bluuebunny/crossref_metadata_2025 huggingface dataset:
Waves on Ice-Covered Oceans
Authors: Hunkins Kenneth
Published: September 2005

Observations of continuous vertical oscillations of ice floes in the Arctic Ocean were made with a gravity meter at Drifting Station Alpha and with a long-period seismograph at Drifting Station Charlie. Results from Station Alpha show that the amplitude of the ice oscillations generally increases with period throughout the observed period range from 10 to 100 sec. Results from Station Charlie show that the source of the oscillations is partially wind motion and partially grinding along the edges of the ice floe. Theoretical calculations for an ice sheet floating on water show that, in the observed period range, a phase and a group velocity minimum exist between the short-period flexural wave and long-period gravity wave branches of the dispersion curve. The group velocity minimum at 16 sec would be expected to coincide with large amplitudes of ice oscillation for a broad-band source. Since the observed maximum occurs at a period greater than 100 sec, the source spectrum must contribute considerable energy at the longer periods.
Propagation of Train Noise and Adjacent Land Use
Authors: Thiessen G. J. , Embleton T. F. W.
Published: September 2005

If an open land area is used as a buffer between a railroad carrying diesel freight trains and a quiet residential suburb, then the noise criteria commonly used would require that the buffer be a mile wide or wider, depending on the traffic. Such extravagant use of land near urban areas can largely be avoided by putting this land to uses with graded sensitivity to noise but with maximum occupation near the tracks. The use of a cutting 12 ft deep for the tracks reduces the noise in the most intrusive band by about 15 db and permits a reduction of the width of the buffer by a factor of about 5. The engine noise, however, requires a deeper cut unless the exhaust is relocated. Trees are not very effective as a barrier. It would require 1000 ft of very dense forest with thick underbrush to get a 15-db attenuation of the most important band of diesel train noise.
Second- and Third-Formant Loci in English Fricative Consonants
Authors: Delattre Pierre C. , Liberman Alvin M. , Cooper Franklin S.
Published: September 2005

The role of formant transitions in the perception of consonants can be studied, using synthetic speech generated from hand-painted spectrograms, either (1) by holding the formants at fixed frequencies and varying the transitions through a broad range or (2) by varying the frequencies of straight (zero transition) formants. Results obtained by the former method for the voiced fricatives of English were presented at the 1960 Fall Meeting of this Society. In the present study, the latter technique is applied (for second and third formants) to the comparison of /v/ and /ð/ without added friction, and to the comparison of /z/ and /ȝ/ with “neutral” friction. On the assumption that second- and third-formant loci are essentially the same for the corresponding voiced and voiceless fricatives, the results to be reported furnish information on transition cues for all eight fricative consonants of English.
Some Aspects of Fundamental Frequency and Emotional Content in Speech
Authors: Lieberman Philip , Michaels Sheldon B.
Published: September 2005

Pitch pulses were electronically derived from the utterances of six male speakers of American English who each read eight neutral test sentences in certain “emotional” modes, i.e., as a question, an objective statement, a fearful utterance, a happy utterance, etc. A fixed vowel POVO type synthesizer was excited by these pitch pulses and the resulting pitch contours recorded. The sets of test sentences and pitch contours were each placed in random sequences and separately categorized by linguistically naive listeners in forced judgment tests. Certain of the modes were not easily identified when the sole acoustic cue was the pitch contour. The results of the psychoacoustic test were then correlated with sonagraphic information.
Effects of Changing Vowel Parameters on Estimates of Loudness
Authors: Lane H. L.
Published: September 2005

The vowel parameters: autophonic level, intensity, and spectral structure were incorporated in a three-dimensional experimental design to investigate vowel loudness. The levels of the autophonic variable were 0, 10, 20, 30 db (relative); the levels of the intensity variable were 50, 60, 70, 80 db (SPL); the levels of the spectral structure variable were fundamental frequency, first formant, first and second formants, and total vowel. The 64 stimuli defined by this three-space were presented in random order to each of 15 subjects who gave numerical estimates of their loudness relative to a standard (1000 cps, 80 db, SPL). Vowel loudness was influenced most by the sound pressure level of the signal. Spectral structure was the second largest factor. The total /a/ was always judged louder than the first and second formants combined when both were presented at the same sound pressure level. The original autophonic level, reflected primarily in the pitch of the vowel, played the third largest role. The first- and second-order interactions of these variables were appreciable. At low intensity levels, vowels with low fundamental frequencies were underestimated, while at high intensity levels high pitched vowels were overestimated. The over-all loudness function for the vowel /a/ was recovered by collapsing numerical estimates over two dimensions. The power laws governing the autophonic response (exponent 1.1) and vowel loudness (exponent 0.4) were used to predict successfully the outcome of cross-modality comparisons in which subjects were instructed to imitate the disyllable “baba” presented with various degrees of first and second syllable stress.
Optical Determination of Ultrasonic Waveforms
Authors: Colbert H. M. , Zankel K. L.
Published: September 2005

