bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomization of Liquids by Mechanical Vibration
Authors: Pickering Norman C.
Published: November 2005

The atomization of liquids by contact with a mechanically vibrating surface has been studied in some detail. The vibrator consists of a horizontal bar resonantly driven at its center by a moving-coil magnetic driver similar to a loudspeaker motor. Liquid is flowed on to the bar and is thrown off as a shower of uniform droplets, the size of which depends on the density, viscosity, and surface tension of the liquid and the frequency of vibration of the bar. High-speed motion pictures of the mechanism of droplet formation explain the unexpected uniformity of particle size. The device has application in industry for production of uniform large particles of spray-congealed or spray-dried materials.
Design of an Experimental-Model Formant Vocoder
Authors: Houde Robert A. , Larkin Wilbur D. , Stewart Leslie C.
Published: November 2005

This paper discusses the design of an experimental-model formant vocoder that employs partial spectral-pattern-matching for the tentative identification of the formants of each short-time spectrum. The speech signal is converted to a sequence of short-time spectra by means of a 55-channel bank of bandpass filters and a sequential sampling switch operating at 100 short-time spectra per second. All of the formantlike energy distributions of each short-time spectrum are identified by matching the spectrum against a set of standard formant patterns. From this set of potential formants, three are selected by rules and are identified as formants one, two, and three. The data describing the three formant frequencies, intensities, and excitation are transmitted to a parallel-formant type of synthesizer. A tape demonstration of the system is presented. [This work was supported by the U. S. Army Electronics Research and Development Laboratory, Fort Monmouth, N. J., and General Dynamics Electronics.]
Performance Analysis of the General-Dynamics-Electronics Formant Vocoder
Authors: Houde Robert A. , Larkin Wilbur D. , Stewart Leslie C.
Published: November 2005

An experimental-model formant vocoder has been developed that employs a modified spectrum-pattern-matching technique to locate potential formants, and a selection-by-rules technique to identify formants one, two, and three from this set of potential formants. The modified pattern-matching technique is a compromise between simple peak picking and complex complete spectrum matching. This paper is a report on the analysis of the performance of this system. The errors produced by the system are discussed. The practical techniques that might be used for correcting certain classes of these errors are presented. [This work was supported by the U. S. Army Electronics Research and Development Laboratory, Fort Monmouth, N. J., and General Dynamics Electronics.]
Segmentation and Mechanical Commutation
Authors: Truby H. M.
Published: November 2005

When speech is displayed visually, for example on sound spectrograms, certain portions of the display—specific time-frequency-intensity increments—are traditionally referred to particular speech sounds or phons or even phonemes. The possibility of segmentation, with reference to these physical increments or to articulation or to any other physical manifestation of the so-called speech continuum, has had an explicit appeal for linguist and engineer alike. Segmentation, however, implies discrete divisibilities along the time axis, and the identification of phoneme-relevant physical boundaries within a stretch of connected speech has long been suspect among linguists. In an effort to establish physical correlates of phonemes, commutation has been variously turned to. Linguistic commutation refers, on the phonological plane, to the “replacing” of a given sound in a particular (linguistically determined) phonetic environment by some other sound so as to bring about a change of meaning. Mechanical commutation is the artifactual counterpart—and because of its nature never a replica—of linguistic commutation and refers to the physical replacing, by tape-splicing or gating or whatever, of a particular time-frequency-intensity increment. In linguistic commutation, the transitional phonetic modifications spontaneous and automatic with the “replacing” of one phoneme by another are taken for granted, and justifiably so, but when mechanical commutation is attempted, there is no associated automatic adjustment of the adjacent phonetic environment as for commutation in the linguistic sense. The audible product of mechanical manipulations is thus, by definition, outside the bounds of language. Perceptual evaluations made in ignorance of this are not reliable. Acoustic and visual-acoustic demonstrations supporting these observations are presented.
Multidimensional Model for Speech Recognition
Authors: Bhimani B. V.
Published: November 2005

Speech sounds do not appear randomly in utterances. Rather, there appears to be a set of preferred positions for these sounds. They also have a set of determinable acoustic modifications that these sounds receive from their environment and impose upon it. That is, as a language consists not only of a vocabulary but also of a grammar that limits its possible verbal combinations, so does speech consist not merely of a set of sounds but also of an embedded or intrinsic structure within which these sounds form sequences. Such a structure is partly the result of capacities and limitations of the speech-producing mechanisms and it is partly shaped by linguistic tradition. It seems possible, therefore, to describe speech acoustic phenomena by a set of logical formulations that form the analytic correlative of the intrinsic sound structure. Moreover, such formulations should be subdivisible in terms of the degrees of freedom of speech-producing organs. Such all organization of rules is an orderly integration of data on the genetive, phonetic, phonemic, and acoustical aspects of speech, and it constitutes a multidimensional model for speech that combines the coherence of analytic form with fidelity to the realities of speech events. [This work was supported by Air Force Cambridge Research Laboratories, U. S. Office of Aerospace Research, under contract No. AF 19(628)-2766.]
Attenuation of Rocket-Engine Noise by Water Injection into the Flame Bucket
Authors: Shulman Arnold L.
Published: November 2005

