bluuebunny/crossref_metadata_2025 huggingface dataset:
Articulation Reduction by Combined Distortions of Speech Waves
Authors: Martin D. W. , Murphy R. L. , Meyer Albert
Published: September 2005

Previous investigators have shown that speech waves can undergo any one of a number of severe forms of distortion in low ambient noise levels without serious reduction of word articulation. There are well-known notable exceptions (e.g., center clipping). However, it is not enough to avoid these exceptional forms of distortion. In the study reported here it has been demonstrated that combinations of speech-wave distortions, which individually are quite innocuous with regard to word articulation, can be devastating in their combined effect, even in the absence of serious noise. Four types of speech-wave distortion were studied, individually and in combination, as follows: gross attenuation of high-frequency components, multiple echo, random amplitude modulation, and gross irregularity of response-frequency characteristic. Ambient noise was also a controlled environmental condition in some phases of the investigation.
Attenuation and Dispersion of Elastic Waves in a Cylindrical Bar
Authors: Zemanek Joseph , Rudnick Isadore
Published: September 2005

The resonance method has been used to study the attenuation and dispersion of the first longitudinal mode of propagation and the dispersion of the first flexural mode of propagation of elastic waves in a cylindrical, aluminum alloy (24ST) rod. Q was found to decrease monotonically from 2.5×105 to 1.2×105 as the frequency increased from 0.84 to 100 kc. Longitudinal and flexural phase velocities are compared to Pochhammer-Chree theory dispersion curves. Agreement of experimental and theoretical curves is within 0.3%. Similar agreement is obtained when normal flexural modes computed by a modified Timoshenko theory are compared to the experimental resonant frequencies. Measurements of torsional mode frequencies indicate dispersion does not exceed approximately 0.01% in the frequency range of approximately 0.5 to 100 kc.
Diffraction of Electromagnetic Waves by Sound Waves
Authors: Schmitt Hans J.
Published: September 2005

For the diffraction of electromagnetic waves from a standing sound wave, the amplitudes of the first diffraction order are calculated from Born's approximation. If the wavelength of the electromagnetic signal is made comparable to the acoustic wavelength, the first diffraction order vanishes periodically with increasing width of the sound beam because of a destructive interference of scattered waves. The sound-perturbed medium becomes also slightly anisotropic. The diffraction of microwaves by a standing sound wave in oil is measured as a function of sound frequency and polarization of the electromagnetic wave.
Temporary Threshold Shift as an Index of Noise Susceptibility
Authors: Jerger James F. , Carhart Raymond
Published: September 2005

Temporary threshold shift after auditory fatigue was measured in 178 subjects with normal hearing prior to their placement in an environment of high-level noise. In addition, two audiograms were made: one, prior to the noise exposure period; the second, eight weeks after its termination. Results indicated that ears showing hearing losses at 3000 and 4000 cps eight weeks after the noise exposure tended to show longer recovery times on the prenoise exposure fatigue test than ears with no change. These findings are discussed in relation to the prediction of noise susceptibility.
Response of Nonlinear Shock Mountings to Transient Foundation Displacements
Authors: Snowdon J. C.
Published: September 2005

The transient behavior of shock mountings disturbed by steplike displacements that invoke large departures of mount stiffness from linearity is described theoretically and compared with the behavior of an ideally linear mounting. The influence of mount damping upon the transient motion of the mounted item is discussed in detail.

For the majority of step rise times considered, a mount that softens upon compression and is not heavily damped is shown to reduce both the acceleration and displacement experienced by the mounted item below the values observed for a linear mounting or, as is normally the case in practice, a mount that stiffens upon compression. The reduction in acceleration can be comparable with 10 db for quite a wide range of step rise times. It is frequently the magnitude of the acceleration to which the likelihood of damage to the contents of the mounted item may be related.
Dynamic Mechanical Properties of Stretched Natural Rubber
Authors: Fitzgerald Edwin R.
Published: September 2005

