bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of continuous background noise on impact noise-induced TTS
Authors: Hétu Raymond , Lazure Réjean
Published: October 2005

The present study assessed the influence of a continuous background noise on the effect of the peak level and the number of impacts producing a 15 dB TTS3 at 4, 6, and 8 kHz. A group of 15 normal-hearing adults were exposed to different conditions of noise. The critical peak level (CL) of an impact noise was first determined. The CL defined as the level producing the criterion amount of TTS3 when the impacts were presented in series of 60 at a rate of one every 2 s. This CL was not altered by the introduction of a continuous broadband noise at 85 dBA. But it was lowered by 3 to 6 dB among one-third of the subjects when the background noise was at 105 dBA. Referring to the latter condition, both the peak and the continuous level were lowered by 4 dB and the number of impacts increased by a factor of 6: no increase in the amount of TTS3 resulted. However, for a tenfold increase in the number of impacts, a 13-dB decrease in the peak and the continuous level did produce a slightly but significantly higher amount of TTS3. Implications of these results are discussed in term of exposure limits to industrial noise. [Work supported by INRS grant ♯ N/D 25-80-25.]
Measurement of short duration high level impact noises
Authors: Brüel Per V.
Published: October 2005

Over the past few years there has been a growing suspicion that in shipyards, and in metal working industries with punch presses and forging processes, etc., the acoustic environment contains very short duration high level impulses. Since impulsive sounds as a rule are of very short duration, the human ear, and the standardized sound level meter can far from measure correctly the maximum sound pressures of impulses, simply because the integration time of the human ear and of the sound level meter is considerably longer than the impulse duration. Furthermore, the relatively long time intervals between short impulses, make the use of a sound level meter with “peak” holding capacity difficult in practice. In this article it is shown how the peak pressures can be measured three times a second and Leq every minute with the aid of two sound level meters (one with 30-μs rise time and the other an integrating sound level meter) and a two channel level recorder. The instrumentation setup is battery driven and can operate without attention for seven days. The acoustic environments of a number of different industries have been measured with this set of instruments. The results show that in metal industries the levels of the short duration impulses are considerably higher than those found in wood industries.
Characterization and calibration of microphone systems for measurement of impulselike sounds
Authors: Nedzelnitsky Victor
Published: October 2005

Measuring the peak value of impulse noise is required by damage-risk criteria for hearing, material design standards, and for characterization of exposure to hazardous sound levels in industrial workplaces and the military. Other areas of application include building design and land-use planning. However, use of current proposed ANSI and IEC standards provides only highly accurate magnitude calibration of microphone cartridges and systems in response to sinusoids, and does not ensure accuracy in measuring the peak values of impulse noise. Convenient approximate methods for audio-frequency measurement include calibration of small, wideband transducers of ultrasonic resonance frequency by means of electrostatic actuators (for phase response and relative magnitude response) and by reciprocity-based methods (for absolute magnitude response at selected frequencies). Such transducer systems can have a fairly flat magnitude response and an approximately linear phase response throughout most of the audio range. Precision sources of transient or impulselike sound are also very useful. Several methods for realizing such sources are discussed; one particularly simple and robust device utilizes aerodynamic impact sound from colliding spheres. For in situ measurements of personal sound exposure, additional consideration must be given to the influences of microphone position and diffraction produced by the torso, head, and external ear.
Effects of stimulus presentation rate on the middle-latency auditory evoked potentials
Authors: Stapells David R. , Suffield J. Braxton , Picton Terence W.
Published: October 2005

The middle-latency evoked potentials were recorded in response to 60 dB nHL 500 Hz tones with rise and fall times of 4 ms and plateau durations of 2 ms. The tones were presented at rates of between 10 and 60/s using 5/s steps. Replicate averages of 2000 evoked potentials each were analyzed using a sweep of 50 ms in ten subjects. The response had a roughly sinusoidal waveform and was repeated twice in the 50 ms period. The size of the response was measured as the average of the peak-to-peak amplitudes in the 50 ms sweep. The amplitude was greatest at stimulus rates of 40 (1.12 μV) and 45/s (1.15 μV). It was about half this amplitude (between 0.54 and 0.75 μV) at rates of less than 35/s or greater than 50/s. The morphology of the response and its relation to stimulus rate were quite similar from one subject to another. These results extend and replicate those of Galambos et al. [Proc. Natl. Acad. Sci. USA 78, 2643–2647 (1981)]. They indicate a steady-state auditory evoked potential with a resonant frequency of 40–45 Hz.
The effects of within-train intensity changes on wave V adaptation
Authors: Burkard Bob , Hecox Kurt
Published: October 2005