Data are presented from a series of small-scale-model rocket tests conducted to evaluate the acoustic performance of a certain type of water-cooled flame bucket. These data are then compared to data from large-scale engine tests. From a least-square regression analysis, these data indicate an acoustic efficiency (η=Wacoustic/Wmechanical) ranging from 6.24 × 10−3 for dry operation to 2.04 × 10−5 for a water-flow-rate ratio (w=ẇwater/ẇpropellant of 5. Nondimensionalized spectra are presented for several representative cases; this information is crossplotted to show the variation of the acoustic efficiency at the characteristic frequency as a function of water-flow-rate ratio. Several flame-bucket configurations are described and a novel scheme is shown that achieves the high water-flow-rate ratio necessary for effective noise reduction. This system utilizes a large reservoir surrounding the flame bucket. A system of weirs allows a large flow of water to be aspirated into the flame bucket during engine operation. Tests indicated satisfactory operation even when the flame bucket was purposely flooded to simulate failure of the weir mechanism.
Farfield-Noise Characteristics of Deflected and Undeflected Rocket Flows from Multiple Nozzles
Authors: Eldred Kenneth McK.
Published: November 2005

The results of current work suggest that the farfield-noise characteristics of deflected and undeflected rocket flows emanating from multiple nozzles can be predicted by techniques previously proposed for sonic flows. The paper reviews the simplified flow models utilized as prediction tools for several cases, and compares prediction with available data.
Temporal Integration in the Human and the Rhesus Monkey
Authors: Clack T. D. , Dey F. , Harris J. D.
Published: November 2005

Intra-primate temporal integration is examined for differences in both the rate and upper critical duration (t0) as a function of frequency. The thresholds of five women and two Rhesus monkeys were obtained monauarally and/or binaurally (MAF) for pure-tone stimuli at 0.25, 0.5, 1, 2, 4, and 8 kcps. The signal durations were in log units from 10 to 1500 msec. The single-lever, go/no-go procedure was similar for humans and monkeys, allowing comparison of responses for possible influences of the decisional behavior upon the obtained thresholds. As in humans, the absolute limens of monkeys show linear changes as a function of log signal duration within the range of sampled time intervals. The t0 values are also similar for humans and monkeys. The slope of the temporal integration function is frequency-dependent, with monkeys showing the greater effect below 1 kcps. Differences in absolute sensitivity, plus the frequency dependence, raise problems for current hypotheses concerning temporal integration. [Work supported by a grant from the Public Health Service, U. S. Department of Health, Education, and Welfare.]
Auditory Responses in Certain Lizards
Authors: Peterson Ernest A.
Published: November 2005

There have been relatively few studies concerning the auditory capacities of the lizard. Because of its intermediate structural complexity, however, the saurian ear offers the opportunity for a number of interesting comparisons with the more highly developed avian and mammalian ears. The present paper describes the results of several investigations in this area performed at the Auditory Research Laboratory, Princeton University. 14 species representing 6 families were studied. Inner-ear potentials, recorded from the round-window membrane, were used as an index of hearing. In relation to the mammalian ear, these ears were generally found to (a) be rather insensitive within a narrow frequency range, (b) have a very narrow dynamic range, and (c) be nonlinear at even low stimulus intensities. It was found, however, that the best individuals of a few species rivaled the sensitivity of mammalian ears in the middle frequencies. The role of the middle-ear mechanisms in sound conduction and sound control was also studied.
Evolution of Binaural Hearing
Authors: van Bergeijk Willem A.
Published: November 2005

Fishes apparently employ the lateral-line organ as an underwater nearfield acoustic detector and their swimbladder-ear system as a farfield detector. It can be shown, however, that the latter system is not directionally sensitive. Since the terrestrial ear evolves from this latter system, directional sensitivity is somehow acquired in the course of evolution. In the underwater near field, time-of-arrival differences are negligible for average-size fish, but the intensity gradient is very steep. The directional sensitivity of the lateral line is, therefore, probably based exclusively on intensity clues. For “zero-difference” azimuth localization, only two neurons (such as the Mauthner neurons) are sufficient. In the terrestrial animal, arrival-time difference between the two ears is significant, while intensity differences may be relatively minor. In view of the time constants of the nervous system, a single cell pair cannot accurately resolve small time differences, and a multiple-cell system, such as the superior olive, is necessary. It is interesting to speculate on the fact that fishes do not have a superior olive but a pair of Mauthner neurons, and that frog tadpoles have Mauthner neurons, which are replaced by a superior olive at metamorphosis.
Thresholds of Acoustic Cavitation in Water
Authors: Barger James E.
Published: November 2005

