bluuebunny/crossref_metadata_2025 huggingface dataset:
Basic Directivity of Jet Noise with Improved Correction for Refraction
Authors: Ribner H. S. , MacGregor G. R. , Lam H.
Published: October 2005

In earlier work of Grande, experimental jet-noise polar plots were corrected for refraction (by experiment) and for convection (by theory) to yield the experimental basic directivity in narrow frequency bands. The experimental correction for refraction at each frequency was obtained from the difference in the directional patterns of a point source placed in the air jet with jet off and jet on. Before refraction, this point source will produce a spherical directional pattern, but the narrow-band jet noise will have an elongated pattern owing to convection. It has been realized belatedly that the refractive change in intensity at corresponding angles cannot be taken as the same for the two different initial polar patterns: there is some violation of energy conservation. To avoid this error, later unpublished measurements by MacGregor have been reworked by Lain, incorporating a correction to the refraction effect measured with the point source. The correction was specified by an assumed functional form as a polar plot; the amplitude was then dictated by the requirement of conservation of energy. The measured jet noise data, processed along the lines of Grande, then leads to much improved agreement of experiment and theory. [Research supported by Air Force Office of Scientific Research.]
Perception of Pitch of Single Period Tones
Authors: Jenkins-Lee J. E. , Schubert E. D.
Published: October 2005

The ability of the normal human subject to perceive a pitch percept from short-duration pure-tone signals, namely, single period sinuosids centered at 250, 500, 1000, and 2000 Hz, has been investigated. Instrumentation developed for this research allowed the experiment to be pre-programmed and progress at a rate established by the speed of the subject's trial response. Five subjects completed 20 programmed sequences of 200 presentations. In each 200-trial program of the 2IFC paradigm, the reference signal was presented first in exactly 100 of the trials in a predetermined, quasirandom sequence. Five frequency ratios were presented; the values, ΔF/F, were 0.200, 0.150, 0.100, 0.050, and 0.025. Psychometric functions derived from the data show that these subjects could reliably differentiate between pitches of single period signals of different frequencies. The mean value of the relative pitch DL in the 250- to 2000-Hz region was found to be 0.10±0.01 when the conventional detection criterion, P(C)=0.75, was employed. It is noted that the deviation is almost symmetrical about the mean; thus, the value of the averaged relative pitch DL is believed to be approximately constant within the range investigated
Auditory Pattern Discrimination in the Absence of Spectral Cues
Authors: Leshowitz Barry , Hanzi Raquel
Published: October 2005

Previous research has shown that brief sounds can be discriminated on the basis of differences in the spectral content of the waveform. The aim of the present work was to assess the importance of spectral processing in the perception of temporal order. In the first study, in an effort to prevent spectral information from serving as the basis for perception of temporal order, sequences of four tones were presented dichotically in a repeated tape loop. Component tones in the sequence were administered to the left or right ear according to a predetermined random order. On each trial, two sequences of tones were presented, and the task of the observer was to determine whether the order of presentation was the same or different for the two sequences. The duration of component sounds required for reliable discrimination was 90 msec. The duration threshold for a diotic presentation was 10 msec. A second study investigated the perception of temporal order for high and low tone bursts presented in a nonrepeated sequence consisting of the two tones, a noise, and a buzz. Here the task was to determine whether the order of the high and low tones in the two sequences was the same or different. The location and temporal order of the buzz and noise in the two sequences were randomized and irrelevant to the discrimination. Temporal order could be perceived when the duration of each component sound was 20 msec. [This research was supported by the National Institute of Health.]
Detectability of the Deletion of a Tone from a Tonal Pattern for the Chinchilla
Authors: Burdick C. K.
Published: October 2005

When presented with repetitive, three-tone patterns, chinchillas learned to make an avoidance response to an infrequent change in the frequency of the second tone but did not learn a response to the deletion of the second tone. This, together with other comparable data, may reflect the manner in which the chinchilla uses hearing in its natural environment.
Perception of Temporal Order: Special Rules for the Initial and Terminal Sounds of Sequences
Authors: Warren Richard M.
Published: October 2005

If a pattern of three or four successive sounds (consisting of hisses, tones, and buzzes) is repeated without pause, listeners cannot identify the order at durations of individual items well above 100 msec, even though each of the component sounds is heard clearly. However, if two of these sounds are each presented once with one following the other, it is possible to identify temporal order for durations below 50 msec. It has been suggested that accurate perception of order with such stimulus pairs might involve special mechanisms permitting identification of items at the beginning and end of auditory sequences [Warren, Obusek, Farmer, and Warren, “Auditory Sequence: Confusion of Patterns other than Speech and Music,” Science 164, 586 (1969)]. The present experiments demonstrate that introduction of a silent interval of 3 sec between repetitions of sequences consisting of three or four successive items each lasting 200 msec facilitates detection of temporal order. It appears that sounds present at initiation and termination of a sequence can be identified readily, and that these cues can be separated experimentally from direct identification of temporal succession. [This research was supported by the National Science Foundation.]
Binaural Detection in a Sequential Detection Paradigm
Authors: Gilliom J. D.
Published: October 2005

