bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Frequency, Wide-Band Hydrophone Input-Circuit Noise Analysis
Authors: Durgin Charles B.
Published: September 2005

There are several sources of noise in a low-frequency wide-band hydrophone input circuit, the most important of which are the hydrophone source impedance, preamplifier input impedance, and the preamplifier active elements. Assuming that a piezoceramic hydrophone is operating below mechanical resonance, and the radiation resistance is negligibly small, noise and signal-to-noise ratio in the input circuit are examined in terms of system parameters, such as cutoff frequency, hydrophone sensitivity, impedance, and dissipation factor, and active element noise. The results are expressed both analytically and graphically, showing the effect of the various noise sources at different frequencies, and allowing a ready comparison between hydrophones. Because of the frequency dependence of some of the noise sources, the analysis is carried out for the case where the noise bandwidth is small with respect to frequency; the results, however, are generally useful, particularly where a narrow-band signal-processing system is used in conjunction with a wide-band hydrophone and preamplifier.
Efficacy of Damping Submerged Cylindrical Shells
Authors: Barnett Norman E.
Published: September 2005

An experiment has demonstrated that a practical mechanical-damping treatment can significantly reduce the resonant vibration of an end-stiffened cylindrical shell in water. High-Q resonances ranging from about 100 to over 2000 were observed for the undamped shell in both air and water for selected and identified low-order flexural modes of vibration (m=1, 3; n=2, ⋯, 10). A commercial viscoelastic damping layer applied to the interior of the shell reduced these resonances, in both air and water, to Q's of 20 or smaller; some resonant amplitudes were reduced by as much as a factor of 100. The radiation resistance of the water was measurable, but the dissipation was negligible compared with that provided by the damping treatment. The potential usefulness of mechanical damping for the control of resonant behavior of submerged structures is, therefore, established, at least for situations resembling those of this experiment. Moreover, a method of investigation essential to the detailed study of the low-order modal behavior of actual submerged vibrating structures is established. [This work was supported by the U. S. Navy Bureau of Ordnance under direction of the Ordnance Research Laboratory.]
Automated Psychoacoustics Laboratory
Authors: McQuillin R. J. , Elkind J. I. , Fox H. L. , Melaragni J.
Published: September 2005

A computer-controlled psychoacoustics laboratory is being constructed. The laboratory will include a PDP-1 high-speed digital computer, standard laboratory instruments, and a switching network which will enable the computer to sense and respond to signals at any point in the system. The computer will be able to generate an auditory stimulus, analyze the response, and decide on a new stimulus. The system will be capable of performing experiments that, at present, are very difficult, or perhaps impossible, that is, those experiments where the equipment is difficult to keep in calibration and those involving fast reaction times on the part of the experimenter. The computer will be able to monitor its equipment at a very rapid rate, and will be able to react in a small fraction of a second to what it senses in the outside world. Some characteristic experiments are discussed. [This work has been supported by the Operation Application Laboratory, Electronic Systems Division, U. S. Air Force.]
Interactions among Bandwidth, Center Frequency, and Type of Distortion in Speech Intelligibility
Authors: Sergeant Russell L. , Harris J. Donald , Brown Lawrence W.
Published: September 2005

Speech of 4 adult males with general American dialect, but with considerably different vocal gesture, was recorded and filtered such that at the widest bandwidth (1500 cps) and optimum center frequency (1600 cps) intelligibility of key words in our revisions of the CHABA medico-legal sentences remained high (95%). Untrained listeners were used, who never heard the same sentence twice. Further distortions of shouting, interruption (8/sec, 0.5 duty cycle), and reverberation (about 3 sec through 1 kc) lowered the intelligibility slightly (12% reduction by shouting) or very markedly (80% reduction by reverberation). For the narrowest bandwidth used (500 cps), the optimum center frequency for all distorted speech was shifted upward to 1900 cps or above. Even with the lowest center frequency used (800 cps), intelligibility remained nearly as good as at the next frequency up (1200 cps), at 1900 cps. The principle of frequency equipotentiality is operating here. The articulation index as it relates to distorted speech is discussed, and modifications are suggested.
Contributions of Meaning Dynamics to Architectural Practices and to Noise-Exposure Considerations
Authors: Colton Ernest
Published: September 2005

An optimum condition for increasing the comprehension of a meaning-dynamic system (E. Colton, “On the Contribution of Synchronization Patterns to Semantic Meaning,” to be published in the proceedings of the Fourth International Congress on Acoustics) is approached by providing suitable aural and visual communication isolation for the creative-source aggregates, while their coordinating links should be placed in the opposite conditions and agminated. The concept of noise addiction is introduced. It is concluded that (a) excessive “well-adjusted togetherness” in any quasi-permanent group, e.g., in the home or the work area, restrains creativity; and (b) many repetitions of long exposures to noise (even of low intensity) are very likely to reduce the comprehension of a meaning-dynamic system.
Zero Crossings, Peaks, and Other Statistical Measures of Random Responses
Authors: Crandall Stephen H.
Published: September 2005