Dynamic shear compliance measurements on a vulcanized natural rubber stock have been carried out from 50 to 5000 cps as a function of static elongation in the range 0–400%. Above 300% elongation several very large resonance dispersions appear in the region 1000–2000 cps, but at lower elongations no such resonances are observed. The appearance of mechanical resonance dispersion thus coincides with the development of oriented crystallinity in the stretched rubber as shown from x-ray diffraction data. On the other hand, the magnitudes of the dispersions decrease with increasing elongation above 300% whereas x-ray measurements indicate the amount or extent of crystallinity increases with stretching above 300% elongation. The resonances thus clearly decrease as the crystallinity becomes more perfect or more extensive and hence appear to reflect the imperfections of the crystalline regions formed by elongation rather than the crystallinity itself. Observed changes in the compliance spectrum with time at each elongation also favor this view. Broad retardation dispersions were observed when the rubber was allowed to contract back to elongations below 300% after long times above 300%. These are tentatively ascribed to an extended amorphous state in which the rubber molecules are kept partially extended by very small randomly oriented crystalline regions which persist for some time after retraction. Another interesting feature of the results is an apparent correlation between the percent crystallinity determined from x-ray diffraction and the reciprocal of the general level of storage compliance 1/J′ at frequencies well below or well above the dispersion region.
Noise Bands versus Pure Tones as Stimuli in Measuring the Acoustic Attenuation of Ear Protective Devices
Authors: Webster J. C. , Thompson P. O. , Beitscher H. R.
Published: September 2005

The sound-exclusion properties (acoustic attenuation) of various earphones and ear defenders and combinations thereof were determined by the binaural, free-field, absolute-threshold-shift technique with the psychophysical method of adjustment. The earphones included dynamic earphones in two different sockets and hearing-aid-type receivers with individually molded inserts. The ear defenders included certain conventional and newly developed earplugs and muffs, and a hard-shelled noise-exclusion helmet.

In a preliminary evaluation of a limited number of devices, both tones and noise bands were used as stimuli, and comparative results are shown. In evaluating the effectiveness of some of the newer devices, noise bands alone were used. For the exclusion of external sound, particularly that below 1200 cps, the order of merit for earphone combinations was: (l) large volume muffs with insert phones; (2) helmet with insert phones; (3) semiplastic sockets with dynamic phones; and (4) helmet with dynamic phones. The best combination provided the following amounts of attenuation in the seven octave bands from 75 to 9600 cps: 14, 22, 28, 33, 38, 44, and 40.
Vibrations of Thick and Thin Cylindrical Shells Surrounded by Water
Authors: Greenspon Joshua E.
Published: September 2005

This report treats the free and forced vibrations of infinitely long, thick and thin cylindrical shells surrounded by water. Exact elasticity theory is used to treat unpressurized shells and an approximate shell theory is employed to treat the effects of static pressure, internal fluid, and structural damping. Comparisons are made between the results of the exact and approximate theories.
Effect of Large Interaural Time Differences upon the Judgment of Sidedness
Authors: Blodgett Hugh C. , Wilbanks W. A. , Jeffress Lloyd A.
Published: September 2005

The maximal interaural time difference that could be introduced into one channel without loss of sidedness was determined for various noise bands. Through the presentation of stimuli by several methods it was found that time values vary with frequency of the noise bands, being greater for lower bands. Marked intersubject differences were found. For the lowest and most effective band used (106–212∼), times ranged from 7.5 to 20.6 msec.
Critical Bandwidth and the Frequency Coordinates of the Basilar Membrane
Authors: Greenwood Donald D.
Published: September 2005

Masked audiograms were used to measure critical bandwidth. On the assumption that critical bands represent equal distances on the basilar membrane and that critical bandwidth increases exponentially with distance from the helicotrema, functions were derived which (1) relate critical bandwidth to frequency and to position on the basilar membrane and (2) relate position of maximum amplitude to frequency. The functions are consistent with Békésy's optical observations and Mayer's psychophysical data. The frequency-position function is f = A (10ax − 1). The coefficient a is numerically identical with the coefficient in the exponential function fitting Békésy's elasticity data. Functions of this form fit data from seven other species and the values of the coefficient a seem related to their respective elasticity, functions The interpretation of critical bandwidth as the frequency interval over which the cochlea sums power is supported by data of Mayer, and the hypothesis that critical bands represent equal distances on the basilar membrane is strengthened, one critical band corresponding to one millimeter. Problems for cochlear theory are posed (1) by the apparent equivalence of critical bandwidth, the derivative of the frequency-position function, and the frequency interval over which spatial integration takes place, and (2) by the proportionality of these three at a given point to the compliance at that point.
Perception of Sounds Characterized by a Rapidly Changing Resonant Frequency
Authors: Brady P. T. , House A. S. , Stevens K. N.
Published: September 2005