Adaptation of the BER was evaluated using stimulus trains containing one or two click intensities. Single-intensity trains consisted of eight clicks presented at 40, 50, and 60 dB nHL. For trains comprised of two click intensities, the first four clicks were presented at 50 dB nHL and the last four clicks at 40 or 60 dB nHL. In the two-intensity trains, the responses to the fifth click (the first response following the intensity shift) were significantly delayed compared to the first click of the 40 and 60 dB nHL control series. For all click trains, wave V latency shifts had asymptoted by click 5, demonstrating that wave V adaptation is not intensity specific. The magnitude of latency shift by the fifth stimulus in the train showed some dependency on the intensity of the initial clicks. We can tentatively conclude: (1) intensity shifts of 10 dB do not interrupt the adaptation process, (2) asymptotic latency shift is attained by the fifth click in the train, even if click intensity is changed mid-train, and (3) under some conditions the magnitude of latency shift may be dependent on the relative intensity of the initial and terminal clicks in the train. [Work supported by NIH.]
BER adaptation paradigm: Stimulus dependencies
Authors: Weatherby Lynn , Hecox Kurt
Published: October 2005

The time course of wave V latency shifts (adaptation paradigm) to a train of eight noise bursts with variable duration, rise-fall time, and intensity was investigated. Wave V latency increased as a function of increasing position in the train for all conditions. Approximately 70% of the total latency shift occurred within the first four stimuli of the train. Unlike click stimuli the asymptotic latency was not attained by the eighth stimulus in the train. Rise-fall time (0, 1, 2, ms) increased the latency of wave V to the first stimulus in the train but the magnitude and rate of adaptation were not affected. Increasing stimulus duration (2, 5, 7 ms) did not affect the latency of the first response in the train but did affect the magnitude and rate of adaptation. Increasing intensity increased the latency to the first stimulus and the magnitude of adaptation. These stimulus dependencies suggest that forward masking contributes to the latency shifts observed in the adaptation paradigm. [This work is supported by NIH.]
Machinery vibration standards
Authors: Catlin Jack B. , Maedel Paul H.
Published: October 2005

Over the past 20 years the use of vibration measurement has grown rapidly in the areas of machinery mechanical condition monitoring and evaluation. As a result of this growth, a number of measurement techniques and measurement parameters have evolved. While there has been some commonality in these techniques and parameters, it has often been found difficult to compare machine condition when the same techniques and parameters were not used. Other associated problems have also resulted. This variability in techniques and parameters indicated a real need for vibration measurement standardization within the United States, and throughout the world. To meet this need, standardization committees were formed by the American National Standards Institute (ANSI) to handle U.S. standardization requirements, and by the International Standards Organization (ISO) to produce vibration standards acceptable on a worldwide basis. Vibration Standards offer a potential of a number of advantages: (1) machinery purchase specification simplification, (2) machine design guidelines, (3) machine evaluation criteria, (4) a more useable data base, and (5) easier interchange of technical information. As a result of these advantages, a number of national (ANSI) and international (ISO) machinery vibration standards have been developed. This paper reviews those machinery vibaration standards which have been published, as well as those which are in-process and planned.
Full-scale and model acoustic experiments on a ro-ro container ship
Authors: de Bruijn Alex
Published: October 2005

To obtain a systematic set of data on noise and vibration due to propeller cavitation a comprehensive program of model and full-scale hydrodynamic and acoustic investigations was carried out during the years 1979–1981 on a single screw 39000 dwt Dutch ro-ro containership (speed, power, full-scale cavitation viewing, noise, and vibrations simultaneously). This paper reviews some of the acoustic results in connection with the possible application of compliant layers on the shell plates in way of the propeller. A simplified acoustic scale 1:10 model of the stern part has been constructed in steel, including proper scantlings, bulkheads, rudder and skeg, and checked for reliability by means of an electrodynamic hydrosounder located at the propeller disk. The model and full-scale ratios of sound pressure in front of the plating to velocities of the shell and of some decks agreed satisfactorily except below 20 Hz (full scale). The acoustic effect of an a priori seaworthy compliant layer, investigated by means of the model, appeared satisfactory, although it was limited by the flanking paths through rudder and skeg. The model also showed that a useful reduction of the transmission of cavitation noise by an increase of the source-to-shell-distance can only be obtained for frequencies above 25 Hz (full scale).
Structureborne sound transmission in fluid filled piping system elbows
Authors: Perreira N. Duke
Published: October 2005

A newly developed technique to analyze structureborne sound transmission in fluid filled piping system elbows based on wave theory is described. It is believed that generalization of the technique can be used to analyze structureborne sound transmission in fluid filled nonplanar piping systems that include bends and branches. To illustrate some of the basic principles of the method, an example is included. The wave theory approach is commonly used in analyzing electromagnetic and acoustic wave transmission in thin waveguides. Use of the technique to analyze structural vibrations is not as common. Other methods used to analyze the dynamics of structures include the differential equation and energy methods. Comparison of the experimental results with that using computational techniques based on the various theories show that the wave theory leads to much more accurate results than the differential equation solution method. Both the differential and the wave theory are based on force and moment analysis using a free body diagram of a differential system element; thus the system responses based on the two theories should be equal. The differences in answers using the two techniques is due to computational and numerical errors. In the wave theory the form of the system deformation functions are assumed while in the differential equation method, the form of the solution is obtained numerically using a finite element method. The wave theory method is not without its own set of problems. The differential equation can include higher order affects such as rotary inertia and Poisson effects; the wave theory method requires that the deformation be written in terms of exponential functions or in terms of the sine, cosine, hyperbolic sine, and cosine functions. This latter requirement of the wave theory method may not allow the higher order affects to be easily included in the system model. This does not seem to be a problem in the analysis of piping systems where the higher order affects are probably not important.
Resonant oscillations of fluid-loaded struts
Authors: Crighton D. G.
Published: October 2005