A survey is made of statistical information that can be calculated for the stationary random response of nonlinear oscillators. The average frequency of zero crossings can be obtained using Rice's method, if the joint distribution of response displacement and response velocity is known. For lightly damped systems, an approximation can be obtained. if the deterministic amplitude-frequency relation for the nonlinear system is known. For lightly damped systems, the probability density distributions for peaks and envelopes can often be calculated. From these distributions follow other statistics, such as the autocorrelation function for the envelope, the expected size of clumps of cycles above a threshold. and the expected fatigue damage due to linear-damage accumulation.
Perturbation Techniques
Authors: Crandall Stephen H.
Published: September 2005

The classical perturbation method furnishes a simple means of obtaining approximate results for the stationary random response of oscillators which are only slightly nonlinear. When the nonlinearity is in the stiffness element, the response-probability-density distribution can be obtained to first order in the perturbation variable and thus, in principle, all the moments of the distribution can be found. When the nonlinearity is in the damping element, it is possible to compute the moments by the perturbation method. The response-probability density can then be represented by an infinite series with the moments as coefficients. A more direct method of obtaining the response-probability density in this case would be desirable, but is apparently unknown. Some results obtained by applying the perturbation technique to a two-degree-of-freedom system with nonlinear stiffness elements are illustrated.
Static and Dynamic Transmission Losses of Partitions
Authors: Raes Auguste C.
Published: September 2005

The conclusions of 10 years of practical experience with a measurement method which the author published earlier [J. Acoust. Soc. Am. 27, 98 (1955)] sum up as follows: Static transmission losses (TL) are defined as the values obtained by standard methods using constant level sounds. Dynamic TL are measured with transients or with varying level sounds. The latter measuring conditions agree much more than the first with practical conditions. TL values measured on traditional types of partitions, (e.g. masonry walls) may vary by ±10 dB from one wall to another of the same type in the same building. For prefabricated partitions, these variations drop to less than ±3 dB. Thus, one sample does not allow us to draw definite conclusions on the TL which should be expected of a type of partition. Three to ten samples should be tested. The time lag of a partition may have a relationship with its sound insulating value. The measurement of the sound TL of any selected partition in any position in a building or a ship is a necessity if sound insulations are to be effectively guaranteed. It has now been done for 10 years.
Computer Methods for Solution of Duct-Noise Problems
Authors: Towne Robin M. , Bozich Daniel J.
Published: September 2005

An IBM 709 FORTRAN computer program has been developed to predict the noise environment within and around complex duct systems. The program includes analytical and empirical procedures for calculating air- and structure-borne noise-attenuation and -regeneration characteristics in the system, each system component, and external sound-transmission fields along the system path. The program is also set up to compare the costs of the various alternative methods of sound-attenuation treatment and to select the most economical solution.
Performance of Nike Commercially Available Communication Headsets
Authors: Oddo E. T.
Published: September 2005

An investigation was conducted to determine the attenuation, intelligibility, and wearability of 9 commercially available communication headsets. The main purpose of the study was to determine which headset would be best suited for use in Nike Zeus checkout trailers. Attenuation tests were conducted using the threshold-shift method according to ASA procedure. Intelligibility tests using Harvard PB monosyllabic word lists were conducted in 4 phases: (1) quiet-to-quiet, (2) quiet-to-noise, (3) noise-to-quiet, and (4) noise-to-noise. The noise environment was simulated in a reverberation room using tape recordings of the noise generated by equipment in the checkout trailer. Determination of wearability and comfort was by subjective evaluation and expert opinion. 3 of 9 headsets tested were found to be acceptable for use in the checkout trailers.
Attenuation in Heavily Doped P-Type Silicon due to Electron-Phonon Interaction
Authors: Mason Warren P. , Bateman Thomas B.
Published: September 2005

Measurements of attenuation for longitudinal and shear wave in p-type silicon doped with 3×1018 boron atoms per cc show an attenuation which increases markedly at very low temperatures. This effect does not appear in a very pure sample, and, by subtracting the attenuations between the doped and pure samples, a measure of the internal friction due to electrons is obtained. For silicon, the effect is very marked for shear waves along 110 with polarization along 100, and is weaker for shear waves with their polarization along 110. For a longitudinal wave along 100, the effect is also weaker. These stress effects correlate with the piezoresistance effect which causes a motion of electrons from one part of the Fermi surface to another. The attenuation results from the finite time of scattering from one position to the other.
Response of Elastic Structure to Random Excitations of Various Correlations
Authors: Roger Marc , Trubert Pierre
Published: September 2005