A new optical method has been developed for determining the shape of ultrasonic waves. Because of the varying index of refraction, collimated light incident on an ultrasonic wave emerges with a modulated phase. By interfering light of fixed phase with the emergent front, information about the waveform can be obtained. The theory provides for determination of ultrasonic waveform including relative phase between harmonics. The process of finding the waveform consists of simply taking the arccosine of experimental results. Comparison of experimental results with theory will be discussed. (This work was supported by the Office of Naval Research.)
Method for Calculating the Ratio p/q of the Photoelastic Constants of Glasses
Authors: Achyuthan K.
Published: September 2005

A method, based on Mueller's theory of photoelasticity [J. Am. Ceram. Soc. 21, 27 (1938)] has been developed for calculating the ratio p/q of the photoelastic constants of glasses. The constant Li, introduced by Mueller to represent the contribution to birefringence due to the deformation of the atomic structure of the ith atom, is taken to be the difference of two quantities Qi and Pi, defined by (ΔR)∥ = Qi ⋅ R and (ΔR)⊥ = Pi ⋅ R, where (ΔR)∥ and (ΔR)⊥ are the changes in the molar refraction R due to unit strain when the light vibration is parallel and perpendicular to the direction of stress, respectively. To calculate the ratio p/q of a glass sample, both Qi and Pi have to be calculated for each separate ion contained in it. The accurate measurements of p/q by Gates and Hiedemann [J. Acoust. Soc. Am. 28, 1222 (1956)] provide sufficient data for calculating the unknown parameters Pi and Qi of the different atoms. The results are discussed in detail and agree with Mueller's values for Li = Qi − Pi. (This work was supported by a grant from the National Science Foundation.)
Probe Microphone with Horn Coupling
Authors: Shaw E. A. G.
Published: September 2005

When an acoustic horn is terminated by a matching resistance and an ideal condenser microphone, theory predicts four distinct regions of operation: (1) a low-frequency region with over-all response asymptotic to the pressure response of the condenser unit, (2) a broad-transition region of relatively low response around the horn cutoff frequency, (3) a normal-transmission region in which the response is virtually independent of frequency, and (4) a high-frequency region of falling response in which the terminal resistance is partially short-circuited by the acoustical capacitance of the condenser unit. The transition region dip is dependent on the ratio S1/S2 of throat to mouth area of the horn and on horn shape. When S2/S1 is 100, theory supported by experiment indicates a dip of 3 db, 8 db, and 13 db below normal transmission level for conical, exponential, and catenoidal horns, respectively. A larger dip is found when the horn is preceded by a uniform-bore probe tube. In practice, the terminal resistance may be vented into a cavity of moderate size in which case a damped resonance occurs in the low-frequency region and the transition region is modified in shape.
Phase Correction of Band-Shifted Signals
Authors: Clay C. S. , Liang William
Published: September 2005

The merit of employing signal-band shifting to transmit and detect a message for correlation purposes has been studied. It was found that the phase distortion introduced in delaying the heterodyned signal impairs the detectability of the correlation system. It is necessary to remove this distortion. Examples of such techniques are given for the cross-correlation function of two heterodyned signals and the addition of signals in a multichannel system. (This work was supported by the Office of Naval Research.)
Effect of Double Clipping in Beam Forming and Correlation
Authors: Anderson Victor C.
Published: September 2005

The performance of a clipper correlator operating on the output of a DIMUS beam-former is dependent upon the input signal-to-noise ratio. It is shown that for special hypothetical distributions of reverberation and noise the predicted false alarm probability is profoundly influenced by the use of clipper processing. This advantage is somewhat offset by the loss in bearing resolution which occurs for high signal-to-noise ratios with the double-dipped processing. (This work represents results of research carried out under contract with the Office of Naval Research.)
Some Experiments in Underwater Sound Absorption
Authors: Rubega R. A. , Culver A.
Published: September 2005

This paper discusses some experimental techniques for the measurement of sound absorbing materials in the 2- to 10-kc range. The experimental technique discussed is that of decay time measurements of a reverberant chamber. Several different kinds of signals have been used—namely pulsed sine waves, pulsed noise, and an impulse signal generated by the discharge of an underwater spark. The spark source was found the most convenient to use. Though at present the measurements are not as precise as those obtained in air-filled reverberation chambers, the method does allow a quantitative comparison of underwater absorbing materials. All analysis of precision of the method will be given. Other methods for measuring absorption will be described briefly. (Sponsored by the Office of Naval Research, Code 411.)
Acoustic Tracking Range for Simultaneously Tracking Three Underwater Vehicles
Authors: Teel W. A.
Published: September 2005

Underwater acoustic methods have been applied to the problem of simultaneously tracking three towed vehicles in a specialized range facility at the U. S. Navy Mine Defense Laboratory. A self-contained transponder in a streamlined body is attached to each vehicle and the transponder position determined with respect to two bottom-mounted transducer arrays spaced 2000 ft apart. The transponder operates without false triggering in the presence of nearby interfering sonic pulses with levels as high as +75 db ref 1 d/cm2. Freedom from pulse type interference is achieved by a novel transponder design that avoids the use of cascaded tuned amplifiers. Tangentially polarized barium titanate cylinders are used for each of the transmitting and receiving transducers. The range covers an area of 1 square mile and the instantaneous position of the transponders is determined once every 2 sec to a precision of ±5 ft within the optimum triangulation area. The resolution of the tracking range is sufficiently high to correctly identify the position of each of two transponders separated by 10 ft with a standard deviation of 3 ft.
Portable, Wide-Range, Transistorized Gate for Acoustic Research
Authors: Fox Charles E. , Hillery Herbert V.
Published: September 2005

