement. The first mode internal tide has no vertical displacement at the sea surface and bottom and a maximum near the base of the main thermocline (depth of about 1200 m). Since the SOFAR axis is also near the base of the main thermocline, and since the pressure effects on sound speed are predominant below the SOFAR axis, the sound speed perturbation due to the first mode internal tide is greatest at a depth (about 550 m) above the SOFAR axis. An internal tide with a maximum vertical displacement of 10 m produces a maximum sound speed perturbation of ±0.7 m/sec.
Loudness Summation between Tones from Two Loudspeakers
Authors: Scharf B.
Published: October 2005

Loudness summation between two equally loud, 500-msec tones centered on 2000 Hz was measured in an anechoic room as a function of the frequency separation, ΔF, and onset time difference, ΔT, between the tones. One tone was presented via a loudspeaker 3 m from the subject and 45° to the left of his median plane, the other tone via a loudspeaker 45° to the right. A comparison 2000-Hz tone was presented via a third speaker in the median plane. Overall loudness increased with ΔF once the critical band was exceeded. When ΔT was 0 msec, loudness summation at 45, 65, and 85 phons was very similar to that between two tones presented through a single earphone. As ΔT increased from 0 to about 100 msec, loudness summation declined gradually; beyond 100 msec, it declined more rapidly. The Haas or precedence effect was evident at ΔT's less than 40 to 60 msec and ΔF's less than about 1000 Hz, where the six subjects usually heard a single sound originating toward the side of the leading loudspeaker.
Binaural Detection Models: Varying Signal Parameters, Noise Identical at the Two Ears
Authors: Osman E.
Published: October 2005

A previously published statistical decision model of binaural detection called the correlation model [J. Acoust. Soc. Amer. 50, 1494–1511 (1971)] is evaluated further for data obtained with tonal signals in noise, where noise is identical at the two ears and of constant amplitude while signal parameters are varied. Equations are based on the model's expressions for the conditional density functions. Predictions of BMLDs (binaural masking level differences) for variation of interaural amplitude ratio and phase of signal are evaluated with regard to data of Egan [J. Acoust. Soc. Amer, 38, 1043–1049 (1965)] and Colburn and Durlach [J. Acoust. Soc. Amer. 38, 93–103 (1965)]. Comparisons of the correlation model, the equalization-cancellation model [Durlach, J. Acoust. Soc. Amer. 35, 1206–1213 (1963)], and a lateralization model [Hafter, J. Acoust. Soc. Amer. 50, 1116–1122 (1971)] are discussed. Predictions for sets of psychometric functions resulting from binaural detection under several interaural listening conditions are compared to data and psychometric functions presented in Egan [Perception Psychophys. 6, 209–215 (1969)]. [Supported by NIH and CUNY.]
Binaural Interaction between Real Tones and the Cubic Distortion Product, 2f1 − f2
Authors: Hafter E. R. , Leshowitz B. S. , Jenkins G. S.
Published: October 2005

Several investigators have shown that the amplitude of the cubic difference tone, 2f1 − f2, does not follow the rules of nonlinear distortion observed for stimuli at high levels. They have concluded that the site of the distortion is certainly higher than the middle ear and perhaps central to the mechanical filtering of the basilar membrane. In this work, we further examine the place of generation by asking whether the cubic difference tone is subject to binaural interaction. To this end, two primary tones at frequencies f1 and f2 were presented to one ear while a third tone at frequency f3 (f3 = 2f1 − f2) was presented to the other ear. In a two-alternative forced choice, subjects were able to discriminate differences in the phase of f3. This demonstration shows that the distortion tone is produced distal to the neural mechanisms of binaural interaction. One advantage of our technique is that it does not confound the distortion stimuli with the addition of probe tones. Consequently, binaural interaction provides a potentially sensitive technique for measuring the level and phase of distortion products.
Detection of Time Differences and Level Differences from a Position away from the Median Plane
Authors: Jeffress Lloyd A. , Sharpley Alan D.
Published: October 2005