An experimental investigation pertaining to a random space-time loading of various correlations acting on a linear elastic structure has been carried out in an attempt to verify the validity of a numerical prediction of the response spectrum of the structure. The verification has been done on a cantilever beam for loadings consisting of 2 random forces of various correlations applied simultaneously at different points, and the response has been measured at a 3rd point. The structural characteristics of the beam needed for the computation of the response have been represented by its transfer function. This has been determined experimentally by a cross-correlation technique using one random load at a time applied to a single point of the beam. The power spectral density of the response has been computed, and a comparison made with the measured power spectral density of the response for the same loading. The response to completely correlated loading has been compared, theoretically and experimentally, to a completely uncorrelated loading showing a definite influence of the cross correlation of the input forces on the determination of the response spectra. However, the root-mean-square value of the response has been found to be relatively insensitive to the cross-correlation effect.
Acoustical-Electrical Analogs of Hydraulic Waves in Elastic Conduits
Authors: Lobel Harry
Published: September 2005

The need for acoustical-electrical analogs to describe hydraulic waves in elastic conduits is more than academic. The stresses of such systems sometimes seem irrational. For no seemingly logical reason, pressures become hypertensive in relation to flow. Modern theory is inadequate to explain this discrepency. These hypertensive pressures are due to the presence of a hitherto unsuspected stress factor. For a dynamical model, pulsations are introduced into elastic tubes filled with fluid. The frequency of pulsations is varied. At the proper frequency, the pulsations become resonant or tuned. At any other frequency, the pulsations are “disonant.” In resonance, pressure is minimum for a given flow; in dissonance, pressure is hypertensive for the same flow. In resonance, pressure and flow are mathematically related in accordance with the 3rd law of motion; in dissonance, the concepts of “action and reaction,” as commonly credited to Newton, are inadequate. There are 2 kinds of stress in dissonance: one is resistive stress which is related to the flow of the fluid; the other is a useless “reactive” stress. The vector sum is the “impedance.” Without differentiating between the resistive and reactive components of impedance, there is no way to correlate energy with work. stress with strain, or pressure with flow. The reactive component of impedance contributes to a waste of energy and a loss of efficiency.
Inhomogeneous and Composite Vibrators
Authors: Skudrzyk Eugen J.
Published: September 2005

Inhomogeneous mechanical vibrators usually consist of homogeneous plates, shells, bars (stiffening rings), and rigid masses and predominantly compliant elements. By generalizing the fundamental concepts of the theory of electrical networks for 3 dimensions, an attempt is made to derive a general theory of complex, 3-dimensional mechanical vibrators that is free of insignificant details. Because of the electrical analogies, the theory of inhomogeneous systems also contains the theory of electrical networks, electrical filters and telephone lines, and electrically coupled circuits. [This work was sponsored by the U. S. Atomic Energy Commission and by the Bureau of Weapons.]
Auditory-Process Models
Authors: Licklider J. C. R.
Published: September 2005

This paper is a re-examination of the sector of auditory theory concerned with periodicity pitch, binaural localization, and the Huggins phenomenon. Several alternative formulations are compared and related to neurophysiological and psychophysical observations. It is suggested that, in parts of the sector, mathematical models must be replaced by computer-program models before much further progress can be made.
Research Directions
Authors: Hirsh I. J.
Published: September 2005

Psychophysical experiments in which sounds are conducted separately to the two ears via earphones yield a body of fairly precise information on lateralization sufficient for a variety of theoretical models—electronic and physiological. The relation between such studies and the localization of actual sources in external space remains to be worked out more completely. Comparison of the abilities to localize among different species should yield data that are ordered in some relation to the size of the head. Localizations outside the horizontal plane remain a relatively untouched area of study in which there has not been sufficient test of the one clearly suggested mechanism involving head rotation that was offered by Wallach thirteen years ago. Both head rotation and other bodily movements appear to be intimately associated with changes in localization brought about through learning. The modifiability of localization responses has been demonstrated, primarily in the horizontal plane, from the early 1900's by Young to very recent years by Held, and surely should contribute to our understanding of the native as opposed to the acquired aspects of localization. Finally, our present concepts will probably need to be expanded in order to account for that degree of localization found in one eared listeners and in users of different types of hearing aids.
Sonic Absorption in Oxygen with CO2 Impurity
Authors: Henderson M. C. , Queen E. J.
Published: September 2005

Measurements of sonic absorption in oxygen at 23°C have been made using the modified Kundt tube reported by the senior author [J. Acoust. Soc. Am. 32, (A) 1511 (1960)]. The relaxation absorption was obtained by subtracting the tube absorption predicted by the Helmholtz - Kirchhoff theory (corrected experimentally by determinations with non-relaxing gases) from the total absorption. CO2 up to 2 mole-percent was used and the frequency-pressure ratio ran from 10 to 5000 cps/atm. Pure oxygen shows maximum absorption per wavelength at about 70 cps/atm. The maximum absorption shifts linearly to higher frequencies by about 430 cps/atm per mole-percent added CO2. An O2-CO2 collision is thus about 600 times as effective in promoting equilibrium as an O2-O2. Although this finding is in apparent disagreement with Knudsen and Fricke [J. Acoust. Soc. Am. 10, 89 (1938)], who found that only CO2 is responsible for absorption in oxygen at any percentage, they worked at higher frequencies and percentages of CO2 whose absorption thus masked that of the oxygen molecule. (This work supported by the Office of Naval Research.)
Dispersion and Absorption of Ultrasonic Waves in Molten Zinc Chloride
Authors: Gruber George J. , Litovitz T. A.
Published: September 2005