A highly portable, transistorized gate has been developed for use in acoustic research and development. When the gate is used with an oscillator and a power amplifier, electrical pulses are generated. The gate includes controls which permit continuous variation of pulse widths from below 1 msec to above 200 msec at repetition rates from 5 msec to several seconds per pulse. The gate also produces a variable delay pulse for triggering an oscilloscope at any time between the end of one pulse and the start of the next pulse, thus permitting precise study of echoes. Controls are included in the gate circuit to force each pulse to be initiated at the same selected voltage level of the gated signal so that all pulses have identical pulse fronts. Frequencies ranging from 5 cps to over 1 Mc/sec can be gated. The rejection ratio is over 60 db up to 100 kc. The gate has been constructed from readily obtainable, inexpensive components. Several applications for the gate are described.
Achieving Deep-Water Capability with Free-Flooding Piezoelectric Transducers
Authors: Marshall W. J. , Hueter T. F.
Published: September 2005

This laboratory has recently developed a pressure relief technique which makes possible the use of piezoelectric transducers at very great depths. The transducer is attached to a free-flooding cavity of the same diameter as the radiating surface. The length of the cavity is a quarter-wavelength at the operating frequency; hence a standing wave is produced in the cavity just as in a closed organ pipe. This presents an impedance to the back of the transducer which balances the system mechanically but does not radiate. This method is analogous to terminating a transmission line with an open quarter-wave stub. Several experimental models have demonstrated the feasibility of this technique.
Experimental Studies of Glass Breakage Due to Sonic Booms
Authors: Parrott Tony L.
Published: September 2005

This paper will contain results of window-glass breakage experiments involving sonic booms from aircraft at both low and high altitudes. Data will be presented from over 250 tests as a result of which about 50 failures were encountered. Results will be correlated with available glass-static-loading data and with details of the airplane shock-wave-pressure signatures. A high-speed movie illustrating the manner of failure of two 3-ft×3-ft windows will be shown.
Sonic Fatigue of Simulated Riveted Joints
Authors: Malme C. I. , Gogos C. M. , Dyer I.
Published: September 2005

The fatigue of a structure clamped to a support with a row of simulated rivets was investigated. The structure consisted of a 2024-T3 aluminum sheet (2 in.×3.5 in.×0.032 in.) cantilevered in a closely fitting slot in a siren test duct. Three aluminum bolts were used to simulate a clamping row of countersunk rivets. This design was chosen because it eliminated membrane stress at the rivet line and provided for control of clamping tension. The cantilever was excited at its fundamental resonance by plane waves of sound propagating at grazing incidence in the duct. The nominal strain at the rivet line was set by controlling the amplitude of motion at the end of the cantilever. Three different rivet diameters were used in fatigue life measurements: 0.125, 0.250, and 0.375 in. Each rivet size was tested at three strain levels. The fatigue lives ranged from 0.4×105 to 4×105 cycles. The fatigue-strain-concentration factors measured in this experiment varied from 1.5 for the 0.125-in.-diam rivet to 1.7 for the 0.375-in.-diam rivet. The concentration factor for the 0.125-in. diam rivet was found to be close to that measured in a subsequent experiment on reversed bending of a cantilever beam with a 0.125-in.-diam hole. An important decrease in fatigue resistance occurred in going from a rivet diameter of 0.125-in. to a diameter of 0.250 in.; a relatively small change was observed from 0.250 in. to 0.375 in. It appears that small rivets will increase sonic fatigue resistance of riveted joints. (Research sponsored by Aeronautical Systems Division, Air Force Systems Command, U. S. Air Force.)
Measured Fatigue Lives for a Resonant Cantilever with Random and Pure Tone Excitations
Authors: Malme C. I. , Smith P. W.
Published: September 2005

A cantilever beam of 2024-T3 aluminum sheet (3.25 in.×1.00 in. × 0.063 in.) was shaken mechanically at its clamped end, the force being applied parallel to the thickness dimension. A 0.125-in.-diam hole near the clamp afforded points of strain concentration. Both pure tone and broadly filtered random forces were used to excite resonant response in the fundamental mode, at about 185 cps. The rms surface strain in a cross section containing the hole ε was monitored and held constant. Life N to first visible appearance of a fatigue crack was measured; lifetimes ranged from about 1×105 to 6×105 cycles. The pure-tone data agree very closely with previous measurements on a riveted cantilever excited by sound. In comparison with available fatigue data for reversed bending in a specimen with small concentration factor, these data yield a fatigue strain concentration factor of 1.6, in good agreement with theory. The measured ratio of rms pure-tone strain to rms random strain yielding the same life-time ranged from 1.5 to 1.6 (3.6 to 4.3 db). The ratio calculated from assumptions of (a) Rayleigh distribution of peak strains, (b) noninteracting accumulation of damage, and (c) Nε8.25 = const, is 1.4 (3.1 db). (Research sponsored by Aeronautical Systems Division, Air Force Systems Command, U. S. Air Force.)
Rotor Dynamics with Emphasis on Attenuation
Authors: Sternlicht Beno
Published: September 2005

