bluuebunny/crossref_metadata_2025 huggingface dataset:
Some auditory and nonauditory effects of low-frequency noises
Authors: Mills John H. , Osguthorpe J. David , Burdick C. K. , Patterson J. H. , Osguthorpe B. Mozo
Published: October 2005

Groups of human subjects were exposed for 8 or 24 h to an octave-band noise centered at 63, 125, or 250 Hz. For a 24-h exposure at 84 dBA, temporary threshold shifts (TTS) increased for 8–12 h and then either decreased or remained constant. TTS was maximal in the frequency region between 350–700 Hz regardless of the center frequency of the exposure. Although TTS was less than 20 dB, complete recovery for many of the subjects required as long as 48 h. Accordingly, the higher level exposure which was planned at 94 dBA for 24 h was reduced to 90 dBA for 8 h. For this condition TTS increased throughout the 8-h exposure. TTS from the 90-dBA exposure for 8 h exceeded the TTS produced by the 24-h exposure at the 84 dBA. Whereas recovery from the 24-h exposure which produced TTS's of 15 dB required as long as 48 h, recovery from the 8-h exposure which produced TTS's of 20 dB required 12–24 h. Thus, the time required for recovery from TTS is determined in part by the duration of exposure. Nonauditory effects included small increases in serum cortisol only during the first hour of exposure. Heart rate, blood pressure, and catecholamines showed small changes. These changes and those of serum cortisol are difficult to interpret because of the absence of a completely counterbalanced design and the lack of rigorous control of the subjects' activity during the noise exposure. [Supported by NIEHS and DAMD.]
Binaural loudness summation as a function of interaural phase angle
Authors: Mulligan B. E. , Goodman L. S.
Published: October 2005

Previous research indicates that binaural loudness summation depends on interaural phase angle only at low signal-to-noise (S/N) ratios where movement of binaural signals “away from” diotic noise has been found to result in increased loudness [I. J. Hirsh and I. Pollack, J. Acoust. Soc. Am. 20, 761–766 (1948); T. H. Townsend and D. P. Goldstein, J. Acoust. Soc. Am. 51, 621–624 (1972)]. This was not found to occur at high S/N ratios. The implication is that interaural phase angle per se has no influence on binaural loudness summation. Results of our research indicate that this conclusion is incorrect. Interaural phase angle of a 250-Hz tone was varied systematically between ±177°. Binaural loudness summation was found to approximate a step function, the step occurring in the vicinity of the Hornbostel-Wertheimer constant (±59°) on each side. Between these two points loudness summation was found to be approximately constant at a level about 4 dB greater than the levels peripheral to ±59°. This finding may reflect the natural limit on interaural phase disparity for a 250 Hz signal originating in a free sound field.
Assessment of the attenuation provided by hearing protectors at high sound levels using reaction time and loudness estimation procedures
Authors: Humes Larry E.
Published: October 2005

Existing procedures for the evaluation of the attenuation provided by hearing protectors when worn by human subjects incorporate threshold-level signals. An unresolved issue is whether the attenuation measured at threshold sound intensities is identical to that at the high intensities for which the protector was designed: Two procedures for providing real-ear attention data at low and high sound levels were investigated here. The first of these, the reaction-time (RT) paradigm, measures the time it takes a subject to respond to the presentation of an auditory stimulus. A function is then derived relating RT to simulus intensity in both the unprotected and protected conditions. From these two functions the attenuation provided at low and high sound levels can be determined. The second procedure, loudness magnitude estimation, is used in an identical fashion. Here, however, loudness-intensity functions are determined in the unprotected and protected conditions with the difference between the functions for these two conditions reflecting the attenuation provided at various sound levels. Results obtained from ten normal hearers wearing ten different protectors (five muffs, five plugs) will be compared to attenuation estimates derived from the traditional real-ear threshold procedure. [Research supported by grant 1-R01-OH00895 from the National Institute of Occupational Safety and Health.]
Relation of physical characteristics of foam earplugs to insertion loss
Authors: Smith Curtis R. , Broughton Roy M. , Wilmoth James N. , Borton Thomas E. , Mozo Ben T.
Published: October 2005

The relation between the physical characteristics of foam earplugs (i.e., weight, length, width, density, expansion pressure, and expansion force) and attenuation in high noise levels (105 dB SPL) was investigated using KEMAR. The results indicated that all commercial polymer foam earplugs have similar physical properties; frequency (Hz) is the single most important variable in determining attenuation of foam earplugs; and chlorination seems to have a pronounced effect on attenuation. The measured attenuation does not change in a consistent manner with changes in physical properties which may reflect an incomplete understanding of cause-effect relationships between the variables studied.
Effects of relative humidity on attenuation of foam earplugs
Authors: Smith Curtis R. , Broughton Roy M. , Wilmoth James N. , Mozo Ben T.
Published: October 2005