Among the inorganic molten salts, liquid zinc chloride is unusual in that it has a high shear viscosity which makes it possible to study its viscoelastic properties by high-frequency sound-propagation techniques. Longitudinal ultrasonic-absorption and velocity measurements were made in the frequency range 5–95 and 5–45 Mc, respectively. Shear-elasticity measurements were obtained in the frequency range 43–118 Mc. The viscosity range covered was 3 60 poise. A single relaxation time was observed for the absorption at each temperature investigated. The data demonstrate the existence of a volume viscosity and the simultaneous presence of both shear and structural-relaxation processes. The ratio of the compressional viscosity to the shear viscosity is 0.8 and was found to be nearly independent of temperature. The activation energies for the shear and compressional flows are approximately equal. Both the longitudinal and sear-dispersion data can adequately be described by a single and the same relaxation time at a given temperature. The variation of the relaxation time with temperature is in accordance with the rate theory. The shear modulus and the relaxational part of the compressional modulus increase exponentially with decreasing temperature. (This work supported by the U. S. Atomic Energy Commission.)
Ultrasonic Propagation in Liquid Metals
Authors: Jarzynski J.
Published: September 2005

A pulse technique has been used to measure ultrasonic absorption and velocity in liquid bismuth and mercury at temperatures up to 450°C and at frequencies of 68 and 92 Mc. In each of these metals, the measured absorption is found to be higher than the absorption deduced solely from considerations of shear and thermal conductivity. The volume viscosity which is introduced to account for the excess absorption is attributed to structural relaxation. The ratio of volume to shear viscosity is independent of temperature and is 4.5 in bismuth and 1.3 in mercury. It is shown that the Hall two-state theory of structural relaxation appears to be applicable to liquid bismuth.
Analysis of the Pulse-Superposition Method for Measuring Ultrasonic Wave Velocities as a Function of Pressure and Temperature
Authors: McSkimin Il. J. , Andreatch P.
Published: September 2005

A discussion is given of the merits of a pulse-superposition method for determining ultrasonic-wave velocities in single crystals as a function of pressure and temperature. For this method [H. J. McSkimin, J. Acoust. Soc. Am. 33, 12 (1961)], the wave frequency is continuously matched to the resonance frequency of the crystal transducer in order to minimize the effect of coupling to the transducer. Ratios of velocities can be determined to within one part in ten thousand. Illustrative data are shown for crystal quartz in the pressure range 14.5 to 30 000 psi at both 25.0° and −195.8°C.
Dynamic Stress-Strain Characteristics
Authors: Benson Robert W.
Published: September 2005

Mechanical hysteresis loops have been obtained for various polycrystalline solids in a manner similar to that used for magnetic materials. Half-wavelength samples are driven mechanically at a frequency of 14 000 cps producing stresses at the center of the sample of 40 000 lb/in2. Stress is measured using transverse ultrasonic waves in a technique similar to that of photoelasticity. Strain is measured for the same portion of the bar, and the resulting information is displayed on an oscilloscope. A description of the fundamental techniques is given. The results are compared to analytical predictions of the behavior of vibrating mechanical systems. (This work is supported by the Office of Naval Research.)
Back Scattering of Explosive Sound by the Deep-Sea Bottom
Authors: Urick R. J. , Saling D. M.
Published: September 2005

The return by the deep-ocean bottom of the sound of an explosive charge consists of an initial burst followed by a long tail representing back-scattered sound at decreasing grazing angles with the bottom. Through analysis of shot records at a number of deep-water locations in the North Atlantic, the back-scattering coefficient of the bottom has been obtained as a function of grazing angle between 30° and 90°. The results indicate that the deep-sea bed behaves as a diffuse or Lambert-law back scatterer at grazing angles from 30° to about 65°; between 65° and 90° (normal incidence), the coefficient rapidly increases, as though specular reflection from normally oriented flat facets of the bottom were occurring. This behavior with angle is similar to that of the sea surface. Analyses in several frequency bands in the range 0.5 to 8.0 kc suggest that the back-scattering coefficient decreases with frequency at a rate of about 2 db per octave.
Investigation of the Propagation of Signals from Deep Explosive Sources to a Deep Hydrophone
Authors: Shaffer John , Guthrie Albert
Published: September 2005

