bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental ocular lesions produced by high-frequency ultrasound
Authors: Lizzi F. L. , Packer A. , Coleman D. J.
Published: October 2005

Animal experimentation has been performed to study the effects of high-intensity, high-frequency (9.8 MHz) ultrasound on tissues of the eye. Several sets of rabbits have been exposed to examine alterations of the cornea, lens, retina, and choroid. Lenticular damage appeared first as haze cataracts observable with slit-lamp techniques. These were found to remain unchanged over observation periods as long as four months. Larger exposure levels resulted in the formation of totally opaque cataracts within the hazed lens segment. The appearance of haze together with their threshold exposure levels is consistent with thermally induced damage. Threshold curves resemble those predicted for thermal lesions in brain tissue. The shortest exposure time resulting in cataract formation was 35 msec. Irreversible corneal damage could also be produced after short exposures (100 msec). Corneal lesions appeared on slit-lamp examination as spherical opacities centrally situated within the corneal stroma. Chorio-retinal lesions were produced via trans-scleral insonification. Visible changes in the choroid are clearly observed during high-intensity insonification of albino rabbits. Transitory and permanent changes in the choroid were produced. Alterations in the overlying retina became visible within approximately one day subsequent to insonification. [Work supported by NIH.]
Theory of semantic and syntactic control of speech timing
Authors: Cooper W. E.
Published: October 2005

A theory is proposed to account for semantic and syntactic effects on syllable duration. The theory is based in part on experimental studies by the author in which a sentence-reading task was used to determine effects of semantic and syntactic variables, quasi-independent of phonetic factors. The results of the studies motivated constraints on the operation of two processing levels, representing semantic and syntactic modes. The distinction between the two levels was prompted by an empirical difference in the domain over which timing effects operated. Syntactic effects were restricted to the domain of a single clause, whereas semantic effects were not. Predictions of the theory are discussed within the framework of a programmatic line of research. [Work supported by an NSF Graduate Fellowship, NIH Grant HD-05168, and grant from the Slosh Foundation.]
Shifts in vowel perception as a function of speaking rate
Authors: Verbrugge R. R. , Shankweiler D. P. , Strange W.
Published: October 2005

In rapid speech, acoustic analysis reveals that steady state vowel targets characteristically are not reached. Lindblom and Studdert-Kennedy [J. Acoust. Soc. Am. 42, 830–843 (1967)] found in an experiment with synthetic speech that listeners showed a shift in the boundary between medial vowels /ε/ and /U/ with variations in the rate and direction of formant transitions. Apparently, perceivers compensate for simulated articulatory undershoot by perceptual overshoot. An experiment with natural speech demonstrated shifts in the acoustic criteria listeners employed in vowel recognition as a function of perceived rate of utterance. Nine American English vowels in /p-p/ environment were produced by a panel of 15 talkers in a fixed sentence frame. The unstressed, rapidly articulated /p-p/ syllables were excised from the tape recording and assembled into listening tests. In one condition, the /p-p/ targets were prefaced by three slowly articulated syllables /hi, ha, hu/. In the other test condition, no precursors were present. Misperception of target vowels occurred with significantly greater frequency when they were preceded by precursors. The results showed evidence of perceivers' adjustment to tempo (as hypothesized by Lindblom and Studdert-Kennedy) on the basis of preceding segments of speech. [Work supported by NIH.]
Specification of beam areas for medical ultrasonic transducers
Authors: Haran M. E. , Herman B. , Harris G.
Published: October 2005

In the development of performance standards for medical ultrasonic equipment, it is necessary to determine an acceptable method for specifying and measuring the beam areas of ultrasonic transducers. In this study, the beam areas from selected ultrasonic diagnostic and therapy transducers were evaluated using two different techniques: a miniature hydrophone scanning system and an acoustic-optic interferometric system. The beam area was defined as the area of the surface in the plane of the receiver consisting of the points at which the intensity is greater than a specified percent of the spatial maximum intensity in that plane. Beam areas were determined for values of this percentage from 1 to 50. Plane wave assumptions were made in determining the intensity. The significance of this study with regard to both medical uses and bioeffects investigations will be discussed.
Evaluation of commercially available portable ultrasonic therapy wattmeters
Authors: Robinson R. A. , Haran M. E. , Herman B. A.
Published: October 2005

Four commercially available portable ultrasonic wattmeters, employing the radiation force principle, were evaluated for their capability of measuring ultrasonic power output in the therapy range (1–30 W). The wattmeters included two American-made models, one English, and one Russian model. They were tested for the following measurement characteristics: reproducibility, sensitivity, resolution, and temperature and frequency dependence. An intercomparison of the four instruments was made from the results of these measured characteristics. In the absence of a national ultrasonic measurement standard, power output from a reproducible ultrasonic generating source was measured with these four wattmeters and an intercomparison was made with measurements made on proven laboratory measurement methods.
Probe corrected near-field measurements on electroacoustic transducers
Authors: Miller E. B.
Published: October 2005

