bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Sound Transmission Through Door Seals
Authors: Sabine Hale J.
Published: September 2005

A small-scale test facility has been constructed for measuring the transmission of sound through slits typical of the crack around a door. The facility consists of an absorptive lined box of concrete block containing a sound source beamed toward the top. The box is covered with a pair of heavy sliding panels having a joint at the center line of the box. Samples of slit configurations, gaskets, etc., are inserted between the panels for measurement. The box is built in a reverberation chamber, and the sound power output W of the slit is measured together with the sound pressure p0 in the box immediately adjacent to the slit. The effective radiating length L of the slit is about 2 ft. The measurements yield a quantity tentatively called the “slit constant” K=W/L p1,2 where p12=p02/2 is the equivalent room average sound pressure for the source side. he quantity K can then be used to compute the equivalent transmission loss TL' of a slit or seal forming the perimeter of a panel of given dimensions. For a 3×7-ft door, TL', defined as the TL of a door which transmits the same total sound power as the perimeter seal, is about 8 db higher than 10 log 1/K, if K is evaluated in feet. Typical data on slit and gasket configurations are presented.
A Double Wall Noise Control Enclosure for an Impulsive Sound Source
Authors: Hoover Robert M. , Williams Lloyd J.
Published: September 2005

The design of a group of double wall noise control enclosures on the upper floor of an existing building is described and some noise reduction measurements are reported. A design objective for these enclosures was to achieve more effective noise reduction than that provided by existing heavy, on grade, double wall, reverberant enclosures, but with reduced weight. This objective was achieved by a combination of a lightweight inner skin, a moderately large air space, a masonry exterior, isolation of the inner room floor slab, and the use of sound absorbing materials. Other noise control measures included sound retarding doors and windows, mufflers in the air supply and return passages, and flexible service connections to the rooms. Peak and octave band noise levels taken inside and outside the old and new enclosures are reported.
Recent Progress in Formant Synthesis of Connected Speech
Authors: Fant C. G. M. , Martony J. , Rengman U. , Risberg A. , Holmes J. N.
Published: September 2005

The formant coded series synthesis system OVE II and associated function generator for converting manually traced parameter lines to time-variable control voltages have been improved in several respects. An associated project on the pole-zero spectra matching of speech sounds has provided optimal coding of available circuitry. Audible quality evaluations of the effects of various types of approximations have been undertaken to some extent.
The Digital Vocoder as a Research Tool
Authors: Morris William H. , Gerber Sanford E.
Published: September 2005

A modular block diagram of the Hughes 12-channel vocoder is shown and a functional description is presented. The advantages of a commercially built digital vocoder as a research tool, such as reliability, modular construction, and digital processing of the output signals, are discussed. A brief discussion of the sampling theorem in terms of spectral analysis is followed by a description of the techniques used in examining the dynamics of clear speech through use of the digital feature of the Hughes Vocoder.
Magnetostrictive Flexural Bar Transducers
Authors: Woollett Ralph S.
Published: September 2005

Although the use of magnetostriction to excite flexural vibrations has had scarcely any practical applications to date, very promising transducers can be made by exploitation of this principle. A basic resonator of this type consists of two flexural bars joined together by common end supports. The bars are necked down where they join the end supports to provide a flexible section, by means of which supported-end boundary conditions are approximated. The resonant frequency of this structure is very close to that of the ideal end-supported bar. To provide for magnetostrictive excitation of flexure, each bar is slotted lengthwise, and windings are placed on each half of the bar formed by the slot. Subsequently, the slot is filled with a hard plastic. An equation for the electromechanical coupling coefficient of this structure has been derived, which includes the effect of slot width. If the ideal end-support condition is realized, the coupling coefficient will be 80% of the coupling coefficient of the magnetostrictive material. A coupling coefficient of 0.25 has been achieved with laminations of nickel-cobalt alloy. Calculations indicate that a surface intensity of 1 w/cm2 in an underwater transducer should be achievable without exceeding the fatigue limit.
Hydrophone Calibrator
Authors: Sims Claude C.
Published: September 2005

A system to provide rapid, reliable, economical calibration of small hydrophones is described. The system is designed for production testing and field use in the frequency range of 100 cps to 3 kc. The hydrophone is placed in an open-ended column of water which is excited by an electrodynamic driver. Acoustic pressure in the tube is calculated from system parameters and compared to measured results for various types of hydrophones. Results agree with open-water data within ±1.0 db.
Near-Field Investigation of a Shaded Transducer
Authors: Baird D. L. , McKinney C. M.
Published: September 2005

An investigation has been made of the near-field phase and pressure amplitude distribution across the aperture of a shaded line-in-cone transducer. The transducer consists of a line of 16 cylindrical elements mounted within and along the axis of a right circular conical reflector. Data were taken for various numbers and combinations of the 16 cylindrical elements. Computed far-field patterns for these various combinations are compared with their respective patterns measured in the far field. (This work was supported by the Bureau of Ships.)
Computation of Far-Field Radiation Patterns from Near-Field Measurements
Authors: Baker D. D. , Horton C. W.
Published: September 2005