By the use of an interaural phase difference of 90° a 50-Hz band of noise, centered at 500 Hz was delayed to the right ear by 0.5 msec. The resultant sound was perceived as lying well to the left of the median plane. To this continuous noise was added a signal from the same noise source so arranged in phase that the signal plus masker appeared to lie either inward or outward from the continuous masker. The signal plus masker could also be moved inward or outward by introducing a difference of level into the two earphone channels. Detection of these movements was compared with detection of movements away from the median plane by employing the N0Sπ condition with α=90° to obtain a time difference, or α=0° to obtain a level difference relative to the median plane. The results show that detection of a time difference from a position away from the median plane is inferior to detection of a time difference around the median plane. However, the results for a difference of level showed no such advantage for the median plane; detection was the same from both reference positions. The findings are taken as further indication of the relative independence of the time mechanism and the level mechanism of the auditory nervous system. [Supported in part by a grant from the Public Health Service, National Institute of Neurological Diseases and Stroke.]
Loudness Enhancement with Monaural, Binaural, and Dichotic Stimulation
Authors: Elmasian R. , Galambos R.
Published: October 2005

In this study of the loudness enhancement phenomenon [e.g., Galambos et al., J. Acoust. Soc. Amer. 51, 141(A) 1972; Sokolich and Zwislocki, J. Acoust. Soc. Amer. 52, 141–142(A) 1972], a tone burst, Tc, was followed 100 msec later by a 70-dB tone burst, S1. Subjects matched S1 in loudness by varying the intensity of a tone burst, S2, presented 1.5 sec. after S1. Tc, S1, and S2 were all 20-msec 5-kHz signals. Increasing Tc in 10-dB steps from 60 to 100 dB SPL yielded a progressively increased subjective loudness of S1. The monaural and binaural paradigms produced greater and more reliable loudness enhancement than the dichotic. With Tc at 100 dB, loudness enhancements averaged over 15 dB for eight naive subjects tested monaurally and eight binaurally. With Tc less intense than S1, a small loudness decrement resulted. With Tc set at 90 dB and S1 at 40 dB, enhancements of over 30 dB, the largest so far observed, were regularly reported in the monaural paradigm.
Monaural and Binaural Free-Field Speech Reception under Noise and Reverberation
Authors: Nábělek Anna K. , Pickett J. M.
Published: October 2005

Speech reception was studied in a single sound-treated room at reverberation times T=0.3 and T=0.6 sec, to compare binaural and monaural reception in the presence of an impulsive noise (16 imp/sec) and a quasisteady noise (a babble of eight voices). The speech and noise sources were fixed at locations, relative to the listener, to give the largest advantage for binaural reception. Binaural gain is taken as the difference in speechto-noise ratios for 60% correct speech reception comparing binaural and monaural results. At T=0.6 sec, binaural gain was 3 dB for both types of noise. At T=0.3 sec the gain was 5 dB for the babble and 4 dB for the impulsive noise. The longer reverberation caused a reduction in reception in both binaural and monaural conditions. These effects were larger for the impulsive noise and for low S/N ratios. The largest reverberation effect reduced reception from 77% to 53% words correct. [Supported by Gallaudet College.]
The influence of Timbre on Apparent Location of Sound in the Median Sagittal Plane
Authors: Butler Robert A.
Published: October 2005

High-pitched tones in the median sagittal plane (MSP) appear to originate above lower-pitched tones irrespective of their actual location. But, is it pitch that governs these judgments? Data from the present experiment suggest that it is not. Pulses were presented at the same repetition rate, 200/sec, but were filtered differently. Twelve Os were asked to identify which of five loudspeakers, 15° apart, generated the stimuli. Each loudspeaker presented the sounds an equal number of times. Their positions ranged from −30° to +30°in the MSP. Those pulses whose spectral content centered about 630, 1600, and 2500 Hz were judged to originate low, median, and high, respectively, in the MSP, despite the sameness of their pitch and despite their actual locations. When the spectral content of the pulses centered about a still higher frequency, 6300 Hz, Os now located their source correctly. Hence, in the MSP, timbre, not pitch, governs location judgments. Whether the judgments are correct depends on the spectral content of the sound.
The Precision of a Human Underwater Sound Localization Response
Authors: Feinstein S. H.
Published: October 2005