The paper presents a theoretical analysis of the dynamics of a rotor bearing system. The analysis is limited to small amplitudes of the rotor motion, and the fluid-film forces are made linear with respect to journal amplitude and velocity. The resulting eight coefficients denoting the spring and damping functions are calculated from the hydrodynamic equations, and are coupled with the rotor. The motion of the force transmitted to the bearing pedestal is obtained. The method enables one to calculate such parameters as critical speed, amplitude of vibration, stiffness, damping and force transmission. Such data are extremely important where structure or noise is a problem, e.g., machinery for submarines.
Modulated Photoelectric Measurement of Vibration
Authors: Schmidt V. A. , Edelman S. , Smith E. R.
Published: September 2005

A modulated-frequency photometric interferometer is described for precise calibration of vibration pickups. The plates of the Fizeau-type interferometer are subjected to sinusoidal vibrations—one plate at frequency f and amplitude ξ0, the other plate at frequency f′ and amplitude γ0, where f>4f′. A photomultiplier examines a portion of the fringe pattern and its output is sent through a bandpass filter tuned to f′. The filtered signal is proportional to J0(4πξ0/λ). Accurate determinations of ξ0 may be made by adjusting this amplitude such that J0(4πξ0/λ) arrives at one of its low-order nulls. This method is analogous to the visual fringe disappearance method currently in wide use for vibration pickup calibration which yields the same functional dependence on amplitude ξ0. The modulated frequency interferometer, however, does not suffer from the errors of human judgment, having an electrical rather than visual output. Nulls of J0(4πξ0/λ) can be located with a precision exceeding that obtainable with visual fringe disappearance.
A New System for Space Communication
Authors: Bauer Benjamin B.
Published: September 2005

In space communication, every means for transmitting maximum information should be provided. The new proposed system transmits the sense of direction as well as voice information between any number of suitably equipped persons. The transmission takes place with omnidirectional radiators. The reception is achieved by means of two limacon receptors, using “stereophonic-binaural converters” to provide the desired space perspective.
Seismic Reflection Measurements in the Straits of Florida
Authors: Goedicke T. R.
Published: September 2005

A series of seismic reflection traverses were run in the Straits of Florida, extending both parallel and at right angles to the shoreline. One traverse was made across the Straits of Florida in an attempt to follow the geological horizons cut by a deep well drilled at Key Largo. Five prominent reflecting horizons could be followed in the subsurface at approximate depths of 500, 800, 1050, 1600, and 2200 m. The three uppermost horizons can be tentatively correlated with geological horizons in the Paleocene and Upper Cretaceous, whereas the lower layers can be correlated with the Lower Cretaceous anhydrite zones found in wells drilled on the Florida Platform. The reflection-seismic traverse across the Straits of Florida from South Riding Rock on the Bahama Platform toward Pacific reef off Key Largo shows these five reflecting horizons which continue more or less parallel to each other from the Bahama Bank toward the west until the “V” shaped trough in the bottom of the Straits of Florida is reached. Between the Bahamas and this point, little relief is seen in the upper reflecting horizons. The lower reflecting horizons of presumably Lower Cretaceous age exhibit gentle warping. Individual reflection trends show changes in phase, and some of the beds show lenticular structures 8 to 15 km in length.
New Applications of Voice-Excitation to Vocoders
Authors: David E. E. , Schroeder M. R. , Logan B. F. , Prestigiacomo A. J.
Published: September 2005

The principle of voice-excitation for a vocoder synthesizer involves generation of a flat spectrum of pitch harmonics or noise from an uncoded subband (“baseband”) of the original speech [M. R. Schroeder and E. E. David, Jr., “A vocoder for transmitting 10 kc/sec speech over a 3.5 kc/sec channel,” Acustica 10, No. 1, 35–43 (1960)]. The necessity for a decision-making pitch detector is thereby removed. The principal advantage of the voice-excited vocoder is its insensitivity to input signal-to-noise ratio and equalization. A voice-excited vocoder with a 720-cps (250–970 cps) baseband and 17 spectrum channels low-passed to 25 cps each, covering the band 970–3700 cps, has been built and evaluated. The test shows an average PB-word intelligibility of 86%, compared to 92% for input speech of the same bandwidth, both with and 18-db signal-to-noise ratio. Quality tests indicate that about 85% of all listeners rate the speech “as good as” the input while only 20% so consider a vocoder using conventional pitch control. The vocoder performed about equally well for each of the 12 speakers in the quality test. Voice-discrimination tests indicate that voice identity is well preserved. Crucial factors influencing the remade speech quality are the accuracy of spectral flattening and the impulse response of the analyzer low-pass filters. Studies of voice-excitation indicate that the baseband, if used for excitation only, can be coded into about 2000 binary pulses per second. Accordingly, the vocoder was modified with the addition of four spectrum channels, and operated with a digitally coded baseband. In total, it is estimated that about 4000 binary pulses per second are required for all-digital transmission. A tape demonstrating these results will be played.
Cochlear Potentials in the Human Being
Authors: Ruben Robert J. , Bordley John E. , Lieberman Alfred T.
Published: September 2005