The Helmholtz formula for the wave equation is used to compute the far-field radiation pattern of a large cylindrical transducer from pressure measurements made near the transducer. Radiation patterns are computed for a plane normal to the axis of the transducer by means of a numerical integration over the surface of a circular cylinder of finite length. The normal gradient of the pressure required in the formula is obtained by a simple approximation. The computed patterns compare favorably with measured far-field patterns. (This work is supported by the Bureau of Ships and the Office of Naval Research.)
Transmission and Reflection of a Plane Dilatational Wave at Normal Incidence on a Viscoelastic Layer
Authors: Thurston G. B. , Wu S. Y.
Published: September 2005

The theory of propagation of a plane dilatational wave is considered for normal incidence on a plane layer. The layer and its adjacent media are assumed to be viscoelastic. Complex transmission and reflection factors are derived for sinusoidal waves. Numerical values of these factors have been computed for propagation through a steel layer and through a butyl rubber layer, these layers separating water and air. The dependence of these factors on the frequency and the thickness of the layer is compared with that for media possessing nondissipative elasticity.
Angular Distribution of the Normal Modes of Vibration in Rectangular Rooms
Authors: Sepmeyer L. W.
Published: September 2005

In rooms used for making sound power measurements as well as for testing acoustical materials diffuse sound fields are postulated. In addition to the requirement for a large number of properly spaced normal modes, good diffusion also requires uniform angular distribution of the modes. Hence, the design and evaluation of reverberant rooms requiring diffuse sound fields require knowledge of the angular distribution of the normal modes as well as their frequency distribution. The angular distribution of the normal modes is determined in one portion of the computer program discussed in the companion paper on the frequency distribution of normal modes in rectangular rooms. This is done by computing the angle each mode makes with the short axis of the room and counting the number which lie within each 10° class interval for each half octave. The criterion used is based on the ratio between the actual number and the ideal number in each class interval. This will be done for the same range of dimension ratios and frequencies used for computing the frequency distributions. The development of the angular distribution criterion will be discussed, and preliminary results will be presented.
Experiments Using a Tilted, Rotating Sample for Absorption Coefficient Measurements in a Reverberation Chamber
Authors: Ortega J. , Rudnick I.
Published: September 2005

Absorption coefficient measurements in reverberation chambers are particularly troublesome at low frequencies. A major part of the difficulty stems from the fact that the eigenmode density is low and that an abnormally high percentage of the modes are axial and tangential. For a sample mounted on the floor many of these modes have grazing incidence and the associated absorption coefficient is abnormally low. A common manifestation of this effect is the occurrence of double slopes in the decay curve. This situation can be partially corrected by tilting the sample. If further the sample is rotated during the decay, no mode can remain grazing, and the rotation will result in a more appropriate average for the absorption coefficient as a function of angle. A comprehensive set of measurements were made to experimentally determine the size of these effects and the results will be discussed. The outstanding result is that nonlinear decay slopes were not observed when the sample was tilted and rotated.
Effect of Masking on the Pitch of Periodic Pulses
Authors: Rosenberg Aaron E.
Published: September 2005

Pitch-matching experiments were performed with stimuli and procedure similar to those employed by Flanagan and Guttman [J. Acoust. Soc. Am. 32, 1308–1328 (1960)] to determine whether selective masking alters the transition region between the pulse rate and pattern-rate modes of perception. In the unmasked condition, for pulse repetition rates below approximately 150 pps, listeners essentially match the pulse repetition rates of the comparison and standard signals; for fundamental frequencies higher than approximately 150 cps (and below 800 cps), listeners match the fundamental frequencies of the comparison and standard signals, even if the fundamental has been removed from the standard by filtering. Present results indicate that if to standard signals in or near the transition region high-pass noise (1000 cps) is added, the “buzz” quality associated with the pulse rate judgment can be masked and a pattern-rate judgment favored. Conversely, low-pass noise (1000 cps) can mask the “tonal” quality associated with pattern-rate judgments and favor pulse-rate judgments. Equally effective narrow-band noise or sinusoidal maskers seem to lie at about 5000 cps for masking pulse-rate pitch and 500 cps for masking pattern-rate pitch.
Equipment for In Situ Measurements of Sound Velocity and Absorption in Sea Floor Sediments
Authors: Shumway George , Huckaby W. B.
Published: September 2005