An extension of the work reported by this author at the Washington meeting, the present study examines sequential detection in two frequency regions assigned to separate earphone channels. The observer's task was to make yes-no decisions concerning the presence of a sinusoidal signal in each earphone channel. A sequential ordering of observation intervals between earphone channels existed for all experimental conditions. The frequency region to be monitored in the right ear was always 630 Hz. Eight experimental conditions were formed by varying whether the order of presentation of observation intervals across earphone channels was fixed or random, whether the frequency region assigned to the left ear was at 630 or 1400 Hz, and whether the Gaussian noise background across earphone channels was correlated or uncorrelated. All experimental conditions were evaluated relative to performance in corresponding single-channel conditions. Results observed include: (1) Knowledge of the presentation order of observation intervals had little effect on performance; (2) A much larger decrement in performance relative to single-channel performance was obtained with a correlated noise background when the frequency region assigned to each earphone channel was the same; no such difference existed when the frequency regions were different. (3) Performance in one channel was lower if a signal event occurred in the opposite channel.
Computer Analysis of City Noise—A Preliminary Algorithm
Authors: Guernsey Richard M.
Published: October 2005

A preliminary computer algorithm was developed to analyze city noise. The algorithm is eventually to be included in an over-all cost effectiveness program for city noise control. The basic problems, some unsolved in the preset state-of-the-art, which have been encountered during the development of this algorithm are discussed. The basic structure of the algorithm is described. It is believed that this algorithm can be readily expanded and improved as the state-of-the-art improves. [This work was supported by Cornell University, Department of Environmental Engineering and Resources for the Future.]
Community Noise Levels in Medford, Massachusetts
Authors: Wesler J. E.
Published: October 2005

An extensive noise measurement survey was made in Medford, Massachusetts, a suburb of Boston, during March and April 1971, in order to assess the effects of transportation noise in a typical urban community, and to obtain validation data for a mathematical model developed to simulate such noise levels. Noise measurements were made at 49 locations distributed randomly across the community, with continuous 24-h measurements at five of these locations. The average median noise levels over the entire community were 55.0 dBA during the morning traffic rush hours, and 51.8 dBA during the midday period. Hourly median levels in a typical residential neighborhood varied from a high of 52.9 dBA from 4:30 to 5:30 P.M., to a low of 35.1 dBA from 2:30 to 3:30 A.M. Noise levels were influenced primarily by highway traffic, with a major highway arterial corridor producing the highest noise levels in the community. Rail noise from commuter trains and through freights did not significantly affect the community noise levels. Aircraft, overflying Medford from nearby Logan International Airport generated levels in excess of 60 dBA for roughly 15% of the measurements period. Repeat measurements at a limited number of locations are planned at semiannual intervals, in an effort to determine general trends in noise levels in this community.
Community Noise Levels of the L-1011 TriStar Jet Transport
Authors: Shapiro Nathan
Published: October 2005

In order to halt the escalation of aircraft noise in the vicinity of airports, the Federal Aviation Administration developed, and in late 1969 issued, the Noise Certification Standards of FAR Part 36. The Lockheed L-1011 TriStar, a wide-bodied trijet transport, had been planned not only to meet the anticipated FAA requirements, but to provide the quietest community environment that was technologically practicable and economically reasonable. Powered by Rolls-Royce high bypass ratio engines, with quiet operation a major design goal, and utilizing specially designed acoustical lining for its nacelles, the L-1011 has demonstrated flyover noise levels substantially lower than the FAA specified limits, and also measurably lower than those of competitive airplanes. As a result, community annoyance levels have been achieved that are 65% to 75% below those of the presently operating older jet transports.
Community Noise Survey and Criteria for a Power Station—A Case Study
Authors: Salter C. M. , Hoover R. M. , Bradley W. E.
Published: October 2005

Power companies are expecting to double their electrical generating facilities every 10 years, and in order to build new facilities these companies need the approval of local and state agencies. In this particular study, the power company had a 560-MW facility completed in the late 1960's and petitioned the state for permission to build an additional 560-MW facility. The acoustical criterion proposed by engineers for Unit 2, now being designed, was nondegradation of the present ambient. The sound level of the combined plant must not exceed the present ambient level of 46–50 dBA at the nearest neighbors in all directions. To achieve this criterion, noise sources will be quieted both in the existing unit and in the future unit. This paper presents the results of our initial community ambient noise survey around the existing plant made to establish the present conditions. The individual noise sources determined at that time to be distinct contributors to the plant noise in the community are described. These sources include a 400-MW autotransformer, air intake louvers to forced draft fans, the main 560-MW transformer, and boiler feed pump equipment. SPL data of these sources, both close-in and in the community, are presented as examples of some typical community noise problems associated with power plants. Also the requirements for noise control as related to the planned addition are discussed.
Loudness Discomfort Levels for Pure Tones and Noise
Authors: Morgan D. E. , Wilson R. H. , Dirks D. D.
Published: October 2005