For many years there have been various attempts to record cochlear potentials from the round window in a human being. Some earlier efforts have met with moderate success. During the past two years, approximately 30 cases have been attempted at the Johns Hopkins Hospital. A multichannel tape recorder has been used to simultaneously stimulate the human ear and record from the round window. The patients all had their tympanic membranes reflected and a small electrode was placed on the round window niche. In most cases, good cochlear potentials were recorded and measured. In addition, clicks were used to stimulate the human ear, and recordings have been made from the round window. The action potentials of the 8th nerve known as N1 and N2 were then recorded. Two groups of patients are now being studied. The first group consists of patients with otosclerosis. A recording is made before mobilization or a replacement of the stapes is done. A second recording is taken after the oval window is free, to show if there has been any objective gain in the cochlear potential. The second group of patients are children with congenital neurosensory hearing loss. Excellent cochlear potentials and 8th nerve action potentials have been recorded in this group. The recording of cochlear potential in man is being used as a diagnostic and exploratory tool in evaluation and understanding of hearing disorders. It is felt that this also gives a valuable tool in understanding some of the basic properties of hearing in the human being.
Auditory Nerve Responses to Low-Pass Transients
Authors: Teas D. C. , Eldredge D. H. , Davis H.
Published: September 2005

Masking has been used to subtract groups of nerve impulses from the whole-nerve action potential of the guinea pig. The form of that part of the whole-nerve action potential which is eliminated by a narrow band of noise is approximately diphasic. This is the expected form of individual nerve impulses recorded from one electrode in the cochlea and the other on the neck. The stimulus variables investigated were intensity and rise time of the acoustic transient, and intensity, bandwidth, and center frequency of the masking noise. The whole-nerve action potential to low-pass transients is composed of impulses that arise from a large extent of the organ of Corti, with a distribution in time that parallels the space-time pattern of the cochlear microphonic. (This research was supported by Bt-366-C2 and NIH-B1726.)
An Equivalent Circuit Study of Fenestration
Authors: Paskusz G. F.
Published: September 2005

This paper describes an attempt to supplement the experimental approach to improving fenestration by circuit analysis. The fenestrated ear is considered an idealized acoustical system and its equivalent circuit is derived. The circuit consists of an input section (outer ear, middle ear, fenestrae), and seven sections representing the inner ear. These are found to be resonant at frequencies between 100 cps and 10 kc. The problem is simplified by assuming the partition between outer and middle ear to be rigid. The other significant parameters are then combined into a variable series capacitance. The resulting circuit is analyzed numerically (digital computer). Response curves are obtained for volume displacement across the basilar membrane as a function of frequency and distance from the input end, with input capacitance as parameter. The computed results and experimental findings (by Békésy) are similar. The startling result of the investigation is that a lowering of the combined window stiffness by a factor of 30 results, in the model, in a 30 db gain over most of the speech spectrum. This is in sharp contrast to controversial experiments in the 1930's by Hughson and Crowe who tried to improve fenestration by increasing the stiffness of the round window.
Correlations and Frequency Spectra of Fluctuations in Sound Signals Transmitted over a Fixed Path in an Estuary
Authors: Smithson J. R.
Published: September 2005

Short pulses of 100-kc sound have been transmitted from a fixed source to an array of fixed receivers at a range of 100 ft in the Severn River. A statistical analysis has been made of 7000 pulses transmitted directly across a sharp, changing velocity gradient, which produced large fluctuations, and of 14 000 pulses reflected from the surface when fluctuations in direct transmission were negligible. Autocorrelations and cross correlations with delays up to 300 sec have been computed for signals received simultaneously on hydrophones with various horizontal and vertical separations. For surface-reflected signals, little correlation was found between successive pulses or between pulses received on separated hydrophones. For direct transmission, the decrease of autocorrelation with time and the decrease of cross correlation with both time and distance have been compared with various theoretical correlation functions. Phase differences between fluctuations on separated hydrophones have been found which are not simply related to the current. Frequency spectra of the fluctuations have been computed. In surface-reflected signals there is fluctuation at frequencies up to 6 cps, while in direct transmission there is negligible fluctuation at frequencies above 0.2 cps. (This work was supported by the Office of Naval Research.)
Acoustic Attenuation in a Liquid Layer over a “Slow” Solid
Authors: Williams A. O.
Published: September 2005

