bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Head Vibration When Walking
Authors: Maxwell R. J. , Burkhard M. D.
Published: October 2005

The action of walking produces vibrational motion of the head which has been measured. Each step may be regarded as producing a mechanical impulse that propagates through the leg, torso, and neck into the head. The body acts as a combination of masses and springs producing a low-pass filtering action but having several characteristic frequencies for which transmission is moderately high. This is consistent with published data on vibration of humans [Goldman and Von Gierke, Shock and Vibration Handbook, Harris and Crede, Eds. (McGraw-Hill, New York, 1961)]. Peak vertical acceleration of the heads of six male subjects walking on asphalt-tile-covered concrete floors ranged from 1 to 9 m/sec2. Frequency of acceleration maxima ranged from 15 to 40 Hz, with spectral analysis usually exhibiting one or two peaks in this range. The implication of these results for the design of head-worn hearing aids is discussed. [Supported by Knowles Electronics, Inc.]
Comparison of A-Weighted Auditory Risk Criteria With Contemporary Octave-Band Estimates of Auditory Damage
Authors: Gasaway Donald C. , Sutherland Harrell C.
Published: October 2005

Recent emphasis placed on adoption of A-weighted sound-level measurements for identifying degrees of auditory risk has prompted investigations which facilitate and clarify compromises associated with the introduction of A-weighted levels. The authors have compared recent estimates of auditory risk which employ A-weighted measures with those utilizing octave-band data. The results derived from this study yielded C-A values that can be used to equate A-weighted measurements with octave-band auditory-risk criteria. Auditory-risk contours are reported for protected and unprotected exposures measured with C- and A-weighted sound levels. These contours also report C-A values from which equivalent A-weighted levels for conditions of attenuation (earplugs, earmuffs, and communication headsets) can be determined for durations of exposure ranging from 2 to 480 min per day.
Sonoluminescence from a “Shuttlecock” Associated with a Single Gas Bubble
Authors: Temple P. R. , Detenbeck R. W. , Nyborg W. L.
Published: October 2005

We start with a single air bubble, approximate diam 0.1 mm, in a liquid of 95% glycerine and 5% water, in a 30-kHz sound field. At moderate amplitudes, presence of the bubble may cause evolution of a cloudy formation or complex. The latter consists of a bubble (near resonant size) with a whitish conical cloud such that the complex somewhat resembles a shuttlecock. The initial bubble is held fixed by radiation pressure at a low amplitude. The sound is then increased abruptly to a desired level in either a continuous or pulsed mode. A definite threshold is found above which light is detected. By inspecting the sound field, it is confirmed that this threshold coincides with that for formation of the shuttlecock complex. The conical cloud evidently consists of many small bubbles moving toward the initial bubble. Formation of the shuttlecock requires time, which at near-threshold amplitudes may be as much as 10 sec. Upon reduction of the sound level, the cloud disappears very quickly but a bubble, similar to the initial one, remains.
Noise Test Scores—1970 Clean Air Car Race
Authors: Dietrich C. W. , Paulhus N. R.
Published: October 2005

The 1970 Clean Air Car Race was the first annual race from MIT to Cal Tech by college students in vehicles that meet stringent air pollution requirements. There were 45 vehicles entered in five engine classifications: internal combustion (both gaseous and liquid fuels), Rankine cycle, Brayton cycle, electric, and hybrid electric. In addition to measuring the exhaust emissions of these power plants (which will probably become the power plants of the future), the noise generated by the vehicle operating under competitive conditions was measured using the A-weighted network (1) with the vehicle at idle (at a measurement distance of 10 ft), (2) with the vehicle at 30 mph cruise (at a distance of 50 ft) and (3) with the vehicle at wide open acceleration (at a distance of 50 ft). The rating scheme assigned equal merit to each of the three measurements. This paper presents additional comments on the race and discusses in detail the noise levels of the various vehicles.
Jet Noise Contribution to Wind Noise in Vehicles
Authors: Yu C.-K. A. , Ribner H. S.
Published: October 2005

A source of “wind noise” in a vehicle with a slightly opened window has been modeled as a slit jet issuing from a plenum (idealized vehicle). The nondimensional power spectra measured inside and outside were quite similar; the curves collapsed together well when plotted against Strouhal number fD/U (f=frequency, D=slit width, U=jet nozzle velocity). The higher frequency sources of the jet noise, being closer to the slit, subtend a larger angle and would be expected to transmit more noise into the plenum. This expectation was confirmed, with inward transmission increasing with both frequency and slit width; at 10 000 Hz and 1.5-in. slit width (maxima for these experiments, with 80-fps jet velocity) the jet noise power transmitted inward through the slit reached 68% of the power emitted externally in the 13-oct band. These were exploratory tests, and there was no external wind. [Work supported by Air Force Office of Scientific Research.]
Truck Tire Noise—A Measurement Program
Authors: Leasure W. A.
Published: October 2005