A review of work in progress at NBS-Boulder on near-field evaluation of electroacoustic devices will be presented. In particular, a method of making probe-corrected measurements will be discussed and experimental results will be presented. This work is based on acoustic theory [D. M. Kerns, J. Acoust. Soc. Am. 57, 497–507 (1957)] having an electromagnetic counterpart that has been applied over the last ten years at NBS-Boulder in evaluating antennas. Given a known receiving probe, this work shows that a single planar scan in the near-field of a moderately directive radiator is sufficient to provide relative distributions of quantities such as pressure, particle velocity, energy density, and intensity. The addition of careful electrical measurements on the transmitter and receiver provide a means of precisely determining absolute field quantities and the related, forward-radiated, acoustic power.
Pulse method for measuring sound absorption in the kilohertz range
Authors: Shields F. D. , Bolen L. N. , Bass H. E.
Published: October 2005

Solid-dielectric capacitance transducers, 25.4 cm in diameter, have been constructed and used to generate and detect pulses of sound waves in the frequency range from 4 to 200 kHz. The waves are propagated inside an aluminum tube, 25.4 cm i.d. and 4.5 m long. One of the transducers generates the sound pulses and can be moved axially along the tube; the second serves as a microphone, detecting the sound pulse and reflecting it at one end of the tube. The transducers are made by stretching metalized Mylar across a polished backing plate. Effects of diffraction, transducer nonalignment, and transverse modes within the tube are discussed. The sound absorption is obtained by the measurement of either the attenuation of the first pulse or the increase in the echo decay rate with distance. Pulse heights are measured with a multichannel pulse height analyzer and an on-line computer. The system has been used to measure sound absorption in humid air. [Work supported by NASA-Lewis Research Center.]
Earmold plumbing for wide-band hearing aids
Authors: Killion Mead C.
Published: October 2005

In conventional head-worn hearing aids, the sound generated by the receiver is conducted to the ear canal through various sections of rubber, metal, and plastic tubing which together make up an acoustical “transmission line” 2–3 in. (5–7 cm) long. By proper choice of tubing and earmold-bore diameters, a stepwise approximation to an acoustical horn can be obtained, reducing the impedance mismatch (typically 20:1 or greater) between the receiver and the ear. Properly damped, such a “horn” results in a smooth frequency response with substantially greater high-frequency output than can be obtained with conventional constant-bore plumbing. The construction and response of a “6-kHz earmold” and a “9-kHz earmold” will be discussed.
Noise criteria for building codes: a critical review
Authors: Yaniv Simone L. , Flynn Daniel R.
Published: October 2005

Traditionally, noise requirements in building codes for buildings such as dwellings are based upon precise and well define rules for rating building elements in terms of their ability to provide sound insulation. While in the developments of these methods, considerations of human response to noise were implicitly included; in fact, there exists very little research data to demonstrate how well these methods fulfill occupant needs for quiet. An alternative approach is to specify a design goal in terms of an over-all cumulative environmental noise level in an occupied space. This approach must be based upon a precise and enforceable procedure for identifying human response to noise as well as requirements for quiet. It is in the development of this procedure that major problems arise as will be shown in this paper. In addition, the implications of this conceptual approach to the problem of specifying performance requirement for various buildings components will be also examined.
Getting effective noise control into law
Authors: Schultz Theodore J.
Published: October 2005

It is one thing to know the technical means for achieving adequate noise control in buildings. It is quite another thing to embody that knowledge in effective regulation. This paper reviews the experience of a number of European countries and certain North American cities, with the aim of assessing the results achieved by their various approaches to the tasks of formulating and enforcing noise control laws.
Demonstrating the fundamentals of fan noise
Authors: Baade Peter K.
Published: October 2005

A compact, portable demonstration rig will be shown which lends itself well to demonstrating the dipole nature of fan noise generation. The demonstration apparatus provides a quantitative insight into the interaction of the dipole source distribution and the acoustic impedance presented by the fan duct. The demonstration also brings out some of the factors giving rise to fluctuating blade lift forces which constitute the dipoles responsible for fan noise generation. Implications of the fundamentals demonstrated for the standardization of fan sound measurements and for the design of ducted fan systems will be summarized with reference to a more complete description [P. K. Baade, “Effects of Acoustic Loading on Axial Flow Fan Noise Generation,” Noise Control Eng. (1976) (in press)].
The sounds physicists make
Authors: Carpenter D. R. , Minnix R. B.
Published: October 2005

A half-dozen physics lecture demonstrations related to vibration and waves will be shown. Emphasis is placed on simple apparatus and application to phenomena observed in everyday life.
Brass musical instruments
Authors: Gossick B. R.
Published: October 2005