A simple model is used to describe how radiation damping limits the resonant oscillations of a cantilever or strut. In the low-frequency limit, radiation damping is equivalent to a fictitious internal dissipation, with a loss factor ηrad slightly higher than typical mechanical loss factors, showing that resonant response is limited only by radiation loss, even for thin struts for which k0a<1. When k0a>1 it is found that ηrad is much larger than any internal loss factor and therefore that high-frequency resonances are heavily damped, regardless of internal dissipation. The pressure field near the strut is also examined, and in the case k0a<1 is found at resonance to exceed the driving pressure by the large factor (k0a)−2. The farfield pressure at resonance may, under some conditions, also greatly exceed the off-resonance scattered field, and this great scattering efficiency of a thin strut at resonance is demonstrated by detailed examination of a particular case.
Dispersion relation for composite waveguide with application to measurements in acoustic impedance tube
Authors: Dubbelday Pieter S. , Capps Rodger N.
Published: October 2005

The amplitude and phase of the reflected wave in an acoustic impedance tube are related to the speed and attenuation of sound in the sample material. It is usually assumed without justification that the pertinent propagation speed is the dilatational speed. To investigate this an analysis was performed on the propagation of axially symmetric waves in a composite waveguide consisting of a solid cylinder immersed in a fluid bounded by a concentric rigid wall. The roots of the ensuing dispersion relation were computed for various materials. The results show that the sound speed in the waveguide may vary between the dilatational and the bar speed, depending on the size of the fluid gap and the elastic properties of solid and fluid. Experiments are designed to verify this effect by changing the sample radius and by excluding the fluid from the gap between sample and wall.
A study of secondary sound channels due to temperature inversions in the Northeast Pacific Ocean
Authors: Chow R. K. , Browning D. G.
Published: October 2005

Above 45 °N latitude the circulation of the Northeast Pacific Ocean is controlled by the counterclockwise Alaskan Gyre of subarctic water. Due to a greater freshwater influx than evaporation, the water column is characterized by the three distinct layers: 0–100 m depth, cold, low salinity water; 100–200 m, zone of strong salinity gradient (halocline); 200 m and below, gradual changes in temperature and salinity. Roden [J. Geophys. Res. 69, 2899–2914 (1964)] has shown that the middle halocline layer is the site of a complex temperature structure with numerous temperature inversions. These temperature inversions result in the formation of secondary sound channels which our analysis shows are widely distributed. Using a PE prediction model the cutoff frequency of a typical secondary sound channel was determined to be approximately 80 Hz. Since depth excess exists at most locations, energy not trapped in the secondary duct remains in the deep sound channel. Relative loss in the two channels is presented as a function of frequency (25–200 Hz) and range (0–100 km) for various source and receiver depths. Under optimum conditions the existence of a secondary sound channel can decrease the average propagation loss by 20 dB.
Low-frequency attenuation in the North Pacific subarctic-subtropical transition zone
Authors: Browning D. G. , Chow R. K.
Published: October 2005

The water mass regions in the North Pacific are relatively well defined. Kibblewhite et al. [J. Acoust. Soc. Am. 61, 1169–1177 (1977)] have shown that each water mass has a characteristic low frequency (below 200 Hz) attenuation. They find the highest attenuation to be in the Subarctic-Subtropical Transition Zone and these values are the highest yet reported in any ocean for this frequency range. It has recently been reported by Focke et al. [J. Acoust. Soc. Am. 71, 1438–1444 (1982)] that such values of attenuation can be modeled using a frequency independent mechanism, exponentially decreasing from the surface, the origin of which is unspecified. We compare these results with attenuation coefficients we have obtained in this zone. The oceanographic and biological properties of this region are analyzed to determine possible scattering mechanisms and their distribution. The effect of the two frontal areas bounding this region on the determination of attenuation coefficients is also examined.
More on replacing transitional acoustic ray fields by a bundle of modes
Authors: Niver E. , Kamel A. , Felsen L. B.
Published: October 2005