Vehicular traffic noise continues to be a major source of complaint, especially near high-speed highways. Of all vehicles on the road today, many consider trucks to be the major offender. Engine operating noise, exhaust noise, brake noise, and tire noise each contribute to the over-all noise level produced by trucks; however, at speeds of 50 mph and greater, which is quite prevalent on today's interstate highways, the noise from tires predominates, provided the truck has a reasonably good exhaust muffler and is in a good state of repair. The lack of an information base of tire noise data available in the public domain has hampered the development of standardized tire-noise testing procedures and the establishment of highway noise reduction criteria, standards, and regulations. This investigation will provide an inventory of data on representative tires and will develop an appropriate and accurate measurement methodology. The test parameters of this investigation include: tread design, tread depth, type of pavement, speed, and loading. A discussion is presented of measurement and analysis techniques leading to the attainment of (1) peak A-weighted sound levels, (2) 13-oct spectrum data, and (3) directionality information shown as equal sound-level contour plots for various truck tires.
Noise Reduction by Earth Berms
Authors: Jensen Paul
Published: October 2005

Acoustical shielding of apartment buildings, town houses, and especially hospitals by walls or earth berms has been used extensively in Denmark during the last years. Acoustical measurements have been conducted to determine the shielding properties of a rampart 30 ft high and 2100 ft long, situated along a highway and with a grassland field on the other side. The sound source was a mobile screw-compressor (usually used for starting up jet engines of airplanes) called an Air Partner. The Air Partner was placed both in the near side and in the far side of the highway. Measurements were obtained for these two source positions and six corresponding microphone positions. The measured results are compared with the theoretic formulas for noise reduction of barriers.
Behaviorally Measured Interactions between Medial Geniculate Nuclei
Authors: Gerken George M.
Published: October 2005

Functional evidence of intergeniculate interaction was obtained from extensive study of one cat with bilaterally placed chronic electrodes. Comparison of behavioral thresholds obtained with unilateral and bilateral electrical stimulation indicates a strong additive interaction. Furthermore, following an electrolytic lesion in right geniculate, which elevated right threshold by more than 250%, thresholds could no longer be measured for unilateral left stimulation, indicating a second type of intergeniculate interaction. The animal alerted to left stimulation but seemed unable to initiate a behavioral response. Response to auditory or visual stimulation was prompt, and absolute auditory threshold was unchanged. Remedial behavioral measures were tried without immediate success, but over a 2.5-month period (41 sessions) the animal showed substantial recovery. Left and right unilateral thresholds recovered to within 20% of prelesion thresholds, but thresholds for bilateral stimulation no longer showed evidence of additive summation. The data are discussed in terms of the locus of detection and the known multisynaptic intergeniculate pathways. [Work supported in part by the National Institute of Neurological Diseases and Stroke.]
Coding and Cytoarchitecture in the Kangaroo Rat Cochlear Nuclei
Authors: Caspary D. M.
Published: October 2005

Eighty-four neurons were recorded from and correlated with cytoarchitectural fields: 21 were located in the globular cell area, 19 in the multipolar cell area, 17 in the small spherical cell area, 11 in the octopus cell area, 8 in the dorsal cochlear nucleus, and 6 in the large spherical cell area. Eight neurons were successfully marked by intracellular injection of procion yellow. Units in small spherical cell area (best frequencies, 0.475–11.500 kHz) rarely display tight phase locking and show a characteristic “onset” response followed by decreased activity. Neurons in the multipolar cell area (best frequencies, 0.10–1.45 kHz) are mostly low-frequency phase lockers. There is great physiological and cellular diversity in globular cell area (best frequencies, 0.24–34.10 kHz). Units in the octopus cell area (best frequencies, 1.4–21.5 kHz) typically display high rates of spontaneous and driven activity. Neurons in large spherical cell area (best frequencies, 0.8–14.5 kHz) have interspike interval histograms of spontaneous activity with short modes and rapid decay. Long modes and a high degree of symmetry characterize neurons in dorsal cochlear nucleus (best frequencies, 0.5–10.9 kHz). [Supported by NIH grants.]
A Simple Polarizable Electrode for EEG Audiometry
Authors: Lenhardt M. L.
Published: October 2005

Electroencephalic energy transmission as a function of frequency for solder electrodes was investigated, since this type of polarizable electrode has multiple advantages over commercial nonpolarizable types for clinical evoked response audiometry. The electrode impedance was measured and replicated at nine infrasonic frequencies (0.1, 0.5, 1.0, 2.0, 3.0, 4.0, 10.0, and 20.0 Hz) in saline solution. The results of the investigation revealed that the impedance decreased as the frequency of a 1-mV sine wave increased. At frequencies of 1 Hz and less, the impedance was high (17–30 kΩ), but dropped approximately 3 kΩ per octave from 11 Ω at 2 Hz to 3Ω at 20 Hz. There does not appear to be any significant advantage of a nonpolarizable electrode (e.g., silver/silver chloride) over the solder-polarizable one as long as the latter has a surface area of at least 4–5 mm2 and the EEG amplifier input impedance is not less than 1 MΩ. Further advantages of cost, construction, maintenance, and application in a population with a high damage risk to electrodes is discussed.
Jet Noise Reduction through Liquid-Base Foam Injection
Authors: Manson Lidia , Burge H. L.
Published: October 2005