The precision of a human underwater sound localization response was defined as the correspondence between the objective azimuth of the sound source and the azimuth indicated by a pointer controller by the subject. It was determined that the pointing response had an average error of 5.98 when the subjects pointed to a visual target located in the frontal plane. When the subjects were required to locate an acoustic target located at some point in 360°, the average error was 19.2°. Front to back (or back to front) reversals occurred at 0° and 180°±45° and amounted to 15.1% of the total responses. A replication of the visual target localization in 360° yielded an average error of 6.98° After 240 training trials in which the subject was allowed to visually correct his auditory localization, the average error in 360° was 13.1° Reversals were reduced to 7.1% of the total responses.
Subliminal Underwater Sound Localization
Authors: Hollien H. , Kinney J. , Feinstein S. , Hollien P.
Published: October 2005

Recently Hollien [“Underwater Sound Localization in Humans,” J. Acoust. Soc. Amer. 52 (1972)] suggested that individuals attempting to localize sound underwater may utilize kinesthetic cues for this purpose. In an effort to obtain data on this issue, two experiments were conducted; in both cases the divers were dressed only in bathing suits and life support equipment. In the first experiment, signals were provided at a pressure level that was approximately 10 dB below the divers' threshold at each of the respective frequencies tested. In the second study, signal strength was at 105 dB SPL (re 0.0002 dyn/cm2), but it was masked out by a sawtooth signal delivered to the divers' auditory mechanism via a set of underwater earphones held against their heads by a neoprene hood. Data from both investigations suggest that underwater sound localization is an auditory function, as there was no evidence that any information was obtained by tactile sensation.
Small Signal Suppression in a Class of Optimal Adaptive Beamformers
Authors: Varga R. S.
Published: October 2005

Optimal adaptive beamformers are often designed to minimize the beam noise response while maintaining a fixed response to an incoming signal. In the real world, improvements in detection performance that could result from noise rejection may not be realized because of a signal suppression effect. In this paper, analysis of a particular adaptive beamformer (ABF) shows the signal suppression effect to be related to the reception of signals whose wavefront departs from an assumed nominal wavefront (usually planar). Experimental results demonstrate that slight distortions in the wavefront of weak signals can cause significant degradation. Moreover, the degradation in signal response for the ABF is uniformly larger than that of the delay and sum beamformer (DSBF), for a given amount of wavefront distortion. In addition, ABF signal degradation is found to be not only dependent upon the amount of wavefront distortion, but upon the background noise field as well. This result is specific to the ABF and not the DSBF. In particular, ABF signal suppression is shown to increase as the noise field anisotropy increases. Thus when the conditions for ABF noise improvement are best, the potential for ABF signal degradation is greatest.
Influence of Input Quantizer Step Sizes on the Processing Gain of Digital Beamformers
Authors: Wang H. S. C.
Published: October 2005

Utilizing a formulation of output power of a digital beamformer with input quantizers of unequal input and output step sizes reported elsewhere [H. S. C. Wang, Quantizer Functions and Their Use in the Analyses of Digital Beamformer Performance (to be published); also see J. Acoust. Soc. Amer. 51, 135(A) (1972)], the optimum quantizer step sizes that yield maximum processing gain are searched by the method of “steepest ascent” with a digital computer. For the case of 2 bits/channel quantization with small input S/N (< −10 dB), the array gain surface as a function of two independent step variables exhibits a maximum that is somewhat greater than the maximum array gain achievable with uniform input quantizers. For larger input S/N (> −10 dB), no maximum can be found, and, as the input S/N exceeds −4 dB, the array gain increases monotonically with respect to both input and output step variables. These phenomena were clarified by a numerical study of a “3-level quantizer” as a limiting case. The large theoretical processing gain at large step sizes is attributed to a threshold effect of the input quantizers.
Effects of Ideal Clipping on Signal to Noise Ratios—A Comparison with Linear Systems
Authors: Hariharan P. R. , Scott R. J.
Published: October 2005