Cavitation thresholds in water have been measured as a function of frequency, dissolved gas, ambient pressure, and suspended-particle size. The apparatus used comprises a 2-1 volume of water enclosed by a spherical glass shell driven at its radially symmetric resonance frequencies by 8 multiresonant piezoelectric transducers. Large acoustic pressures can be produced, ranging from 10 bar at 27 kc/sec to 200 bar at 1.16 Mc/sec. The threshold data can be divided into three regions: In region A—defined by f<200 kc/sec, acoustic pressure Pa<3 bar, and air saturation presure Ps>600 mm Hg—small air bubbles grow by rectified diffusion and stabilize at the pressure nodes. In region B—defined by f<200 kc/sec, Pa>3 bar, and Ps<500 mm Hg—transient cavities are formed that can be detected visually and aurally. In region C—where f>200 kc/sec, Pa>5 bar, for any value of Ps—transient cavities are formed, but their presence can be detected acoustically only. The threshold tends to a slope of 12 dB/octave for frequencies above 1 Mc/sec. Experiments on cavitation at pressures larger than the threshold indicate that only a finite number of cavitation events can be produced in a given sample of water when it is isolated from contamination by airborne motes. In this way, water can be “strengthened” by a factor of at least 8 by repeated cavitation.
Experimental Studies of Controlled Cavitation
Authors: Howkins S. D.
Published: November 2005

Experiments were made with bubbles, under various different conditions, using a microscope and a high-speed (Fastax) camera for applied sound frequencies in the range 100–5000 cps and also at 20 kc/sec. In commencing an experiment, a single air bubble of measured volume was placed just under the lower face of a solid bar dipping into a liquid. A number of interesting events were observed as the bar was set into vibration and its amplitude increased up to the threshold for collapse cavitation. These include surface-wave phenomena and microbubble throwoff, as noted by Willard, as well as fragmentation, coalescence, migration, and other time-dependent effects. The motion of a bubble depends on the proximity of its size to resonance. Measurements of the resonant frequency for bubbles in the lower frequency range gave values higher than those prediceted by Strasberg for a bubble near a rigid boundary but lower than those for the case of an isolated bubble. Under certain conditions, when a macroscopic bubble is present, effects such as erosion, usually associated only with collapse cavitation, were seen to occur at relatively low sound amplitudes. Photographs of damage done to prepolished solid specimens placed near to the bubble were taken with an interference microscope. [Work supported in part by U. S. Air Force Office of Scientific Research grant AF 62–63 and National Institutes of Health, U. S. Department of Health, Education, and Welfare, grant GM-08209.]
Model for the Persistent Microbubble
Authors: Turner W. R.
Published: November 2005

As evidence has increased that microbubbles reside in natural waters, a number of investigators have speculated as to the stabilization mechanism. Two independent conditions must be satisfied: (a) the interchange of gas by diffusion between the bubble and the surrounding liquid must be equalized; (b) the positive buoyancy of the bubble must be neutralized. The model microbubble is hypothesized as being stabilized by minute particles picked up on the bubble surface, which compress upon outdiffusion of gas to form a wall capable of supporting the hydrostatic pressure. This permits the internal pressure to drop to that of the gas dissolved in the liquid, thus satisfying condition (a). The particulate mass neutralizes the buoyancy, thus satisfying condition (b). Recent experimental evidence suggests that microbubble stabilization may be critically affected by trace chemicals, such as detergent. Further, the stiffness added by the compressed wall appears to raise the resonant frequency of the bubbles and modify the damping constant, and the wall's elasticity may affect the cavitation threshold. [Work sponsored by the U. S. Office of Naval Research.]
Scattering of Plane Acoustic Waves by Arrays
Authors: Harbold Mary L. , Steinberg Bruce
Published: November 2005

A previous paper described amplitude measurements, made with a probe microphone, of the acoustic field of a plane wave scattered by obstacles of finite dimensions. A new 8-channel recording system has now been set up, which includes among its data not only the amplitude of the output of a moving probe microphone, but also the output of a phase meter measuring the phase angle between the output of the probe microphone and that of a reference microphone. The phase meter covers the full 360° and provides means of marking on the trace whether the phase angle is lead or lag. First tests were run at the surface of a single cylinder and a single sphere to check the accuracy of the equipment. The results for the area surrounding a single infinite cylinder were compared with scattering of electromagnetic waves by King and Wu. The multiple scattering of two parallel cylinders was investigated and the results were compared with predictions of theory for forward, backward, and 90° scattering for various kb (where b is the spacing between cylinder axes). Predictions were made for two spheres and verified, and the same techniques were applied to multiple arrays. [Research supported by the U. S. Office of Naval Research.]
Some Further Remarks on the Fitzroy Multiaxial Reverberation Formula
Authors: Fitzroy Dariel
Published: November 2005

New information is added relative to the author's multiaxial reverberation formula, originally presented as an invited paper at the 56th Meeting of the ASA in 1958 and later published [D. Fitzroy, J. Acoust. Soc. Am. 31, 893 (1959)]. It includes experiences with off-parallel boundaries and the allocations of sound absorption contributed by an audience where such absorption is effective along different axes. This paper also includes further results of field experience.
Diffraction of Sound by an Array of Rectangular Reflective Panels
Authors: Leonard R. W. , Delsasso L. P. , Knudsen V. O.
Published: November 2005