An experimental investigation has been made of the sound absorbing properties of liquid-base foams and of their ability to reduce jet noise. Protein, detergent, and polymer foaming agents were used in water solutions. A method of foam generation was developed to permit systematic variation of the foam density. The sound emitted by a 1-in. diam cold nitrogen jet was measured for subsonic (300 m/sec) and supersonic (422 m/sec) jets, with and without foam injection. Noise reductions up to 10 PNdB were measured. The investigation included measurements of sound absorption coefficients for both plane normal incidence waves and diffuse sound fields. The intrinsic acoustic properties of foam, e.g., the characteristic impedance and the propagation constant, were also determined.
Sound Propagation and Absorption in Foam: A Distributed Parameter Model
Authors: Manson Lidia , Lieberman Seymour
Published: October 2005

Liquid-base foams are highly effective sound absorbers. A better understanding of the mechanisms of sound absorption in foams was sought by exploration of a mathematical model of bubble pulsation and coupling and the development of a distributed parameter mechanical analog. A solution by electric circuit analogy was thus obtained and transmission line theory used to relate the physical properties of the foams to the characteristic impedance and propagation constants of the analog transmission line. Comparison of measured physical properties of the foam with values obtained from measured acoustic impedance and propagation constants and the transmission line theory showed good agreement. We may therefore conclude that the sound propagation and absorption mechanisms in foam are accurately described by the resonant response of individual bubbles coupled to neighboring bubbles.
Investigation of the Feasibility of Making Model Acoustic Measurements in a Wind Tunnel
Authors: Bies D. A. , Schultz T. J. , Soderman P. T.
Published: October 2005

An investigation into the possibility of making acoustic measurements on model flight vehicles in the National Aeronautics and Space Administration Ames Research Center 40-ft×80-ft wind tunnel is discussed. The wind tunnel has a test section 40 ft high, 80 ft wide, and 80 ft long. It is of closed return construction and 2000-ft centerline circumference. The tunnel is capable of a maximum dynamic pressure of 120 lb/ft2. The tunnel is quite reverberant, but because of its very large dimensions and unique shape, it is unlike the conventional enclosures normally encountered by acousticians. A measurement program designed to investigate some of the unique acoustical properties of the tunnel as they might apply to the proposed model study is reviewed. The conditions under which the measurement of total sound power and of the direct field of a source are feasible are also discussed. [This work has been sponsored by the NASA Ames Research Center under contract.]
Acoustic Waves in a Cylindrical Duct of Finite Length
Authors: Guess A. W.
Published: October 2005

The propagation of acoustic waves in a hard-walled circular cylindrical duct of finite length is studied theoretically. Acoustic waves are generated at one end of the duct by an imposed time-periodic excitation, and the duct is terminated at the other end by an arbitrary acoustic impedance. The steady-state solution in the interior of the duct is represented as a sum over various modes, which are either “propagating” or “nonpropagating.” The amplitude of a nonpropagating mode varies axially down the duct (amplitude of a propagating mode remains constant) and is the sum of negative and positive exponential terms in distance from the source. Both propagating and nonpropagating modes can transfer acoustic energy down and out the end of a finite-length duct (in contrast to the result for an infinite-length duct). For each mode, an expression is derived for the characteristic impedance, and an approximation is given for the terminating impedance when the duct is open-ended. The results (especially with “spinning-waves”) have possible application to the study of noise from the inlet ducts of turbo-fan engines.
An Improved Underwater Earphone
Authors: Schumann J. , Abbagnaro L. A. , Bauer B. B.
Published: October 2005

Am inproved underwater earphone, insensitive to depth, has been developed following the theoretical approaches reported earlier [B. B. Bauer and E. L. Torick, “Calibration and Analysis of Underwater Earphones by Loudness Balance Method,”J. Acoust. Soc. Amer. 39, 35–39 (1966)]. This new transducer offers good efficiency and yields speech reproduction comparable to most air acoustic earphones. The earphone design provides tympanic, rather than bone-conduction sensing, thereby providing directional signal information to the listener. Pairs of these devices have been used successfully in a directional communication system for underwater swimmers. Threshold levels and some man-earphone equal loudness contours were obtained for this device.
A Miniature Transducer with Resistance to Immersion in Water
Authors: Sebesta G. J. , Carlisle R. W.
Published: October 2005

A miniature variable-reluctance microphone-reproducer is described which has wide application in military emergency communication radio and the like. The device is less than 13 in.3 in size. The magnetic mechanism utilizes a U-shape folded armature having one end fixed to a pole structure. The latter has a U-shape and retains a pair of thin magnets adjacent to one end of the armature. The acoustical diaphragm is thin aluminum with a corrugated rim. This diaphragm is protected by a metal cover having a small hole, which is covered with a damping pad. Suspended on a frame over this cover is a rubberized fabric water barrier. Ambient pressure is relieved by a capillary tube partially filled by a fine wire. Used as a microphone, the response is fairly flat from 200 to 1000 Hz and rises to an optimum around 3000 Hz. The sensitivity is −75 dB re 1 V/μbar, at 1000 Hz. When used as a reproducer it is normally held close to the ear, and the response with 5-mW drive is of the order of 76 dB above 0.0002 μbar around 3000 Hz, falling off below this frequency. The water barrier arrangement permits short-term immersion to 18-in. depth.
Acoustic Response of a 6-ft Microwave Dish with Various Microphone Configurations
Authors: Harvey F. K. , Wallace R. L.
Published: October 2005