The failure of ray acoustics in transition regions near single and multiple caustics, bottom glancing and critically incident rays in a vertically stratified ocean can be repaired by replacing these ray fields with a bundle of guided modes plus truncation remainders. The theory for this equivalence is exact, and has been verified by direct numerical implementation of the various constituents [E. Niver, A. Kamel, and L. B. Felsen, J. Acoust. Soc. Am. Suppl. 1 71 S66 (1982)]. The study has now been extended by treating the remainder not only as a modified (“collective”) ray field as presented previously [L. B. Felsen, J. Acoust. Soc. Am. 69, 352 (1981)] but alternatively as a modified (collective) modal field. Moreover, asymptotic considerations have been employed to simplify the computer program. Detailed numerical comparisons for a model profile reveal the accuracy and numerical efficiency of various mode and remainder options as applied to the transitional ray fields noted above. It is shown that modal replacement of rays near single or multiple caustics also accounts for non-negligible evanescant ray fields. Moreover, it is preferable to treat the remainders as a modified modal field instead of a modified ray field since the width of the equivalent mode bundle can be reduced thereby. [Work supported by ONR Ocean Acoustics Branch.]
A comparison of acoustic propagation predictions for surface duct environments using ray-theoretic and parabolic-equation computer codes
Authors: Tolstoy A. , Franchi E. R. , Nicolas K. R.
Published: October 2005

An important type of under water acoustic environment involves a deep water SOFAR channel with a superimposed (winter) surface duct capable of trapping acoustic energy. In this paper we examine the effects predicted by a computer model of three ducted sound-speed profiles on acoustic propagation at 300 Hz. The purpose of this study was to better understand the capabilities and limitations (both theoretical and numerical) of a ray theoretic model for predicting mid- and long-range signal transmission loss (TL) in the winter North Atlantic. Several source and receiver configurations (combinations with one or both in and out of the duct) have been studied. To test validity, the ray theoretic calculations are compared to previously accepted results predicted by a propagation model based upon the parabolic equation. It is found that both model predictions agree qualitatively (TL measurements and acoustic field patterns are comparable), while any quantitative discrepancies are explained by the theoretical or numerical limitations of the different approaches. We conclude that when both the source and receiver are at least several wavelengths from the sea surface, ray theory can be quite accurate in its prediction for these ducted environments. [Work supported by Naval Electronic Systems Command, Code 612.]
Multipath propagation in a deep ocean including modified rays near grazing incidence at the bottom
Authors: Pannatoni Ronald F.
Published: October 2005

A ray description of acoustic propagation between communicators submerged in a deep ocean may include rays that almost graze the interface between water and sea-floor sediment. For example, this can occur in range-independent environments where the squared refractive indices in water and in sediment decrease linearly with depth. Four pairs of such rays connect communicators near the surface and separated in range by at most 4(H/γ)1/2, where H is the ocean depth and γ is the gradient of square refractive index in water. One ray in each pair is entirely waterborne; the other intercepts the sediment and grazes a caustic. We present a uniform asymptotic analysis of these ray pairs that incorporates diffractive finite frequency effects as in the modified ray theory of Murphy and Davis. These effects include the appearance of a frequency-dependent caustic and a modification of the usual π/2 phase shift experienced by the classical ray that intercepts the sediment. Comparison of these results with normal mode calculations is excellent. Vector diagrams (after Bartberger) also identify mode groups corresponding to the modified rays.
A formula for the ray density over a caustic surface for variable index media
Authors: Burkhard Donald G.
Published: October 2005

The acoustic ray density becomes infinite over caustic surfaces and therefore cannot be used as a measure of the concentration of rays at or near the caustic. A finite substitute measure, the density of rays tangent of the caustic, may be obtained by dividing an element of incident flux by the area of the caustic formed by the associated rays. This provides a measure of the energy density over different regions of the caustic. As an example the ray density over the caustic is evaluated for a linear depth dependent index of refraction.
Analysis of short-range sound transmission through fronts in shallow water
Authors: Rousseau T. H. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

Effects of sound-speed variations, produced by fronts in shallow-ocean regions, on short-range ray transmissions between fixed source and receiver are investigated. A parametric model is used in which the front is represented by a sound-speed jump in an otherwise constant-speed channel. The propagation and frontal models are sufficiently general to permit determination of acoustical effects for fronts of varying strengths and for arbitrary orientations and positions relative to the propagation range. Frontal influences on travel time and geometrical spreading loss are determined, and expressions for per-ray and total field quantities are developed for various source and receiver depths. Using our results, it is shown how the determination of the location of a source is influenced by the presence of a front. Further, it is demonstrated how predictions of the location, strength, and orientation of fronts may be obtained from acoustic receptions at a receiver using the known location of a source. [Work supported by ONR.]
Some theoretical problems on mode filtering in shallow water
Authors: Shang Er-Chang , Gao Tain-Fu
Published: October 2005