Numerous articles have been published that show there is a S/N ratio loss of 1.17 dB when sinusoidal signal and narrow-band noise, with low input S/N ratio, is passed through a hard limiter. In this paper, we analyze the effects of wideband noise on signals due to clipping. It is shown that the resulting loss in S/N ratio depends not only upon the shape of the input noise spectrum but also on the location of the signal. Results are presented for real world spectra as measured in the ocean, and it is shown that for certain kinds of spectra the loss could be as high as 10 dB.
Focused Optical Imaging Systems for Vibration Measurements
Authors: Clark J. A.
Published: October 2005

Images of a vibrating surface can be formed by focused (lens type) scanning, and holographic (lensless) optical systems. In this paper, methods for adapting focused optical systems to obtain vibration measurements are reviewed. Included in the review are methods for determining the state of vibration from displacement, slope, and velocity measurements. The use of optical, spatial, and temporal filters, as well as reference beam interferometers is described. In particular, recent advances in the design and application of confocal mirror interferometers to vibration measurements are described. Real-time and time-averaging variations of each method are noted. The types of data obtained with each method and procedures for interpreting the data are discussed. Characteristics of the various methods such as sensitivity, cost, and convenience for in-air and in-water measurements are summarized.
Applications of Optical Holographic Interferometry in Acoustics Measurements
Authors: Cain D. , Johnson C. , Mayer G.
Published: October 2005

Holographic techniques are presently in wide use as an instrumentation tool in the area of vibration analysis. This paper outlines the basic concepts of holography and reviews several state-of-the-art holographic techniques that are being used or could be used for research tools and data aquisition in acoustics. The advantages and disadvantages of time-average, real-time, double-pulsed, stroboscopic, and temporarily modulated holographic interferometry and speckle interferometry are discussed. The various holographic techniques are compared with more conventional vibration measurement methods with regard to cost, accuracy, completeness of data, and range of applicability. In conclusion, several potential applications in acoustics research are presented for consideration.
Electromagnetically Generated Elastic Stress Waves in Rods and Pipes
Authors: Leftheris Basil P. , Lee P. C. Y. , Cakmak A. S.
Published: October 2005

A convenient laboratory method for producing highamplitude elastic stress waves in rods and pipes is described and compared with existing impact methods [C. S. Yang and R. J. Hassett, “Transient Stresses in Axisymmetric Bodies of Varying Area,” Exp. Mech. 12, No. 7 (July 1972)]. The method employs electromagnetic repulsion of good electrical conductors to convert electromagnetic energy to mechanical energy stored in the elastic stress wave. A description of the apparatus and its design features is given as well as equations that predict the amplitude and duration of the elastic waves. The apparatus was used to study the stress wave characteristics of pipes. In particular, a stress wave with speed of propagation higher than the longitudinal phase velocity in elastic isotropic solids predicted by Chang, Cakmak, and Lee [K. P. Chang, P. C. Y. Lee, and A. S. Cakmak, “Propagation of Axially Symmetric Waves in Hollow Elastic Circular Cylinders Subjected to a Step-Function Loading,” J. Acoust. Soc. Amer. 49 (1971)] was found experimentally using the new method.
Sound Propagation over Open Terrain from a Source near the Ground—A Brief Review
Authors: Sutherland Louis C.
Published: October 2005