Several salvos of nine explosive sources were lowered from a drifting ship to a depth of 2000 ft in water 14 500 ft deep, and the sources were fired seriatim at 1-min intervals by electrical detonation. Thus, all sources of a given salvo were fired approximately at the same point in the ocean. The arrivals at the hydrophone, suspended at 1000 ft below the surface from an anchored ship, were recorded in eight half-octave frequency bands between center frequencies of 63 and 720 cps, along with timing-signals and radio-transmitted shot instants by use of two six-channel photographically recording oscillographs. The degree of uniformity of the arrivals from the shots of each salvo is shown, and some observed effects of reflection from ocean bottom and surface are discussed. (This work was supported by the Office of Naval Research.)
Effects of Radiation Impedance Variation on Sonar-Transducer Performance in a Large Array
Authors: Johnson H. M.
Published: September 2005

The transducer elements in a large array have different radiation impedance because of the acoustic interaction effects among the elements. Thus, the performance of a transducer element operating in an array depends upon its position in the array, the array geometry, and the operating mode of the array. There have been numerous calculations of the performance of transducer elements in arrays. With the possible exception of simple arrays, the usual theoretical performance analyses are made with the help of one or more simplifying assumptions, which leave the computed result in doubt. This paper describes the results of a series of measurements of the performance of efficient, high-k, moderate-Qm transducer elements in a typical, large sonar array. The results are compared with theoretical studies of similar arrays.
Variation with Loudness of the Harmonic Structure of Clarinet and Bassoon Tones
Authors: Backus John
Published: September 2005

Previous work [J. Acoust. Soc. Am. 33, 806 809 (1961)] indicated qualitatively that the number of higher harmonics in the clarinet tone decreases as the tone becomes softer. This matter has been investigated in more detail. The artificially blown clarinet described earlier was set up in the anechoic chamber at UCLA. The standing wave in the instrument was observed by means of a microphone in the mouthpiece; the sound radiated was observed by means of another microphone 3 ft distant at 90° from the axis of the instrument. Microphone outputs were analyzed on a Model LP-1a panoramic analyzer. The loudness of the clarinet tone was monitored by means of a General Radio sound-level meter. The harmonic structure of the clarinet tone for several different notes of the scale was recorded at four different loudness levels. It was found that the higher harmonics disappeared as the tone became softer, the number of harmonics decreasing from as many as 15 or more for loud tones to 1 or 2 for soft tones. The same experiments were performed with the bassoon with somewhat similar results, except that the soft tones may still have considerable harmonic content. (This work was supported by a grant from the National Science Foundation.)
Grammatical Influences in Speech Perception
Authors: Miller George A.
Published: September 2005

Most of our studies of speech perception have been conducted with lists of isolated words chosen to represent the phonetic structure of the language. There is good reason to believe, however, that intelligibility depends, at least in part, on the context in which the words occur and on the listener's expectations about them. In particular, the context provided by grammatical structure can provide valuable perceptual clues. This paper discusses a series of experiments designed to study how human listeners use grammatical context in order to facilitate their perception of speech.
Thickness Vibrations of Piezoelectric Plates
Authors: Tiersten H. F.
Published: September 2005

The thickness vibrations of an infinite anisotropic plate with electrodes coated on both surfaces are investigated using the linear piezoelectric equations. In general, the three fundamental solutions of the differential equations are found to couple at the traction-free surfaces of the plate. The solution reduces to the well-known uncoupled solution for the purely elastic case when the piezoelectric constants are zero. The transcendental equation which determines the resonant frequencies is derived. The theory is applied to a ferroelectric ceramic in two special cases: one with the plate polarized in the thickness direction, and the other with the plate polarized in its plane. In either of these special cases, the three solutions of the differential equations uncouple. Two of these solutions are identical with the purely elastic solutions and cannot be excited electrically, whereas the third differs from the purely elastic solution and can be excited electrically. The frequency obtained from this piezoelectric solution shows that the resonant frequencies are not integral multiples of the fundamental.
Inherent Limitations of Piezoelectric Transducers
Authors: Schloss F.
Published: September 2005

The effects of electrical termination of the transducer on the response curve and resonant frequency are discussed. It is also shown theoretically and experimentally that the resonant frequencies obtained by driving the transducer either electrically or mechanically may differ considerably. A limiting relationship between sensitivity, electrical capacity, resonant frequency, and stiffness has been derived for accelerometers and force gauges. How closely these limits have been approached in actual transducers is shown.
Analysis of the Depletion Layer Transducer
Authors: Strauss W.
Published: September 2005