The perception of sounds characterized by a moving resonance was investigated a series of experiments. Stimuli were generated by exciting a tuned circuit with a short train of pulses of repetition rate 100/sec. The resonant frequency of the tuned circuit was changed in a piecewise linear manner over a 500-cps range. Subjects matched the test stimuli by adjusting the resonant frequency of a fixed (i.e., nonvarying in time) resonant circuit until the test and comparison stimuli were judged to be most alike. Results indicate a strong tendency for subjects to adjust the frequency of the fixed resonant circuit until it is close to the terminal resonant frequency of the time-varying circuit. This tendency depended to some extent on the direction and rate of the frequency change in the test stimulus. The implications of the results for auditory theory and speech perception are discussed briefly.
Further Investigation of the Effects of Intensity upon the Pitch of Pure Tones
Authors: Cohen Alexander
Published: September 2005

Typical methods for observing pitch changes with intensity for pure tones consist of varying the frequency of one tone of fixed intensity (the comparison tone) so as to match the pitch of a second tone of fixed frequency (the tone under test) when the latter is set at different intensities. Differences between the comparison and test-tone frequencies, when equated in pitch under these conditions, are ascribed to their intensity differences and used as a measure of the pitch intensity shifts for the test tone. The comparison and test tones may differ in frequency, however, even when they are matched in pitch under equal intensity conditions. These frequency differences, called pitch-matching errors, may be identical to those noted above for comparable conditions and consequently nullify the apparent pitch-intensity shifts. This possibility was studied in two experiments which sought to reproduce the pitch intensity relationship as defined by the data of Stevens and Snow. In more than half the comparisons made under various frequency and intensity conditions, apparent pitch shifts for 50, 75, 100, 200, 400, 700, 1500, and 6000 cps were found to be not significantly different from pitch-matching errors. When averaged, the remaining shifts followed the directions of Stevens' curves but were small (2% or less). Pitch-intensity functions for the lower frequency tones were particularly variable and generally bore little relationship to Snow's functions for such tones.
Acoustic Wattmeter
Authors: Schultz T. J.
Published: September 2005

The author has constructed a device which gives pointer indications of acoustic intensity over a 50-db range at frequencies up to 10 000 c/sec.

The signals from a pair of pressure-sensitive condenser microphones, mounted back to back in a space roughly the size of a dime, are treated electronically to provide pressure and velocity signals which are then multiplied and averaged in a specially designed moving-coil dynamometer to give precise pointer readings.

The theory of operation of the apparatus is discussed and the paper concludes with a brief account of the test results of the acoustic wattmeter.
Comparison of the Acoustical Performance of Calfskin and Plastic Drumheads
Authors: Hardy Howard C. , Ancell James E.
Published: September 2005

This investigation reports acoustical differences found for drumheads made of Mylar plastic instead of the conventional calfskin. Two identical bass drums and two identical field drums were fitted with heads of the two materials. A professional drummer was engaged to adjust and play these drums with several tension adjustments. A tape-recorded analysis was made of their sounds, including single impact beats and steady rolls. The sound spectra of the quasi-steady-state drum rolls were determined by half-octave bands, by a method similar to that of Sivian, Dunn, and White. Spectra of the peak sound-pressure levels were obtained with a General Radio impact sound analyzer. The buildup and decay of the drum sounds were analyzed in chosen frequency bands by use of a high speed level recorder. The chief physical differences found are: (1) the calfskin head is capable of a much larger range of tension adjustment, and (2) under certain conditions has more damping. When the bass drum is tuned to concert tightness, there is a significant difference between the spectra of the plastic and calfskin drumheads and in the time variation of sound output. For the field drum there is little spectral difference, but the calfskin gives a more staccato beat with less “metallic” ringing.
Transducer Calibration by Impedance Measurements
Authors: Sabin Gerald A.
Published: September 2005

A self-reciprocity free-field response calibration of a resonant electroacoustic transducer may be determined in a small water-filled tank by only two electrical impedance measurements at each discrete frequency point. The use of a pulse technique permits the measurement of electrical impedance under two conditions: (1) in a free field and (2) under the influence of a totally reflected signal. The vector difference between these two impedances together with the reciprocity parameter (J) establish the free-field response. No measurement of voltage, current, or power is required; the ratio of the hydrophone voltage to the projector current is measured as an impedance vector. This method is particularly applicable in the ultrasonic frequency range.
Response of Hard-Spring Oscillator to Narrow-Band Excitation
Authors: Lyon Richard H. , Heckl Manfred , Hazelgrove C. Brian
Published: September 2005