Two studies have been conducted to measure the loudness discomfort levels (LDLs) for subjects with normal hearing. First, the LDL for a 1000-Hz stimulus was measured utilizing the method of constant stimuli, the method of adjustment, and a tracking method. The method of constants provided the most reliable judgments among subjects over six trials. In the subsequent study, LDLs were measured utilizing the method of constants for pure tones at octave frequencies from 125 through 4000 Hz and for two bands of random noise. LDLs (in dB SPL) varied as a function of the stimulus employed. LDLs were highest at low frequencies (through 500 Hz) and relatively constant for 1000, 2000, and 4000 Hz and for the wide-band noise.
Seamount Reflections from the CANNIKIN Underground Explosion
Authors: Northrop John
Published: October 2005

Hydroacoustic signals were recorded from the five megaton Amchitka Island underground explosion (code name CANNIKIN) of 6 November 1971. SOFAR depth hydrophones of the Missile Impact Location System (MILS) off the islands of Midway, Wake, and Oahu in the Central Pacific were used as detectors. In the low-frequency (<20 Hz) band, the main signal was followed by reverberations that persisted for several hours after the shot. Arrival times of some of these reverberations were correlated with those computed for reflections from seamounts in the Emperor Seamount Chain and the Hawaiian Arch. Reverberations from more distant reflectors were separated by quiet periods or “windows” of several minutes duration. The azimuthal and temporal distribution of the “windows” versus the reverberation maxima is investigated in relation to low-frequency ambient noise in the ocean.
A Mathematical Model for Volume Reverberation. II. Simulation
Authors: Jobst W. J. , Smits T. I.
Published: October 2005

A technique for simulating reverberation due to small fish or other discrete scatterers is presented. A simulated ocean volume is filled with Poisson distributed scatterers according to a model proposed by D. Middleton. Each scatterer is assigned a random location and a random reflectivity. By adjusting the simulation parameters, the simulated reverberation envelope was made to agree statistically with the envelope of reverberation observed experimentally in the ocean. The simulation is particularly useful for estimating the true probability distribution of scatterer reflectivity and true scatterer density from experimental data influenced by a transducer beam pattern.
Interaural Intensity Differences in Dichotic Speech Perception
Authors: Thompson C. L. , Stafford M. , Cullen J. K. , Hughes L. , Lowe-Bell S. , Berlin C. I.
Published: October 2005

Three studies are reported in which the intensities of dichotic stimuli were varied. In Study 1, one signal remained at 80 dB SPL while the other was varied from 30 to 80 dB in 10-dB steps. In Study 2, one ear was held at 50 dB while the other ear's signal was varied from 30 to 80 dB in 5-dB steps. In Study 3, the signals were varied from 30 to 80 dB SPL in 10-dB steps but with equal intensities to the two cars. Eleven subjects were used in each of the former studies and 12 in the latter. Study 1 shows asymmetry in favor of the right-ear messages even when they are 10 dB less intense than the left. Data of Studies 2 and 3 also show asymmetries but in a more complex fashion.
Extension of Interaural Delay for Intelligibility
Authors: Gerber S. E.
Published: October 2005

At the previous meeting we presented some data to suggest that a notch appears in the intelligibility function at integral multiples of 50 msec. The data were extended only to delays of 150 msec on a relatively small group of listeners. The present paper reports data on a virtually identical study extended now to 275 msec in 25 msec steps, with and without noise added, and tested on a highly reliable listening panel. The significance of these data is discussed, and consideration is again given to the coherence of the signal and the noise.
The Measurement of the Bulk Modulus Loss Factor of Small Solid Specimens
Authors: Wilson Geoffrey L.
Published: October 2005

The bulk modulus loss factor of small, relatively loss-free solid specimens is one of the most elusive elastic constants to measure, as it is essential that the losses in the apparatus be reduced below those of the sample. One technique uses the change in decay time when the sample is introduced into a resonant body of liquid. Early experiments involved the use of a longitudinal standing wave in a tube, but losses due to wall friction were excessive. Wall friction losses have been minimized by the use of a radial resonance in a spherical container, and with the use of a vacuum jacket to reduce acoustic radiation, a Q as high as 80 000 has been achieved; however, there were practical difficulties due to asymmetries in the vessel and to multiple resonances in the walls. The present experiments involve a compromise, using a predominantly radial mode in a cylindrical vessel. Both thin walled (resilient) and thick-walled (nearly rigid) vessels have been used. The limitations inherent in these measurements will be discussed.
Speed of Sound in Liquid Metals and Alloys
Authors: Jarzynski Jacek
Published: October 2005

The speed of sound c in liquid metals and alloys is calculated using the perturbation theory of liquids and the pseudopotential theory of metals. An effective hard-sphere diameter, as defined by the Gibbs-Bogoliubov inequality, and its density dependence are determined for each metal from thermodynamic data. The structure independent contribution to c is calculated from the expression for cohesive energy given by Heine and Weaire [Solid State Phys. 24 (1970)]. The results, including the temperature and pressure dependence of c, are in quantitative agreement with experimental data.
Macromolecular Interaction in the Absorption of Sound in Erythrocytes
Authors: Kremkau F. W. , Cartensen E. L. , Aldridge W. G.
Published: October 2005