The performance of parabolic microphones using a 6-ft microwave dish as the reflector is examined over the voice range. As is well known, if a single microphone is placed at the focal point of the reflector, the performance of the combination is strongly dependent on frequency. The beam width decreases and the gain increases as the frequency rises. More uniform performance is obtained by replacing the single microphone with a linear array in the focal plane. This tends to make both gain and beam width independent of frequency.
Basic Elements in Piano Scale Design with Plain Strings
Authors: Kent Earle L.
Published: October 2005

Consideration must be given to space limitations, string tension, string diameter, inharmonicity coefficients, tensile strength of wire, and the musical character of the tones produced by the strings, in establishing the scale design for the plain strings in a piano. Mathematical expressions involving these basic elements are well known, but a study of several commercial pianos indicates that it is probable that empirical and graphical methods are relied upon for scale design more than the use of mathematics that relate all of the basic elements. Modern computers provide means for optimizing smooth string-to-string relationships in scale design without the drudgery that would be involved otherwise. A flexible mathematical tool for smooth scale design is provided when expressions are developed that correlate vibration frequencies, string mass, string length, string tension, the energy in the vibrating string, tensile strength, and the inharmonicity due to string stiffness.
Intelligibility of Temporally Interrupted Speech
Authors: Powers Gerald , Speaks Charles
Published: October 2005

Previous experiments have demonstrated that intelligibility of interrupted speech is dependent upon several parameters including interruption rate, speech-time fraction (STF), ON time, OFF time, and message rate. Our experiments suggest a more parsimonious model that incorporates only ON time and OFF time expressed relative to average word duration. Messages spoken at rates of 186 and 246 wpm were interrupted at rates ranging from 0.42 to 20.0 ips for STFs of 0.67, 0.50, and 0.33. At slow interruption rates, intelligibility was dependent primarily on STF. Intelligibility functions then passed through a minimum located in the vicinity of 1.0–2.5 ips, followed by rapid recovery to nearly 100% intelligibility at 10 ips. The exact location of minimum, however, varied with both message rate and STF. The data can be viewed more simply by a model that incorporates two switching parameters, ON time and OFF time, and temporal characteristics of the message. Equal-intelligibility contours will be described that illustrate the nature of the trading relation between ON time and relative OFF time that is required to maintain a criterion intelligibility level.
CHAOS Clipped Hydrophone Array Output Simulator
Authors: Nickles J. C.
Published: October 2005

A clipped array simulator has been developed for use in testing and evaluation of DIMUS beamformers and associated processors. It provides 96 simulated clipper outputs, consisting of two directional signals plus uncorrelated noise. Steering and signal-to-noise ratio for each of the two signals are externally controlled either by a paper tape reader, using a program tape prepared in advance, or by an on-line computer. Mixing of the signals and noise is performed on the binary data, using a time partitioning technique, which is shown to produce the same correlation matrix as would analog summation followed by clipping.
Self-Demodulation of Pulsed Carriers
Authors: Davy B. A. , Muir T. G. , Hixson E. L.
Published: October 2005

Nonlinear effects cause demodulation of a pulsed carrier such that a signal proportional to the second time derivative of the square of the pulse envelope develops in the insonified medium. Several different types of pulse envelopes, i.e., rectangular, triangular, and trapezoidal, were utilized to modulate a 455-kHz carrier. The projector was a 3-in.-diam circular piston located at a depth of 10 ft in a fresh-water lake. A low-pass filter was used to eliminate any of the carrier frequency signals not absorbed by the water. The amplitudes and beam patterns of the self-demodulated waveforms were measured. [This work was sponsored by the U. S. Navy Office of Naval Research and the National Science Foundation.]
Analysis, Testing, and Design of Lined Ducts
Authors: Wirt L. S.
Published: October 2005

Lined ducts containing flow and intense sound have been extensively studied in recent years. Parametric studies have revealed so many variables that design procedures are obscured. Analysis by solution of the convected wave equation has been complicated by uncertainties about the actual modal distribution and by uncertainties about the actual boundary impedance. As a result, when discrepancies occur between experimental and analytical results, it is difficult to interpret whether the wave equation solution, the modal assumption, the impedance value, or the test procedure is deficient. The simultaneous refinement of all four factors has resulted in a very satisfactory correlation between theory and duct test results and provides a basis for lucid duct design procedures and the evolution of new linear materials. A duet test facility has been built which appears to provide equipartition of energy. The impedance of nonlinear materials has been redefined and measurement methods modified. Contours of equal duct attenuation in the impedance plane have been generated and prove to be simple in shape. From these a design methodology is deduced which may be applied to any linear material and which eliminates many redundant parameters. The new methodology had led directly to the creation of new linear materials.
Analytical Model for the Acoustical Behavior of Ring-Reflector Arrays
Authors: Wilkinson J. P. D.
Published: October 2005