With the intent of making in situ measurements of sound velocity and absorption in deep sea sediments from the bathyscaph Trieste, equipment for this purpose, useful also in shallow water, has been developed and field tested. Three probes, each containing two transducers 0.5 m apart, are fastened to a rigid beam for simultaneous insertion into the sediment. The receiving probes lie 1 and 2 m distant from the source probe. Pulse-actuated magnetostrictive transducers are used as sound sources, and barium titanate cylinders as receivers. Measurements at two depths in the sediment are possible by using upper or lower transducers. The travel time interval between reception of the transmitted pulse at the near and far receivers is measured on a decade scaler counting a precision oscillator. Oscilloscope presentation of the signals arriving at the two receivers along with the time of gating assures the operator of satisfactory operation and aids in setting certain controls. A frequency range between 7 kc/sec and 30 kc/sec is used, with filtering provided in the receiving circuit to allow measurements in a number of frequency bands. Absorption measurements are made by matching superimposed oscilloscope traces of the signals from the near and far receivers by means of precision bridge T attenuators in two matched amplifier channels.
Mimicry and the Perception of a Phonemic Contrast Induced by Silent Interval: Electromyographic and Acoustic Measures
Authors: Harris Katherine Safford , Bastian Jarvis , Liberman Alvin M.
Published: September 2005

In the preceding paper of this session (J2) it was found that a phoneme boundary divides a continuum of silent intervals into two perceptual categories. The purpose of the present experiment was to see if the subjects' mimicry of the same acoustic continuum is graded, or whether it is, like the perception, categorical. Acoustic and electromyographic recordings were made of the productions of subjects during mimicry of each of the above stimuli. The acoustic records showed that time intervals introduced in mimicry were indeed categorical; however, the possibility remained that the speakers were, in some sense, making tentative or partial p gestures in the middle range of the continuum. Electromyographic recordings were used to test for the subjects' tendency to make such gestures. The electromyographic results were also entirely categorical: Either there was a normal burst of muscle potential at the lip (indicating a p gesture) or there was not. Thus, there was no evidence that subjects produce intermediate gestures, such as partial closure, in response to stimuli near the center of the continuum.
Identification and Discrimination of Phonemic Tones
Authors: Abramson Arthur S.
Published: September 2005

Measurements of the fundamental frequency patterns of many sets of tonally differentiated words yielded average curves for the five phonemic tones of Standard Thai (Siamese) on both short and long vowels. Experiments were then run to determine the role of fundamental frequency patterns in the perception of these tones. There were three major results: (1) Thai subjects easily identified tones in isolated monosyllables. (2) Highly intelligible tones could be synthesized on the Haskins Laboratories intonator with the average tonal contours that had emerged from the measurements. (3) When the five frequency contours were imposed synthetically on each of five utterances minimally distinguished by tone, the pitch contours overrode the effects of all other features observed in the stimuli. The overriding role of these contours opens the way to the study of discrimination at phoneme boundaries in the domain of prosodic features. The mid and high tones of Thai were chosen as a suitable pair for a start in this direction. These experiments had two results: (1) Shape difference is a stronger cue than pitch height for phonemic identification. (2) The hypothesis that there will be little or no sharpening of discrimination at this kind of phoneme boundary was supported or at least not contradicted.
An Accurate Estimate of the Glottal Waveshape
Authors: Mathews M. V. , Miller J. E. , David E. E.
Published: September 2005

The volume velocity function of the glottis can be computed from a pitch-synchronous spectral analysis of the speech pressure wave. The method consists of computing the Fourier coefficients of a pitch period, locating the formant frequencies, removing the formant poles from the spectrum, and regenerating the glottal waveform from the residual by Fourier synthesis. To obtain accurate results it is necessary to record the original speech without phase distortion while maintaining at least 55–60 db signal-to-noise ratio. The data reported here were derived from recordings originating with a WE-640-AA condenser microphone in a free-space room feeding a digital tape recorder. Two male speakers uttered six vowel sounds between h and d at different pitches and intensities. The glottal waveforms were examined to determine both shape and phase with respect to the speech wave as a function of the sound, the pitch and the intensity. Sequences of periods were studied for variations from period to period.
Ultrasonic Modification of Human Brain Structures for Treatment of Neurological Disorders
Authors: Fry William J.
Published: September 2005

The methodology of preparation and irradiation by focused ultrasound of brain structures in human patients to favorably modify symptoms of various neurological disorders will be described. This includes the method of brain landmarks location and subsequent geometric positioning of the focus of the ultrasonic beam in arrays of sites in specific structures. The determination of values for the irradiation parameters appropriate for producing selective changes in the tissue components, including the control of auxiliary physical variables which specify the state of the tissue during exposure, will be discussed. Design characteristics of the irradiation, calibration, positioning, and control instrumentation necessary to achieve optimum effects at the present time will be outlined. The techniques and results of irradiation will be illustrated by a motion picture showing human patients undergoing treatment. The modification of abnormal involuntary movements during successive ultrasonic treatment sequences in individuals suffering from Parkinsonism and dystonia musculorum deformans will constitute the clinical material of the motion picture.
Recording of Heart Wall Motion with Ultrasound
Authors: Reid John M.
Published: September 2005