Demonstrations which bear on the following questions will be presented: (1) How does a mute influence the normal modes? (2) Is a trumpet a passive system plus feedback or a passive system driven by an external periodic force? (3) What influence does the design of the mouthpiece and the design of the bell have on tonal spectrum? (4) What is the distinction between what brass instrumentalists refer to as centered and uncentered tones?
Relationships between comfort, annoyance by aircraft noise, and endurance
Authors: Loeb Michel , Vanderhei Sharon L.
Published: October 2005

Thirty-six subjects were trained to make psychophysical judgments, then asked to rate music and paintings, and then to make category ratings and magnitude estimates of annoyance produced by recorded “overflights” of jet aircraft ranging in intensity from 90 to 105 dBA (peak). They were then asked to immerse their hands in 32°F water as long as they could. Ambient room temperature was 70°F for half of the subjects and 90° for others. Half of each group were men and half women. Room temperature did not significantly influence annoyance ratings. Tolerance for cold water was significantly less at 90° than at 70° for men but not women; men were significantly more tolerant of cold water (but not less annoyed by noise). At 70° there were significant, appreciable negative correlations for men and women between category noise annoyance and cold water tolerance, but not at 90°. It is suggested that perhaps there may be some generalized factors determining reaction to various stressors.
Model for prediction of ride quality in a multifactor environment
Authors: Leatherwood J. D. , Dempsey T. K.
Published: October 2005

A model is being developed which permits the understanding and prediction of passenger discomfort response to combined noise and vibration environments. The model has general applicability to diverse transportation systems and provides a means of developing ride-quality design criteria as well as a diagnostic tool for identifying the vibration and/or stimuli causing discomfort. Results of several experimental studies have provide the basic framework about which the ride quality model is constructed. These results include (1) the determination that the vibration-stimuli response can be represented by a linear relationship, (2) the development of equal discomfort curves for linear and angular sinusoidal vibration, and (3) the determination of within-axis masking effects for the vertical and roll axes. Results of supporting studies indicate that subject demographics such as age, weight, and sex do not play an important part in subject ratings; that acceleration and frequency interact significantly for both vertical and roll axis vibrations; and that a simple predictor such as overall rms acceleration level of a vibration is not an adequate predictor of subject discomfort.
Auditory aid to deaf speakers in monitoring fundamental voice frequencies
Authors: Villchur E. , Killion M. C.
Published: October 2005

Profound deafness is often accompanied by a loss in frequency-discriminating ability. When such deafness dates from infancy, the deaf person may never learn to speak with the inflections of fundamental voice frequency that are part of the conventions of language and that contribute to speech intelligibility. Visual and tactile devices have been built to help the frequency-insensitive deaf speaker-monitor, and thereby learn to control, the pitch of his voice. This paper describes an auditory pitch-monitor device, in which voice-pitch information is presented by way of subsonic-frequency, square-wave modulations of the low-frequency portion of speech. The modulation frequencies track the changing fundamental voice frequencies. The advantages sought in this device, compared to previous devices, are (a) the deaf person does not have to integrate signals from more than one sense into his perception of voice pitch and (b) the device is wearable, making possible a closer relationship between speech-therapy sessions and everyday communication. Preliminary experimental results will be reported, and there will be a demonstration.
Real-time speech spectrographic display (SSD) with implications for speech training for the deaf
Authors: Stewart L. C. , Larkin Wilbur D. , Houde Robert A.
Published: October 2005

At the Austin meetings of the Society we reported on work with the Visual Speech Training Aid (VSTA), a speech parameter display [J. Acoust. Soc. Am. 57, 518 (A) (1975)]. The VSTA demonstrated the utility of a visual display for training stress and elimination of inappropriate pauses and nasality in deaf speech. It was similarly useful in displaying voice-voiceless distinctions and appropriate pitch range and contours for most deaf speech. However, the need for a visual display to reliably indicate articulation led us to develop a real-time speech spectrographic display (SSD). The sound-spectrographic type of display is attractive because it has adequate frequency resolution to display formants and fricatives in speech, yet the time resolution is sufficient to display stops and to show vocal-fold periodicity during voiced sounds. The real-time instrument developed produces and stores a frequency-time-intensity display on a video monitor while the sound is being spoken. The resulting speech spectogram closely resembles the standard broad-band spectrogram in time, frequency, and grey-scale resolution. Preliminary evaluations which are highly encouraging are reported.
Effect of hearing-aid microphone location on the intelligibility of hearing-aid transduced speech
Authors: Franks J. R. , Feth L. L. , Daniloff R. G.
Published: October 2005

The effect of hearing-aid microphone location upon speech intelligibility was investigated using ten normal-hearing, young adult listeners. A closed-response-set speech discrimination task was recorded in the presence of a spatially separated noise through a hearing aid mounted on a dummy head. Recordings were made in both anechoic and reverberant sound fields (Rt = 0.5 sec). Three experimental listening conditions were employed-microphone does placed (a) in the top of the hearing aid case; (b) in the bottom of the hearing aid case; and (c) in the auricle, over the earmold. A fourth condition of ear open with no hearing aid was used as a reference condition. Results indicated that the location of the microphone does have an effect on the intelligibility of the speech signal, and that the effect is dependent upon the characteristics of the sound field. For both sound fields, the bottom microphone location provided the least intelligible speech signal. The results for the top and auricular locations indicated that the speech signals were of equivalent intelligibility. The highest speech intelligibility scores were obtained under the reference condition. Reverberation in the sound field tended to reduce the intelligibility for all listening conditions. [This research was supported by a grant from NINCDS.]
Reversals in ear advantage with dichotic listening: Effects of alignment
Authors: Niccum Nancy , Speaks Charles , Carney Edward
Published: October 2005