A numerical method is presented for the analysis of the underwater behavior of a ring-reflector array. The array is treated in two-dimensional form. The analysis can predict the acoustic radiation pattern of such an array, as well as the stress distribution in the ring and the reflector, and the electrical admittance of the ring. The ring is modeled as a ceramic ring driven by an applied voltage. Magnetostrictive rings can also be accounted for with almost equal ease. The reflector may be modeled as a continuous sheet, or a series of rods. In either case, any losses from damping can be accounted for by the analysis. The analytical approach is based upon the use of a sheet of acoustic sources and a sheet of force sources that are overlaid on the ring and reflector boundaries.
The High Drive Properties of Whisker Reinforced Piezoelectric Ceramics
Authors: Lester William W.
Published: October 2005

The properties under high drive conditions of disk specimens of whisker reinforced composite ceramics are compared with the similar properties of commercially available nonreinforced ceramics of the same general family. The ceramics are of the lead zirconate titanate type with the whisker content of two grades of alpha alumina (sapphire) in five weight percent amount. Observations are made of stress, strain, electric field, resonant frequency, modulus, and electrical impedance. It is found that the whisker reinforced materials exhibit good linearity of stress, strain, resonant frequency, and modulus at high drive when compared with commercial samples of the same family, which are often markedly nonlinear. The conclusion is drawn that specimens, even of “soft” type ceramic, when whisker reinforced, are made “hard” in many of their properties. [This work was supported by the Office of Naval Research.]
The Acoustical and Mechanical Properties of Sonite
Authors: Higgs R. W. , D'Amico P. M. , Speerschneider C. J.
Published: October 2005

The acoustical and mechanical properties of Sonite have been measured as a function of isostatic compression and ambient pressure. Materials with original densities of 20 and 35 lb/ft3 were isostatically compressed to 2500, 5000, and 10 000 psi for several cycles to achieve dimensional stability. The sound velocity and attenuation at 40 kHz were obtained using a water-filled impedance tube. For 20-lb/ft3 Sonite samples separately compressed to 2500 and 10 000 psi, the sound velocity was 910 m/sec at 500 psi and 1640 m/sec at 10 000 psi, respectively. For 35-lb/ft3 Sonite similarly prepared, the sound velocity was 1020 m/sec at 500 psi and 1460 m/sec at 10 000 psi, respectively. Some anomalous behavior was observed in the 35-lb/ft3 material at low compacting pressures. Using a delay line technique at 1 MHz, the materials were found to exhibit transverse isotropy. The elastic and anelastic volume change of these materials with pressure was also measured. Details of the results will be presented and discussed.
Detection of Thermal Cracks in Railway Wheels Using Ultrasonic Surface Waves
Authors: Dalvi N. G. , Finch R. D.
Published: October 2005

One-quarter scale model wheels were used and thermal cracks were simulated by inscribing flaws on the wheels' tread. Surface wave pulses of approximately 200- to 600-kHz frequency were generated on the tread with piezoelectric probes. Two methods were employed for detection of the simulated thermal cracks. In the attenuation method, the increase in attenuation of a surface wave over several circuits on the wheel indicates the presence of cracks. In the pulse-echo method, an echo from a crack is used. Experimental results show that both methods are feasible. Using the same probe and at the same frequencies the attenuation method is able to detect shallower flaws than is possible with the pulse-echo method. The ratio of attenuation coefficient with a flaw present to that without, is termed the flaw attenuation factor. Values of this parameter have been determined and it is found that in the ranges tested it increases exponentially with increasing flaw depth.
Physiological Noise as a Low-Frequency Masker: The Cardiac Cycle
Authors: Soderquist D. R. , Lindsey J. W.
Published: October 2005

It is often stated that an absolute threshold is a special case of a masked threshold. The masking in the former situation is usually assumed to be physiological noise inherent in living organisms (i.e., breathing, heartbeats, circulation, etc.). This study quantifies the effects of one such physiological masker, heartbeat, on the detectability of a low-frequency tone (100 Hz, 100 msec in duration). Using a yes/no signal detection paradigm, binaural sensitivity (d′) was examined as a function of the place where the signal occurred within the cardiac cycle. The independent variable was the temporal delay in signal onset following the EKG R-wave. Eight signal delays were selected (0.0–700 msec, in 100 msec steps) and presented to Ss in separate sessions. The sessions were presented randomly with each session consisting of 500 trials. The initial 100 trials were used as warm-up and as settling-in by the S; the last 400 were used to calculate the sensitivity index. The experiment was replicated by each S and the d′ estimates calculated over the two replications (800 trials). The Ss were extensively trained, and the signal intensity was such that baseline data yielded a d′ of approximately 1.50–2.00. Initial results reveal a cyclic function with a decreased (lower) sensitivity at signal delays of 100, 300, and 600 msec following the onset of the EKG R-wave. In contrast, maximum sensitivity occurs with the onset of the R-wave and 200 msec afterward. The effect is relatively small, however, with the largest change in sensitivity (highest to lowest) being approximately 0.60 d′ units.
Auditory Adaptation and the Coding of Loudness
Authors: Weiler Ernest M. , Loeb Michel
Published: October 2005