An ultrasonic echo-ranging apparatus using a pulse transmitter and high gain broadband receiver connected to a barium titanate transducer has been used to obtain echoes from the walls and septa of the beating heart. The apparatus can be used over a center frequency range of 0.5 to 2.5 Mc. The sound beam is directed into the heart through the spaces between the ribs, and has been applied directly to exposed hearts of dogs. Curves representing the distance of the walls from the transducer can be recorded during the cardiac cycle. The interpretation of records obtained using frequencies of 1 and 2 Mc on dogs and human volunteers is discussed.
Ultrasonic Absorption and Reflection by Lung Tissue
Authors: Dunn Floyd , Fry William J.
Published: September 2005

The acoustic reflection and absorption coefficients of both normal and diseased (pneumonitis) excised lung tissue (dog) were experimentally determined at a frequency of 0.98 Mc/sec. It is found that the physiological saline-lung interface reflects 50% of the sound energy impinging at normal incidence. The acoustic amplitude absorption coefficient per unit path length of lung tissue is 4.7 cm−4. The very high absorption exhibited can be explained as the result of radiation of acoustic energy by the pulsating gaseous structures of the lung tissue. The theory indicates that the absorption coefficient of lung tissue should approach a minimum as the frequency is increased above 1 Mc/sec and should then increase at still higher frequencies. The diseased lung exhibited an acoustic absorption coefficient approximately 25% less than that of normal lung specimens. (This work was aided by a grant from the American Thoracic Society.)
Noise Considerations in the Design and Operation of the Supersonic Transport
Authors: Hubbard Harvey H. , Maglieri Domenic J.
Published: September 2005

The main sources of noise for the supersonic transport are noted to be power plants, aerodynamic boundary layers, and shock waves. Discussions are given on the state of knowledge of these noise environments and the manner in which noise considerations may affect the design and operation of this type of aircraft. Engine noise problems related to aircraft structural damage, exposure of ground crews, and reactions of communities near airports are discussed for various proposed power plants including the turbofan. Boundary layer noise considerations include possible fatigue damage to external skin surfaces at high dynamic pressures as well as the internal noise environments which may affect voice communications and passenger and crew comfort. Sonic boom considerations include the generation and propagation as well as the associated effects on structures, equipment, and personnel. Special attention will be devoted to discussions of operating procedures useful for minimizing sonic boom disturbances on the ground.
Application of a Blowdown Wind Tunnel for Large Scale Acoustic Environmental Testing
Authors: Mayes William H. , Edge Philip M.
Published: September 2005

A unique application of a blowdown wind tunnel for intense noise testing of large components or of entire vehicles will be described. The above facility, which is primarily used for thermal structures testing, has a 12-ft diam exhaust jet which generates an extensive noise field useful for test purposes. Sound pressure levels in excess of 140 db exist over distances of about 100 ft in the radial direction and 200 ft in the axial direction. Sound pressure levels up to 160 db and a wide range of noise spectra are available. An example of the use of this facility in the environmental testing of a manned space vehicle is cited and some of the main findings are presented.
Model Studies of Some Methods of Jet Noise Generation for Laboratory Testing
Authors: Modlin C. Thomas , Edge Philip M.
Published: September 2005

A description will be given of some studies relating to means of increasing the noise generated by jets to enhance their use as laboratory noise sources in research and environmental testing. A series of special nozzles having two-in. exit diam. and incorporating several types of upstream bends were investigated over a range of temperatures up to 700°F. Over-all sound pressure levels and one-third octave band spectra were measured in the near and far noise fields. Compared to conventional converging nozzles, those incorporating upstream bends resulted in increases of up to 15 db in the over-all sound pressure levels in the near field. Some further increases were obtained as a result of increasing the air temperature. Significant changes in the spectra were also noted and will be described.
High-Altitude Acoustic Research
Authors: Wescott John W.
Published: September 2005

The sources and characteristics of sounds at altitudes of 60 000 ft were investigated with a balloon-borne acoustic probe and telemetering system. The system is described and samples of analyzed data presented. Wideband background levels of 0.2 d/cm2 were measured consistently. Spectral energy per cycle was found to decrease with frequency by about 6 db per octave, a result in good agreement with current theories of noise radiated by turbulence. Cross-correlated data from a two-probe array indicated that most of this energy propagates from lower altitudes. It follows that a major source of high-altitude acoustic noise is lower altitude atmospheric turbulence. In addition to background noise, some specific types of acoustic signals have been detected and identified. Analyzed samples are presented. Some observed Doppler effects are discussed and their possible use for calculating absorption coefficients of low frequency sound in air is explained. (The acoustic probe and financial support for this work were furnished by the U. S. Army Signal Missile Support Agency under contract.)
Added Reliability for Preflight and Inflight Acceleration Measurements
Authors: Orlacchio A. W.
Published: September 2005