An investigation of the diffraction of sound by rectangular panels, similar to those that have been used for acoustical purposes in concert halls and other auditoriums, confirms certain expectations based on well-known properties of both optical and acoustical diffraction: namely that, for wavelengths that are (1) large as compared to the dimensions of the panels and the spacing between them, the incident sound on the panels is essentially all transmitted; (2) small, the panels reflect nearly all the sound incident upon them; and (3) of the same order of magnitude as the dimensions of the panels and spacings, there are complex diffraction effects that are manifest both in the transient and steady-state properties of the surrounding sound field. For example, a horizontal array of sixteen 2×4-ft panels with spacings of 14×18 in. in a room 15.6×25×13 ft introduced a prominent nonlinear decay in the reverberant sound for frequencies between about 500 and 2000 cps. Thus, whereas the rate of decay at 1000 cps was about 136 dB/sec with or without the panels in the room for the initial 25 dB of decay, for the subsequent decay the effect of the panels was to prolong the sound—with the panels in, the average rate of decay for the next 20 dB was reduced to 52 dB/sec, whereas with the panels out it was 62 dB/sec.
Acoustics of La Grande Salle, Place des Arts, Montréal, P. Q., Canada
Authors: Johnson Russell
Published: November 2005

This multipurpose auditorium, designed by Affleck, Desbarats, Dimakopoulos, Lebensold, and Sise, was inaugurated 21 September 1963. About one-third of its 2980 seats are located on the main floor, with the balance distributed in three balconies and three tiers of boxes along the side walls. It is equipped with a mechanized concert enclosure of wood secured to a steel frame, as this hall was built to provide a home for the Montréal Symphony Orchestra, ballet, opera, and revues. The front third of the audience chamber is approximately 80 ft wide, but the balconies at the rear of the house were designed with much more width to accommodate the number of seats specified by the building owner. Most of the wall surfaces, including the rear walls, were constructed of plaster applied directly to concrete masonry units or poured concrete to obtain sufficient low-frequency reverberation. The small areas of wood paneling are securely cemented to heavy masonry walls for the same reason. To obtain sufficient reverberation for music, the upper boundary of the audience chamber was constructed approximately 80 ft above the main floor. Small sound-reflecting surfaces were installed below the “upper ceiling” to aid definition. These small surfaces were designed in the form of an interwoven grid, which conceals the air-supply ducts, the loudspeaker equipment, and theatrical and audience lighting equipment. The basic design of the auditorium was accomplished between September 1958 and January 1959. This paper reports the results of acoustical measurements performed in the hall since its completion and observations made during a wide range of speech and music performances.
Acoustics of Clowes Memorial Hall, Butler University, Indianapolis, Indiana
Authors: Johnson Russell
Published: November 2005

This 2100-seat auditorium, inaugurated 18 October 1963, on the campus of Butler University, serves as the home of the Indianapolis Symphony Orchestra and as a convocation hall for the University. This auditorium, designed by John M. Johansen and Evans Woollen, III, has three shallow balconies that extend down the side walls of the hall to within 30 ft of the proscenium opening. The roof-deck serves as the upper limit of the acoustical chamber, and several feet below the roof-deck is suspended an array of plywood sound-reflecting panels. The side walls are plane surfaces (minimum dimension, approximately 15 ft) parallel to the main axis of the hall. The side-balcony spandrels are also plane surfaces, of exposed concrete, parallel to the main axis. Much of the wall surface consists of plaster applied directly to concrete masonry units, and the remainder is plywood panelling secured to furring strips. All rear-wall surfaces are hard plaster, parallel to the proscenium wall. The aisle areas of this auditorium are extensive, and to secure sufficient reverberation for music no carpet was installed in the aisles of the three balcony tiers. The design for this hall was essentially complete by late fall 1959. This paper presents results of acoustical measurements in the hall and direct evaluations made during actual events in the hall during the past few months.
Techniques for Automatic Recording of Impedance and Admittance of Transducers under High Power
Authors: Dranetz Abraham I.
Published: November 2005

Systems are described for the direct measurement and automatic frequency recording of two-terminal series resistance and reactance or parallel conductance and susceptance while the device under test is driven under high power. For admittance measurements, the system places a constant voltage of up to 300 V (rms) across the unknown; the current produces a proportional voltage, which is resolved into in-phase and quadrature dc outputs calibrated directly in units of admittance for graphic recording. For impedance measurements, the current through the unknown is maintained at a constant amplitude level (by feedback) between 0.01 and 3 A (rms); the voltage developed across the unknown is attenuated and resolved into dc outputs calibrated in in-phase and quadrature units of impedance for recording. Measurements of current can be made either by means of resistors or current transformers, which complement each other to cover broad impedance and power range measurements up to 25 kcps.
Measurements of Electromechanical Coupling in Condenser Microphones
Authors: Koidan Walter
Published: November 2005