An investigation was performed to test various predictions made by Small, based on data of Hood, Egan, and others. More adaptation occurred with equal test and adapting intensities than with the same test intensities and adapting intensities 10 dB less. No significant decrease occurred with the test and adapting values equal to one another over the case with an equal test intensity and an adapting intensity 10 dB greater. There was, however, significantly less adaptation that when the adapting tone was 30 dB greater. The first two findings are in accord with Small's theory (unmodified); the last is not. Generally with test and adapting tones equally intense, adaptation increased up to an asymptote at approximately 60 dB and then failed to increase significantly through 80 dB. Essentially, this agrees with Jerger and with Palva and Karja. Possible interpretations are discussed.
Structure of Phonemic Information in the Nasal Output
Authors: Sharpley Alan D.
Published: October 2005

The relative informational content of the acoustic output of the oral and nasal cavities was evaluated by means of the diagnostic rhyme test. Eight listeners served under three experimental conditions (nasal output alone, oral output alone, and electronically mixed oral and nasal outputs) and a control. The oral output exhibited a significant deficiency in nasality information. The nasal output exhibited a significant deficiency in the information as to the states of five other consonant attributes, but nevertheless contained significant amounts of information concerning these attributes.
Recognition of the Sex of Esophageal Talkers
Authors: Weinberg B. , Bennett S. , Horn Y. , Li K.-P. , House A. S.
Published: October 2005

The sex of 18 male and 15 female adult esophageal talkers was identified correctly about 90% of the time by a group of naive listeners (n = 18). Various physical parameters of the speech signals were analyzed in an attempt to find correlates to the listener's judgments. Phonation time, rate, and, in particular, fundamental frequency did not account for the listener's performance. Spectral characteristics derived through correlation matrix [K.-P. Li, G. W. Hughes, and A. S. House, J. Acoust. Soc. Amer. 46, 1019–1025 (1969)] Were highly related to the recognition performance of the listeners, suggesting that the judgments might have been related to some measure of vocal-tract size. [This research was supported in part by the National Institute of Neurological Diseases and Stroke and in part by the Air Force Cambridge Research Laboratories.]
The Susceptibility of the Chinchilla Ear to Damage from Impulsive Noise
Authors: Luz G. A. , Mosko J. D.
Published: October 2005

Chinchillas were exposed to the same levels of impulsive noise as were a group of monkeys. The impulses (of 168-dB peak pressure) resulted in large hearing losses in the chinchillas, although only slight losses were observed in monkeys exposed to the equivalent number of impulses, and no losses were observed in humans exposed to more than the equivalent number of impulses. This finding appears consistent with past knowledge of the anatomical differences between the ear of the monkey and the chinchilla.
Effect of Snowmobile Noise on Small Rodents
Authors: Haag F. G. , Walker W. A. , DeMartino G. N.
Published: October 2005

The relationship between immediate activity response and snowmobile noise level was measured for 30 female white mice ranging in age between 90 and 120 days. The mice were divided into three groups: the first was exposed to 85±4 dB (flat); the second to 95±4 dB (flat); and the third was a control group. The sound was a tape recording of several snowmobiles. The predominate tones were at about 500 and 1000 Hz. The mice were exposed for a period of 1 min for approximately three times each day. The experiment lasted for 24 days. Once each day the motion of each mouse was measured in an activity box during the exposure and for 5 min following the exposure. The data does not show a statistically significant difference in immediate activities between the exposed and nonexposed mice. The over-all stress response was measured by adrenal gland weight. At the end of the experiment, the adrenal gland weight was determined for each mouse. There was no statistical difference in adrenal weight per unit body weight between the exposed and control groups.
Ground Motion from Sonic Booms
Authors: Mickey Wendall V. , Bayer Kenneth C.
Published: October 2005

There are over 1100 seismograph stations throughout the world which could be used to monitor sonic booms. The United States has 287, Asia 337, and Europe 185. Most of these stations measure ground motion in three orthogonal planes making possible the determination of the angle of incidence of the impinging wave yielding a gross values for aircraft speed. Ground motion in terms of earth particle velocity is generated by the overpressure. The seismic data provides: (1) exact time of occurrence, (2) gross overpressure, and (3) approximate aircraft speed.
Analyses of Propeller Vortex Noise
Authors: Brown D.
Published: October 2005

A detailed experimental program of noise measurements was conducted on a low-speed 4-ft diam propeller with variations in blade number, tip shape, tip speed, and blade angle. Narrow-band analyses of the noise data indicated blade passage harmonics of up to the 60-mB order are present and dominate the frequency regime usually associated with broad-band “vortex” noise. Additionally, a high-frequency component, in the region of seven times the Strouhal frequency, is extremely apparent in the data. This component is sensitive to tip shape and tip angle of attack and in some cases dominates the over-all sound-pressure level near the propeller axis. A similar phenomenon has been previously observed in helicopter noise spectra, but neglected owing to its apparent insignificance relative to the rotational noise. An interpretation of these findings and semi-empirical approaches to the prediction of their component levels are presented.
Further Discussion of Broad-Band Fan Noise
Authors: Kelly J. C.
Published: October 2005