The noise field generated by a source near the ground can be significantly influenced by reflection and/or absorption by this ground surface. The measurement and prediction of outdoor noise sources must include consideration of this influence. Practical situations where this influence can be significant are categorized. The range of acoustic characteristics of ground surfaces are considered and the corresponding range of ground-to-ground propagation effects reviewed for steady-state noise sources near flat ground surfaces with and without various types of common ground cover. Both theoretical and empirical models for prediction of ground-to-ground propagation effects are considered. Shortcomings in the current state-of-the art are reviewed in order to suggest areas requiring further research.
Atmospheric Ray Tracing
Authors: Roberts B. G. , Bebbs E. H.
Published: October 2005

A study that has received added consideration in the past few years is the propagation of sound in the atmosphere. This was occasioned by the introduction of jet aircraft and the resulting noise which required locating airports in such a position so as to minimize the undersirable effects. A study of the acoustical ray paths in the atmosphere would provide criteria for selecting an appropriate location. A computer program has been written for the CDC-3800 computer to predict the acoustical ray paths in the atmosphere, as well to determine the transmission loss in air. The program accepts data in the form of a temperature or sound speed versus height profile. A wind velocity profile may also be entered. The program will produce a printplot of the ray trajectories, as well as a printplot of the transmission loss. A CALCOMP plot of the ray trajectories may also be obtained. By observing the locations where the rays strike the surrounding terrain and the resulting transmission losses, a suitable location can be obtained to produce the least annoyance.
Absolute Determination of Acoustic Intensity by the Method of Radiation Force on a Solid Elastic Sphere
Authors: Averbuch A. J. , Fry F. J. , Dunn F.
Published: October 2005

Hasegawa and Yosioka [J. Acoust. Soc. Amer. 46, 1139 (1969)] have modified King's theory [Proc. Roy. Soc. A137, 212 (1935)] of acoustic radiation force on a solid sphere suspended freely in an inviscid fluid in a plane progressive sound field to include the elastic properties of the solid. Evaluation of the acoustic radiation force function γp(= F/πa2E), where F is the radiation force on the sphere of radius a and E is the mean energy density in the plane progressive sound field, has been extended to cover the range of values of ka (k, the wavenumber) from 0 to 50 for type 440 stainless-steel ball bearings and water, and compared with experimental studies in which wavelength and radius of the sphere have been varied.
A Portable Ultrasonic Radiometer
Authors: Stewart Harold F. , Robinson Ronald
Published: October 2005

The prototype of a portable ultrasonic radiometer for use as a field survey intrument of therapeutic ultrasonic equipment has been developed by the Bureau of Radiological Health. This instrument employs a solenoid balance arm principle. One end of the balance arm has a movable helical coil, which moves inside a fixed helical coil, and the other end has an airbacked target 6 cm in diameter, which intercepts the entire ultrasonic field. Near frictionless rotation of the balance arm is achieved using a jeweled fulcrum. A reference position of the target is predetermined as the null point, and upon application of the ultrasonic power, deflection of the target occurs. Current through the solenoid is used to reposition the target at the null point, and the current required is an indicator of the total ultrasonic power. A digital readout system directly displays this power output utilizing a manual zeroing capability. The instrument provides a wide dynamic range of 100 mW–100 W with a reproducibility error of less than ±10%. The advantages of the resulting system over other measuring systems such as the chemical microbalance, radiation pressure float system, hydrophone, calorimeter, etc., are portability, ease of measurement, digital readout, manual zeroing capability, direct linear measurement method, closed system, ease in setup, and comparable accuracy and reproducibility.
Ultrasonic Field Measurements for Flaw Analysis
Authors: Rose Joseph L. , Meyer Paul A.
Published: October 2005