The effects of relative humidity (RH) on attenuation of foam earplugs is important because many people work in high noise levels that have controlled RH conditions. Five types of foam earplugs were tested for attenuation in 100 dB SPL white noise under three conditions of RH; <5%, 50%, and 80%. Attenuation measurements were made utilizing KEMAR. A Fast Fourier Transform (FFT) was used to manipulate, store, and output the collected data. In general, there is not a significant difference in attenuation between the various foam earplugs measured under different RH conditions. However, one type of foam earplug would not stay compressed long enough to get them inserted into either KEMAR'S or our ear canal at 80% Rh.
Evaluation of phonemic responses to four standardized speech discrimination tests under telephone listening conditions by normal and hearing impaired individuals
Authors: French-St. George Marilyn , Stoker Richard G. , Craig Chie H.
Published: October 2005

This study compares the phonemic responses of normal and hearing impaired subjects under telephone listening conditions in quiet and in a background of multitalker noise (65-dB SPL). Four standardized speech discrimination tests (CID W-22, NU ♯6, SPIN and Boothroyd's Isophonemic word lists} were utilized. Prerecorded word lists were presented to the subjects, via a standard telephone handset. the output of which simulated typical telephone line acoustic characteristics. The noise was presented from a loudspeaker (0 azimuth). Subjects repeated back each word that they heard and broad phonetic transcriptions were made of their responses. The results will be analyzed to address the following questions: (1) are subjects' responses to particular tests differentially affected under the various telephone listening conditions? and (2) Is there a test or combination of tests which would be suitable for future research and clinical evaluation of the telephone listening abilities of the hearing impaired?
A comparison of three conversational tests for the evaluation of voice communication equipment
Authors: Schmidt-Nielsen A. , Everett Stephanie S.
Published: October 2005

Intelligibility tests (e.g., Rhyme Tests or PB words) and quality tests (e.g., various rating scales) are often used to evaluate and compare voice communication systems. Whether tape recordings or live talkers are used, such tests are unidirectional and do not involve active two-way communications. Particularly in cases where the speech is likely to be degraded, as in low data rate digital voice communications, it is important to assess the actual usability of the system in a two-way situation where the talker can try to adapt his speaking habits to the special requirements of the system. Tests were conducted over a clear channel and nine digital voice processors with data rates from 800 to 32 000 bits/s. Three different conversational tests were used and their ability to differentiate among the processors was compared. [Work supported by ONR.]
Intelligibility of artificial electronic larynx speech as produced over the telephone
Authors: Rothman Howard B. , Goldstein Lewis P. , Flynn Patria A.
Published: October 2005

Currently, there are several methods of acquiring oral speech communication following total laryngectomee. These include esophageal speech, air bypass, tracheo-esophageal puncture, and pneumatic and electronic larynges. Historically, esophageal speech has been the method of choice with the electronic larynx relegated to use by those unable to learn esophageal speech. This attitude is changing and the use of electronic larynges has become more accepted by laryngectomees and service professionals. Recent literature concerning artificial larynges has dealt with comparing the intelligibility of these devices with other users, esophageal speakers, and normals. Some studies suggest that electronic larynges be used for telephone conversations as they provide greater intensity and intelligibility. The present study compares the intelligibility of four available electronic larynges when recorded over the telephone and under high fidelity conditions. Data analysis will provide percent intelligibility scores for the four devices under both conditions and spectral analysis will provide information relative to the perceived intelligibility of each device.
An experimental determination of transfer impedances for resilient mounts
Authors: DeWoody R. T.
Published: October 2005

Resilient mounts are used in shipboard isolation systems to reduce the structureborne noise transmitted by the hull from machinery. The transfer impedances of resilient mounts are needed to determine the transmitted noise. The only resilient mount data generally available are the load deflection curves and low-frequency dynamic stiffness. That data is not adequate for predicting the transmitted structureborne noise for frequencies above a few hundred hertz. This study deals with the experimental determination of the transfer impedances for Navy and commercial types of resilient mounts. A mount test fixture was designed and constructed. Four types of Navy mounts were tested (6E900, 6E2000, 5B5000H and 5M10000H) with static loads ranging from 50% to 125% of rated loads. Several types of commercial mounts and isolators (Aeroflex, Barry, Firestone, and Peabody Noise Control) were also tested. An impact hammer was used for the vibration source. Force and acceleration data were recorded on the input and output sides of the mount under test. Test data were recorded in the frequency range from 20 Hz to 25 KHz. The results were compared with test results from other sources when available.
Nasal articulation in homorganic clusters in American English
Authors: Zue Victor W. , Sia Eng-Beng
Published: October 2005

In an earlier study of the acoustic characteristics of medial /t, d/ in American English [V. W. Zue and M. Laferriere, J. Acoust. Soc. Am. 66, 1039–1050 (1979)], it was found that the duration of the nasal murmur is significantly longer preceding /d/ than /t/. However, we were unable to measure the time during which the velum was open, since it is difficult to determine the onset of nasalization from the acoustic signal alone. In order to further investigate the timing relationship of articulators during the production of these homorganic clusters, data on minimal pairs such as “can't/canned” were collected from ten speakers, five male and five female. We simultaneously recorded the speech signal and a nasal signal obtained from a small accelerometer attached to the outer surface of the nose. The energy in this nasal signal is used as a measure of the degree of velum lowering. Preliminary results indicate that the onset of nasalization with respect to vowel onset for /nt/ and /nd/ clusters is approximately the same, suggesting that the voicing contrast between /t/ and /d/ is encoded in the articulatory gesture of velum lowering. [This work was supported in part by NIH Contract 5RON-NS04322.]
Glottal area variations: A comparison between transillumination and high-speed filming
Authors: Baer Thomas , Löfqvist Anders , McGarr Nancy S.
Published: October 2005