It has become essential to the proper functioning of the missile that a positive means for checking the accelerometer after installation be made available. A newly developed technique for making pre-flight and in-flight calibration checks on both piezoelectric and dc type accelerometers will be presented. A method for actually vibrating the piezoelectric accelerometer seismic mass over a wide frequency range and g level will be described in detail. The piezoelectric activity of the sensing element is obtained, and a meaningful calibration check may be observed immediately before count down flight. On the low-frequency accelerometers which incorporate magnetic damping, the damping cup and, hence, the seismic mass are displaced a known value of g with application of a dc voltage. This approach is used on potentiometer, variable reluctance, and differential transformer types of pickoffs.
Zero Shift in Piezoelectric Transducers
Authors: Jensen Hartley J.
Published: September 2005

“Zero Shift,” as applied to acceleration measurements, is a term that refers to spurious changes in the recorded zero value. The changes are the result of faulty instrumentation response to the measured acceleration. Zero shifts caused by insufficient RC time constant, amplifier saturation, and cable effects, are well known and are not considered in detail. Zero shifts caused by spurious transducer output signals resulting from large magnitude shock (order of 1000 g) are of principal concern. Consideration is given to (a) separation of zero shifts caused by the transducer from those resulting from other causes; (b) the effect this phenomenon has on the accuracy of the indicated shock motion; (c) the various possible sources of the zero shift (progress in this area will include the work of various manufacturers as well as Sandia); and (d) a review of the experimental results obtained at Sandia using transducers designed for minimum zero shift.
Effect of Nonaxial Motion on Accelerometer Calibration
Authors: Smith E. R. , Epstein W. S. , Pierce E. T. , Edelman S. , Jones E.
Published: September 2005

It is usual to monitor harmonic distortion, noise, and hum in the pickup signal during calibration but this is not enough to ensure suitable motion for accurate calibration. This paper describes calibration of all accelerometer on two shakers which were monitored for nonaxial motion. The nonaxial motion was detected by comparing the signals from three small pickups cemented equidistantly around the periphery of the shake table and the signal from the pickup being calibrated which was mounted at the center of the shake table. Each of the four pickups provided the signal for the vertical axis of a Lissajous figure. All of the Lissajous figures had a common horizontal signal which came from the oscillator driving the shaker through a calibrated phase shifter. A special eight channel electronic switch was used to put all of the Lissajous figures on the same CRO. During axial pistonlike motion all of the figures behaved similarly. During nonaxial motion the relative sizes and inclinations differed. The phase shifter provided a means for measuring differences in the phase of the motion at the pickup locations. Valid calibration points fell on a smooth curve. Points taken when the monitoring system showed nonaxial motion for a given shaker at a particular frequency fell off the curve while the calibration point taken at the same frequency with the other shaker which showed good motion fell on the curve.
“Incompressible” Acoustic Near Field as a Spatial Distribution of Sources Generating the Far Field
Authors: Ribner H. S.
Published: September 2005

Principle: Suppose one calculates an “incompressible” flow (pressure field p(0)) by substituting Laplace's equation for the wave equation in a given acoustic problem. Then the far field p(1) is a solution of the wave equation for a spatial distribution of matter sources of strength −c0−2∂p(0)/∂t. (Boundary condition: zero normal velocity.) This is readily demonstrated. Physical significance: Since the fluid is actually compressible, isentropy gives −c0−2∂p(0)/∂t=−∂p(0)/∂t. This density fluctuation is precisely equivalent to a volume fluctuation of the fluid elements. Pulsating sphere: A pulsating sphere generating an “incompressible” field p(0) may be replaced by a rigid sphere surrounded by a cloud of sources of strength −c0−2∂p(0)/∂t; this will generate the far field p(1). Aeolian tones: The principle helps explain nonvanishing generation of sound by a stationary rod in an air jet. The sound energy flow at a stationary surface must be zero: the sound is actually emitted from the region of fluctuating compression surrounding the rod. Jet noise: [J. Acoust. Soc. Am. 31, 245 (1959)]. The “incompressible” approximation to the field within the jet is p(0). Source-like pulsations of the fluid elements in response to p(0) are considered to generate the far-field sound p(1). The source strength, modified for convection, is −c0−2Dp(0)/Dt. (This work has been supported partially by the Air Force Office of Scientific Research of the U. S. Air Research and Development Command.)
Measurement of Speaker Recognition
Authors: Surgent L. V. , Yost L. H.
Published: September 2005

A procedure was developed for assessing the relative capabilities of voice transmission systems with respect to “speaker recognition.” Sets of five speakers each are composed randomly from a larger population. A listener is trained by an anticipation method to identify, by fictitious names, the members of a set of speakers, as heard over one of the systems to be evaluated. Following training, five additional speakers (“strangers”) are added to the initial five and all ten presented in random order over the same or a different system. Listeners are tested to see if they can (a) distinguish the five “strangers” from the five members of the initial set (IFF-type speaker recognition) and (b) name the five speakers met during training (speaker identification). A different sentence (approximately 10-sec duration) is used for each presentation of a set of speakers in both training and testing. Experimental designs for comparing two or more systems simultaneously will be discussed. The method will be compared with other approaches. (The study on which this paper is based was sponsored by ARDC and RADC under contract.)
Design of Distributed-Loudspeaker Speech Systems
Authors: Gardiner Martin F. , Kaye David H.
Published: September 2005