The purpose of this paper is to introduce experimental sonic field measurement procedures that can be used to analyze ultrasonic transducer wave generation characteristics and wave reflection patterns from specially shaped flaws in solid materials. This work is essential for understanding principles of ultrasonic nondestructive evaluation in homogeneous isotropic materials as well as advanced composites and multilayered bonded structures. Very little work to date has been done on this subject except for the work related to the classical flat bottom hole equivalent that is so widely used in ultrasonic inspection test standards today. It is shown in the paper that sonic field pressure profiles obtained in both pulse-echo and through-transmission modes can be used to characterize flaw shapes, sizes, and locations. The following details are included: (1) Experimentally obtained pressure profiles in solid blocks are compared with results obtained from a theoretical solution for wave propagation in a solid material. The effects of transducer frequency, diameter, and type on the sonic field pressure profile are discussed. (2) Experimental ultrasonic field pressure profile measurements are compared with results obtained from a finite difference two-dimensional computer code for elastic wave propagation across a rectangular flaw in a solid block. Applications of the computer code to other problems in flaw detection are presented. (3) Ultrasonic pressure profiles are presented for wave reflection patterns across such flaws as cracks and elliptically and circularly shaped holes. Guidelines for establishing inspection standards based on this work are presented.
Use of Orthogonal Fields in Magnetostrictive Scroll Transducers
Authors: LeBlanc C. L. , Sherman C. H.
Published: October 2005

A linear magnetostrictive theory is used to investigate the alternating small signal characteristics of a thin-wall scroll transducer polarized and driven with orthogonal magnetic fields. The concept of orthogonal excitation, advocated by researchers in the International Nickel Co., is studied from this linear viewpoint, and values for the effective electromechanical coupling coefficient are presented in terms of the material coupling coefficient k33 derived by applying collinear polarization and excitation magnetic fields along the axis of principal strain. Although the effective coupling was found to depend quite heavily on the magnitude and orientation of the resultant magnetic fields, no case was encountered where the effective coupling exceeded k33. However, it is expected that orthogonal excitation will have genuine advantages under large signal driving conditions, and two special cases of high-amplitude drive (linearized and unpolarized drive) will be discussed.
Gradient Loudspeakers
Authors: Olson Harry F.
Published: October 2005

The directivity of gradient-type loudspeakers depends upon the difference in phase of the generated sound pressures, or powers of the difference in phase of the generated sound pressures, between two or more points in space. The directivity of the conventional wave-type loudspeakers depends in some manner upon wave interference of the sound emanating from the elements of the radiating surface. To obtain any semblance of directivity from the wave-type loudspeaker, the radiating surface must be comparable to the wavelength. Therefore, the dimensions of the wave-type loudspeakers become relatively large in the low audiofrequency range. In contrast, gradient-type loudspeakers are small compared to the wavelength. For sound reproduction requiring directional loudspeakers, the gradient-type loudspeaker provides the features of relatively small size and uniform directivity with respect to frequency.
Analysis of the Operation of Electret-Key Transducers
Authors: Sessler G. M.
Published: October 2005

The operation of electret-key transducers [see G. M. Sessler and J. E. West, Proc. Int. Congr. Acoust., 7th, Budapest (1971), Paper 23 E 1] is studied analytically. In particular, the relations between generated voltage and change in transducer capacitance due to large-amplitude diaphragm displacements are derived for transducers terminated by a combination of resistive and capacitive components. Numerical results for the voltage generated by diaphragm displacements with trapezoidal time dependence are also given. Finally, a comparison of calculated and measured responses is made. With certain modifications, the present analysis applies also to other electret transducers, such as graphic electret tablets, electret line transducers, and electret vibration transmitters.
A Study of Larynx Height in Speech Using the Thyro-Umbrometer
Authors: Ewan William G. , Krones Robert
Published: October 2005

The thyro-umbrometer consists of an array of seven rectangular photocells 14 in. × 1 14in., placed on one side of the subject's neck (arranged so the long axis of the photocells is normal to the surface of the throat) with a point light source on the other side. The shadow of the subject's thyroid prominence is cast on the photocells. The output of each photocell is fed to a small computer, which locates the laryngeal prominence at the level of that photocell producing the least voltage. Preliminary results in tracking the larynx height and F0 reveal that (1) as has been widely reported in the literature, larynx height and F0 are positively correlated, but (2) larynx height is greatly affected by vowel and consonant articulation; specifically, (3) voiceless stops have consistently higher laryngeal position than phonetically similar utterances containing voiced stops. [Supported by the National Science Foundation.]
Perception of Rhythm and Accent in English Words and Phrases
Authors: Pruzansky Sandra , Wish Myron
Published: October 2005