A theoretical analysis of the operation of the depletion layer transducer has been made, taking into consideration both the backing and the delay medium. This transducer differs from the conventional type in that the boundaries of the piezoelectrically active region vary with applied voltage. For plane elastic waves in a semi-infinite piezoelectric semiconductor, it is possible, under certain restrictive assumptions presented here, to solve the piezoelectric equations, including the effect of moving boundaries. For the case of small signals, the time-average sonic power flux propagating away from the depletion layer has been found as a function of drive amplitude, frequency, layer thickness, and backing distance. From the sonic-flux expression, conditions on the layer thickness and backing distance can be deduced which lead to optimum operation at a given frequency. Under favorable conditions, an intrinsic bandwidth of 70% is possible. Some remarks on the mechanism and extent of harmonic production are also made.
Measurement of Small Values of Electromechanical Coupling Coefficient in Piezoelectric Transducers
Authors: Shibayama Kimio
Published: September 2005

The electromechanical coupling coefficient k is usually derived from the difference between resonance and antiresonance frequencies fR and fA of a particular mode obtained from observations of the maximum and minimum values of electrical impedance. A simple relationship between fR, fA, and k exists only when the mechanical Q is infinite and the electrical losses negligible. This relationship breaks down when k2Q<2, a region which is important since the minor modes of barium-titanate transducers may have Q values of several hundreds and k<10%. For example, it has been found that, with 4<k Q<1/2 k, the apparent value kapp of k, derived directly from observations of fR and fA, is locked to Q rather than k by the relationship kapp≃(2/Q)12. The region k<20% and 100<Q<1000 has been analyzed and the resulting formulas processed by computer. The final data are presented in graphical form, making it possible to derive accurate values of k and Q from observations of the magnitudes and frequencies of the impedance maximum and minimum.
Mechanical Audiofrequency Delay Line
Authors: Ashley George H.
Published: September 2005

The mechanical audiofrequency delay line reported at the sixtieth meeting of the Acoustical Society has been developed into a practical delay line. A time delay of 15 msec is obtained with a 0.4-mil-diam platinum-alloy wire with transverse wave velocity of 90 m/sec. Any number of magnets up to about 100 can be placed along the active length of the wire and adjusted to generate any signal within the limits of the time bandwidth of the delay line. Transverse waves propagating up the wire are detected by a displacement pickup located at the top, which consists of a lamp casting the shadow of the wire on the edge of a silicon solar cell. The transverse waves propagating down the wire, both from the originating magnet and the reflection off of the upper end, are absorbed by viscous damping in a liquid termination consisting of a 0.5-m height of liquid propane. The reflections from the termination are about 22 db down at 300 cps and much less at higher frequencies. The group delay at 15-msec delay corresponds to phase errors of less than 6° in the frequency range from 300 to 3000 cps.
Electronic Imaging of Ultrasonic Fields
Authors: Lawrie W. E. , Feith K. E.
Published: September 2005

An ultrasonic image-converter system is described which provides two-dimensional visual images of incident-sound fields. The system is based on an electronically operated image-converter tube, similar to a television-camera tube, except that the photosensitive surface is replaced by a slab of piezoelectric x-cut quartz. The spatial distribution of sound pressure produces a similar distribution of piezoelectric potential at the ungrounded quartz surface which is scanned by a 500-v electron beam. The output of the converter, dependent upon secondary emission from the quartz, is used to generate a cathode-ray tube display of the sound field. Constructional details of the continuously pumped converter tube are described, including electrode configurations, crystal bonding, and vacuum techniques. With the water-immersed converter face irradiated by a pulsed 7-Mc/sec collimated sound beam directed normally to the face, a 12-mm-diam metallic wire intercepting the sound beam is easily discernable on the cathode-ray tube display. Laminar-type defects measuring 0.75 mm diam and 0.01 mm thick, simulated in a steel plate and oriented normal to the sound beam, are resolved by suitable electronic processing of the converter output pulses. Applications to flaw detection and medical diagnostics are discussed.
Truck-Noise Limits
Authors: Potter Stannard M.
Published: September 2005

With the advent of high-speed truck traffic brought to many previously-quiet residential areas by the construction of our interstate highway system, the truck-noise delinquent is affecting an increasingly high percentage of our national population. The noise-abatement program instituted by the Thruway Noise Abatement Committee and some of its findings are discussed. A survey of vehicular noise-abatement programs, conducted during the past eight years since Milwaukee first adopted a noise-limiting ordinance, indicates a generally unfavorable experience. The variation of limits enforced, measurement obstacles, and lack of legal precedent in acoustics have invalidated attempts to ban ineffective mufflers. Technological changes resulting from improved truck manufacture, refinements in the subjective evaluation of noise, electronic innovations, and certain court decisions have improved the probability of more successful antinoise enforcement in the future. A case is made for an interim limit of 80 dba at 50 ft, and a new series of limits is proposed as possibly less controversial. The foregoing is discussed in the light of the new international standards being proposed for truck-noise measurement.
Boundary-Layer Noise Transmission through Ribbed Structures
Authors: Lyon Richard H.
Published: September 2005