This paper continues the discussion of broad-band fan noise concepts begun in a paper presented to the November 1970 ASA meeting [J. C. Kelly, “Broad-Band Fan Noise,” J. Acoust. Soc. Amer. 49, 108–109(A) (1971)]. It reopens by questioning the total validity of unsteady aerofoil theory. In particular, it examines the importance of the trailing edge condition both from an aerodynamic and an acoustic viewpoint. It also asks whether the modeling of flow distortions as two-dimensional gusts can be upheld at the higher reduced frequencies. The conclusion is that it is probably necessary to discard such theory altogether for the high reduced frequency engine flow distortion fan interactions which we expect to generate broad-band noise. The more positive aspect of this second paper is the substitution of a model that can discern between propagating and nonpropagating reduced frequency components of the flow over a finite surface. This leads to a delineation between M8, M6, and M3 power law regimes for acoustic radiation from the surface.
Problems in Building and Manipulating Large Stiffness Matrices
Authors: Hackney J. R.
Published: October 2005

Large computer systems have enhanced the use of finite element methods to build structural stiffness matrices with many degrees of freedom. The building and manipulating of these matrices as required for dynamic analyses presents many difficult problems. Often these problems are encountered by the analyst during final phases of a project. When this happens, schedules are missed and costly computer reruns are required. The purpose of this paper is to focus attention on more common problem areas and to suggest methods of solutions to these difficulties. Problem areas that are discussed include: (1) determination of correct input parameters for structural analysis computer programs, (2) reduction of unconstrained structural stiffness matrices, (3) reordering and rearranging structural stiffness matrices, (4) assemblage of matrices by stiffness coupling techniques, (5) methods of checking unconstrained stiffness matrices, and (6) eigenvalue solutions for determining resonant frequencies and mode shapes of structural systems.
The Use of Large Matrix Techniques to Obtain Dynamic Models of Spacecraft
Authors: Wada B. K. , Bamford R. M. , Gayman W. H. , Alper M. E.
Published: October 2005

The evaluation of the dynamic characteristics and response of large complex structures effectively utilizes large matrix techniques to generate parameters necessary for the dynamic analyses. However, small matrix techniques, in core analyses, are desirable for the dynamic analyses. The discussion is based on analyses of spacecraft with consideration of test requirements, availability of damping parameters, availability of experience or subsystem hardware, and transfer of data between organizations. Various considerations on large matrix techniques for the problem reduction and the advantages of small matrix techniques for dynamics solution will be discussed. The presentation is based on experience at Jet Propulsion Laboratory in performance of dynamic analyses for projects with schedule and cost constraints.
Noise Exposure, Tolerance, and Isolation for Educational and Entertainment Buildings
Authors: Christoff Jerry P. , Veneklasen Paul S.
Published: October 2005

A matrix approach is described for the analysis of sound-isolation requirements. In one dimension we have the variety and circumstances of increasing noise exposures resulting from sources and distances. Orthogonally, we have tolerance criteria based on functional or esthetic considerations in order of decreasing levels. In the third orthogonal dimension we have the spectral analysis of either exposure or tolerance. The grid intersections of this three-dimensional matrix form a difference spectrum that specifies the sound-isolation requirements for placing a given activity or edifice in a given noise field. An isolation spectrum may be specific and differ for various surfaces of the building: hence, the design challenge presented to the acoustical designer. This form of analysis clearly exposes the complexities of sound-isolation technology, often ignored in the architect's or owner's naive notion of the acoustician's function. It discloses that one number ratings of sound magnitude, goal, and exclusion are superficial and that the cost- or weight-conscious designer will choose a balanced sound-control design to suit quantitatively definable circumstances. Specific examples are analyzed for schools, churches, auditoriums, hospitals, TV, and recording studios.
Exterior Shell Building Design for Office Occupancy Adjacent to Aircraft Runways
Authors: Oliphant Kenward S.
Published: October 2005

This paper describes a series of acoustical isolation designs affecting the building shell and its required penetrations for office occupancy, from jet runways where aircraft under takeoff conditions pass within 150 ft of subject building. Outside sound-pressure levels on building roof together with inside sound-pressure levels will be presented for the completed structure.
Directional Hearing with the Submerged Ear
Authors: Ray Brian , Stephens R. W. B.
Published: October 2005

In two independent series of tests involving scuba divers, the ability of the subject to indicate the direction of a wide-band sound source was measured. For the first test the diver was weighted so as to be freely suspended in midwater with no reference as to his orientation in the horizontal plane. An efficient blackout was clamped to his face mask. A photographic technique was used to record 178 judgments by six subjects. The sound source was moved between each judgment to avoid error due to reflections from bottom topography. The results were analyzed to provide an independent measure of the subjects self-consistency and mean pointing error. In the second tests the blindfold subjects were provided with a firm seat on the seabed. They were asked to indicate from which of two possible directions the sound was generated. The angle subtended by the two source positions was varied. In all, 1300 judgments were recorded. The freely suspended subjects were able to indicate the sound direction within a standard deviation of 50°, whereas the seated subjects indicated to within 20°. It is suggested that the difference between these results is attributable to the latter observers having a reference as to their orientation. To confirm this, further tests of the first type were recorded where the diver was provided with contact with the seabed. In these cases the deviation was reduced to 20°.
A Miniature Ceramic Microphone
Authors: Killion Mead C.
Published: October 2005