The response of an oscillator with a nonlinear stiffness of the hard-spring type to narrow band Gaussian random noise is analyzed theoretically by using the method of quasi linearization. The particular point of interest is the possibility of an occurrence of multiple valued response or “jumps” such as one observes when the exciting force is sinusoidal. It is argued that while it does not seem possible to have multivalued response with wide-band (white noise) excitation, the response to narrow band excitation might exhibit such behavior owing to the temporal correlation of the source with the response. Numerical computations of the response curves do suggest multivalued response. In experiments with a nonlinear oscillator, multivalued response was observed, but agreement between theory and experiment may only be claimed to be qualitative.
Comment on “Experimental Study of the Scattering of Acoustic Energy from Solid Metal Spheres in Water”
Authors: Goodman Ralph R.
Published: September 2005

Hampton and McKinney recently reported that the backscattered target strength from a sphere is essentially invariant for short pulses but fluctuates rapidly for long pulses as the frequency is changed by a few percent. By a Fourier transform analysis it is shown in this letter that the above result is to be expected. A small change in frequency does not significantly change the transform of the short pulse but drastically shifts the long pulse transform. The argument only holds if the steady-state scattering amplitude is rapidly varying over the frequency range considered, a condition which is met by the Hampton and McKinney experiment.
Axial-Shear Vibrations of an Infinitely Long Composite Circular Cylinder
Authors: Baltrukonis J. H. , Gottenberg W. G. , Schreiner R. N.
Published: September 2005

Exact general solutions of the three-dimensional elasticity equations of motion in polar cylindrical coordinates are written for axisymmetric and antisymmetric axial shear vibrations. The frequency equation follows immediately from the boundary conditions for the problem of the infinitely long, composite cylinder with two concentric circular-cylindrical layers which are perfectly bonded at their interface. The branches of the frequency equation are plotted and analyzed. The conditions are pointed out under which it is possible to obtain reasonably accurate estimates of the natural frequencies by assuming that the motions of the casing and core are uncoupled.
Effect of Damping on the Natural Frequencies of Linear Dynamic Systems
Authors: Caughey T. K. , O'Kelly M. E. J.
Published: September 2005

An analysis is presented of the effect of weak damping on the natural frequencies of linear dynamic systems. It is shown that the highest natural frequency is always decreased by damping, but the lower natural frequencies may either increase or decrease, depending on the form of the damping matrix.
Derivation of the Free-Space Scalar Green's Function
Authors: Robey Donald H. , Potts Donald H.
Published: September 2005

The free-space Green's functions which satisfies the inhomogeneous scalar wave equation is derived by a simple and direct method.
Nonlinear Response of a Simple Clamped Panel
Authors: Smith P. W. , Malme C. I. , Gogos C. M.
Published: September 2005

Measurements are reported of some characteristics of the response of a simple panel to a steady periodic sound pressure intense enough to cause nonlinearity in the response. The panel is a 2-in. wide, thin aluminum strip, clamped at its ends with the clamp faces 12 in. apart, and left free on its edges. Attention is focused principally on the fundamental resonance point, which occurred at frequencies as large as twice the low-level resonance frequency.

Measurements of the frequency and strain at resonance, under various levels of excitation, are compared with predictions from a simple one-mode nonlinear dynamic equation. For good agreement it is found necessary to include not only a nonlinear stiffness but also a nonlinear damping term. Theoretical predictions of the nonlinear stiffness from the physical characteristics of the panel are in error by a factor of 4.7 when based on an assumed mode shape for transverse deflection which is identical with the linear characteristic function of a clamped-clamped beam.
Long-Range Shallow-Water Transmission
Authors: Mackenzie K. V.
Published: September 2005