Transillumination as a tool for studying laryngeal behavior in speech has been in use for considerable time, but it has not been extensively compared with other techniques for obtaining information on laryngeal vibrations. Two studies, comparing area variations obtained by transillumination and high-speed filming, reported conflicting results concerning the reliability of transillumination. The present experiment was designed to further explore the information that can be obtained by transillumination. Simultaneous transillumination signals and high-speed films of the glottis were obtained from three subjects producing steady phonation and pitch changes. Measurements of glottal opening were made at three different points along the glottis in the anterior-posterior dimension. Preliminary results indicate that transillumination reliably shows the timing of glottal opening and closing movements during the vibratory cycle. [Work supported by NINCDS.]
Adaptation to restricled-jaw conditions by cortically injured speakers
Authors: Tobey Emily A. , Harris Katherine S.
Published: October 2005

Restrictions, or limitations, to the characteristic flexibility of a speaker may occur following cortical injuries. In order to investigate the nature of these restrictions, spectral and temporal measures of CVC's contained in a carrier phrase were acquired from eight [four right and four left] cortically injured speakers under normal and restricted-jaw speaking conditions. Duration of tokens produced under normal-speaking conditions revealed right-hemisphere injured subjects produced shorter segments, and left-hemisphere subjects produced longer segments relative to Control subjects. Control subjects systematically lengthen all segments during restricted-jaw speaking; however, cortically injured subjects did not show a similar systematic lengthening pattern. Control subjects produce lower-F2 values which increased with practice and approached normal-speaking frequencies. A similar practice effect was not found for the cortically injured speakers. Taken overall, frequency and duration response patterns indicate cortically injured speakers have difficulty integrating spatio-temporal information underlying articulatory maneuvers during normal and abnormal peripheral conditions. [Supported by NIH and LSU General Biomedical Research funds.]
Tongue and jaw gestures during the production of /d/ and flap in nonsense phrases
Authors: Stone Maureen , Hamlet Sandra L.
Published: October 2005

Three experiments measured tongue position (electropalatography) and jaw movements (strain gauge) during the production of nonsense phrases composed of repetitions of the syllable “da.” In experiment I, jaw acceleration was found to vary with allophonic variation rather than with stress level. Experiment II found that four acoustic patterns corresponded to several jaw displacement and acceleration patterns. Experiment III examined the relationship between tongue-palate contact, jaw movement, and the acoustic wave. The pattern of tongue-palate contact was loosely correlated to jaw movement and strongly related to acoustic pattern. Listeners judged specific acoustic patterns to be roughly associated with the production of the phonemes /d/, flap, and tap.
Articulatory movements in /t, d/ production
Authors: Laferriere Martha , Fujimura Osamu
Published: October 2005

Articulatory movements in the production of medial /t/ and /d/ in American English were studied by means of a computer-controlled x-ray microbeam system which tracks pellets attached to a speaker's articulatory organs [Fujimura et al., Comput. Bin. Med. 3, 371–384 (1973); Kiritani et al., J. Acoust. Soc. Am. 57, 1516–20 (1975)]. Velum, mid-tongue, and tongue blade pellet movements were recorded during the articulation of words containing /t/ and /d/ in three environments—before a stressed vowel (a tub/a dub), after a stressed vowel (heater/heeder), and after stressed vowel + /n/ (tenter/tender). Parameters which contribute to articulatory gestures in these three environments are discussed: velocity and directionality of tongue movements, closure and movement durations, and the relative timing of velum and tongue blade movements. [We wish to thank Professor S. Kiritani and the University of Tokyo for their cooperation.]
Further studies of transmission loss of sandwich panels
Authors: Dym Clive L. , Lang Dennis C.
Published: October 2005

Further studies are presented of the effects of various structural and material parameters on the transmission loss through acoustic panels. The work was based on models previously used to study the transmission loss of sandwich panels made up of soft elastic cores whose basic properties were isotropic, the core being sandwiched between two relatively stiff skins which are also isotropic [C. L. Dym and M. A. Lang, J. Acoust. Soc. Am. 56, 1523–1532 (1974); and Dym et al., J. Acoust. Soc. Am. 59, 364–367 (1976)]. In the present instance the core is taken to be orthotropic and the two skins, each of which is itself isotropic, are no longer assumed to have the same material properties and geometry. Calculations of transmission loss are presented and the effects of the orthotropy of the core and the asymmetry of the skin structures are examined. The implications of this analysis for future optimization studies are pointed out. [Work supported by NSF.]
Acoustical characteristics of partitioned spaces under a modular grid of vertical sound absorptive surfaces
Authors: Kleinschmidt Klaus
Published: October 2005