Whereas it has been recognized for some time that the absorption of sound in suspensions of erythrocytes is primarily a macromolecular phenomenon, recent observations have led us to believe that interactions between macromolecules may play a significant role as well. Two tests of the interaction postulate are reported: (1) Bovine erythrocytes fixed in acrolein and glutaraldehyde are sufficiently stable that they can be subjected to fairly harsh environmental changes without loss of hemoglobin or change in microscopic structure. This stability results from cross-linking of macromolecular hydrophobic groups by the fixing agent. The specific absorption of fixed erythrocytes is greater than that for normal cells by as much as a factor of 3.5 at 90 MHz. The new relaxing elements added by fixing are concentrated at frequencies above 10 MHz. (2) Interaction of ionic groups should be increased by decreasing the dielectric constant of the suspending medium. Suspension of fixed erythrocytes in the solvents ethylene glycol and ethanol further increases the absorption by as much as a factor of 3.5 at 10 MHz. The relaxing elements added with solvent change are skewed toward frequencies below 30 MHz. Scattering, viscous relative motion, and thermal absorption have been ruled out as explanations for the observations. The explanation is more apt to lie in some forms of chemical or structural relaxations.
In-Ear Measurement of Noise
Authors: Brammer A. J. , Piercy J. E.
Published: October 2005

A measure of the sound field at the base of the concha, obtained by using a miniature microphone located within the ear, provides information on the acoustical signal entering the ear canal. When combined with a portable tape recorder, the apparatus can be used to evaluate an individual's exposure to noise and appears to be particularly suited for use in directional sound fields that vary in the vicinity of the head. In order to compare the data obtained with existing criteria for hearing conservation, or sound level meter measurements in a diffuse field, a transfer function is used to produce the equivalent diffuse field that would exist at the center of the head in the absence of the subject. The device has been used to measure the noise levels experienced by operators of snowmobiles and chain saws as a function of time, and the attenuation and, in some cases, amplification of sound produced by some common forms of crash helmet and headgear. An over-all accuracy of ±2 dB is obtained from 100 to 5000 Hz by using a spectrum shaper and a built-in calibration system.
Auditory Temporary Threshold Shift in Snowmobile Users
Authors: Chaney R. B. , McClain S. C.
Published: October 2005

It has been determined that the noise levels of many snowmobiles and other all-terrain-vehicles frequently exceed criterion values of safe exposure as a function of time. However, there are obvious limitations to the use of the CHABA criteria for determining hazardous noise exposure, since typical snowmobile use does not approximate the extent of exposure implied by the “working-lifetime” concept. Thus, the empirical determination of the amount of TTS resulting from “typical” exposures, whatever they may be, seemed to provide a more relevant approach to the question of whether snowmobile noise poses a hazard to hearing acuity of operators and passengers. TTS measurements were obtained on a number of individuals of all ages under field conditions (within 1–15 min of termination of exposure). Significant amounts of TTS were observed to be occurring in a large proportion of the persons tested. The implications of this study are discussed in terms of the users, the manufacturers, and the CHABA criteria for hazardous noise exposure.
Noise and Measurement Problems Associated with Hard-Hat Diving Helmets
Authors: DiMattia A. L. , Pennella J. J.
Published: October 2005

The deep-sea hard-hat diver must be supplied with a copious air flow through his helmet at rates far in excess of his need for life oxygen. If reckoned in terms of free air movement, this flow increases with depth of dive and is required to reduce carbon dioxide content resulting from exhaled diver's breath. At a typical depth, the flow rate may be 28 ft3/min or about 800 liters/min. All this air passing through a number of control valves, entrance ports, and discharge valves causes much turbulence, with attendant noise known to reach well into the damage risk levels. This paper explores some special problems encountered in the measurement of diver helmet noise and describes a series of noise measurements performed in a typical helmet under simulated diving conditions.
Insert Earphone Pressure Response in Real Ears and Couplers
Authors: Sachs R. M. , Burkhard M. D.
Published: October 2005

Pressures measured in five real ears and the standard 2-cm3 and Zwislocki couplers have shown that (1) Pressure in Zwislocki coupler is essentially identical to pressure in real ears (with no ear mold leaks) below 500 Hz implying an equivalent real ear volume of about 1.2 cm3. Pressure in 2-cm3 coupler is about 4 dB lower. (2) Between 500 Hz and 5 kHz, the real ear minus 2-cm3 coupler difference increases with frequency about 2.5 dB/oct to about +12 dB at 5 kHz. The real ear minus Zwislocki coupler difference, however, is no more than ±2 dB up to 5 kHz. (3) Above 5 kHz, there is evidence that pressure in real ears decreases with frequency relative to both couplers. Real ear pressure was measured using a probe-tube microphone (corrected to read ear drum pressure); five types of insert earphones (hearing aid receivers) were used. When dealing with insert earphones whose source impedance is very high relative to the input impedance of the coupler (this is usually the case), it is sufficient to measure the insert earphone pressure on the 2-cm3 coupler. Real ear drum pressure can then be determined by applying a correction curve (either graphically or by electronic filtering) to be presented. The Zwislocki coupler would then serve as a laboratory standard for comparison.
Semantic Labeling of Hearing-Aid Acoustics
Authors: Revoile S. G.
Published: October 2005