Computation of propagation losses are presented for 200- to 2000-cps sound in 25-fathom water to ranges of 250 miles over different bottoms for a zero gradient (isospeed), and out to 50 miles for a both weak negative gradient and a strong negative gradient. The ray method is used, together with the assumption of random phase after the first bottom reflection, to formulate the theory. The resulting computed transmission loss anomalies exhibit a marked dependence on: (1) the ratio of source depth to wavelength, (2) the sound-speed gradients, and (3) bottom reflection losses at small grazing angles. The bottom reflection losses are strongly dependent on the attenuation in the bottom. Some long-range experimental data are presented which show a quantitative agreement with the computed curves out to ranges of 40 miles.
Radiation from Circular Pistons of Elliptical Profile
Authors: Silbiger Alexander
Published: September 2005

While extensive information is available on flat pistons and on spherical radiators, no data have been given in the literature for the intermediate case of convex circular pistons of elliptical profile. In order to fill this gap, this paper presents information on the radiation loading and on the near and far field of such pistons. For the case of a free piston it is found that at small ka (where 2a is the diameter or major axis) the reactance decreases with increasing thickness (minor axis), while the resistance increases at small ka and decreases at large ka with increasing thickness. In the intermediate ka-region, that is, when the wavelength in the fluid is of the order of magnitude of the dimensions of the piston, the dependence of the impedance on the thickness is more complicated. For the case of a piston in an infinite baffle the behavior of the reactance is similar to that for the free pistons. The resistance however is independent of the thickness in the limit of small ka and decreases with increasing thickness at larger ka. The effect of flexure on the impedance is briefly considered for the case of the free piston.
Calculation of the Loudness of Complex Noise
Authors: Stevens S. S.
Published: September 2005

Charts and formulas are presented for the calculation of the loudness of noises having approximately continuous spectra. By means of direct loudness matches it is shown that the loudnesses in octave bands can be combined according to the formula St = Sm+0.3(ΣS − Sm), where St is the loudness (in sones) of the total noise, Sm is the loudness of the loudest band, and ΣS is the sum of the loudnesses of all the bands. The loudnesses of the octave bands can be determined from measurements of their sound pressure levels by means of a chart based upon a new determination of the equal loudness contours for bands of noise. Other charts and formulas are presented for half- and third-octave band widths.

Measurements were also made of the dependence of loudness on such factors as (a) separation between noncontiguous bands, (b) width of very narrow bands, and (c) rate and level of square wave modulation.
Criteria for Office Quieting Based on Questionnaire Rating Studies
Authors: Beranek Leo L.
Published: September 2005

In order to discover what are the maximum noise levels that office personnel find acceptable and what their reactions are to noisy offices, a survey was carried out at a large air base. A questionnaire composed of 15 rating scales was administered to 190 people scattered over 17 different locations on the base. The rating scales allowed the workers to assess such things as the “noisiness” of their environment and to appraise the effect of noise on various aspects of their work, such as their ability to converse or to use the telephone.

The results obtained with the rating scales were compared with various physical measures of the noise. A high correlation was found between perceived noisiness and the measure called “speech interference level” SIL, which is the average of the sound pressure levels measured in the three octave bands between 600 and 4800 cycles per second. An even higher correlation was found between the ratings of noisiness and a computed measure of loudness level. More than two-thirds of those questioned stated that speech communication was an essential part of their activities and that the more intense noises in their offices interfered with it. These correlations provide a basis for setting criteria for the maximum noise acceptable in terms of SIL and of loudness level. These results, plus those from a previous study, suggest that the maximum continuous noise levels acceptable for office spaces in which speech communication is important should not exceed an SIL of 40 db. Office employees are accustomed to a noise spectrum of a form that yields a loudness level of about 22 units higher than the SIL. Complaints are encountered when the loudness level exceeds the SIL by 30 or more units. Thus, with an SIL of 40 db the loudness level should preferably not exceed about 62 phons. Only under special conditions with this SIL would it be advisable to exceed a loudness level of 70 phons.

For intermittent noises, such as the noises produced by aircraft operations, evidence is presented to show that the mean (average) value of the SIL and loudness level should not exceed the numbers for steady noises if the work of office employees is not to be disturbed.
Problems of Field Measurement of Transmission Loss as Illustrated by Data on Lightweight Partitions Used in Music Buildings
Authors: Lane R. N. , Mikeska E. E.
Published: September 2005