A reversal in ear advantage for double-contrast pairs of synthetic stop-vowel syllables was reported at the 90th meeting of the Society. The ear advantage was an REA=51% for voiceless-left, voiced-right pairs, but an LEA=27% for voiced-left, voiceless-right pairs. We evaluated the generality of this reversal by using two criteria for syllable alignment: onset of periodicity and onset of burst. Three listeners who had demonstrated the reversal in a previous experiment were tested. The reversal was preserved in both alignment conditions, suggesting that it was not influenced by temporal delays inherent in either alignment criterion. The results will be discussed in terms of the “lag effect” [Berlin et al., J. Acoust. Soc. Am. 53, 699–709 (1973)] and will be contrasted with findings obtained with natural CV's [Supported by PHS Grant No. NS-12125.]
Dichotic intensity trade for stops with differing vowels
Authors: Cullen J. K. , Berlin C. I. , Tobey E. A.
Published: October 2005

The effect of unilateral intensity variation on the interaction of dichotically presented stop-vowels has been shown to result in a reciprocal performance trade between the ear receiving the attenuated signal and the unaffected ear [Brady-Wood and Shankweiler, Haskins Labs Stat. Rpt. 34, 119–126 (1973); Cullen et al., Brain Lang. 1, 307–322 (1974)]. These studies, however, employed only like vowel pairings. The study reported here employed the vowels [æ, i, u] plus the stops [b, d, g] to investigate intensity trade with differing vowels and stop formant transitions. Trading was observed for all pairings, although distorted in some cases by performance ceiling and floor effects. Other results suggest factors in addition to acoustic overlap enter into performance limits and trading relationships observed in dichotic speech studies. [Work supported in part by NH 11647-01 and NIGMS SF I-F03-GM-52343.]
Speech audiometry via bone conduction
Authors: Edgerton B. , Danhauer J. L. , Barnard T. , Beattie R.
Published: October 2005

This study was designed to determine (1) values for SRT's obtained via bone conduction using the NU cassette recording, (2) the relationship between BC PTA's and BC SRT's for normals, (3) short-term reliability of BC SRT's, and (4) characteristics of articulation functions for spondees obtained by BC and by AC. An average BC SRT was determined for 50 normally hearing young adults using mastoid placement. While relationships between BC PTA's and BC SRT's were not in agreement with those indicated by earlier investigators, the average SPL values for the BC SRT's were. Test-retest reliability for BC SRT's was very high. A comparison of articulation functions indicates that the perception of speech as a function of intensity does not differ significantly for air or bone conducted transmission systems.
Vocal-tract determinants of resonance frequencies and bandwidths
Authors: Fant G.
Published: October 2005

This is a review of recent years' development of the theory of vocal transmission focusing on the spatial distribution of energy, resonance bandwidths, perturbations in area and in length dimensions with applications to nonuniform sealing of vocal-tract dimensions, and discussions of “resonance-cavity” relations. In addition to the well established influence of the vocal-wall impedance on the tuning of very low F1 resonances, there are also indications that F1 of [a]-type vowels could be significantly influenced by the tuning of the vocal-wall mass shunt which, according to our measurements, should be heavier in the region of the lower pharynx than anywhere else. New measurements of the closed-tract resonance and bandwidth for males and females are reported and also some observed differences in male-female cavity size and shape.
A vowel feature space from acoustic speech waveforms
Authors: Wakita H.
Published: October 2005

Speech sounds can be defined in three major domains: articulatory, acoustic, and perceptual. Some of the parameters in the articulatory domain have already been brought into the acoustic domain for vowel normalization [H. Wakita, J. Acoust. Soc. Am., 57, S3(A) 1975)]. This result can be related to some parameters in the perceptual domain. This paper discusses an attempt to build a unified vowel feature space from acoustic speech waveforms by using currently available techniques. After applying vocal-tract shape and length to normalize the corresponding formant frequencies to those of an acoustic tube having a certain reference length, it is shown that the normalized formant frequencies can be related to the invariant quantities in the perceptual domain which are obtained from multivariate analysis of data in perceptual experiments. Thus, it is possible to define an equivalent vowel feature space in any of the three domains. In its application to automatic acoustic-phonetic transformation for arbitrary speakers, vowel normalization based on vocal tract length can then be performed without directly estimating the length.
How do different speakers say the same vowels?
Authors: Papcun George , Harshman Richard
Published: October 2005