In the two equations that describe the steady-state, single-degree-of-freedom operation of condenser microphones, there appears an electromechanical coupling term that can be defined as φ=(p/e)u=0, where p is the sound pressure, e the applied voltage, and u the volume velocity of the diaphragm. The value of φ at zero frequency should be the same as its value in the audiofrequency range, where it is constant. This hypothesis was verified by measurements on several microphones. The value of φ at zero frequency was determined by applying a static pressure to the diaphragm and measuring the change in polarizing voltage required to keep the diaphragm at a fixed reference position. The static pressure was measured with a low-pressure manometer and the polarizing voltage with a differential voltmeter. In determining φ at audiofrequencies, sound pressure was measured by the reciprocity technique. Agreement within about 0.2 dB was obtained between the two methods, which are somewhat independent of each other.
Underwater Sound Reflection from Layered Media
Authors: Barnard G. R. , Bardin J. L. , Hempkins W. B.
Published: November 2005

Underwater sound-reflection experiments were conducted in an 8-ft-diam, 7.16-ft-deep laboratory tank equipped with a transducer-positioning system. A 5-in. shaded, circular piston operating at 100 kc/sec was used to insonify layers of various fluid and solid media supported near the bottom of the tank by a 4×4-ft tray. Measurements were made to determine the reflection coefficients as a function of grazing angle for several models of layered media. These experimental results are compared with calculated values, using modified versions of the equations presented earlier by Brekhovskikh. In each experiment, the sound velocity and attenuation were known for each layer and these values were used in the calculations. When plane, bounded waves are incident upon well-defined layers of isovelocity uniform-density materials, the relatively simple layered mathematical models presented are sufficient to describe the experimental results.
Time Variability of Ambient-Noise Directionality
Authors: Arase T. , Arase E. M. , Weigle F. G. , Perrone A. J.
Published: November 2005

Measurements of the time variation of ambient noise of the deep ocean at fixed elevation angles have been made in 13-octave bands in the frequency range 200–1500 cps. This is the same frequency range used by Fox [J. Acoust. Soc. Am. 35, 811 (1963)]. The fixed angles are the up- and down-going refraction-surface-reflection (RSR) angles at this depth and result in observations of noise typical of the deep ocean at this depth. The measurements of the level of ambient noise are correlated with simultaneous weather observations. The noise distributions are shown to be peaked at the RSR angles at low sea states and at other angles at high sea states. [Hudson Laboratories, Columbia University Informal Documentation No. 45. Work supported by the U. S. Office of Naval Research.]
Catechol Amine Activity in the Inner Ear: Histochemical Study by Electron Microscopy
Authors: Hilding David A.
Published: November 2005

When we showed that acetylcholinesterase activity was demonstrable in the large, vesiculated cochlear-nerve endings, several investigators wondered if epinephrine or nor-epinephrine would be found in the other afferent nerve endings. Wood discovered a technique for localizing catechol amine (epinephrine and nor-epinephrine) by electron microscopy. We modified this procedure for use in the inner ear. We found no catechol amine activity in the cochlear-nerve endings, but did find certain cells in the region of the stria vascularis that gave a positive reaction. These cells are usually found near the blood vessels. Several authors have previously discussed the importance of these vessels to variations in cochlear function. Several feel that autonomic stimulation reduces the sensitivity of the end organ. Yet, Perlman and Kimura were unable to produce any change in the caliber of stria vessels by such stimulation. No autonomic nerve fibers or endings have been found in the stria or spiral ligament. A special type of cell located near the blood vessels of the stria vascularis and containing large vesicles of catechol amine may prove to be the anatomical link between these theories of autonomic control and the vessels themselves.
Brain-Stem Neuronal Coding of Binaural and Monaural Tones
Authors: Moushegian George , Rupert Allen L. , Whitcomb Milton A.
Published: November 2005

Within the auditory medulla, there exists a class of neurons that, when stimulated by binaural tones, demonstrates a large latency shift. The range of this shift beyond the monaural latency varies from several milliseconds to 60 msec, depending upon the intensity of sound in the ear opposite the driving ear. Also, units in this part of the brain are responsive to changes in the binaural phase difference of low-frequency sinusoids. These units are inhibited by in-phase binaural tones; however, as the phase angle is increased in small steps to 180°, this inhibition is decreased. Beyond 180°, where now the opposite ear leads in phase, inhibition is effective again, and at 330° the response grouping of the unit is identical to its response grouping at 30°. Monitoring of the cochlear-microphonic responses at the two ears throughout these phase studies shows that no peripheral cancellations or distortions are taking place. Evidence for introfiber volleying is shown by medullary units. These units discharge, during stimulation by monaural tones, with interspike intervals that are equal to and multiples of the period of the stimulating tone up to approximately 2.0 kc/sec. This intra-fiber volleying is maintained down to the unit's threshold at each of the effective frequencies.
Binaural-Click Analysis by Brain-Stem Auditory Neurons
Authors: Rupert Allen L. , Moushegian George , Whitcomb Milton A.
Published: November 2005