A facility requiting great flexibility in the size and arrangement of partitioned spaces for evaluating various computer systems was designed with fixed lighting and air conditioning diffusers. Sound absorption is provided by a 5-ft (1.5 m) by 5-ft grid of vertical acoustical panels consisting of fibrous glass and perforated metal facing approximately 15 in. (0.38 m) high and 2 in. thick. Measured room to room noise attenuation and the effective ceiling sound absorption coefficient compare favorably with a conventional continuous horizontal acoustical ceiling and partial partitions which extend to 2 to 3 ft below the ceiling. The open grid system eliminates the need to change the duct and diffuser layout and permits unrestricted access to the open plenum space for modifications of services and maintenance. Fire protection systems can also be hidden from view in the darkly painted plenum. The room to room noise reduction values of such an open grid system can be predicted by a simple model.
Acoustical properties of glass fiber roof fabrics
Authors: Moulder Ron , Merrill Jim
Published: October 2005

Woven glass cloth that has been coated with a hydrocarbon is used extensively as a roof membrane in air or tension supported structures. Previous presentations have been made on the acoustical environment of some of these structures. This paper will focus on the acoustical properties of the roof fabric as measured in the laboratory. Sound transmission loss values were measured for two coated fabrics with and without inner liners. Tests were conducted in accordance with the ASTM test method E90-75. Sound absorption tests were also conducted on these same roof configurations in accordance with ASTM test method C423-77. The data generated from these tests should be most helpful to the designer or consultant in determining the acoustical impact both inside and outside fabric roof structures.
The absorption of airborne sound by a damped, impervious, resonant membrane
Authors: Zalas John M.
Published: October 2005

The sound absorption coefficients of honeycomb panels covered with a thin polyurethane membrane were measured in 13 octave bands from 100 Hz to 4 kHz. The results suggest that significant sound absorption can be achieved by properly selecting the panel geometry and material properties. The important design parameters are: honeycomb cell shape, cell size and thickness, along with membrane modulus and internal loss factor. When optimum design is achieved, three resonance phenomena (membrane resonance, mass/air/mass resonance, and standing waves) result in broadband absorption over 3 octaves wide. A U.S. patent has been granted on panels based on this concept and their use is especially promising in severe environments where cleanliness and washability are required.
Decorrelation of narrow beam reverberation at 75 kHz
Authors: Tomooka Lee , Pinkel Robert
Published: October 2005

Doppler acoustic remote sensing techniques are currently being developed for oceanographic research. These infer the motion of the media from the Doppler shift associated with scattering from many randomly distributed naturally occurring moving targets. Sophisticated codes with a large time bandwidth product have yet to be extensively applied in this field of remote sensing. Unlike in classical detection situations, in random scattering the ultimate velocity precision attainable with such codes does not depend on the duration of the code, but rather on the degree of random motion of the scatterers. The width of the distribution of scatterer velocities is proportional to the width of the Doppler spectrum. The precision in the determination of the mean velocity in a given scattering volume is inversely proportional to this Doppler spectral width. An attempt has been made to determine the random motion of typical oceanic scatterers using simple sinusoidal pulses of varying duration transmitted at 75 kHz. A narrow beam sonar mounted on the research platform FLIP was used. The sonar was mounted at a depth of 85 m and directed horizontally. Pulses of duration from 10 to 120 ms were transmitted. From the decay time of the autocorrelation function of the echoes, the rms variability in scatterer velocity can be inferred. The prospects for improving the performance of Doppler scattering sonars through the use of coded pulses will be discussed.
Synthesis of efficient digital beamformers
Authors: Gabel Robert A. , Kurth Richard R.
Published: October 2005

Digital interpolation beamforming [R. Pridham and R. Mucci, J. Acoust. Soc. Am. 63, 425–433 (1978)] permits a reduction in A/D conversion rate, telemetry bandwidth, and memory throughput, relative to nearest-sample-selection beamforming, at the expense of an increase in arithmetic operations. However, conventional synthesis techniques for the up/down sampling interpolator filters used in such a beamformer are typically based on specifications which are not directly related to the beamformer response; thus an excessive computational rate may result. This paper describes an alternative approach to the synthesis of arithmetic digital beamformers, involving the design of the individual digital filters which perform delay interpolation on the hydrophone signals for a given steering direction. It is shown how to set specifications on the amplitude and phase frequency responses of these filters based on beam pattern tolerances. Optimal digital interpolator synthesis methods then yield computationally efficient beamformer solutions. Examples are presented for several array geometries.
Constraints on engineering
Authors: Bouyoucos John V.
Published: October 2005

The practical requirements for low-frequency underwater sound sources are reviewed, with the volume velocity and force levels needed as a function of power level and frequency placed in perspective. The principal features of a representative selection of low-frequency transducers in use today are set forth, and the opportunities for improvements in performance are assessed with regard to the limitations of materials, seals, pressure compensation, and other aspects that affect size, weight, reliability, cost, etc. Finally, selected comments are made on suggested research and development or other studies that might lead to improvements in the state of the art of low-frequency transduction.
Constraint on source output imposed by nonlinear transmission effects in the medium
Authors: Blackstock David T.
Published: October 2005