As a basis for developing a principled approach to interspeaker vowel normalization, a rigorously controlled uniform “dialect” was created. This was done by having phoneticians imitate a set of vowels chosen from Spanish, Japanese, and English. A computerized system allowed them to hear both the stimuli and their efforts at imitation repeatedly until they were satisfied with their efforts. Thus, rather accurate imitation was achieved. Because of their differing physiognomy, and possibly perceptual and other factors, different phoneticians produced different formant frequencies in their imitations. Regression analyses and related techniques are used to develop functions for predicting the formant frequencies of any vowel spoken by a particular speaker from other vowels spoken by that speaker. [Work supported by US PHS and NSF.]
Spectral characteristics of English stops in prestressed position
Authors: Zue Victor W.
Published: October 2005

Spectral characteristics of English stops in prestressed position, both in singleton and in clusters, are examined in detail using a data base designed for controlled acoustic phonetic research [Victor W. Zue, “Acoustic phonetic data base for the study of selected English consonants, consonant clusters, and vowels,” J. Acoust. Soc. Am. 57, S34(A) (1975)]. The study being presented here is based on the analysis of some 1200 stops spoken by three male speakers. Results on the spectral characteristics of the stops at the release, during the transient, and following the onset of voicing will be presented as a function of (1) the voicing characteristics of the stop; (2) the place of articulation of the stop; and (3) the phonetic context (i.e., the influence of the following vowel or sonorant). Results on inter- and intraspeaker variability will also be discussed.
Effect of aspiration on the fundamental frequency of the following vowel
Authors: Hombert J. M. , Ladefoged P.
Published: October 2005

The fundamental frequency of a vowel following a voiceless obstruent is higher than after a voiced obstruent. The effect of a voiceless vs a voiceless aspirated stop on the frequency of the following vowel is not as straightforward. In Korean the onset F0 of a vowel is higher after the voiceless aspirated series (Han, 1967). These data were used (Hombert, 1975) to explain that when both series are involved in a tone development, the aspirated series generally give rise to a higher phonological tone. However, Gandour (1974) presents data showing that in Thai vowels following voiceless aspirated stops have a slightly lower F0 onset. In this study five American English and five French speakers spoke 6 CV words (C = [p, t, k, b, d, g] and V = [i]. Fundamental frequency measurements were made at the onset of the vowel and 20, 40, 60, 80, and 100 msec after vowel onset. The voiceless series has a different effect in each language. The F0 onset is higher after the American 31English series. Physiological data (glottal opening measurements) accompanying these differences will be discussed.
Use of echo sounders operated at high acoustic frequencies in the marine environment and some comparisons with oceanographic parameters
Authors: Pieper R. E.
Published: October 2005

Qualitative and quantitative scattering measurements at high acoustic frequencies were compared to the distributions of zooplankton, nekton, and other oceanographic measurements. Scattering was recorded at 100 and 200 kHz from depths of high euphauslid concentrations. No scattering was recorded at 11 kHz at these depths on some cruises. When scattering was recorded at 11 kHz at the depths of the high-frequency scattering layer, the scattering records were qualitatively different and indicated the presence of fishes within the high-frequency scattering layers. The high-frequency scattering was also often correlated with oceanographic discontinuities such as thermoclines, haloclines, oxyclines, and the chlorophyll maximum. Variations in scattering strengths at the same depth plane were recorded. This patchiness in distribution of scattering at the high frequencies appeared to be correlated with aggregations of euphausiids. [Work supported by ONR.]
Acoustic characteristics of populations of epipelagic schooling fish
Authors: Smith Paul E.
Published: October 2005

Pelagic schooled fish populations have acoustic characteristics derived from their individual reflection or backscattering properties, their tendency to school, the tendency of schools to be aggregated in groups, and the tendency for populations of different species to be aggregated in regions of high productivity. In addition to those static properties, the different species populations can be expected to have characteristic swimming and feeding behavior at the individual level and foraging behavior at the school level. Schooling-level foraging behavior is affected by the fact that a school of fish eats far more than is produced per unit of school area. The foraging behavior of schools is expressed as the number of unit areas to be grazed per unit of school area. For example, a moderately compact school of anchovy (0 dB target strength) might contain 15 kg of fish per square meter of sea surface. Food requirements of such an aggregation probably exceed 40 g C/m2/day but primary productivity of the northern anchovy is only of the order of 0.5 g C/m2/day. Therefore, an individual anchovy school must cover a minimum of 80 times its own area each day. Other fish species appear to school in less compact schools and probably have other food requirements. Schooling and foraging behavior also differs by day and night. Work in California waters has demonstrated acoustical techniques for the estimation of fish size and school motion. These acoustic parameters remain to be combined with static and dynamic, biological and geographic knowledge of fish populations to provide practical acoustic means of fish target identification. Similarly, the acoustic characterization of water masses and particularly the distribution and abundance of epipelagic schooled fish targets which we are investigating appear to be lacking for most of the world ocean in the upper 100 m.
Internal proton transfer and ultrasonic absorption by proteins
Authors: Slutsky L. J. , White R. D.
Published: October 2005