Since the mode filtering is a certain sort of “space filtering,” the matter of the utmost concern is the “side lobe” produced by some simplified processing in practice instead of the ideal orthogonal operation. In this paper the following problems were discussed theoretically: (1) “side lobe” produced by using an integration in water column instead of half-space; (2) “side lobe” produced by using a finite discrete sampling; (3) “side lobe” produced by using a hard-clipped eigenfunction; (4) “side lobe” produced by the inclination of the vertical array. Some analytic results and numerical examples were shown for a special case in which the sound-speed profile is isovelocity in water column. It was found that the effect of array inclination was serious and a phase compensation approach was proposed.
Attenuation of low- and high-frequency waves in a random medium
Authors: Wenzel Alan R.
Published: October 2005

A theoretical analysis of the wavefield radiated by a point source in a one-dimensional random medium has been carried out. Approximate expressions for the mean intensity and mean energy flux as a function of propagation range, based on general results obtained previously, have been derived for the limiting cases of low and high frequencies. These expressions show that, in both cases, the mean intensity and mean energy flux decrease more rapidly with range than would be the case in the absence or randomness. This more rapid rate of decrease with range can be interpreted as an excess attenuation. These results are similar, in general, to those obtained previously for the intermediate-frequency case. The low-frequency results are found to be in qualitative agreement with observations of excess attenuation of sound propagating through turbulence. At high frequencies, the results indicate that the excess attenuation is always much smaller than the attenuation due to absorption. This is also in agreement with observations, which generally show no significant excess attenuation at high frequencies. [Work supported by NORDA.]
Short-range, high-frequency acoustic propagation fluctuations
Authors: Vent Robert J. , Kaye G. Thomas
Published: October 2005

A series of one-way high frequency acoustic propagation experiments were conducted off southern California in an area east of San Clemente Island. Source and receiver were located at depths of 137 and 107 m, respectively, below the diurnal thermocline. The source frequency was 30 kHz; the pulse duration was 0.5 ms and the pulse repetition rate was 0.5 s−1. A series of fixed ranges were used extending from 180 to 920 m. In addition, temperature fluctuations were observed over the experiment depth range with a thermistor array. For a representative data set, energy density spectra of the acoustic and temperature fluctuations reveal similar forms. At a range of 385 m with a record length of 1 h (1800 transmissions), the standard deviation of the received acoustic intensity was 0.5 dB with a coefficient of variation of 12%. The sound-speed fluctuation patch size was calculated to be 1 m. [Work supported by NAVSEA.]
Formation of silicon microstructures for high performance integrated sensors
Authors: Wise K.
Published: October 2005

Recent progress in the development of sophisticated, low-cost microcomputers has stimulated the adoption of electronic instrumentation and control in many areas not formerly involved with electronics. In most of these new applications, the realization of the desired system has been found to be limited not by microcomputer performance, but by the lack of suitable sensors to couple the computer to a nonelectronic world. The most promising solution is to extend integrated circuit technology to allow the formation of the needed transducers together with their interface circuitry on a single monolithic chip, constituting an integrated sensor. The ability to precisely shape silicon in three dimensions in an essential requirement in the realization of a variety of transducers. This paper will review and illustrate the available techniques for chemically or electrochemically shaping silicon. The development of a chronically implantable array of recording electrodes for the study of signal processing in the brain and, perhaps, the eventual control of neural prostheses will be discussed. Fabrication techniques and trade-offs involved in the realization of high-performance integrated sensors will also be given.
Integrated circuit pressure transducers
Authors: Ko Wen H. , Fung C. D. , Shao B.-X. , Shen W. J.
Published: October 2005

Solid state electronic and integrated circuit technology can be used to design and fabricate miniature, high performance transducers. Two examples of silicon diaphragm pressure transducers, with electronic components on the chip, will be discussed. (1) A capacitive pressure transducer for the measurement of very small deformation of a silicon diaphragm has been studied. This transducer has the potential for better long-term stability, higher sensitivity, and less mechanical interference. These theoretical expectations have been confirmed by a pilot design. Two successful designs incorporating the oscillator, capacitor bridge, and amplifier circuits on the chip are now being evaluated, and the results will be discussed. (2) Piezoresistive pressure transducer design considerations, fabrication processes, and evaluated results will be presented. This mm-size device can be used for both differential and absolute pressure measurements. By integrating electronic circuits on the transducer chip, a new approach to transducer design has been developed that can upgrade the performance of the transducer and generate a new family of “intelligent transducers.” Some of the functions and advantages of this approach will be briefly discussed.
A foil electret transducer for use under varying static pressure
Authors: Busch-Vishniac I. J. , West J. E. , Kubli R. A.
Published: October 2005

We have built a foil electret microphone for use under-the-cuff in an automatic blood pressure monitoring system. The microphone uses a 50-μ-thick FEP diaphragm charged to − 250 V and suspended 35 μ above a back electrode. A flat sensitivity over a pressure range of 40 to 250 mm Hg (5.3 × 104 to 3.3 × 105 dyn/cm2) is required for this transducer. The sensitivity is maintained at a constant level by allowing the first contact between the electret and the back electrode to occur at 20 mm Hg. Although the microphone senistivity changes quickly from 0 to 20 mm Hg, it is relatively flat in the pressure range of interest. This design technique canbe used to provide a flat sensitivity for any foil electret microphone subjected to a varying static pressure.
Feasibility of optical hydrophones using multimode optical fibers as sensing elements
Authors: Shajenko Peter
Published: October 2005