An important limit to the transmission of sound is set by nonlinear propagation effects. Because of these effects the peaks of a high-intensity sound wave tend to travel faster than the troughs. A sinusoidal wave tends to distort into a sawtooth wave, which because of its rich high-frequency content, suffers rapid absorption by the medium. The distortion therefore leads to extra attenuation of the wave. The extra attenuation can become so severe that saturation occurs. That is, the sound pressure level at the receiver reaches a limit that cannot be exceeded regardless of the acoustic power generated by the source. Extra attenuation also affects beam patterns because the most intense part of the beam is attenuated faster than other parts. The severity of nonlinear propagation distortion depends on frequency and source size as well as on amplitude. A relatively simple graph has been developed that indicates the importance of nonlinearity for a given source. [Work supported by ONR.]
Recent developments in large-scale, moving-coil underwater sound sources
Authors: Willard Bernard S.
Published: October 2005

The intrinsic advantages of moving-coil transducers as low-frequency, broadband acoustic projectors are discussed, as well as the relative merits of single, large-scale units versus arrays of smaller units. Recently developed low-frequency projectors which can be towed behind a ship at significant speeds and depths are shown. The principal areas of study were heat dissipation, coil and coilform configurations, structural design, and magnetic materials. Of particular interest is the use of samarium cobalt magnetic material which offered many more advantages to this field than was originally expected. Several novel approaches to transducer configuration are also shown.
Characteristics and capabilities of the flextensional projector
Authors: Rynne Edward F.
Published: October 2005

A perennial interest in low-frequency projectors has led to the examination of the air-backed class IV flextensional projector technology. This technology is capable of providing high power at low frequency in a compact, lightweight package. Despite such recognized capabilities it has seen only limited application due to the complexities of design and manufacture and to the scarcity of data on performance and reliability. In this paper, the results of tests at Seneca Lake on four identical, state-of-the-art flextensional projectors will be presented. The four projectors were tested both individually and in a line array configuration. The test results will be compared with the predictions of a mathematical model developed at the Naval Ocean Systems Center. The high level of agreement between model and experiment allows the model to be used in assessing design tradeoffs for various applications. Specific tradeoffs in terms of power bandwidth, size, weight, and thermal characteristics will be discussed. [Work sponsored by NAVSEA 63R12.]
Development of hydraulically powered, low-frequency, underwater sound projectors
Authors: Hugus III G. D.
Published: October 2005

Hydraulic power is attractive for use in underwater acoustic projectors in the low audio and infrasonic frequency range. This is because of the capability of hydraulic power systems to produce the necessary large linear displacements and forces. The advantages, disadvantages, and design considerations of hydraulically powered underwater projectors of different configurations will be discussed in this paper. Also discussed will be the development of a hydraulically powered projector to be used for transducer calibration. This projector has the design requirement to produce 160 dB re 1 μPa source level at 1 m in the frequency range of 1 to 10 Hz.
Radiation of sound into the ocean bottom during mode disappearance at a critical depth
Authors: Pierce Allan D.
Published: October 2005

A theory of mode disappearance at a critical depth has previously been developed for propagation in a Pekeris waveguide of slowly varying depth [A. D. Pierce, submitted to J. Acoust. Soc. Am., July 1981; preliminary results reported in J. Acoust. Soc. Am. Suppl. 1 69, S69 (1981)]. Present paper extends the theory to instances where the sound speed and density are not constant in the water layer. The key assumption, partly justified by the method of matched asymptotic expansions, is that the impedance at the water-bottom interface, as seen by disturbances in the bottom fluid, is the same (before the critical range) as predicted by the adiabatic mode theory. Beyond the critical range, it is found by analytic continuation. Disturbance in the bottom is given in terms of Airy functions of complex argument. Solution predicts a cylindrically spreading (as r−1/2) wave of narrow beamwidth, which originates from the transition region and which propagates obliquely downward into the bottom fluid. The width of the beam and the angle it makes with the interface are relatively simple functions of the environmental parameters. The shape of the modal profile beyond the critical range does not vary substantially, but the amplitude decreases asymptotically as 1/x5/2.
Uses of monostatic and bistatic echoes from (calibration) spheres for inverse scattering
Authors: Gaunaurd G. , Überall H.
Published: October 2005