The measured pH and frequency dependence of ultrasonic absorption in aqueous solutions of proteins and model compounds are reported and compared with an estimate of the contribution of internal charge-transfer processes to the acoustic relaxation spectrum of protein solutions based on the approximate method employed by Kirkwood and Shumaker [J. G. Kirkwood and J. B. Shumaker, Proc. Nat. Acad. Sci. 38, 855 (1952)] to compute the contribution of the fluctuation dipole moment to the dielectric relaxation spectrum. The agreement with experiment is quite good and there appears to be a reasonable case for perturbation of internal proton-transfer equilibria as a major or principal to ultrasonic absorption in protein solutions at physiological pH.
Influence of subarachnoid structures on transmenninges ultrasonic propagation
Authors: Johnston R. L. , Dunn F.
Published: October 2005

The ultrasonic dose threshold for irreversible lesion production in mammalian brain exhibits a frequency dependence believed to be ascribable to the outer brain menninges. Thus, the collagenous trabeculae of the subarachnoid space, interposed between the arachnoid and the pia mater, are implicated because of increased elastic moduli associated with their structural supporting role. A three-layer model yields acceptable agreement and provides physical parameters commensurate with these involved anatomical structures. Normalization of existing data [Dunn, Lohnes, and Fry, J. Acoust. Soc. Am. 58, S12 (1975)], by this method of analysis, provides a frequency-independent lesion threshold describable by the relation, IT12 = 200 W/cm2/sec−12. [This study was supported by a grant from the NSF.]
Ultrasonic properties of mammalian testes
Authors: Brady J. K. , Johnston R. L. , Goss S. A. , O'Brien W. D. , Dunn F.
Published: October 2005

The ultrasonic absorption and reflection properties have been investigated over the frequency range of 0.7 to 7 MHz, 37° C, for in vitro preparations of freshly excised, sexually mature mouse, rabbit, and cat testes. The experimental animals were mature mice of proven fertility, 15–20 weeks of age, a young cat, and a rabbit of unknown fertility. The transient thermoelectric method of absorption measurement and the pulse-echo reflection method were used. The absorption coefficient is approximately an order of magnitude less than other soft tissues of high water content, with a positive frequency dependence. [This work was supported by a grant from the Institute of General Medical Sciences, NIH.]
Intensity and state dependence of acoustical absorption coefficients in mammalian tissues
Authors: Handler R. A. , Lele P. P.
Published: October 2005

There is still considerable uncertainty regarding the mechanism(s) by which high intensity, pulsed (one or a few cycles) ultrasound can damage mammalian tissues. Thermal mechanisms, which are known to mediate damage with burst mode (hundreds of cycles) or cw insonation, are believed to be of negligible importance in pulsed insonation because of the subthreshold magnitude of temperature rise as calculated from estimates of peak acoustic intensities and “known” acoustic absorption coefficients of tissues. This has led some investigators to invoke the existence of mysterious mechanical mechanisms to explain the occurrence of tissue damage at acoustic intensity levels at which cavitation is known to be absent. Similarly, some form of nonthermal phenomena are invoked to explain differences in the results obtained from insonation with “equivalent” amounts (intensity X duration) of ultrasound in burst and pulsed modes, respectively. Implicit in these arguments is the assumption that the acoustical absorption coefficient is invariant and does not depend on the intensity of ultrasound or the state of the tissue. Thus, customarily, “known” absorption coefficients, measured with low intensity ultrasound, have been used to calculate temperature rises in tissues subjected to high intensity insonation. However, theoretical analyses, as well as experimental studies in mammalian tissues, indicate that the acoustical absorption coefficients in tissues, far from being invariant, are in fact dependent both upon the field intensity as well as the tissue state. [Work supported by the US PHS.]
Internal scattering of ultrasound in biological tissues in vitro
Authors: Mansfield A. B. , Senapati N. , Lele P. P.
Published: October 2005

The patterns of signal amplitude vs angular position which result when diagnostic level ultrasound is internally scattered by phantoms of precisely known geometry and various normal and pathological tissues were measured. The physical phenomenon is similar to Bragg diffraction which is seen when a wavefront impinges upon a regular array of scatterers whose size is smaller than and whose spacing is of the same order as the incident wavelength. The internal geometry of the targets and the ultrasonic wavelength determine a series of maxima and minima occurring with a specific predictable angular pattern. Matched pairs of 1–4-MHz unfocused transducers were used as transmitter and receiver, respectively. The duration of the transmit pulse was long enough (10–20 msec) for a continuous wave approximation, but short enough to be spaced away temporally from the tank wall reflections. The signals received from the specimen were time-gated, rectified, and integrated. The transducers were swept through an arc of ∼120°. The pattern of the scattered amplitude vs angle showed a characteristic average intermaximal separation which was a function of both the target structure and the ultrasonic wavelength. [Work supported by the US PHS.]
Acoustical measurement of gas-flow velocity
Authors: Cook Richard K.
Published: October 2005