The traditional goal of the hearing aid transducer designer has been the maximization of speech perception under adverse conditions. The resulting transducers have thus had a frequency response extending from roughly 300 to 4000 Hz, falling off rapidly above and below those frequencies. An alternate goal—a more “natural” sound—necessitated a new approach. A ceramic microphone with a built-in FET preamplifier was designed to occupy only 0.006 cu in. and yet have a wide smooth frequency response. Studies made on an electrical analog of the microphone verified the availability of several potentially useful frequency responses. The actual shape of the final frequency response was dictated by head and ear diffraction studies, amplifier considerations, and listening tests.
The Interaction of Ultrasound and Mammalian Central Nervous System Tissue
Authors: Fry F. J. , Dunn F.
Published: October 2005

Threshold dosage parameters necessary for lesion production by focused ultrasound have been determined in the frequency range 1–6 MHz for adult cat and rat brain. The intensity range studied extends from 100 to 20 000 W/cm2, and no appreciable dependence upon frequency is observed below cavitation levels. A thermal mechanism is operative in the lower intensity ranges (from about 102 W/cm2 and below) and, in the intermediate intensity range, the data imply that a nonthermal, but as yet not understood, mechanism dominates wherein neural tissue can be modified selectively. Embryonic neural tissue, represented by the spinal cord of day-old mice, is affected functionally at much lower dosage levels than for the structural modification of adult animal neural tissue. Such data obtained using the mouse cord at 1 MHz and at 500 kHz and at base temperatures of 2°–45°C imply a nonthermal mechanism operative over much of the range investigated. Interaction effects not associated with lesion production indicate a reversible type phenomena for some aspects of the electrical conduction process in the visual pathway in brain. Other interaction effects to be discussed are the ultrasonic visualization, in the monkey and man, of fluid filled space-soft tissue interfaces, gray-white matter interfaces, and ultrasonically produced lesions. Trauma induced by simple needle insertion will be discussed also.
The Vibratory Pattern of the Round Window in Cats
Authors: Khanna Shyam M. , Tonndorf Juergen
Published: October 2005

The middle ear was removed surgically, and the cochlea was acoustically driven in a tightly closed system built over the oval window niche. Sound pressures were monitored by a probe microphone, its opening being located about 3 mm above the footplate. The round window was coated by a fine bronze powder. Vibration patterns were obtained by time-averaged holography. Initial technical difficulties were presented by the small size of the window (holographic resolution), its complex shape (viewing angle), and the oozing of fluid from its mucus-membrane covering (obscuring the window). Because of the window's small size, a relatively simple pattern had been expected. However, even at low frequencies, the pattern was already complex. This complexity made the evaluation of volume displacement difficult, and also that of inner-ear impedance. Results will be compared to those of an earlier study [Tonndorf et al., Ann. Otol. 75, 752 (1966)], which evaluated inner-ear impedance on the basis of displacement measurements of the round window obtained by a capacitive probe, while the displacement pattern was unknown. [Supported by a number of NIH grants.]
Further Observation on Cellular Changes of Acoustically Stimulated Organ of Corti
Authors: Lim David J. , Melnick William
Published: October 2005

This report is a more detailed electron-microscopic observation of fine cellular changes occurring in the sensory cells of the organ of Corti following acoustic stimulation than a report made at the last Society meeting. It was observed that the most striking change was related to the endoplasmic reticulum. It was further noted that the endoplasmic reticulum is connected to the outer membrane of the nucleus, and more significantly, to the subsynaptic cisternal membrane. This finding supports the concept that the endoplasmic reticulum participates in the neural conduction of the sensory cells as in the case of the striated muscle cell sarcoplasmic reticulum. This new concept will be discussed in detail together with its functional implication. [Supported in part by an Air Force contract from WPAB and by the Deafness Research Foundation.]
Vibration Exciters with Interchangeable Heads
Authors: Booth Galt
Published: October 2005

A new concept in electromagnetic vibration exciter design, in which the entire dynamic portion of the vibration exciter can be quickly changed, provides optimization of performance characteristics for specific applications. Since a head with the specific performance characteristics needed for the job can be selected, it is no longer necessary to use a compromise design. The performance characteristics discussed include those applicable to 200g testing, the testing of large objects where high side load capability and a rigid table are essential, the measurement of structural modes, impedances, and transfer functions, and confirmation calibration of accelerometers and other transducers. The design objectives and solutions are presented for the stiff highly damped suspension systems that make interchangeable heads possible. The moving element skeletons of five different heads are described in detail, showing how the different performance criteria for various applications are achieved. Included in the program are three different vibration exciter sizes with four or five heads for each.