The use of multimode optical fibers in an interferometer to sense the strain imposed on the fiber was experimentally demonstrated. A phase shift of 2 × 10−4 rad with a 1.4-m-long optical fiber was measured. Use of low-coherent light sources such as an LED to reduce fiber noise, improve performance, and simplify design of an optical-hydrophone is discussed.
Sound radiation measurement with nearfield holography
Authors: Maynard J. D. , Williams E. G.
Published: October 2005

With holography, an entire 3D wave field can be reconstructed from data obtained on a single 2D surface. Such high information content has made holography a powerful research tool, and useful extensions from its original optical domain to other wave fields, such as sound, have naturally been pursued. However, it has usually been assumed that the resolution of a holographic reconstruction is limited by the wavelength of the radiation; this limitation severely diminishes the usefulness of holography for sound fields when the wavelengths are many times larger than the objects to be imaged. We have developed a new technique called nearfield holography, which eliminates the wavelength resolution limit and in addition permits a determination of: (1) the complete sound pressure and particle velocity fields produced by the source; (2) the mode of vibration of the surfaces of the source; (3) the vector intensity field (showing flow of acoustic energy) around the source; (4) the farfield directivity pattern; (5) the total power radiated into a half-space. A particularly interesting application of nearfield holography occurs in the study of sound radiation from musical instruments. [Work supported by ONR.]
Recent progress in measurement methods for studying acoustic radiation
Authors: Hodgson Thomas H.
Published: October 2005

The need to locate and describe sources of noise from complex machinery has meant that recently there has been tremendous progress in measurement techniques. This is particularly true in the areas of acoustic intensity measurement, both in the free-field and on the radiating surface, and in coherence function signal processing and modal analysis. These methods have been applied to both steady-state and transient noise sources such as impact machinery. This paper will review this progress in measurement methods for studying acoustic radiation which are very applicable to analysis of the source radiation problem in musical acoustics, where the sound sources can be both complex and transient in nature.
Impedance and impulse response measurements using low-cost components
Authors: Ibisi M. I. , Benade A. H.
Published: October 2005

A thin 27-mm-o.d. disk transducer (from Radio Shack 273-060 signaler) is RTV sealed to the end of a measurement tube whose 15 mm i.d. not only approximates the transducer disk's nodal circle but also the i.d. of a clarinet, sax, or trumpet mouthpiece. A 10-mm-o.d. electret microphone element (Radio Shack 270-092) mounted through the tube wall near the piezo driver picks up the resulting pressure signal. When the high mechanical impedance driver is excited by a sinusoidal sweep via a 6-dB/oct integrator, the resulting pressure signal gives an excellent view of the input impedance of the air column over the musically useful range to 3.5 kHz since the driver resonance is at ω0/2π≃5 kHz and bandwidth g≃ω0/6. A ramplike drive voltage (running between op-amp supply limits) of the form A (1 − e−gt/2) for θ⩽t⩽2π/ω0, and constant thereafter, gives a clean pressure pulse ≃ const.(1 − cos ω0t) whose FWHM≃0.1 ms is convenient for impulse response studies. Drive signal spectrum, piezoelectric coupling, and driver-to-tube coupling each minimize transducer second-mode ringing effects. Driver-to-mike proximity effects are small, visible, calculable, and easily allowed for in both impulse and sinusoidal drive usage. The driver is not quite rigid, perturbing the air column slightly, but corrections are straightforward. Applications for research and in teaching labs will be described. [Assisted by NSF.]
Full field visualization towards developing improved ultrasonic test procedures
Authors: Burger C. P. , Miskioglu I. , Hughes R. G.
Published: October 2005

Improved procedures for quantitative ultrasonic evaluation of materials and structures depend upon improved knowledge of the ways in which acoustic waves in solids interact with geometric details and with typical defects. Full field visualization of the dynamic elastic field as it propagates through a structure is a powerful physical aid in developing such an improved understanding. This paper describes how a multilaser, Cranz-Schardin type, high-speed polariscope was used to photograph the full field dynamic progression of a Rayleigh surface wave past geometric details at the surface of a solid. The resultant spatial information of the surface stresses is used to extract frequency information for the incident, reflected and transmitted waves at a step on the surface. The characteristic features of the FFT that relate to the step height is identified and confirmed in ultrasonic tests on steel samples. This integrated, three pronged, experimental/numerical approach holds great promise towards developing more effective ultrasonic test procedures. [Work supported by NAVSEA, NOOO14-81-CO2475.]
A phonetically relevant auditory-perceptual space
Authors: Miller James D.
Published: October 2005