We examine some features of a proposed absolute acoustical method for measurement of gas-flow velocity. The proposed method is to meet a need for measurement of the mass flow of a hot gas (gasoline engine exhaust) through a 5-cm tube, at Mach numbers up to about 0.10, and therefore at Reynolds numbers up to about 100 000. The proposed method uses longitudinal modes at one or more harmonic frequencies below the cutoff frequency. We present some analytical results (a) for the phase velocity at several profiles of mean flow, (b) for the distribution of sound-pressure amplitudes and phases in a single harmonic wave, and (c) for the Doppler-shifted instantaneous spectrum arising from a microphone whose longitudinal location is sinusoidally modulated in time. In the latter case the use of a ratio, of the modulation frequency to the signal frequency, having the same value as the Mach number seems to be advantageous for measurement purposes.
Preliminary in-duct measurement of spinning modes in the inlet of a rotating vehicle
Authors: Kraft R. E. , Posey J. W.
Published: October 2005

The effectiveness of duct-lining acoustic noise suppressors is strongly dependent on the modal content of the acoustic pressure wave generated by the source. Conventional rotor-stator interaction criteria such as that of Tyler and Sofrin [S.A.E. Trans. 70 (1962)] predicts the spinning mode orders most likely to be present, but provides no information on relative participation. Modal analysis suppression prediction programs require source modal information as input to the calculation. In an exploratory effort, the General Electric Company and NASA Langley Research Center developed, designed, built, and tested a multielement spinning-mode probe apparatus. The device was tested in a 12-in.-diameter vehicle in a NASA Langley anechoic chamber. The results of the modal measurement for several operating speeds are presented. Data repeatability and problems encountered in the measurement are considered, and recommendations are made for future improvements in the method.
Measured spatial filtering characteristics of membranes and plates
Authors: Martin N. C. , Leehey P.
Published: October 2005

Two rectangular plates and a membrane were designed to be used as spatial filters for measuring the low-wavenumber components of turbulent boundary layer wall pressure fluctuations. For such stuctures it is convenient to define wavenumber filter-shape functions which are obtained from spatial transforms of the normal mode shapes. This suggests that it is possible to determine experimentally the wavenumber filter shapes by measuring the normal mode shapes. Detailed measurements of selected mode shapes were made for a membrane, a clamped plate, and a simply supported plate. The mode-shape data was then transformed numerically to obtain typical wavenumber filter shapes for the structures. These measured wavenumber filter shapes compare favorably with theoretical predictions; however, to obtain reliable results it was necessary to attain both frequency and spatial matching of the excitation to the desired resonant mode. [Work supported by the Sensor Technology Program, ONR.]
Nondestructive flow-resistance measurements of porous face sheets on fully assembled honeycomb acoustic panels
Authors: Purves R. B.
Published: October 2005

Conventional methods for measurement of flow resistance normally require a direct flow of air through the sample. The procedure is clearly inapplicable to a fully assembled honeycomb panel with an impervious backing sheet. This paper describes a device which is able to measure the flow resistance of the porous face sheet on a fully assembled panel. In this device air flows into the panel from a set of nozzles which partially cover some of the honeycomb cells. Exhaust takes place through the portion not covered by the nozzles. The flow resistance is calculated from the flow rate and the pressure drop. Of several configurations tested, the one adopted consists of a rubber disk with a series of concentric channels for inflow and outflow. The flexible nature of the “puck” allows it to be used for contoured panels.
Evaluation of the Zwislocki coupler and KEMAR for use in hearing-aid processing
Authors: Punch J. L.
Published: October 2005

A calibrated-probe-tube technique was employed in a comparative investigation of the real-ear frequency response of a hearing aid and the real-ear response as processed through the hearing aid and two coupler systems. The swept-tone output of the aid was delivered to a Zwislocki coupler, and later to one eat of the manikin KEMAR [M. D. Burkhard and R. M. Sachs, J. Acoust. Soc. Am. 58, 214–222 (1975)], which housed the same Zwislocki coupler. Outputs were recorded on magnetic tape and subsequently transduced by a TDH-49 earphone. Resultant sound levels were measured in the right ear canal of 11 subjects. Conventional frequency responses were also measured utilizing the two coupler systems. The acoustic input channel and input monitoring point were held constant under each condition. Responses of both coupler systems paralleled closely the live, real-ear, response of the aid. Minor and major differences were observed in the lower and higher frequencies, respectively, between hearing-aid-processed and real-ear sound levels.
Method for calibrating electroacoustic transducers by measuring the average near-field pressure
Authors: Yahjian A. D. , Miller Eric B.
Published: October 2005