Ewing and Press have discussed acoustic propagation in a liquid layer, over a solid with both compressional wave speed c2 and transverse wave speed ct exceeding c1 for the liquid. When, instead, c2>c1>ct, sound is only partially trapped in the liquid layer, with steady “leakage” into transverse waves. Such a case has been measured in a laboratory model (water over rubber) [R. K. Eby, A. O. Williams, R. P. Ryan, and P. Tamarkin, J. Acoust. Soc. Am. 32, 88 (1960)]; perhaps a compact sand bottom acts similarly. The problem is solved by satisfying acoustic boundary conditions at the interface, for a transverse and two compressional waves; when ct vanishes the equations reduce to the liquid-liquid (Pekeris) case. The eigenvalue for each normal mode is now complex, betokening “leakage.” The real part is altered (relative to liquid-liquid) as if the density of the bottom were decreased. The imaginary part gives an attenuation coefficient, for sound traveling into the liquid layer, roughly proportional to (ct/c1)3, with a complicated dependence on other parameters. The calculation can be extended to include absorption of transverse waves in the bottom—probably the usual situation in a “flabby” material. (Work supported in part by the Office of Naval Research.)
Some Measurements of the Absorption Coefficient of Soil Using the Impedance Tube Technique
Authors: Prout James H.
Published: September 2005

In any field testing involving horizontal propagation of sound, it is desirable to know how much is absorbed by the ground. Since the sound absorption properties of the ground are affected by many factors, it is usually necessary to make an estimate of this effect. This paper describes an experiment to measure absorption coefficient of the soil by means of an impedance tube. Controlled laboratory tests are described which measured the effect of moisture content and particle size on the absorption coefficient. Effects of grass on absorption coefficient are also noted. (This work was sponsored by Project Michigan under a U. S. Army contract.)
Factors which Determine the Sound Transmission Loss of Walls
Authors: Watters B. G.
Published: September 2005

Walls are commonly delineated by a cross-sectional drawing. Although a “one-dimensional” description may be sufficient for building the wall, it does not generally convey enough information from which to calculate accurately the transmission loss. For single walls, the size and the detail at the edges are important [M. Heckl and K. Seifert, “Untersuchungen über den Einfluss der Eigenresonanzen der Messräume auf die Ergebnisse von Schalldāmmessungen,” Acustica 8 (1958); and I. Dyer, WADD Tech. Rept. (to be published)]. These two factors will be discussed in detail in the following paper. For walls separating reverberant rooms, the relative volumes, the sound absorption, and the symmetry of the rooms are important [M. Heckl, “Die Schalldämmung von homogenen Einfachwänden endlicher Fläche,” Acustica 10 (1960)]. For any wall, the angle of incidence of the sound wave is important [A. Eisenber, “Über die Schalldämmung von Glasscheiben und Fenstern,” pp. 34, 35 in Bauforschung im Wohnungsbau, Schwenk and Company, Frankfurt-am-Main, Germany]. The transmission loss of a wall is seen to be a function of many parameters, only one of which is the composition of the wall cross-section. The role of these other parameters and their importance for the testing and use of walls will be discussed.
An Artificial Talker Driven from a Phonetic Input
Authors: Kelly John L. , Gerstman Louis J.
Published: September 2005

This paper describes a method of producing artificial speech from a phonetic input, i.e., symbols representing the names of phonemes corresponding to a given text are fed into a machine and the acoustic waveforms of connected speech emerge. The experimental work was accomplished on an electronic computer (IBM 7090), but the scheme is simple enough to permit realization with analog hardware. The talking machine program is divided into two parts. The first part simulates a more or less conventional resonance synthesizer of the tandem variety, requiring nine control signals; buzz intensity, hiss intensity, pitch, plus the center frequencies and bandwidths of three formants. Initially, this part of the program was used alone in experiments for which the inputs were detailed specifications of the control signals derived from spectrograms and physiological data, sampled at approximately three times the phonemic rate. Results from this phase were later combined with known results in speech perception to produce the rules used by the second program. That program accepts for its input the names of phonemes punched on IBM cards and produces the control signals to drive the resonant synthesizer.
Measurements on Lithium Sulfate Crystals and Lead Metaniobate Ceramic at 10 000 psi
Authors: Sims Claude C.
Published: September 2005

Measurement of the electroacoustic characteristics of lead metaniobate and lithium sulfate as volume expanders in the frequency range 100 cps to 3 kc is described. Two identical stacks of crystals are placed in a small chamber at the same time. The measurement technique is based on the assumption that the change is acoustic impedance of the pressure chamber with with hydrostatic pressure is known, and that consequently any changes in the characteristics of two like crystals, one receiving, the other transmitting, can be determined by measuring the change in the output as a function of pressure. Also, if the electrical impedance of the crystals do not change, then, by reciprocity, any change in the sensitivity of the crystals would multiply the change in the receiver by the change in the transmitter. The possibility of compensating errors is therefore eliminated. Changes in response characteristics measured under pressure by this method are less than ±0.5 db.
Evaluation af a Boundary Layer Stabilization Coating
Authors: Barger J. E. , VonWinkle W. A.
Published: September 2005