Hearing aids were measured electroacoustically prior to their issuance to 50 hearing-impaired subjects. For each aid, measurements were conducted with the gain of the instrument at the level set by the subject. After one month of use the subjects completed questionnaires concerning the acoustic quality of these hearing aids. The questionnaire included a checklist of 94 descriptive labels previously obtained from the unrestricted linguistic output of hearing-aid users regarding their hearing aids acoustic qualities. Among the labels on the checklist, the subjects marked those which were appropriate for describing “good” quality or “poor” quality, and the quality of their own aids. Subjects showed greater agreement in their choices of labels appropriate for describing poor quality than for describing good quality. The most frequently chosen labels will be discussed, along with presentation of the relationship between these semantic labels and the hearing aids' electroacoustic characteristics.
On Some Parameters of Hearing Aids with Compression
Authors: Nábělek Igor V.
Published: October 2005

Introduction of compression into hearing aids increases the number of variable electroacoustic parameters of hearing aids. The evaluation of the influence of each individual parameter on hearing aid performance is difficult even with ordinary hearing aids. In addition to the variability in the frequency range, regularity of frequency response, harmonic distortion, etc., hearing aids with compression differ in the range of compression, degree of compression, threshold of compression, etc. One of the significant characteristics is the time constant of compression. Its importance in hearing aids performance is still to be clarified. In the paper the necessity of good description and specification of this parameter for comparability of measurements in different laboratories will be discussed. The values of the release and attack durations, and of overshoots, as determined by measurement, are dependent on the choice of several parameters. The influence of the hearing aid volume control setting, of the operating point on the input-output curve, of the range of the input SPLs, and of frequency will be discussed and shown in several examples.
Auditory Sensitivity in the Tadpole (Rana catesbeiana)
Authors: Weiss B. A. , Stuart B. H. , Strother W. F.
Published: October 2005

Auditory sensitivity in six bullfrog tadpoles was investigated by electrophysiological techniques. Tonal stimulus intensities that generated a standard potential of 0.1 μV in the inner ear showed a hearing range from 100 to 4000 Hz with maximum sensitivity near 1 dyn/cm2 (0.1 N/m2) in the lower portion of the range. The data also indicated that tadpoles lack the place mechanism of adult frogs and thus place as a mechanism appeared at the amphibian metamorphosis in the course of the evolution of vertebrate hearing.
Auditory Sensitivity in the Agouti (Dasyprocta punctata)
Authors: Hartig G. M. , Bayram W. M. , Poynton A. , Peterson E. A.
Published: October 2005

A conditioned suppression technique has been applied to five agoutis and behavioral thresholds measured. Each animal was water deprived and allowed to drink only in the experimental situation. Training was effected by pairing audible tone pulses with shock until the subject learned to cease drinking reliably in the presence of a signal. Auditory thresholds were then assessed at octave intervals. Maximum sensitivity occurred at 8 kHz (0 dB re 2 × 10−4 dyn/cm2), a high frequency cutoff at 64 kHz, and a low-frequency cutoff at 500 Hz. Low-frequency sensitivity may have been impaired by masking or TTS resulting from the loud licking noises produced by this species, although control studies have not verified this hypothesis. It is the authors' opinion that hearing in the Agouti is oriented toward the higher frequencies despite the presence of certain low-frequency structures such as the large bulla. The observed high-frequency bias supports previous findings regarding this animal's basilar membrane.
Guided Interfacial Waves with Applications to Cochlear Mechanics
Authors: Clifton R. J.
Published: October 2005

Waves are considered which propagate along a membrane separating two compressible, inviscid fluids. Capillary forces and membrane tension are assumed to provide the stiffness for the membrane. Dispersion relations are derived for cases of (i) an unbounded region, (ii) a channel for which the particle velocity at the sides is perpendicular to the interface, and (iii) a slit for which the particle velocity at the sides is parallel to the interface. The solution for the latter case is obtained by first solving the problem of diffraction of interfacial waves by a rigid plate in the plane of the interface. Results of case (iii) are used to examine the importance of interfacial waves for wave propagation in the cochlea. Preliminary evidence indicates that such waves may be of primary importance for frequencies in the upper part of the audible range.
Eardum Displacement Following Stapedius Muscle Contraction
Authors: Yonovitz A. , Harris J. D.
Published: October 2005