The plane-wave scattering matrix description of linear electro-acoustic transducers is used to prove that the integrated complex pressure has the same magnitude over parallel planes within the fluid surrounding arbitrary transducers. In addition, the magnitude of this force is related by a simple proportionality to the far-field amplitude in the direction normal to the planes. Further analysis and application of these results to plane piston transducers yields a generalization of the plane-wave reciprocity parameter and suggests a direct (though approximate) near-field technique for determining the far-field and total acoustic power output for an arbitrary directive radiator using a piston receiver. Preliminary experimental data indicates the validity of the theoretical results.
Variability in the noise testing of light motor vehicles
Authors: Olson N. , Piercy J. E. , Embleton T. F. W.
Published: October 2005

There have been complaints about the variation from day to day and site to site in the noise levels of light motor vehicles when measured with standard test procedures. A study aimed at the resolution of the sources of this variation is described. A light-, a heavy-, and a medium-weight automobile were each tested (repeatedly) on three different paved sites under a variety of atmospheric conditions. The levels from a calibrated point source simulating the noise from an exhaust pipe was measured under the same conditions with the source stationary, and also with the source carried through the standard pass by procedure on a coasting vehicle. Vertical gradients of ambient wind and temperature were monitored. Preliminary analysis of the results indicates that the major source of the variation is refraction in the wake of the moving vehicle.
Mill trial of fly-shuttle-loom noise-control components
Authors: Hanson W. J. , Cudworth A. L.
Published: October 2005

A series of laboratory tests evaluating the acoustical performance of several modified fly-shuttle-loom components was reported on in a paper entitled “Noise reduction in the fly shuttle loom” presented at the 87th meeting of the Acoustical Society of America [J. Acoust. Soc. Am. 55, 537(A) (1974)]. A multiloom mill trial was initiated to determine the performance of these parts in a production environment. First, a series of life tests were conducted to establish each part as a reasonable substitute relative to the standard parts. During this phase, installation problems and associated adjustments were determined in cooperation with textile mill personnel. A block of looms, sufficiently large to represent a typical weave room, was treated with components which were considered acceptable based on life tests and performance in the previous report. Each type of component was installed independently to facilitate acoustical evaluation of that particular component. Noise measurements were obtained between each phase of installation which provide not only the overall A-weighted reduction but also any distinct spectral variation. The data obtained provide an indication of the noise reduction expected in the weave room based on treatment of a representative group of looms rather than projecting from results of single loom tests previously performed in a semianechoic chamber.
Sound radiation from randomly vibrating cylinders of finite radius, with applications to textile-loom noise reduction
Authors: Sutterlin M. W. , Pierce A. D.
Published: October 2005

Recent studies of textile-loom noise suggest that the picking stick is the major contributor to the overall noise level produced by an automatic textile loom. This has led to research directed towards a better understanding of how sound is generated and radiated by the picking sticks. The present paper is concerned with the radiation of sound from randomly vibrating beams of circular cross section. Vibrations on the beam are considered as two traveling waves moving in opposite directions. The result is then averaged over all possible phase differences, assuming all to be equally probable. Expressions for the radiation efficiency are compared with previous results based on a modal approach. Predictions of the octave band sound pressure level based on the theory and on vibration data satisfactorily compare with experimental measurements.
Noise and ground vibration from pile-driver operation
Authors: Brittain F. H. , Ross J. W. , Angus R. N.
Published: October 2005

Both noise and ground vibration from construction operations, particularly pile drivers, are potential sources of annoyance of nearby residents. Further ground vibrations may adversely affect sensitive instruments and computers. The results of measurements of both noise and ground vibration from pile-driver operation are presented. Both overall noise and ground vibration levels and frequency content, particularly that below 20 Hz, are presented. The effect of accelerometer mounting is indicated.
Responses of sound level meters to impulsive sounds
Authors: Young R. W. , Cowen S. J.
Published: October 2005

Responses of a standard sound level meter to various pulses as brief as 1 msec were obtained by computer simulation. The results are relevant to specification of transient responses of sound level meters and to practical measurement of impulsive sounds for hearing conservation. The RC-averaged sound levels here considered are peak, impulse, fast, and slow, based, respectively, on squared-pressure time constants of 125 nsec, 35 nsec, 125 nsec, and 1 sec. The time-integrated (not averaged) level called sound exposure level was also calculated. The transfer function found for the A-frequency weighting is 4.13 × 106f4/(jf + 20.6)2(jf + 107.7)(jf + 737.9)(jf + 12 200)2, where f stands for frequency. As an example of fast time averaging, for a 50-msec tone burst at 2 kHz the flat sound pressure level was −4.8 dB relative to continuous sound pressure level at 2 kHz, but the A-weighted sound level of the burst was −3.9 dB relative to continuous A-weighted sound level; for a 50-msec burst at 20 Hz the flat level was relatively −4.8 dB, but the A-weighted level was relatively +3.1 dB. For a real sonic boom of 100-msec duration with small, real oscillations around 500 Hz superposed thereon, the peak flat sound pressure level exceeded the A-weighted sound exposure level by 42 dB.