This paper considers the relation of various design parameters of distributed-loudspeaker speech-amplification systems to the two principal design criteria: “intelligibility” and “naturalness.” A convenient design procedure is described involving the calculation of the speech “articulation index” for the system. Some of the results of recent experiments on the evaluation of distributed-loudspeaker speech systems will be included.
Improved Instrumentation for Impulse Noise Analysis
Authors: Harbold George J. , Greene James W.
Published: September 2005

A longitudinal study of impulse-type noise is being conducted by the Department of Neurophysiology and Acoustics, U. S. Naval School of Aviation Medicine, Pensacola, Florida. As a part of the study, efforts were directed toward improvements in the techniques and instrumentation usually used to quantify the rise times, peak pressure levels, and decay patterns of impulse noises. This paper reports an improved instrumentation for impulse noise analysis. The limitations imposed by condenser microphones, magnetic recorders, and level recorders in response to transients associated with blast phenomena were investigated. In view of these serious limitations, the use of alternative techniques and systems was explored. The use of high-intensity crystal microphones and a storage-type scope was found to provide sufficient accuracy and flexibility for the variety of explosive transients encountered in field studies of many weapons. Pictorial evidence will be presented to illustrate the extent to which the limitations of earlier systems were overcome.
An Automatic One-Third Octave Band Analyzer for Noise and Vibration Analysis
Authors: Ginty G. F. , Collier R. D.
Published: September 2005

The problem of rapidly analyzing large volumes of acoustic data in analog form has been successfully met with a semiautomatic system. The principal feature of the system is the ability to process signals simultaneously in 31 parallel 13-octave filters over a frequency range of 10 to 10 000 cps over selected time periods. This is accomplished through storage capacitors, and provides a choice of two averaging times for average-amplitude modulated signals or peak value. A rotary selector stepping switch scans capacitor voltages sequentially, applying them to a dc logarithmic amplifier. The output is plotted on a Mosley X-Y plotter in the form of a bar graph. The instrument occupies a standard 6-ft rack. Sample results from vibration and sound-pressure level analyses are discussed.
A Wide-Band Carrier System for Condenser Microphone
Authors: Fox Herbert L.
Published: September 2005

A carrier microphone system has been developed for measuring very low sound pressure levels over a bandwidth from static pressure to 100 000 cps. The system is suitable for use with conventional condenser microphones and other types of capacitive transducers. This paper discusses (1) the problems of carrier systems vs direct bias systems in achieving low noise in the low- and high-frequency region, (2) a method of using tuned circuits at the carrier frequency without restricting the input bandwidth to the Q of the individual tuned circuits, and (3) the use of electrostatic methods of actuation to obtain equivalent pressure calibration in a carrier system. An equivalent acoustic noise floor less than Fletcher's minimum audible field curve over the entire audio bandwidth has been achieved. Pressure calibration of condenser microphones to 100 kc has been accomplished with the system described. (This work was supported in part by a U. S. Air Force contract.)
Lagrangian Formulation and Network Analogs for Multi-Mode Electromechanical Transducers
Authors: Rosato Frank J.
Published: September 2005

The Lagrangian equations which are useful in the solution and interpretation of the electrodynamic characteristics of multimode transducers of the piezoelectric and magnetostrictive types are presented. In order to bring such electromechanical systems within the framework of the Lagrangian theory, use is made of thermodynamic potentials defined for piezoelectricity and magnetostriction. [A table of such potentials for the piezoelectric case is given in the book by W. P. Mason, Piezoelectric Crystals and Their Application to Ultrasonics (D. Van Nostrand Company, Inc., Princeton, New Jersey, 1950), p. 34.] The two most useful potentials for Lagrangian application are found to be the internal energy density U and the electric enthalpy H2. These potential functions, together with the kinetic energy function, are used in constructing Lagrange's equations for electromechanical systems. These equations are essentially equations of dynamic equilibrium constructed in terms of the kinetic and potential functions, which are expressed in terms of generalized coordinates. They are shown to lead to a system of electromechanical equations for the transducer which have a structural resemblance with the mesh and nodal equations of coupled electric networks. Hence, they may be represented by electric network analogs wherein the mechanical terminal variables are generalized force and generalized velocity. These network analogs are shown to offer several distinct advantages over the conventional filter-type analog networks: They are insensitive to the location or distribution of the external forces, they exhibit explicitly the characteristic modes and the electromechanical coupling to each mode, and they lend themselves more readily to analog electrical measurements. The analog networks obtained for several transducers will be presented. (Work performed by the author at the Acoustics Research Laboratory, Harvard University, sponsored in part by the Office of Naval Research.)
Binaural Detection of Single Frequency Signals in the Presence of Noise
Authors: Gardner Mark B.
Published: September 2005