Previous studies have shown that medial superior-olivary (accessory nucleus) units of cat show a decrease in probability of response and an increase in latency when stimulated by binaural clicks of appropriate intensive and time differences. Recent findings from the same medullary region reveal a complex synaptic organization of neurons, some of which are differentially responsive to large and some, as previously reported, to small interaural time differences. The former units, which show binaural interactions to large time differences (ca. 10 msec), are driven consistently by both monaural left and monaural right clicks. When, however, binaural clicks with large time disparities are delivered, the response probabilities to both clicks are significantly decreased. Some of the units that show binaural interaction to small time differences regularly fire twice to a monaural click. These units, in contrast to the former ones, discharge only to one ear stimulation, never to both. To binaural clicks, either one of these spikes or both may be inhibited as time or intensive differences of the clicks are systematically changed. The spike latencies also of both responses are dependent upon these parameters of the clicks.
On the Mechanism of the Hartmann Whistle
Authors: Smith T. J. B. , Powell Alan
Published: November 2005

The Hartmann whistle normally consists of a flat-bottomed, cylindrical resonant cavity that is axially aligned with a supersonic air jet of the same diameter. Discrete-frequency oscillations of the enclosed air column are driven at large amplitudes when the cavity is located within certain regions of the cellular structure of the jet. Research on this phenomenon [J. Acoust. Soc. Am. 34, 1984(A) (1962)] has been extended by optical and acoustical studies of the pulsator—an adaption reported by Hartmann in 1919 but never subsequently developed. In this form, the whistle has the small cavity replaced by a large Helmholtz-type resonator with the same orifice diameter, resulting in a large-amplitude aeroacoustic oscillator with a periodic time of several orders of magnitude greater than for the regular whistle. The discovery of the bistable condition of the normal “shock-disk” located in the airstream between nozzle and cavity orifice leads to radical advances in the theory of operation. It is supported by observations of axially interacting supersonic air jets and by studies using a hydraulic analog. The theory makes possible an explanation of the discovery that the 2-dimensional analog operates, while a 2-dimensional air system does not do so at all well. [Experimental details to be published in Eng. Rept. 64-20.]
Chlorine-Release Test for Cavitation Measurements
Authors: Liu Shih-Ping
Published: November 2005

A new method is described for measuring the cavitation intensity in an ultrasonic-cleaning system. It is based on the sonochemical liberation of chlorine from carbon tetrachloride dissolved in water [see A. Weissler, Chem. Eng. Progr. Syrup. Ser. 47, 22, 1951]. The potassium iodide in the solution reacts with chlorine gas and releases iodine. The iodine concentration is then determined by using a spectrophotometer. It is found that the amount of chlorine produced by cavitation is directly proportional to its irradiation time; more chlorine is released at elevated temperature; the cavitation intensity increases with addition of surfactant up to a point beyond which further additions have no additional effect on cavitation; responds approximately linearly with power input to tank; changes periodically with water height in the tank and the distance between consecutive peaks corresponds to a half-wavelength of generated frequency in water. The method is also evaluated against the removal of graphite from alumina ceramic rings. The result indicates that the chlorine-release test has a quantitative relationship with cleaning efficiency.
Ultrasonic Spectroscopy of Steel
Authors: Gericke Otto R.
Published: November 2005

An electronic test instrument has been developed for the study of ultrasonic-attenuation spectra. The instrument utilizes the pulse-echo test procedure and operates with a single piezoelectric transducer employed for both transmission and reception of ultrasonic test signals. Special electronic circuitry provides equalization of the frequency-response curve of the piezoelectric transducer with the result that ultrasonic test frequencies covering a range of 3–12 Mcps can be transmitted and received simultaneously. The described ultrasonic spectroscope has been applied to examine the microstructure of steel specimens and it has been found that the ultrasonic-attenuation spectrum is strongly influenced by the average grain size of the specimen. Working in the spectral range of 3–12 Mcps, discrimination between specimens having grain diameters varying from 2 to 8 (ASTM scale) has been accomplished. In comparison to conventional multiple-back-echo attenuation testing carried out at various frequencies sequently applied to the specimen, the method of ultrasonic spectroscopy offers the advantages that measurements can be carried out more rapidly and are not influenced by test-surface loading due to the affixed transducer. A further benefit can be derived from the fact that the over-all back-echo amplitude serves as a reference signal for checking equipment sensitivity and coupling conditions.
Vibration-Data Analysis. Part I. Theoretical Considerations
Authors: Bendat Julius S.
Published: November 2005

The mathematical and physical concepts deemed to be important in analyzing periodic and random vibration data are presented. Overall procedures are outlined for evaluating single records and a collection of records with particular details on measuring and interpreting (a) probability-density functions, (b) correlation functions, and (c) power spectral-density functions.
Generalized Matrix Method for the Design and Analyses of Vibration Isolation Systems
Authors: Smollen Leonard E.
Published: November 2005

The effective rotational and translational stiffnesses of a set of isolators arbitrarily oriented with respect to the c.g. of an isolated rigid mass are developed by matrix techniques. Influence coefficients for determining isolator loadings due to arbitrary g loads are also presented in matrix form. Matrix equations of rigid-body motion for a general isolation system are presented and conditions for decoupling translational and rotational motions are determined. The application of the matrix techniques developed to the design of vibration isolation systems is illustrated through several examples.
Thirty Years of Vocoder Research
Authors: Dudley Homer
Published: November 2005