We study the summed backscattering amplitude |∫(π, ka)| returned by tungsten carbide spheres in water, insonified by phase acoustic waves. After verifying the agreement of the Faran/Hickling classical theory with recent measurements [Dragonette et al., J. Acoust. Soc. Am. 69, 1186–1188 (1981)] we analyze the partial waves contained within the summed amplitude in the light of the resonance scattering theory. We computationally isolate the resonances both in the frequency ∫ and in the mode-order n domains, by appropriate background subtraction. We generate and display the three-dimensional “response surface” [i.e., Brill et al., J. Appl. Phys. 52, 3205–3214 (1981)] of the fluid-loaded sphere and show how its two distinct families of resonance frequencies are well approximated by Love's “spheroidal eigenvibration” [A. Love, Mathematical Theory of Elasticity (Dover, New York, 1926), p. 283]. We display bistatic plots of the scattered amplitude |∫(θ, ka)| versus ka at certain fixed values of θ that make ∫n vanish, and versus θ at certain fixed values of ka that also make ∫n vanish. We then show how the information in these plots is used to determine the sphere's composition from its bistatic returns.
Scattering effects of a sphere in a cylindrical resonant cavity
Authors: Barmatz M. , Gaspar M.
Published: October 2005

The resonant frequency, acoustic pressure and quality factor were measured for various plane-wave modes of a cylindrical cavity as a function of sphere position along the tube axis. The apparatus consisted of a 5.7-cm-i.d. Plexiglass cylinder fitted with an adjustable plunger at one end. The sound energy entered along the tube axis and the sound pressure was measured with a microphone attached flush at the center of the plunger. Positional variation in the acoustic parameters relative to empty chamber values will be presented for various sample sizes, chamber volumes, and pressure levels. The changes in the resonant frequency depend on the ratios of the sample to chamber volumes, Vs/Vc, cross-sectional areas, As/Ac, and diameter to length, Ds/Lc. For small values of these ratios the frequency shift is proportional to Vs/Vc. These measurements will be compared to a one-dimensional theoretical model. [Work supported by NASA.]
Resonance frequency shift of an acoustic chamber containing a rigid sphere
Authors: Leung E. , Jacobi N. , Wang T.
Published: October 2005

The resonance frequency shift of an acoustic rectangular chamber due to the pressure of a rigid sphere has been measured for the n = 1, 2 modes as a function of sphere size and position. The position dependence has sinusoidal and dc components. A simple excluded volume model and boundary perturbation theory were used to explain the data. The calculations can account for the sinusoidal behavior, but not for the dc shift. Also measured were the frequency shift, due to a thin disk of the same cross section and a cylinder of the same cross section and volume as the sphere, and the p2/p1 ratio at the wall as a function of sphere position. [Work supported by NASA.]
Computer models for media transmitting plane waves
Authors: Remillard Wilfred J.
Published: October 2005

Transmission, reflection, attenuation, and dispersion of small signal plane waves depend on the characteristics of the medium and its boundaries. Given sufficient time one could presumably use Smith chart-type analysis and determine the effects on plane waves of variations in these characteristics. Since all of the operations that can be performed on Smith charts can easily be programmed as FORTRAN subroutines, it follows that one can model a given situation on a digital computer. The main program consists of initialization of the media parameter, followed by successive calls to the various subroutines. Examples are given of some of these models and their effects on plane waves.
Using nearfield holography to study energy flow from musical instruments
Authors: Strong W. Y. , Beyer T. B. , Bowen D. J. , Williams E. G. , Maynard J. D.
Published: October 2005

We have developed a technique called nonwavelength limited, or nearfield, acoustical holography that can experimentally determine the radiated pressure field, particle velocity field, and the vector intensity field of low-frequency (below 1500 Hz) sound sources where the source is often smaller than a wavelength. Mappings which show the rate and direction of the acoustic energy flow from the source (nearfield) out to the farfield may be constructed. These mappings are valuable for locating sound sources and determining their strengths. Most of our early work focused on relatively simple sources, but recently we have been looking at more complex sources such as musical instruments, specifically guitars and cellos. The instruments are intact and string excited. Holographic reconstructions of the top of the guitar show both the plate motion and the motion of the air in the rose. Preliminary results indicate that the rose is a dominant source of the radiated sound energy over the first two octaves of the guitar's range. Maps of the energy flow around and away from the instrument will be presented.
Brass wind instrument impulse response measurements
Authors: Benade A. H. , Smith J. H.
Published: October 2005

Apparatus has been built for pulse reflectometry of brass instruments. The current version uses spark excitation and an electret microphone at the mouthpiece rim terminating plane. Selectable low pass filtering in the microphone channel reduces noise and aids in the visual interpretation of reflected pulses via control of signal bandwidth. Discontinuities of air column cross section, taper, etc. can be located and identified using familiar techniques from electrical reflectometry. Multiple-reflection patterns characteristic of prototype musical shapes must be taken into account. These are being worked out. Reflectogram FFT's give input impedance functions in good agreement with those obtained via swept frequency capillary excitation methods. Studies of several tubas show that availability of both time and frequency domain representations of the response function greatly increases diagnostic power for the evaluation and correction of instruments. Comparisons will be made with reflectometer data of Krüger (Zwota, DDR) and the tuba impedance measurements of Caussé (IRCAM, Paris). [Work supported by NSF.]
Recent plate mode findings compared with tests on the free plates of Stradivarius violin
Authors: Hutchins Carleen M.
Published: October 2005