Field measurements of airborne sound-transmission loss involve several practical difficulties and limitations as compared to the laboratory standard test procedures for such measurements. Data from field measurements are valuable to architects and acoustical consultants, in spite of these limitations. A workable procedure for field measurements is described, along with a discussion of the difficulties. Measured transmission loss data are presented for double plaster walls on cork isolation, double plaster walls on concrete slabs, double concrete block walls, double brick walls, single concrete block walls, and a floor slab with resiliently suspended plaster ceiling.
Onset and Growth of Aural Harmonics in the Overloaded Ear
Authors: Lawrence Merle , Yantis Phillip A.
Published: September 2005

The threshold of overload and the growth in intensity of the aural harmonics are determined by the exploring tone method for frequencies of 100, 350, 1000, 2000, and 5000 cps. It is found that the level of a test tone at which it first overloads the ear can be quite accurately determined and that the range of beats between the second harmonic and the exploring tone, as the latter is changed in intensity, is considerably narrower at the overload threshold level than at higher levels. As the test tone is raised in intensity the loudness of the harmonic increases rapidly.

Overloading occurs at approximately the same sound pressure level for all frequencies so that the range of linear response is around 8 db at 100 cps, 30 db at 350 cps, and 50 db at 1000, 2000, and 5000 cps. All harmonics are detected when they reach a certain consistent level above threshold for that frequency. The exact level depends upon the subject.

These results are considered as additional evidence that distortion in the ear takes place within the sensory cells as part of the electromechanical process and is not due to any nonlinearity of the mechanical response of the ear.
Some Measurements of Interaural Time Difference Thresholds
Authors: Klumpp R. G. , Eady H. R.
Published: September 2005

Thresholds for the detection of interaural time difference were determined by ten listeners (1) for band-limited random noise (150–1700 cps), (2) for a 1000-cps tone, and (3) for a 1-millisecond click. The average interaural time differences corresponding to 75% correct detection in the symmetrical two-alternative tests were (1) 9 microseconds, (2) 11 microseconds, and (3) 28 microseconds. Ranges of individual thresholds and group psychometric functions are presented.
Perception of Pitch, Timbre, and Loudness
Authors: Jenkins Robert A.
Published: September 2005

If a narrow bandpass filter is driven by a periodic train of narrow rectangular pulses, the resultant wave train elicits a strong pitch perception which varies monotonically with the pulse repetition rate. This periodic wave train can be used as a pitch reference to match against various stimuli. Consideration of double wave train stimuli with various delays establishes sharp dichotomy between the perception of pitch and timbre. Further evidence is adduced in support of the development of a partial model of psychoacoustic perception which is plausible in terms of the known physiologic mechanisms. In brief, the total acoustic stimulus undergoes a differential filtering action along the cochlear partition due to the resonant characteristic of the cochlear structure. The response characteristic of any particular segment of the partition exhibits a single broad peak and consequently has a relatively fast time response. The envelope of the response is assumed to be detected by a relaxation detector having a relatively wide dynamic range, and periodicity of the envelope is detected by a delay-line detector. The second-order time envelope of the cochlear-partition response defines a function over the length of the partition. The shape of the envelope (along the partition) of the absolute value of this function elicits the perception of the timbre structure of the total stimulus. The total area under this envelope elicits the perception of the loudness of the total stimulus. This combination of broad-band spectral filtering, envelope detection, and delay-line periodicity detection provides both a mechanism for relatively sensitive pitch discrimination and for spectral discrimination with relatively fast time response.
Loudness Adaptation for Bands of Noise
Authors: Carterette Edward C.
Published: September 2005

Loudness adaptation may be measured by a simultaneous loudness balance, or, as in the two experiments reported below, by a median plane localization of a dichotically presented acoustic stimulus. The loudness of a steady auditory stimulus generally decreases with time. That is, the intensity of a comparison stimulus in the rested ear is ordinarily set below the intensity in the stimulated ear.

Two experiments were done on loudness adaptation for bands of noise. In Experiment 1, using 36 subjects, loudness adaptation for a wide-band thermal noise of 100–5000 cps was studied as a function of five SPL's: 40, 70, 90, 100, and 105 db over all. The mean maximum loudness adaptation obtained was 2.3, 9.9, 11.4, 14.4, and 16.3 db, respectively. The mean standard deviation for all measures was 6.1 db, and the distributions of the sets of measures tended to be skewed toward greater adaptation.