A program of active research on the vocoder was initiated in July 1934. The first public demonstration of the vocoder was at the Harvard Tercentenary in September 1936. Since then, there have been studies of the underlying nature of speech and the recognition of speech-sound elements in transforming from the spoken to the written word or setting up other automatic voice operation. There has also been much research directed toward straightforward bandwidth compression and such compression as an aid to the attainment of other goals. The entire field of research in speech analysis and/or synthesis is reviewed, including a discussion of limitations and requirements. A demonstration tape is played from an improved 2400-bit/sec digitized vocoder.
Study of Vocoder Filters by Computer Simulation
Authors: Rader Charles M.
Published: November 2005

A number of vocoders, identical except for the bandpass filters employed, were simulated on a digital computer. Each vocoder used a two-bank synthesizer and was excited by undistorted 3.3-kc/sec speech. Thus, the system provides no compression, but the effect of the filter banks is not masked by the effects of improper excitation. By listening to A-B comparisons of vocoder outputs with various filter banks, it was possible to compare the effects of different types of bandpass filters on speech quality. In general, we have found that a vocoder filter should have an impulse response whose envelope resembles a short, single-lobed pulse. A well-known filter that satisfies this requirement is the Bessel filter. We have also verified that the amplitude-frequency responses of adjacent filters in a bank should intersect at 3 dB of attenuation. Attention was concentrated on 3-pole filters of the Tchebyshev and Butterworth-Thompson types, including the Bessel filter. We briefly studied 1-pole filters, 4-pole Bessel filters, and Lerner filters. The filter bandwidths were uniformly 120 cps, with 26 filters covering the 3.3-kc/sec band.
Measurement of the Transmission Loss of Finite Depth of Circular Apertures
Authors: Wilson George P.
Published: November 2005

To provide experimental verification of an approximate solution for the diffraction of sound waves by a circular aperture in a plane rigid wall of finite thickness, a series of experiments was conducted on the transmission of reverberant sound through steel pipes inserted individually into a thick wall between two reverberation chambers. Usually, recommended methods of evaluating the transmission loss proved inadequate because long, narrow apertures have sharp, resonant peaks. By electronically averaging and equalizing the outputs of four microphones in each chamber and using a slowly sweeping sine wave with a small superimposed warble, it was possible to record continuous plots of the aperature transmission loss with high resolution of frequency and amplitude. Experimental acuracy of 1 dB was possible over most of the frequency range of 300–12 000 cps, diverging to 2 dB at the frequency extremes and for apertures with sharp resonances diverging to about 4 dB at the peaks. The accuracy was limited by reading the “average” of the recorded fluctuating sound level, which was most difficult at resonant peaks. For larger-diameter apertures, which gave data relatively uninfluenced by flanking sound, the agreement with theoretical results was within 1 dB over most of the frequency range.
Coupling of Sound and Panel Vibration below the Critical Frequency
Authors: Smith P. W.
Published: November 2005

Prior analysis showed that the sound power radiated from reverberant vibration of a simply supported panel is proportional to the length of the panel's perimeter when the frequency is below the critical frequency. A simple physical interpretation was made in terms of the mode shape of resonant modes. Other analyses for power radiation from a single straight boundary on an infinite panel indicated that twice as much power radiates from a clamped edge as from the simply supported edge, the spatial mean-square velocity being held constant. It is shown here that the increased radiation from clamped edges is also predictable from simple considerations of the mode shape. Moreover, among all boundaries having a purely reactive rotatory impedance, and restricting transverse displacement to zero, the clamped edge is found to be the most efficient radiator. For some impedances, power radiation is found to approach zero. [Work supported by the National Aeronautics and Space Administration.]
Experience in the Construction of an Acoustical Laboratory
Authors: Ostergaard Paul B. , Goodfriend Lewis S.
Published: November 2005

The planning and design of an acoustical laboratory. Drawings and photographs of wall and floor isolation are shown, and the methods used to preserve the isolation features while the workmen were on the job are described.
Description of the Cedar Knolls Acoustical Laboratories
Authors: Huntley Ralph , Ostergaard Paul B.
Published: November 2005

The laboratory facilities are described from the acoustical-testing point of view. Among the topics covered are the volumes and surface areas of the rooms, the size and geometry of the opening between the rooms, the empty-room reverberation times, the design of the moving vanes and other diffusing elements, the upper limit for sound-transmission-loss measurements, the instruments and methods used for measurements of decay rates, and sound-pressure-level differences.
Criticism of the ISO Impact-Noise Test
Authors: Mariner T.
Published: November 2005

Essentially, all codes that provide for control of impact noise in buildings rely on tests and acceptance criteria based on the impact machine described in document ISO/R140-1960(E). The author offered earlier philosophical criticism of this type of test in a Letter to the Editor [J. Acoust. Soc. Am. 35, 1453 (1963)]. At the fall conferences of the Building Research Institute, in a special session on impact noise, he and his associates offered, on 19 November, experimental evidence of serious reversal of rank-ordering of some floors when the ISO machine was substituted for real footfall impact. A study of the European literature to trace the development of the ISO machine and impact-noise tests has revealed a continuous line of evidence unfavorable to the ISO test, including recitation of serious discrepancies between ISO test data and living experience in residences, which makes its very difficult to understand how the ISO test has obtained such wide acceptance. Because a large body of important information seems to have been unnoticed or ignored, this paper reviews some significant steps in the development of the ISO machine, some of the serious deficiencies cited in the literature, and some of the physical explanations of these discrepancies.
Comparison of Reverberation-Chamber and Impedance-Tube-Absorption Measurements
Authors: Olynyk D. , Northwood T. D.
Published: November 2005