Subjects were presented pairs of three-syllable words and phrases and were asked to indicate how much the elements of a pair differed in rhythm and accent. In one session, subjects read the words aloud; dashes were placed between syllables to make the words and phrases orthographically similar. In another session subjects listened to the pairs spoken by a single speaker; there was no written presentation of the stimuli. Separate multidimensional scaling analyses of the two sets of data revealed that three of the dimensions underlying each set were basically similar, but there were some interesting differences between tasks. The three similar dimensions were related to the location of the syllable with primary stress and the number of stressed syllables. In an earlier study using the same stimulus set and judgment task, Wish had found three dimensions closely corresponding to the present ones. Two dimensions found in the earlier study, where stimulus words had been printed without intersyllabic dashes, now appear to be based on orthographic rather than acoustical differences between stimuli.
Electromyographic Study of the Tones of Thai
Authors: Erickson Donna , Abramson Arthur S.
Published: October 2005

In our desire to study the effects of laryngeal muscle activity on the rather complex use of fundamental frequency changes in a tone language, we have done an electromyographic analysis of the production of the tones of Thai. We chose the Thai language because its five phonemic tones differentiate words primarily by means of characteristic f0 contours. In the experiment, we asked four native speakers to say 45 short sentences. Included in this list were the five tones in nine contexts: the three long vowels /aa ii uu/ and the three labial consonants /b p ph/. Our findings indicate that for all four speakers, the activity of the cricothyroid muscle increases with the raising of f0, and the activity of the strap muscles—the sternohyoid, sternothyroid, and thyrohyoid muscles—increases with the lowering of f0. [This research was supported by the National Institute of Dental Research, NIH Grant.]
Dichotic Perception of Lexical Tone by Speakers of Cantonese and English
Authors: Benson Peter J. , Smith Timothy S. , Arreaga Linda
Published: October 2005

Current models of dichotic listening do not predict whether linguistic word tones would be perceived more accurately by the right or the left ear. In this experiment five Cantonese words, all having the segmental structure /ma/ but differing in tone, were presented dichotically to two groups of Ss. One group consisted of right-handed native speakers of Cantonese, the other of right-handed native speakers of English. Ss in both groups were first trained to identify the tones using iconic tone letter symbols, and were then tested dichotically. Overall, there was a slight but nonsignificant left ear effect for both groups. In the Cantonese group, four Ss showed a left ear effect, and three showed a right ear advantage. In the English group, three Ss showed a slight right ear effect, three Ss a left ear effect, and one S no ear differences at all. These results suggest that individual subjects are probably using somewhat different strategies in identifying lexical tones, and would not support claims that tonal stimuli are perceived in either a linguistic (speech) or a musical mode of processing.
Conventional and High-Frequency Hearing of Aviators as a Function of Flight Time and Type Aircraft
Authors: Fletcher John L.
Published: October 2005

Conventional (500–6000 Hz) and high-frequency audiograms (4000–18 000 Hz) were obtained from aviators flying jet (prop or pure) fixed wing and from others piloting rotary wing (helicopter) craft. These pilots varied widely within the three categories of aircraft, i.e., jet, prop, or rotary, in the number of hours logged in the aircraft. Data were therefore analyzed in terms of type aircraft flown and exposure category (based on number of hours flown). Results indicate a progressive decline of hearing level with number of hours flown, with the decline first detected at the frequencies above the conventional range, gradually progressing with continued exposure into the conventional (and therefore speech) range. Results are discussed in terms of the relative hazard of various types of aircraft, and in terms of the importance of tests of high-frequency hearing to hearing conservation. [Supported by the Office of Naval Research, Engineering Psychology Programs, Work Unit NR 197–002.]