The radiation of sound by ribbed panels which are excited by boundary-layer turbulence is analyzed. The separate roles of forced and free wave radiation are delineated. Normally, free wave radiation will dominate, but forced wave radiation may become important at higher frequencies. The free-wave-vibration spectrum used is that of Dyer. The noise transmission is computed from the radiation resistance laws of Lyon and Maidanik. Some comparisons are made with experimental work reported by Ludwig and Ribner. (Work supported by the Office of Naval Research.)
Experimental Analysis of Middle-Ear Sound Transmission
Authors: Møller Aage R.
Published: September 2005

The ultimate purpose of most investigations on the middle ear is to get more knowledge about sound transmission through the middle ear in man. Various types of experiments have been performed on normal human subjects and on different animals. The methods used with human subjects are necessarily different from those used with animals. The purpose of this paper is to relate certain results obtained with different methods. The behavior of the middle-ear reflex has been examined through impedance measurements. In addition, reflex effects on middle-ear sound transmission have been studied. Recent animal results on sound transmission and acoustic input impedance are discussed in relation to current conceptions of middle-ear functions in man.
Vital Staining of the Cochlea
Authors: Tonndorf J. , Duvall A. J.
Published: September 2005

Commonly, the cochlea is presented in the form of histological cross sections necessitating complex mental reconstructions when one is interested in the architecture of the whole organ. The present talk consists of showing a series of color photomicrographs taken in the cochlea of live guinea pigs after the bony shell of the 4th and 5th turn has been removed. In order to make the various contained structures visible, stains were applied which Békésy [J. Acoust. Soc. Am. 25, 770 (1953)] had recommended for such purposes: Methylene blue, Janus green B, and Safranine O. Methyl blue has also been found useful in the present experiments. Such a method of observation not only provides the experimenter with a three-dimensional view of the organ, but it also avoids some of the artifacts of histological preparation, notably the shrinkage and curling-up of the tectorial membrane. (This research was supported by a research grant from the Public Health Service, U. S. Department of Health, Education, and Welfare.)
Notes on Nonuniform Shock Propagation
Authors: Meyer R. E. , Ho D. V.
Published: September 2005

The propagation of a spherical or cylindrical shock wave, the propagation of a plain shock in a stratified atmosphere, and the travel of a shock through ducts of various kinds form a family of closely related physical problems involving thoroughly nonlinear acoustics. In all such situations, the changes in the shock are partly due to the nonuniformity of the environment into which the shock travels, but the development of the shock is also determined in part by nonlinear acoustic-wave interactions occurring behind the shock. A discussion of the physical process taking place behind the shock leads to the derivation of a wavelength relation offering a precise comparison of the relative influence which the environment and the acoustic waves have on the local development of the shock. One interpretation of this wave-strength relation leads to the Whitham approximation for the case of negligible acoustic-wave influence. Another interpretation leads to higher approximations for the initial stage of shock propagation. The connection with some recent numerical and asymptotic work is also indicated.
Plane Piston at Finite Amplitude: Second Harmonics
Authors: Williams A. O. , Westervelt P. J.
Published: September 2005

The growth of harmonics in finite-amplitude acoustic beams is often measured with circular plane-piston sources, but then compared with plane-wave theory. The growth of second harmonics in the beam from a plane piston at finite amplitude is calculable after expanding the linear first-harmonic beam in plane waves. It can be shown that any two plane waves starting from the plane z=0 interact to produce a growing second-harmonic wave only if all three waves have identical directions. With this guidance, pairs of plane waves in the linear expansion for the piston are selected, combined, and added to give for the second-harmonic field a definite integral involving products of Bessel functions. Absorption can be included. Two special cases can be evaluated fairly easily and accurately: the field along the beam axis, and the signal on a centered receiver considerably larger than the source. The latter result agrees reasonably with measurements by Ryan, Lutsch, and Beyer [J. Acoust. Soc. Am. 34, 31 (1962]. (This work was supported by the Office of Naval Research and by the Wright Air Development Center.)
New Procedure for Calculating Finite-Amplitude Distortion
Authors: Cook Bill D.
Published: September 2005

An iterative process is described for the calculation of the distortion of a plane finite sound wave in a dissipative dispersive medium. The method of calculation is a discrete-interval process of considering the distortion of the wave while propagating through a small distance, correcting for the absorption, and then considering this new wave in a similar manner. This iterative process allows calculations by computer for the region beyond the “discontinuity distance.” The spatial change of the spectral composition is used for the calculation of absorption coefficients describing the energy loss from the total wave and from the fundamental component of the wave. These absorption coefficients are found to be remarkably different.
Optical Effects of Ultrasonic Waves Producing Phase and Amplitude Modulation
Authors: Hargrove L. E.
Published: September 2005