Recent findings indicate that in the best violins we have been able to make so far eigenmodes 1, 2, and 5 in the unattached top violin plate lie in a harmonic series with mode 5 around 370 Hz and modes 2 and 5 in the back at matching frequencies. An early test on the disassembled plates of a fine concert Stradivarius violin corroborates these findings.
Nonlinear vibrations in plates and gongs
Authors: Rossing Thomas D. , Fletcher N. H.
Published: October 2005

Certain types of gongs show a frequency shift, up or down, when struck. In order to understand this nonlinear behavior, we have studied a variety of flat and curved plates under varying amounts of radial tension or compression. Flat plates show a nonlinearity of a hardening type, whereas most curved plates show softening behavior. The degree of nonlinearity appears to be sufficient to explain the frequency shift observed in Chinese opera gongs [T. D. Rossing and R. E. Ross, J. Acoust. Soc. Am. Suppl. 1 64, S150 (1978)]. [Work supported by the U.S.-Australia Cooperative Science Program and by the Australian Research Grants Committee.]
Performance of several mufflers for induced draft fans
Authors: Wood Eric W. , Hoover Robert M.
Published: October 2005

Community noise problems due to the operation of induced draft fans were investigated at several installations. Custom designed mufflers have been installed, evaluated, and found to be satisfactory. Special features include significant attenuation of tonal noise at frequencies of less than 500 Hz and the ability to operate in contaminated gas streams.
Portable programmable calculator programs for HVAC noise applications
Authors: Conant David A.
Published: October 2005

Several RPN programs suitable for HP-97 and -41C calculator use are briefly described in terms of their applications, accuracy, savings, and ease of use. Also presented are guidelines for approaching tabulated reference data and general calculator programming in a way that expedites clarification of the noise problem apart from tedious data reference and solution of algorithms.
Thermal noise, active filtering, and stochastic properties of the cochlear echo
Authors: Bialek William , Schweitzer Allan
Published: October 2005

Current theories of the cochlear echo phenomenon invoke reflection from a point of impedance mismatch along the basilar membrane. This impedance discontinuity may have an active component, and the propagation characteristics of the basilar membrane between the mismatch and the oval window may also be modified by active phenomena; nonetheless, these theories do not involve the instability of an active filter in the strict sense. We believe that active mechanical filtering at the stereocilium itself is necessary if the problem of Brownian motion of the stereocilium is to be resolved [A. Schweitzer and W. Bialek, J. Acoust. Soc. Am. Suppl. 1 68, S42 0980)]. Here we discuss the driven instability of such a system, and show that it can reproduce several of the observed properties of the echo. The active filter model predicts that the initial portion of the echo will consist of amplified thermal noise, and the possibility of observing this noise will be discussed.
Acoustic sensitivity and frequency selectivity of the guinea pig inner ear after total destruction of cochlear hair cells
Authors: Cazals Y. , Aran J.-M. , Erre J.-P. , Guilhaume A.
Published: October 2005

After selective destruction of all cochlear hair cells and preservation of vestibular hair cells in guinea pigs treated with massive doses of the aminoglycosidic antibiotic amikacin, acoustic stimuli can still evoke a series of neural responses recordable from the inner ear up to the auditory cortex [Y. Cazals et al., Science 210, 183–186 (1980)]. The responses present equivalent absolute thresholds from 63 Hz to 16 kHz and exhibit well defined tuning curves of a low-pass filter type which make them akin to responses from hearing organs. Complete or partial destruction of the vestibule combined with a complete cochlear destruction demonstrate that such responses originate from the inner ear and most likely from the saccule. These results support the hypothesis of a hearing function of the saccule in a mammal, a role already demonstrated for lower vertebrates. The tuning properties could originate from the coupling of the ciclia with the otolithic membrane. [Work supported by Inserm grant 8-ASR-6 and DGRST grant DN/80.7.0233.]
Multipolar residual spiral ganglion neurons
Authors: Webster Douglas B. , Webster Molly
Published: October 2005

Guinea pigs drug deafened with a combination of kanamycin (400 mg/kg S.C.) followed 2 h later with ethacrynic acid (40 mg/kg I.V.) have a stable number of spiral ganglion neurons by 8 months post-treatment which is 13% of the normal spiral ganglion population [M. Webster and D. B. Webster, Brain Res. 212, 17–30 (1981)]. Three μm serial sections of the spiral ganglion of such drug deafened guinea pigs sacrificed either 9 months or 16 months following treatment were cut. Each section was photographed and the profile of each neuron was traced onto acrylic sheets. Stacking the acrylic sheets allowed a three-dimensional visualization of each neuron. In the 9-month post-treatment animals, the spiral ganglion neuronal types were: 6% unipolar, 53% bipolar, 38% multipolar, and 3% questionable. In the 16-month post-treatment animals, the spiral ganglion neuronal types were: 3% unipolar, 17% bipolar, 78% multipolar, and 2% questionable. These data suggest that following long term organ of Corti loss, the residual spiral ganglion neurons sprout new processes. [Work supported by NIH grants NS-12510 and NS-11647.]
Differential sensitivity in the guinea pig olivo-cochlear bundle
Authors: Stopp Phyllis E. , Whitfield I. C.
Published: October 2005