Simultaneous monitoring in human subjects on the same ear of eardrum displacement by tympanomanometry, and acoustical impedance by the Madsen bridge, provided information concerning contraction of the stapedius muscle and its effect on eardrum displacement. Extensive control procedures were employed to elicit only the stapedius: lower-intensity auditory stimulation, electrocutaneous stimulation of the homolateral external ear canal, and anesthetization of nerves leading to the tensor tympani. (1) Extremely small biphasic and monophasic eardrum movements were seen in the stapedious-only ear to auditory and electrocutaneous stimulation; the form of the response was much less predictable to auditory stimulation. (2) At higher sound intensities, relatively large inward and biphasic movements of the eardrum occurred in the normal ear, unquestionably resulting from contraction of the tensor tympani. These results were further validated in a group of stapedetomized ears, without the stapedius but with normal tensor tympani. (3) Biphasic responses did not occur in the tensor tympani-only ear only monophasic inward responses. (4) Upon air-jet stimulation to the orbit of the eye, these subjects had an accentuated tensor response in that large inward movements of the eardrum occurred as compared to those in normal ears, suggesting that there is an alteration of the tensor response by the presence of the stapedius muscle. Estimates of the actual eardrum displacements were calculated based on a model of the external ear canal and eardrum.
Tympanic Muscle Effects on Middle-Ear Transfer Characteristic
Authors: Nuttall Alfred L.
Published: October 2005

The change in the magnitude and phase of sound transmission through the guinea-pig open-bulla middle ear is measured when two levels of independent, isotonic, tympanic muscle contraction are effected by direct electric stimulation of the muscle bodies. Both middle-ear muscles attenuate the passage of low-frequency vibration giving the largest attenuation for frequencies below 300 Hz, the tensor tympani producing 28 dB maximum attenuation, the stapedius producing 10 dB. In the 1- to 3-kHz frequency range, both muscles are capable of generating an apparent gain in transmission: the tensor tympani giving a gain of 5 dB at 2.5 kHz for maximum contraction, the stapedius 0.5 kHz at 2.5 kHz for maximum contraction. The phase shifts for all contraction cases were leading phase functions. Changes in the magnitude and phase of the transmission are modeled by a second-order low-pass system where the break-frequency increases and the damping ratio and low-frequency magnitude decrease with muscle contraction. The transfer function with maximum tensor contraction had a break frequency of 2.5 kHz with a damping ratio of 0.31, while the stapedius maximum contraction gave a break-frequency of 1.57 kHz and a damping ratio of 0.71. These transmission changes are accounted for the most part, in the model, by a decrease in compliance of the middle ear, but there are also increases in resistance and inertance over the flaccid muscle state.
Animal Exposure to Infrasound
Authors: Johnson Daniel L.
Published: October 2005

The AMRL dynamic pressure chamber (a hydraulic device that produces intense infrasound) recently became operational. Preliminary to human whole body exposures, a variety of experiments with animals are being performed in order to evaluate physiological limits. A monkey, a young baboon, and six dogs of various sizes anesthetized with pentobarbital were exposed from 1 to 4 h at the maximum levels the chamber is capable of producing (172.5 dB from 1 to 8 Hz and falling off 7.6 dB/oct to 158 dB at 30 Hz). EKG and respiration rate (via chest impedance measurements) were recorded. The only observed physiological effects were a decline in respiration rate and some reddening of the tympanic membrane. Except for three of the dogs, these animals were then given exposures in which they were not anesthetized. Exposure levels were gradually increased until all animals received the maximum chamber SPL for 1–14 h. Their behaviors were subjectively observed to be normally calm and occasionally restless. At no time did the animals appear in discomfort or show signs of nystagmus or dizziness. The lack of adverse results of these high exposure levels will be discussed.
Mathematical Considerations in Digital Simulations of the Vocal Tract
Authors: Portnoff M. R. , Schafer R. W.
Published: October 2005

The formulation of a digital simulation of speech production involves two basic steps. The first step is a mathematical representation of the physics of sound generation and propagation in the vocal tract. These processes are of a continuous nature and are generally represented mathematically by differential equations. The second step is the transformation of the mathematical description of the physical processes into a discrete-time model in the form of a set of difference equations suitable for implementation on a digital computer. As a result of this second step, a number of mathematical issues arise that are unrelated to the physics of speech production. These issues often receive insufficient consideration. In fact, it is easily shown that intuitively reasonable discrete-time approximations often have undesirable characteristics. The theory of digital signal processing provides a means for understanding these issues and for formulating accurate digital simulations. This approach is illustrated by a discussion of a simulation involving a soft-walled nonuniform acoustic tube excited by a two-mass model of the vocal cords.
Further Theoretical and Experimental Bases for Quantal Places of Articulation for Consonants
Authors: Stevens Kenneth N.
Published: October 2005

Previous theoretical studies of the acoustic behavior of a vocal-tract model consisting of a tube with a narrow constriction located at different points along its length have suggested that there is a series of constriction positions for which the sound output has well-defined quantal attributes. It has been hypothesized that these positions correspond to places of articulation that are used to produce consonants in a variety of languages. Recent work has refined the theoretical basis on which these places of articulation are predicted, and has shown that the shape of the constriction as well as its positions plays a role in determining the distinctive acoustic attributes of the output, particularly for consonants produced with the tongue blade. Furthermore, data on the acoustic properties of stop and fricative consonants from several different languages have been collected and have been shown to be consistent with the theoretical framework. The predicted places of articulation account for consonants in the pharyngeal, uvular, and velar regions, and several consonant classes in the dental-alveolar-palatal regions. [Work supported in part by National Institutes of Health and in part by the Office of Naval Research.]
A Dynamic Analysis of Two-Dimensional Muscle Force Contributions to Lower Lip Movement
Authors: Abbs J. H. , Netsell R.
Published: October 2005