The turbulent boundary layer which forms over submarines at even moderate speeds is found to deter from the vessel's effectiveness in at least two ways: drag increase and noise excitation of the hull plates with attendant increase in the near-field noise interference. Several means exist to minimize the extent of the turbulent boundary layer, although only the distributed damping coating appears amenable to shipboard use. The coating discussed in this paper was of the type first proposed By Dr. M. Kramer of the Coleman-Kramer Company. The coating used was fabricated by the U. S. Rubber Company under the direction of Dr. F. W. Boggs, who has, in addition, presented an improvement to the theory of Dr. Kramer. Two gravity propelled missiles were used as test vehicles; one served as a control and the other was covered with the sample coating. Four very small pressure transducers were mounted at the surface of the missiles along their length. These hydrophones were used to give the details of the boundary layer at their respective locations. Data are presented from which estimates of the effect on transition Reynolds numbers by the coating can be made. Also presented are the pressure coefficient and power spectrum of the boundary layer at various locations on the missile, e.g., various pressure gradients. One parameter of the coating itself is varied to adjust the coating performance to the test Reynolds number.
A Study of the Underwater Noise Produced by a Symmetrical Air Flow Generator
Authors: Coop J. J.
Published: September 2005

Aircraft such as helicopters, which may hover over water, produce a rather high level of underwater noise. This noise may be produced by engine exhaust, rotor noise, gear noise, or rotor downwash. In an attempt to separate these noise sources, a two-blade rotor having a diameter of about 8 ft was mounted on a 12-×12-ft platform together with a piston motor and an electric motor, as power sources. Provisions were made for three modes of operation, namely: (1) piston engine driven rotor, (2) electric motor driven rotor, and (3) piston engine driving motor as a generator with rotor disconnected and power dissipated into a resistive load. The piston engine power in mode (3) was made equal to that of mode (1). A constant tip speed and pitch angle were used. Measurements were made at the Philadelphia Naval Base, where the water depth was about 40 ft. The rotor unit was suspended over the water by a crane and the rotor operated by remote control. One-third octave band levels of both air and water noise were recorded. From 400 cps to about 2 kc the underwater noise level produced by the rotor exceeded the exhaust level by about 4 db. The results indicated that the underwater noise was produced by airborne noise rather than by rotor downwash.
Acoustics of the Jerusalem Congress Hall (Binyanae Ha'oomah)
Authors: Beranek Leo L. , Klepper David L.
Published: September 2005

The 3200-seat Congress Hall in Jerusalem, Israel, was completed in the spring of 1960 after a construction period of some ten years. The original primary design goal was to provide a place for large assemblies, the most important of which was the semiannual meeting of the World Zionist Congress. During construction, the repeated use of the partially completed “unroofed” structure for outdoor concerts led to the reconsideration of the original design goals to give primary emphasis to music. The hall now has become the home of the Israeli Philharmonic while still serving its function for congresses and other uses. This paper traces the development of the acoustical design goals as well as discusses the important acoustical design features, the results of measurements made in the completed hall, and the reactions of musicians who have played in the hall.
Calculation of Loudness: 1961 Revision
Authors: Stevens S. S.
Published: September 2005

Steps have been taken to improve the procedure for calculating the loudness of a complex sound. Two changes have been made. (1) The equal loudness contours for bands of noise in a diffuse field [see Noise Control 3, 11–22 (1957)] have been approximated by straight lines in a log-log plot. (2) The spacing of the contours has been altered to reflect the nonlinear growth that takes place in the loudness level of bands of noise when their width exceeds the critical bandwidth. The basic formula for the addition of loudness across frequency remains the same: the total loudness St is given by St=Sm+F(ΣS−Sm), where Sm is the loudest band and F has the values of 0.3, 0.2, and 0.15 for octave, half-octave, and third-octave bands. The revised procedure has the advantages that it can be described more easily and it agrees better with the available measurements on loudness level.
Pitch of High-Pass Filtered Periodic Pulses
Authors: Guttman Newman , Flanagan James L.
Published: September 2005

Earlier pitch-matching experiments [J. Acoust. Soc. Am. 32, 1308–1328 (1960)] using patterns of various polarity configurations showed two modes of pitch perception associated with unfiltered stimuli. A third mode appears when the fundamental-frequency component of the pulse train is rejected. The modes appear successively as frequency increases and correlate objectively with pulse rate, fundamental frequency and the lowest frequency component present in the stimulus. By using similar stimuli and procedure, the present study investigates the effects of severe high-pass filtering (2 and 4 kc). Under these conditions, basilar membrane displacement is restricted to medial and basal regions where the impulse response is short compared to the apical end. The subjective response is to prolong the frequency range over which the pulse-rate mode operates. In some cases the fundamental mode does not appear until the fundamental frequency of the stimulus approaches or becomes greater than the cutoff frequency of the filter. In other words, the classical residue (fundamental) pitch associated with the range 200–500 cps may not be heard. As shown in our previous experiments, these subjective phenomena can be related to the displacement response of the basilar membrane. Simulation of displacement is accomplished by electrical analog networks of the middle ear and membrane.
Pitch Retention by Compensatory Frequency Tracking
Authors: Harris J. Donald , Pikler Andrew G.
Published: September 2005