The hair cells in the basal region of the cochlea are more susceptible to damage from ototoxic agents than are those of the rest of the cochlea, a result suggesting a chemical difference between the regions. We have recently obtained experimental evidence for a similar chemical differential in the cochlear efferents. Attempts to label efferent neurons with HRP by perfusion of scala tympani through holes in the apex and basal turn were uniformly negative, whereas perfusion via the round window labeled cell bodies in the superior olivary region. It was not necessary to introduce the perfusate via the round window; the previously unsuccessful perfusion via the basal hole became successful as soon as the round window was opened. We have been unable to obtain any satisfactory explanation of this phenomenon in terms of washing out of the perfusate or of different anatomical distributions of the fibers, and are driven to the conclusion that there is some chemical difference between the efferent terminals which results in the HRP being taken up only by those endings in the lower basal and “hook” regions.
Steep gradients in amino acid profiles between endolymph and perilymph
Authors: Thalmann R. , Comegys T. H. , DeMott J. E. , Thalmann I.
Published: October 2005

Using high performance liquid chromatography, we have determined 19 amino acids (AAs) in cochlear and utricular endolymph, cochlear and vestibular perilymph, and cerebrospinal fluid (CSF) of the guinea pig. Glutamate and aspartate are markedly higher in both cochlear and utricular endolymph than in perilymph, confirming our previous studies on cochlear endolymph based on enzymatic cycling [Thalmann et al., J. Acoust. Soc. Am. Suppl. 1 66, S47 (1979)]. The remaining AAs are significantly lower in both endolymphatic compartments, in most cases by an order of magnitude. Nevertheless, significant differences between the AA profiles of cochlear and utricular endolymph exist. AA concentrations of perilymph of scala vestibuli and vestibular cistern are higher than in CSF, in two cases by an order of magnitude. In scala tympani the AA composition is highly variable depending upon sampling method and surgical manipulation preceding sampling (relief of CSF pressure, obstruction of cochlear aqueduct). Without surgical interference, those AAs which are very low in CSF are considerably lower in scala tympani than in scala vestibuli, suggesting substantial natural or artifactual admixture of CSF. These same AAs increase in concentration when CSF pressure is relieved or the cochlear aqueduct blocked. [Supported by NIH grants NS14334 and NS06575.]
Similarity judgments of pitch: A test of octave equivalence
Authors: Kallman Howard J.
Published: October 2005

Octave equivalence refers to the musical equivalence of notes separated by one or more octaves; such notes are assigned the same note name in the musical scale. The present series of experiments was an attempt to determine whether octave equivalence would be incorporated into subjects' similarity ratings of pairs of tones or tone sequences. In the first experiment, subjects on each trial rated the similarity of two successively presented tones. The results failed to show evidence of octave equivalence. In the second experiment, subjects rated the similarities of pairs of successive intervals. It was thought that the use of successive intervals would evoke a “musical set” and might result in octave equivalence effects. The results provided some evidence of octave equivalence although the effect was not great. The range of pitch values presented and the musical context were manipulated in subsequent experiments. Octave equivalence effects were most apparent given a musical context and a restricted range of pitch values. The implications of these results for music perception research will be discussed.
Effect upon intensity and low frequencies due to a sound moat in the new Chapel/Recital Hall at the Interlochen Center for the Arts
Authors: Mulder George
Published: October 2005

Graphic results of a study of the application of music-acoustical principles in the low frequencies of pipe ranks in the Aeolian-Skinner Organ of the new Dendrinos Chapel/Recital Hall of the Interlochen Center for the Arts. The effect upon pitch and timbre as well as the intensity and frequency resulting from the sound moat under the stage of the new structure reveals a reassessment of physical features and psychological responses in musical understanding. However the direct acoustical estimations and provisions agree with earlier assumptions, especially J. F. Schouten's “subjective tones.”
The localization of speech shaped noise under normal and occluded conditions
Authors: Kerivan J. E.
Published: October 2005

Localization in the median horizontal plane for a speech shaped noise was evaluated under varying degrees of occlusion for 25 trained subjects, all with normal hearing. Binaural test conditions were (1) unoccluded; (2) occluded, ear plug; (3) occluded, earmuff; (4) occluded, helmet; and (5) occluded, helmet with faceplate. The object of these conditions was to measure the degradation of localization ability for speech shaped noise when wearing earplugs, muffs, or helmets. The subjects' task was to center a noise signal in the median horizontal plane to a visual reference point fixed @ 0° azimuth, see [J. D. Harris, Acta Otolaryngol. Suppl. 298 (1972)]. Significantly worse localization occurred with the helmet conditions as compared to all others, followed in turn by performance with earmuffs, then plugs and finally unoccluded. Localization performance was negatively correlated to overall attenuation of the various test devices. This indicated that spectral shape of the sound source, modified by the insertion of the devices, was not the prepotent cue for median horizontal plane localization. It would appear that temporal characteristics of the source are modified more by helmets and muffs than by plugs, and this seems to best describe the test results. [Work supported by NMRDC project M0100.PN.001-1010 while author was at NSMRL, Groton, CT]