Movements of the lower lip in the anterior-posterior and inferior-superior dimensions were recorded along with EMG activity from the orbicularis oris inferior (OOI), depressor labii inferior (DLI), and mentalis (M). Observations of activity in these muscles in relation to simultaneous displacement, velocity, and acceleration of lower lip movement suggest that (1) DLI and OOI act primarily to apply forces in the inferior and superior dimensions, respectively; (2) mentalis is a primary force for protrusion of the lower lip; and (3) the lower lip can be characterized, in a preliminary way, as a simple second-order mechanical system. The implications of the technique and the specific findings will be discussed in relation to development of an analog computer model of the labial-mandibular mechanical system. [Research was supported in part by grant from NIDR.]
Real-Time Ultrasonic Imaging by Bragg Diffraction
Authors: Wade G.
Published: October 2005

Bragg diffraction is one of several principles presently being examined in research to produce optical images of objects irradiated by ultrasound. !n this method, laser light is diffracted from the scattered ultrasonic wavefronts as originally predicted by Brillouin in 1921. Historically, some of the first experimental attempts to use ultrasound for imaging were made by Sokolov in his Leningrad laboratory more than 40 years ago. One of the approaches he employed was remarkably similar to the approach presently being pursued and suggested in 1966 by Korpel of Zenith. In our laboratory, we have carried out experiments involving sound frequencies of 15, 18, and 25 MHz and more recently 3.6 MHz. The images obtained at the higher frequencies are at least comparable to those of competing ultrasonic methods. At the lower frequency, special care must be taken to avoid interference between the image beam and the undiffracted light. This paper will discuss the practical problems encountered and will present theorectical calculations to compare several competing approaches presently being pursued.
The History and Current Status of Liquid-Surface Acoustical Holography
Authors: Brenden Byron B.
Published: October 2005

The interaction of acoustic energy with a free liquid surface provides a means for rapid formation and readout of an acoustical hologram. Although a two-step holographic process is possible, involving recording the liquid-surface hologram on a photographic transparency, the real-time imaging capabilities are of most interest and provide the basis for all of the current use of equipment in industrial testing and biological imaging. The use of acoustic lenses to focus the object field of interest into the hologram is particularly useful for achieving good resolution. Industrial test applications and imaging of biological systems in real time are best illustrated using video tapes or motion pictures.
Summary of Progress and Future Directions in Acoustical Holography
Authors: Metherell A. F.
Published: October 2005

The author will summarize the papers presented by the preceding invited speakers and review other developments in the field. Current problems and directions for future progress will be discussed.
Coherence of Signals, Noise, and Reverberation in the Sea
Authors: Urick R. J.
Published: October 2005

Separated hydrophones in the sea show varying degrees of coherence, or waveform similarity, depending on separation, frequency, and kind of sound observed. Over the past 10 years, we have measured the phase coherence of different kinds of signals, noise, and reverberation between vertically separated hydrophones. Such information is basic for the optimum design of arrays. This paper summarizes these measurements. When plotted against normalized separation the coherence as measured by the clipped correlation coefficient is found to lie, as it should, between the value of unity for a plane wave and a curve for isotropic noise; it depends on the vertical angle within which the sound arrives at the two hydrophones. The most coherent sounds observed were signals in convergence zones; the least coherent, the reverberation received from great depths in the deep sea.
Project KIWI ONE: Very Low Frequency Acoustic Propagation Measurements in the South Pacific Ocean
Authors: Browing D. G. , Schumacher W. R. , Thorp W. H. , Bannister R. W. , Denham R. N.
Published: October 2005

A very low frequency acoustic propagation experiment was conducted along a 10 000-km great circle track between New Zealand and the Galapagos Islands. Sound signals set to detonate at the sound channel axis were dropped at 30-km intervals along the entire route by a jet aircraft flying nonstop from Panama to New Zealand. Values of propagation and attenuation loss for the frequency range 10–1000 Hz have been computed from data obtained from listening stations located at both ends of the track.
Low-Frequency Sound Attenuation in the Indian Ocean
Authors: Browning D. G. , Jones E. N. , Thorp W. H.
Published: October 2005

With the support of the French Navy, a low-frequency sound propagation experiment was conducted to obtain attenuation coefficients in the Indian Ocean for the frequency range 200&–10 000 Hz. The experiment was conducted along a 500-km track, which was characterized by a broad sound channel with an axis depth of 250 m. The results are compared with previous measurements in the Red Sea and Atlantic Ocean.
Long Range Acoustic Transmission Loss in the Northern Denmark Strait
Authors: Bradley D. L. , Colvin G. M.
Published: October 2005