It is well known that when signal and noise sources occupy different spacial positions, detection of the signal is influenced by the orientation of the observer. This paper presents a study of these and related factors as they affect the detectability of single frequency signals using a binaural transmission system. An adjustable-rate pulse-tone method of signal presentation was employed. The two microphones were supported in free space both with and without an artificial head. For the former, various “heads” were used to provide “interaural” separations of 2.5–13 in., while for the latter, where phase differences alone are present, data were taken for linear and rotational separations of the microphones. The results indicate that over-all detectability is a function of the combined binaural phase relationships of both signal and noise and of the monaural intensity relationship of the two signals at the ear having the higher signal-to-noise ratio. In agreement with other studies, the importance of phase differences was found limited to frequencies below about 2000 cps while the importance of pressure-level differences increased as a function of frequency above about 250 cps.
Third Order Elastic Moduli of Germanium
Authors: Mason W. P. , McSkimin H. J. , Bateman T. B.
Published: September 2005

Measurements have been made for all 6 third-order elastic moduli of germanium by measuring ultrasonic velocities in selected directions when directed static stresses are applied to the crystal. Three measurements are obtained by using hydrostatic pressures, three by using a static compression along the 〈001〉 axis, and six by stressing the axis with measurements being made along with the 〈001〉 direction and the 〈11̄0〉 direction. By using the finite strain formulas of Murnaghan, the measured velocities are related to the 3 second-order elastic moduli and the 6 third-order elastic moduli for a cubic crystal. The 12 sets of measurements provide considerable overlap and the probable errors are shown to be moderate. The values obtained are C111=−1.22±0.08×1012 d/cm2; C112=−1.450±0.15; C123=+2.16±0.21; C144=−0.17±0.19; C166=−6.07±0.28; C456=−1.65±0.19.
Some Measurements of Wave Velocities and Elastic Moduli for Cadmium Sulphide
Authors: McSkimin H. J. , Bateman T. B. , Hutson A. R.
Published: September 2005

Because the literature indicates a rather large spread of values for the elastic moduli of single crystal cadmium sulphide, additional measurements made on a specimen of low conductivity and on one of high conductivity are reported in this paper. The effect of light on certain of the measured wave velocities in the former will be discussed briefly. The method of estimating uncertainties is detailed, and a procedure for removing the ambiguity in the sign of c13 is discussed. In units of 1011 d/cm3 and for a temperature of 25°C the zero field elastic moduli are: c11E=8.581, c12E=5.334, c13E=4.615, c33E−9.370, c44E=1.487. Estimated uncertainties are less than 0.2%.
Mutual Interactions of High Energy Ultrasonic Beams
Authors: Sachs Thomas D.
Published: September 2005

The conflicting claims as to production of nonlinear interactions between sound beams arising from second order terms, as presented by Ingard [J. Acoust. Soc. Am. 28, 367 (1956)] and Westervelt [J. Acoust. Soc. Am. 29, 199, 934 (1957)], were investigated by a pulse method. Time separation of initial beams and scattered field was possible using appropriate geometry. The scattered field was investigated for 14 different relative beam angles including 0 deg. The incident 1010 kc and 1410 kc beams had space-average peak pressures of 4.2 and 6.9 atm, respectively, with a minimum interaction volume of 150 cm3. Sensitivity was sufficient to detect interactions at least 70 db below those predicted by Ingard. No interactions whatever were found in spite of the divergent character of the initial beams. (This research was done in the Physics Department of the University of Innsbruck, Austria, in partial fulfillment of the requirements for the Ph.D. degree.)
Steady vs Intermittent Noise Bursts for Evoking and Maintaining Middle Ear Muscle Reflex Reactions
Authors: Mendelson E. S. , Kemmerer D. L.
Published: September 2005

Since middle ear muscle reflex contractions reduce sound transmission from the outer to the inner human ear, their safe and effective induction is a protective problem. There are reports that (1) the reflex threshold is lowest at audible midfrequencies; (2) persisting noise causes longer maintained contractions than does persisting pure tone; (3) noise reduces auditory acuity less than pure tone at the same SPL; and (4) diplacusis is more readily caused by pure tone than by broadband noise. Mid-frequency noise therefore seems likely to be the safest and most effective stimulus for intentional, protective activation of middle ear muscle reflexes. Cochleo-tympanic tests have been conducted upon two subjects, with noise, essentially flat from 1200 to 4800 cps, alternating short bursts of intermittent and steady stimulation at the same nominal SPL's, to estimate the practicability of reducing the total duration of the stimulus without positive loss of its effectiveness. Limiting repetition rates at which intermittent stimuli appeared as effective as steady stimuli for eliciting and maintaining the reflex reactions were found to vary with the SPL of the stimulus.
Random Fatigue of Hard Spring Resonators
Authors: Smith P. W.
Published: September 2005