Reverberation-chamber-absorption measurements on some 50 samples of commercial acoustical materials were compared with values predicted from impedance-tube measurements on the same materials. The predictions involved calculating the random-incidence absorption for the standard 9×8-ft patch of material. At the frequencies 125, 250, 500, 1000, and 200 cps, various degrees of correlation were found between impedance-tube data and reverberation-chamber results involving mountings 1, 2, and 4 (adhesive, furring strips, and rigid backing, respectively). Of special interest were results at 250 cps in which the absorption was sensitive to type of mounting. For mountings that permitted diaphragm vibration of the material, the reverberation-room results were substantially higher than predicted values based on rigidly backed samples. Remnants of this behavior appeared at 500 cps for the thin materials, but otherwise correlation was good at this and higher frequencies. Highly absorptive materials correlated better than those with low absoption, for which reverberation-room results still tended to be somewhat higher than predicted.
Effect of Wall Material on Organ-Pipe Tone—An Evaluation of Some Earlier Experiments
Authors: Backus John
Published: November 2005

Dayton C. Miller has described experiments on a double-wall organ pipe of rectangular cross section in which the space between the wails could be filled with water, producing substantial alterations in pitch and tone [Science 29, 161 (1909)]. These experiments have been quoted by Miller and others as demonstrating the influence of the wall material on the tone quality of woodwind instruments. Calculations of the elastic deformations to be expected under internal pressure show that Miller's results are due to the rectangular cross section of his pipe and would be absent for one of circular cross section. This result was verified in this laboratory by constructing a double-wall cylindrical organ pipe, for which no measurable changes in tone were produced when the space between the walls was filled with water. This result is also verified by the experiments of Boner and Newman on cylindrical organ pipes [J. Acoust. Soc. Am. 12, 83 (1940)]. The small differences in pitch and quality among the thinner pipes noted by these authors can be explained by assuming the pipes to have a slightly elliptical cross section. For cylindrical organ pipes of reasonable wall rigidity, the steady-state tone quality should not depend on the wall material.
Absorption Cross Section of a Pipe Organ
Authors: Benade A. H.
Published: November 2005

Each chromatic rank of pipes in an organ provides a set of resonant absorbers for reverberant sound. The average absorption of a pipe near resonance is σ̄=(2π2/.06) (c2/ω3) × (Γr/Γ) (Γw+Γm). The resonance width Γ is the sum of the widths Γr, Γw, Γm, arising from radiation, wall losses, and viscosity in the mouth region. If the pipes are scaled so that α∼lβ, much computation is saved, since absorption by the pipe that resonates on its nth harmonic is expressible via the properties of the pipe whose fundamental is ω, and having radius a, radiating area S, and month end correction E. Thus, an open pipe near its nth harmonic has Γr=(S/2πlc) n2β−1ω2, and Γw=(2Ac/anβ) (ω)12. For metal pipes, Γm ≅ (4c/π) (2μ/ω)12(1/α)2(1/n)2β+1/[1+(ωEnβ/c)2]. Losses are somewhat changed by resonances in the pipe foot. The net absorption of an organ can alter the room reverberation time appreciably.
Directivity of a Cylindrical Source
Authors: Ricard James H.
Published: November 2005

The directional properties of cylindrical transducers were studied, using a computer simulation program. The transducers are composed of omnidirectional sources mounted on the surface of a hollow cylinder with its axis vertical. The sources are evenly spaced around the circumference of the cylinder, and the rings of sources are evenly spaced vertically. The properties are studied as a function of (a) source diameter, (b) source height, (c) number of sources on horizontal ring, (d) source spacing in vertical direction, (e) number of staves of sources activated. The derivation of the directivity of the source is presented. The accuracy of approximation of the directivity index of cylindrical source by the sum of the horizontal and the vertical directivity index is indicated. In addition, the approximation of such a transducer by a continuous cylindrical shell source is discussed.
Properties of Cylindrical Arrays of Circular Rings II
Authors: Camp Leon W.
Published: November 2005

This is a continuation of work reported on at the 65th Meeting of the ASA. Since adequate methods, aside from the use of empirical data, have not been developed for predicting the behavior of these arrays, additional data are interesting. Rings of mean diameter 6, 12, 22, 26, and 34 in., with various wall thickness and heights, have been assembled into arrays. Some of these show multiple resonant effects. With high-level driving, there is some distortion of resonance of the acoustic pressure wave. [Work partially supported by the U. S. Bureau of Ships under contracts Nobsr 89245 and 89424, and by the U. S. Office of Naval Research under contract NOnr 266 (66).]