The accuracy of compensatory tracking of a reference frequency of 250 cps was studied. Over a duration of 6 min this standard was changed at a rate of 3 cycles/second in such a way as to keep each of three programs within the limits of 114 cps on the low, and 370 cps on the high side. One program was symmetrical around 250 cps, one was always the same as or higher than 250 cps, another always the same or lower. Each program contained seven 10-sec plateaus interspersed at 30-sec intervals at 250 cps. Programs and tracking responses were displayed in terms of cps vs time on a paper tape recorder by the device of mounting rotary attenuators on the same shafts as those of the capacitors which allowed for frequency changes. Frequency could be read to the nearest couple of cycles. Analysis of variances showed that, while the 6 trained but generally unmusical S's were somewhat different, the three programs and the three replications of each program did not act as sources of variance. All S's were continuously “undershooting” the programs except on the plateaus. The errors ranged from less than the precision of recording up to 9 cps. It would thus seem that over a 6-min span even unmusical S's can retain rather precisely a pitch sensation in the face of drifts which could, if uncompensated, lead to pitch changes of more than an octave. Evidently the compensated program is sufficient to allow S to simulate a rudimentary form of absolute pitch.
A Scaled-Model Experiment of Wave Propagation in a Randomly Inhomogeneous Medium
Authors: LaCasce I. E. O. , Stone R. G. , Mintzer D.
Published: September 2005

When a series of uniform pulses is transmitted in the ocean, the received pulses vary about an average amplitude in a random manner. A theory developed by Mintzer [J. Acoust. Soc. Am. 25, 922 (1953)] predicts that V2∼k2α2ar, for kr≫1 and ka≫1, where V is the coefficient of variation defined as the fractional standard deviation of a series of pulses, k=2π/acoustic wavelength, α the rms index of refraction variations from unity, a the mean correlation distance, and r the range from source to receiver. In a scaled-model experiment the refractive index variations are caused by heating the medium (water) from below, thus causing turbulent convection. The experimental apparatus will be described and the observations of the dependence of V on the range between source and receiver and on the acoustic frequency will be presented. (Supported by the Office of Naval Research.)
A Scaled-Model Experiment of Wave Propagation in a Randomly Inhomogeneous Medium—II
Authors: Stone R. G. , Mintzer D.
Published: September 2005

When a tank of water is heated from below, the turbulent mixing of warmer, more buoyant water produces thermal inhomogeneities and related variations in the index of refraction. The acoustic fluctuations are determined experimentally as a function of the microstructure parameters. The significant parameters of the microstructure are separately measured with thermistors; provision is made to determine the temperature fluctuations at a single point or the correlation of the fluctuations at two points. The relations between the acoustic and the microstructure fluctuations are then determined, and compared with the theory of Mintzer. There is the interesting possibility of determining the parameters of the temperature microstructure by means of acoustic waves. (Supported by the Office of Naval Research.)
Calculations of Caustic Lines in an Ocean of Constant Velocity Gradient Layers
Authors: Murphy D. A.
Published: September 2005

It is generally recognized that caustics exist in convergence zones near the surface of the ocean. The shapes of these caustic lines along their entire extent from the surface to the bottom of the ocean has been recently studied. Each caustic line consists of two branches connected at a cusp where the caustic first appears caused by a folding wave front. A systematic study of the formation of caustics in media of constant velocity gradient layers has been made. The study starts with the infinite medium with one isovelocity layer above one constant gradient layer and progresses to a many layered ocean closely approximating a real velocity profile and limited by a surface. Calculations of ray paths and wave fronts were made with the IBM 709 computer in order to determine the caustic lines. Plots of range versus initial angle were used to explain points of interest on the caustics. The effects of surface shadow on the caustic lines were shown, and wave fronts in this region were explained. It was found that a two-layer ocean demonstrates the essential features of the caustic lines.
Digital Computer Calculation of Wave Fronts in a Layered Medium of Constant Gradients
Authors: Ostler E. M.
Published: September 2005

An IBM computer program has been written to compute equitime surfaces in a medium of constant velocity gradient layers. The ability to generate wave fronts in this manner allows a more thorough investigation to be made of shadow zones and caustic regions, than was formerly possible. It is also now possible to study directly the phase deviations along an array in a medium which closely approximates the real ocean. The usual ray-tracing techniques of geometrical acoustics are used but, in addition to the usual range and transmission time calculations made at interfaces, depth and range coordinates are calculated for prespecified transmission times. These coordinates then define an equitime surface. The equations used in these calculations are simple rearrangements of the equations for range, depth, and transmission time. A constant phase surface can be generated from the equitime surface by introducing appropriate phase shifts at the boundaries.
Maximixing the Directivity of Arrays of Non-directional Acoustic Receivers
Authors: Lubell A. H.
Published: September 2005

The conditions under which maximum directive gain and receiving directivity are equivalent are reviewed. Then a fundamental method of calculating directivity from given correlation functions for signal and noise based on the original treatise by Faran and Hills is presented. Numerical results are given for line arrays and a particular class of two-dimensional arrays that appear to have optimal realizable directivity of significance in the design of small receiving arrays. Empirical relationships are given for nominal values of directivity and beamwidth of uniform line arrays used for the reception of broadband signals in a background of broadband isotropic noise.