Computations have been made for the effect of a nonlinearity of the hard spring type upon the fatigue damage ensuing on excitation of a resonator by a stationary, broad-band, random Gaussian force. The fatigue theory used assumes a simple accumulation of damage in proportion to a power of the peak values of response strain, without interactions between peaks. Two cases are distinguished: (a) strain proportional to displacement; (b) strain nonlinearly dependent on displacement, as is the surface fiber strain in a bar with pinned ends. Numerical results are presented that indicate for case (a) a continuous decrease, with increasing nonlinearity, of the rate of accumulation of damage, while for case (b) this damage rate increases to a maximum, as large as 3.4 times the linear estimate, and then falls below the value for linear response. Distortion of the curves for peak-strain density and for fatigue-damage density is discussed. (Research sponsored by Air Research and Development Command, U. S. Air Force.)
Narrow Band Excitation of the Hard Spring Oscillator
Authors: Lyon Richard H. , Heckl Manfred
Published: September 2005

By using the technique of “quasi-linearization,” the response of a hard-spring oscillator to a band of random noise is calculated. Comparison is sought with the limiting cases of wide band (purely random) and determinate sinusoidal excitation. It is shown that the limiting cases are approached in a satisfactory manner. In particular, multivalued solutions are obtained as the bandwidth of excitation is diminished but do not occur when the bandwidth is suitably broad. Experimental illustration is included. (Supported in part by the Office of Naval Research and the National Science Foundation.)
Some Investigations on Grillage Vibrations
Authors: Heckl Manfred
Published: September 2005

The vibrations of grillages consisting of beams crossing each other at right angles were investigated theoretically and experimentally. It was found that at low frequencies grillages behave like orthotropic plates. At high frequencies (when the distance between the intersections is much larger than the beam bending wavelength) more complicated vibration patterns are observed. For the special case of point excitation, a certain highly frequency dependent attenuation occurs at the intersections closest to the source. No additional attenuation could be measured at some distance from the source, due to excitation of torsional waves at the intersections. (Supported by the Office of Naval Research.)
The Hamograph: A New Amplitude-Rhythm Control Device for the Production of Electronic Music
Authors: Schaeffer Myron
Published: September 2005

The production of electronic music forces the composer to tackle certain new problems which require unusual and often difficult technical solutions. Some of these are the synchronization of melodic units into a contrapuntal texture; the organization of sounds into complex rhythmic continuities; shaping individual sounds in relation to attack, continuum, and decay patterns; exact repetition and/or with tempo variations of rhythmic patterns with or without alteration of pitch. The principle of the Hamograph is that of drawing with conductive ink or of pasting metal foil contours on 35-mm continuous loops which are read by a series of silver brushes so arranged that the signal circuit is modified in intensity by means of a resistor chain which in turn controls the volume of the final signal in the aural monitor or recording device. This device provides a simple means of organizing multiple sound sources into useful musical objects by (1) creating and repeating complex rhythmic patterns without splicing; (2) creating complex rhythmic montages without splicing or transfer; (3) repeating exact envelope patterns with same or varying timbre; (4) programming sections of a composition using prepared sound objects without transfer; (5) changing the tempo of rhythmic organizations without change of pitch; and (6) modifying elements of the control plan without reconstructing the total control system.
New Tool for the Exploration of Unknown Sound Resources for Composers
Authors: Bode Harald
Published: September 2005

When applying suited means in order to modify known natural or electronically created sounds, more or less unusual and some very usable new phenomena may be originated. The methodic exploration, evaluation, and exploitation of these will be rewarding for the composer, who is searching for new resources. As a tool for these purposes, a new modular sound and envelope shaping, modulating, and modifying device has been developed, which may be combined as an integral unit with an alternating sound pattern creating apparatus. These devices may be applied in many ways to modify one or several audio phenomena as well as by using in a predetermined way one feature to affect another. These systems comprise an arbitrary selection of modules, some of which are well known in audio and communication techniques, but many combinations of which represent unusual systems with interesting functions. A relatively simple version of this type of modular assembly with a surprising variety of performance features has been built and used for experimental purposes. It will be briefly described here as a whole and in some of its details; a selection of significant tape recordings will be demonstrated.
Aid to Music Composition Employing a Random-Probability System
Authors: Olson Harry F. , Belar Herbert
Published: September 2005

The art of music composition can be learned to some extent by following the work of composers and by studying the fundamentals of music. Composition can be stimulated by various experiences and may be aided by research. However, the process which operates in the mind of the composer is not understood. Even without such knowledge, it is possible to develop machines which can aid the composer in his search for melody which is the essence of most music. Although the ability to create is a gift, even great composers have at times turned to various aids for assistance. In this connection, random-probability systems allow the generation of sequences of notes in a series which are not completely random nor completely ordered, but each note is selected in a random fashion with a probability which depends upon preceding notes. Such a machine has been developed and has been operated to generate a sequence of an almost infinite series of notes according to trinote probabilities found in the music of Stephen Foster. Combined with sound synthesizers, the machine provides additional instrumentation for the musical laboratory. However, the ultimate output of even the best equipped laboratory still depends upon the composer.