The vowels, based on averages of Peterson and Barney [J. Acoust. Soc. Am. 24, 175–184 (1952)], can be described independently of the age and sex of the talkers in a space with axes: x = log(F3/F2), y = log(F1/F0′), and z = log(F2/F1), where F0′ = aF0, F1, F2, and F3 are the center frequencies of the first three formants and F0 is the fundamental. The constant a varies across speakers, but the average value for men is 1.478 times that for children and women. So described, the vowels fall within a tetrahedron, whose properties will be described, and their spatial organization appears to reflect their perceptual and articulatory organization and to suggest rules for the enlargement or compression of their spectra. Distances between vowels are in log frequency and are easily converted to cents, semitones, or octaves. As examples, the neighboring vowels, /ɪ/ and /ɛ/ are separated by 0.76 octaves while the distant vowels, /ɑ/ and /i/ are separated by 3.2 octaves. New vowel data and possibilities for locating the consonants in the space will be mentioned. [Supported by NINCDS Grant NS 03856.]
The effects of linguistic context on temporal and F0 properties of speech
Authors: Ohde Ralph N.
Published: October 2005

Research examining acoustic properties of speech frequently use isolated syllables or syllables embedded in carrier phrases for analysis. Although it has been argued that these contexts represent rather limited speech situations [N. Umeda, J. Acoust. Soc. Am. 70, 350–355 (1981)], it is not clear that the influences of these contexts on speech are comparable. In order to determine the effect of these contexts on several acoustic properties of speech, three male subjects recorded repetitions of voiceless aspirated /ph,th,kh/ and voiced /b,d,g/ stops in combination with the vowels /i,e,u,o,a/ in both isolated CVC syllables and CVC syllables embedded in carrier phrases. Fundamental frequency (F0) was measured for the first five glottal periods and voice onset time (VOT) was determined for each utterance. The three acoustic properties selected for purposes of comparison were VOT, the percent decrease in F0 from the first to second glottal period, and the absolute value of F0 for the first five glottal periods. The results revealed that the greatest differences in VOT between isolated syllables and syllables produced in carrier phrases were for voiceless stops, i.e., 37 ms or greater across place of articulation, whereas for the F0 properties variation between these contexts was greatest for voiced stops. In general, however, the findings for F0 were similar in direction to results obtained in fluent reading. [Work supported in part by NINCDS.]
Context-induced vowel duration change and intrinsic vowel duration
Authors: Caisse Michelle
Published: October 2005

This study investigated the pattern of duration change of vowels of different quality (and intrinsic duration) when spoken in contexts which differently affect duration. Stressed vowel duration was measured in five contexts; test stimuli included all 15 English vowels and diphthongs. Duration change induced by context appeared to be independent of intrinsic vowel duration and vowel quality, and was best described as a constant which combines additively with some measure of intrinsic vowel duration. Results of other studies which examined similar data are discussed.
Evaluation of vocal efficiency in voice disorders by calculation of intrapulmonic pressure
Authors: Tanaka Shinzo , Gould Wilbur J.
Published: October 2005

Vocal efficiency was investigated by simultaneously measuring the intrapulmonic pressure, the mean flow rate and the sound intensity. The intrapulmonic pressure during sustained phonation has been successfully and noninvasively calculated with a pneumotachograph and a body plethysmograph. Normal and disordered subjects were examined, and the variation of vocal efficiency for each patient from the averaged values of ten normal subjects was investigated. The vocal efficiency is represented by a ratio of the sound power to the aerodynamic power, and the aerodynamic power is expressed in terms of intrapulmonic pressure times mean flow rate. The result suggests that the variation of vocal efficiency can reprepsent overall severity of the voice disorder. The relative contributions of intrapulmonic pressure and mean flow rate to the efficiency can classify the pathological lesions into three types such as leakage of air through the glottis, a mass on the vocal fold, and the stiffness of the vocal fold.
Relationships between vowel air expenditure and fricative air flow in VCV syllables by normally hearing and hearing-impaired speakers
Authors: Whitehead Robert L.
Published: October 2005

In a previous investigation, Whitehead et al. [J. Acoust. Soc. Am. Suppl. 1 64, S51 (1978)] speculated that significantly reduced air-flow rates for intervocalic fricatives produced by some hearing-impaired speakers may have been the result of air wastage on the initial vowel. In the present investigation, the volumes of air expended during production of the initial vowel in VCV syllables by ten normally hearing females, ten moderately to severely hearing-impaired females with intelligible speech and ten profoundly hearing-impaired females with semi-intelligible speech were calculated and compared with the average volume velocities for the intervocalic fricatives. The results indicated that the semi-intelligible hearing-impaired speakers produced the initial vowels with significantly greater air volumes than the other two groups of speakers. Further, for the semi-intelligible speakers, significant negative correlations indicated the existence of a relationship between the volume of air expended on the initial vowel and the average volume velocity for the intervocalic fricative. Such a relationship did not appear to exist for the other groups of speakers. [Work supported by U. S. Department of Education.]
Tuning curves and pitch matches in unilateral, low-frequency hearing loss: A case study
Authors: Florentine Mary , Houtsma Adrianus J. M.
Published: October 2005