Long range acoustic transmission loss measurements were made in the northern Denmark Strait area utilizing two aircraft. One aircraft flew prearranged tracks, dropping standard U. S. Navy explosive charges, while the second aircraft remained in the area of deployed calibrated sonobuoys, acting as a receiving platform. Received signals were recorded broad band aboard the monitoring aircraft. These broad-band recordings were analyzed by filtering, squaring, and integrating to obtain energy density in selected 13-oct bands. The Weston values of source level for the explosive charges were used in the calculation of transmission loss. Transmission loss data for several octaves are shown as well as the results of calculations of a loss per unit distance factor [J. D. MacPherson, J. Brit. IRE 26, 293 (1963)]. This factor is obtained by assuming spherical spreading to 1 kyd and cylindrical spreading thereafter and calculating the difference between this assumed transmission loss and the measured transmission loss.
Comparison of Under-Ice and Open Water Transmission Loss Measurements in Barffin Bay
Authors: Tulko T. J.
Published: October 2005

An experiment was conducted under early winter conditions to obtain underwater acoustic transmission loss data in ice-free water and water with a broken cover of sea ice under similar refractive conditions. Measurements of sound transmission and ambient noise were obtained using modified calibrated sonobuoys and standard U. S. Navy explosive sound sources. The received acoustic signals were recorded broad band and later analyzed in selected 13-oct bands. Transmission loss data are presented with the results for ice-covered water compared with the results for ice-free water. Acoustic transmission loss in Baffin Bay under refreezing conditions is higher in ice-covered water than in open water.
Acoustic Flux Density for Ray Propagation in Discrete Index Media and in Gradient Index Media
Authors: Burkhard D. G. , Shealy D. L.
Published: October 2005

General formulas are derived for the energy per unit area per unit time (flux density) over an arbitrary receiver surface for acoustic ray propagation in discrete index media and in gradient index media. The equation of the deflected ray coupled with the equation for the deflecting surface and the equation for the receiver surface provide a transformation which maps an element of deflecting area onto the receiver surface, thereby enabling one to calculate the flux density over the receiving surface. A formula for the flux density along a ray path is obtained as a special case. An equation for the caustic surface is obtained from the latter. As an example, flux density contours are calculated over a planar surface for plane-wave acoustic radiation reflected from a sphere embedded in a gradient index medium.
Acoustics for Opera: Our Experience at Indiana University's New Musical Arts Center
Authors: Kirkegaard R. Lawrence , Newman Robert B. , Schultz Theodore J.
Published: October 2005

The new 1460-seat Opera Hall at Indiana University has been widely acclaimed for its architecture, its advanced theater technology, and its acoustics for opera and concert. This paper describes the physical characteristics of the hall in general and its acoustical characteristics in particular. Both objective data and subjective evaluations of its opera and concert uses are presented and compared with design criteria and functional objectives.
Practical Determination of the Linear System Impulse Response of a Room
Authors: Martin Norman C.
Published: October 2005

A review is made of the possible methods to obtain the impulse response of a room. Included in this review are shock stimulus, swept frequency analysis, and correlation technique using a white noise input. The latter technique is readily adaptable to computer processing (either hard wired or soft wired). The difficulties associated with each method are put forward as are the advantages. Emphasis is placed on the correlation technique because of the advantages that can be gained from further processing of the gathered data. It is pointed out that, with the correlation technique used, although the effects of the system up to the source input (say a speaker) are totally removed, the speaker modification to the actual room impulse response is a difficult quantity to deal with. Because of the inherent rise time in any impulse response, the speaker impulse response is not minimum delay (or minimum phase) and hence an exact convolution inverse operator is not stable. Methods to deal with this are discussed and practical results from a Wiener filter approach are presented. [Supported in part by two grants from NASA.]
Effects on Speech Perception of Modifying the Impulse Response of a Small Room
Authors: Berkeley D. A. , Curtis T. H. , Allen J. B.
Published: October 2005

A linear model of the ear as a parallel bank of filters and the image solution for room response are outlined. These models are used to predict the perception of speech under certain controlled variations in the impulse response of a small room. Using either a hardware digital filter or a computer simulation, room impulse responses have been measured, modified, and their effect on speech examined. The investigations included linearizing the phase of and truncating the impulse response, examining an all-pass filter with a real room phase characteristic and observing the effect of the time complement of a truncated impulse response.
Miniature Anechoic Room Design
Authors: Viebrock W. M. , Crocker M. J.
Published: October 2005

The design of a small portable anechoic room is discussed. The room was constructed with double wall vibration-isolated panels. The wall transmission loss was predicted using London's theory. The room suspension system was designed using a lumped-mass model for isolation from floor vibrations. The design of the room utilized 8-in.-long polyurethane foam wedges. Using an impedance tube, mea- surements predicted a lower cutoff frequency of 270 Hz for the design of wedge chosen. Inverse square law measurements and noise reduction measurements of the completed miniature anechoic room are given. [This work was supported by Westclox Division, General Time Corporation, LaSalle, Illinois.]