For conditions under which the refraction of light within the ultrasonic beam may be neglected, the light wave front emerging front the sound beam is phase modulated without amplitude modulation along the wavefront. Raman and Nath developed a theory for such conditions. When the ultrasonic frequency, amplitude, and/or beamwidth become large, significant amplitude modulation occurs. The analysis then becomes more complicated, e.g., the solutions of Extermann and Wannier and of Wagner. A new theoretical approach for this region is presented. The ultrasonic beam is considered to consist of N adjacent ultrasonic beams. For N sufficiently large, only phase modulation is considered within each of the N intervals, and the final diffraction spectrum is considered to result from N successive diffractions. The successive-diffraction concept has the advantage that the results are calculated by iterations, using an electronic computer. Numerical results are presented and compared with measurements. [This work was supported by the U. S. Army Research Office (Durham) and by the Office of Naval Research.]
Speech-Processing Systems
Authors: Olson Harry F. , Belar Herbert , de Sobrino Ricardo
Published: September 2005

The following speech-processing systems are described and demonstrated: (1) phonetic typewriter—the conversion of speech to the typed page; (2) speech analysis, conversion to a code, transmission of the coded signal, and the synthesis of speech from the code; (3) application of language translation of speech to the typed page and to synthesized speech.
Pitch-Synchronous Time-Domain Estimation of Formant Frequencies and Bandwidths
Authors: Pinson Elliot N.
Published: September 2005

A technique for the measurement of vocal tract formant frequencies and bandwidths during voiced speech is described. A theoretical justification for the method is presented, based on a model of the vocal tract which is linear and stationary over time intervals of the order of one pitch period (approximately 0.01 sec). In brief, the technique consists of selecting a portion of one pitch period of a speech waveform during which the glottis is closed. This finite-duration signal is approximated in a weighted-least-squares sense by a function of the form f̂(t) =  ∑ t=1N e−πBit(ai cos2πFit+ci sin2πFit), where ai, ci, Fi, and Bi are selected to minimize the weighted-squared error between f̂(t) and the actual speech signal of interest, f(t). It is shown that Bi and Fi are estimates of the bandwidth and frequency, respectively, of the ith formant. A digital-computer program was written to perform the minimization. The program was used to determine the bandwidths and frequencies of the first four formants of the vowels i, ɔ, and ɑ in the context b(vowel)t. Two male speakers produced most of the speech waveforms. The technique seems to be most reliable for the first two formants. It yields results which appear to have a smaller variance than those obtained by previously reported methods, although the variance is still substantial.
Considerations of Reverberation, Variable by Nonelectronic Means, in the Design of a Small Concert Hall
Authors: Johnson Russell
Published: September 2005

This paper presents a brief discussion of the design of the Warner Concert Hall at the Oberlin Conservatory of Music. This hall has been designed for music performance only, but even so, some variation is required in the acoustics: There is considerable emphasis on organ instruction at the Conservatory; at the same time, there will be extensive use of this concert hall for piano recitals requiring much less reverberation. The acoustical design provides for significant changes in the reverberation time for various types of music performance, and also provides adjustment for changing audience size.
Transmission Loss of Leaded Building Materials
Authors: Ostergaard Paul B. , Cardinell Richmond L. , Goodfriend Lewis S.
Published: September 2005

A number of architectural-partition materials have been tested for sound-transmission loss with and without a 0.125-in. lead sheet adhesively bonded to one side. A series of tests with and without lead on panels with and without 2×4-in. wood studs indicates that a new series of building products having high TL are practicable, using conventional building materials with a lead sheet adhesively bonded, as well as the imaginative combinations of lead with many new substrate materials. Evaluating methods for new lead-bearing materials are outlined. (This work was supported by the Lead Industries Association Expanded Research Program.)
Classrooms in Use
Authors: Fitzroy Dariel C.
Published: September 2005

A preliminary discussion of the results being obtained in a national survey of classroom acoustics sponsored by the Educational Facilities Laboratories of the Ford Foundation. Included is information on some concepts in teaching methods and the apparent acoustical requirements imposed by new ideas in schoolroom design required by these new methods.
The School Auditorium
Authors: Cavanaugh William J.
Published: September 2005

Traditionally, auditoriums have played an important role in school facilities. They serve a multitude of functions, including lectures, large-group assemblies, as well as for the school theatrical and music programs. Examples of auditorium design are described, and the extent to which they satisfy the varied acoustical requirements is discussed.
School Music Departments
Authors: Goodfriend Lewis S.
Published: September 2005

Educational requirements, architectural limitations, and budgetary restrictions often beset school music departments. Conflicting in many ways, these problems are usually at cross purposes with good acoustics. Providing just adequate sound isolation and some diffusion and blending, while limiting noise, taxes the acoustical designer's ingenuity. Suitable designs combine simplicity with basic acoustics.
Design of School Sound Systems
Authors: Davis P. H.
Published: September 2005

Recent trends in school planning require that the sound equipment be suitable for use as an active teaching instrument and be adapted to the most flexible utilization of school space. This paper considers some of the resulting design factors, including (1) interchannel crosstalk, (2) switching noise, and (3) frequency response.