Psychoacoustical tuning curves and interaural-pitch matches were measured in a listener with a moderately severe hearing loss of primarily cochlear origin below 2 kHz. The simultaneous-masked tuning curves at 1 kHz in his impaired ear show that as the level of the probe increased from 4.5 to 13 dB SL, (1) the frequency location of the tuning-curve tip decreased from approximately 2.85 to 2.20 kHz and (2) the lowest masker level increased from 49 to 83 dB SPL. The tuning curves for different probe levels appear to reflect tuning properties of different populations of nerve units. The tuning curve in his normal ear was comparable to data from other normal listeners. The interaural-pitch matches were measured from 0.5 to 6 kHz at 10 dB SL in the impaired ear and approximately 15 to 20 dB SL in the normal ear. Results show reasonable identity matches (e.g., a test frequency in the impaired ear was matched relatively close to the same test frequency in the normal ear), although variability was significantly greater for pitch matches below 2 kHz. The pure-tone pitch matches of this listener in the impaired frequency region appear more easily explained in terms of temporal theories than place theories of pitch perception. [Work supported by NIH.]
Psychophysical tuning functions, dichotic stimuli, and pulsation thresholds
Authors: Soderquist David R.
Published: October 2005

Using a dichotic mode of stimulus presentation, four psychophysical tuning curves were obtained: input filter pattern, input extension pattern, output filter pattern, and output extension pattern [J. Verschuure, Acustica 49, 288–295 (1981)]. Stimulus parameters for all tuning functions were: durations 60 ms, rise/decay 10 ms, interstimulus interval (delta-t) 0.00 ms (no overlap between pulsator offset and signal onset). Stimuli were presented in sequential pairs (pulsator then signal), alternating between ears; e.g., left ear (pulsator-signal), right ear (pulsator-signal), left ear (pulsator-signal), etc. The alternation between ears was temporally controlled to insure no overlap (delta-t = 0.00 ms) between signal offset in one ear and pulsator onset in the other. Pulsation thresholds were obtained by the method of adjustment for each of the four tuning patterns. Results indicate that pulsation threshold patterns could be perceived when the stimuli were presented dichotically, i.e., the perception of “continuity” was synthesized by central processes. Tuning patterns, generated with the dichotic stimuli and based on the centrally synthesized pulsation thresholds, appear to be similar to those in the literature. Contrasts of the four tuning patterns will be presented.
Relation between simultaneous-masking psychophysical tuning curves and cubic-difference-tone amplitudes for Fm < Fp
Authors: Norton Susan J. , Wier Craig C.
Published: October 2005

The detection of cubic difference tones (CDTs) generated by the masker and probe could influence the shapes of simultaneous-masking psychophysical tuning curves (PTCs) if listeners increase the masker level until the CDT, as well as the probe, becomes inaudible. To test this possibility, simultaneous-masking PTCs were measured for a 125-ms, 2000-Hz probe at 30, 45, and 60 dB SPL temporally centered in a 250-ms masker in four normally hearing listeners using a method-of-adjustment procedure. The amplitudes of CDTs produced by the combination of masker and probe from the low-frequency side of the PTC (Fm < Fp) were then determined using pulsation-threshold and cancellation procedures. In all cases, a CDT was measurable, i.e., above masked threshold, indicating that CDT threshold did not establish the tuning-curve masker level. Measurements of CDT amplitude as a function of L 1 for fixed L 2s (30,45, and 60 dB SPL) also suggest that for pulsed masker and probe stimuli, listeners did not rely upon the masking of the CDT in the simultaneous-masking PTC task. [Work supported by the Deafness Research Foundation and NIH.]
Fabric air-supported and tensile roofs for large structures—A review of fabric roof technology
Authors: Geiger David
Published: October 2005

The use of fabric for the roofs of large audience spaces and similar structures is a relatively new technology. It had its beginning with the large air supported structure for the U.S. Pavilion at the 1970 Worlds Fair in Japan. This technology has continued to produce the very large tensile structure at the Jetta Airport in Saudi Arabia, and the large stadium with an air-supported fabric roof that recently opened in Minneapolis and the similar facility that is nearing completion in Vancouver, British Columbia. A review of the major projects that have utilized this technology during the past twelve years is useful in applying the fabric roof concept to future structures.
Acoustical problems in large structures employing fabric roofs
Authors: Coffeen Robert C.
Published: October 2005

Because of the physical characteristics of fabric roofs, acoustical problems in structures using such roofs cannot normally be resolved using traditional techniques. This presentation discusses the existing and potential acoustical problems of several existing and proposed facilities that utilize both air supported and tensile fabric roof systems. Also presented will be sound absorbing data for a newly conceived tensile roof system.