In Experiment 2 (12 subjects), the loudness adaptation for a 1500-cps tone was compared with that for bands of noise whose centers (mel scale) were at 1500 cps, and whose over-all SPL's were equal to the SPL of the pure tone. The band limits in cycles per second were 1280–1120, 1075–1950, 720–2600, and 100–4900. For each band, adaptation was measured for 50, 70, and 90 db SPL over all. The essential results are: (1) Loudness adaptation for 1500 cps is about 8.5 db greater than the maximum adaptation for any noise band at any SPL; (2) Adaptation is small (4.5 db) at 50 db for all bands of noise; it is complete within one minute and is about equal for all band widths; (3) At 70 and 90 db, time taken for complete adaptation increases and the two widest bands give greater adaptation than the two narrowest bands. At 90 db a trend becomes clear: the wider the band, the greater the degree of adaptation and the longer the time required for maximum adaptation to be attained.
“Human ‘Cross-Correlator’”—A Technique for Measuring Certain Parameters of Speech Perception
Authors: Cherry E. Colin , Sayers Bruce Mc A.
Published: September 2005

A human listener is here regarded as a “cross-correlator”; his two ears are treated as “input terminals,” stimulated with the acoustic input signals f1(t) and f2(t+τ), while his vocal responses are treated as the output “correlation function.” The two signals are, respectively, pure and distorted versions of the same signal (perhaps speech). The delay τ is randomly set and the listener answers right or left, as the source of sound appears to him to lie. The “correlation function” then corresponds to the probability distribution of his correct judgments. Such functions represent the degree of aural fusion, and show up strikingly the invariants of speech signals which are significant in aural perception.
Stimulus vs Response Uncertainty in Recognition
Authors: Swets John A. , Sewall Susan T.
Published: September 2005

We raise again, in the framework of a very simple recognition task, the question of the relative efficacy of specifying the stimulus alternatives before and after the stimulus is presented. Our experiments show information given before the observation to facilitate recognition and information given after the observation to have little, if any, effect. We conclude that the facilitative effect of restricting alternatives, in the task studied, depends on a perceptual mechanism rather than on a response mechanism. These experiments are discussed in connection with two current psychological theories: the theory of signal detectability, which is essentially a perceptual theory, and the theory of individual choice behavior, which is essentially a response theory. The results of another experiment, the only other experiment discovered to date for which these two theories make different predictions, are also reported. In this experiment, too, the results are in agreement with the detection theory.
Some Preliminary Experiments on Binaural Time Delay and Intelligibility
Authors: Schubert Earl D.
Published: September 2005

Comparisons are made of the intelligibility of continuous speech in noise under three listening conditions: Speech arriving simultaneously and in phase at the two ears; speech arriving at one ear later than the other; and speech arriving simultaneously, but in opposite phase in one ear. Time intervals between ears ranged from 200 μsec to 7 msec. Delaying speech to one ear under these conditions does increase intelligibility but is little, if any, better than the simple expedient of wiring the phones so that the wave form at one ear is inverted with respect to the other. With the materials and method used, the maximum increase occurs with a delay between ears somewhere between 0.5 and 1 msec, though there is some indication that delays 1 msec and longer may be slightly better under the most difficult listening conditions tried.
Effects of Vocal Force on the Intelligibility of Speech Sounds
Authors: Pickett J. M.
Published: September 2005

Measurements were made of the intelligibility of speech heard in noise and produced by different amounts of vocal force. Vocal force ranged from the weakest voiced whisper to a very heavy shout. The results show less than 5% deterioration in intelligibility over the range from a moderately low voice to a very loud voice (55 to 78 db in a free field at one m from the lips). Beyond these points intelligibility decreases abruptly and in a linear relation to decibel change in vocal intensity. Listeners' errors are analyzed to determine the effects of the extremes of vocal force on the intelligibility of different parts of the syllable and of different vowels.
Identification and Discrimination of Components of Elementary Auditory Displays
Authors: Pollack Irwin
Published: September 2005

The absolute identification and differential discrimination of the sound level of tones were studied over a wide range of sound levels under comparable experimental conditions, and the results of the two experiments were compared in comparable units. Absolute identification improves and differential discrimination deteriorates as the range of sound levels examined increases. The net effect of these complementary changes is that the information associated with differential discrimination is roughly of the same magnitude as that associated with absolute identification.
Response of Strings to Moving Noise Fields
Authors: Maidanik Gideon , Lyon Richard H.
Published: September 2005

A re-examination of Lyon's experimental results on turbulent excitation of strings is made in the light of new information on boundary-layer turbulence and on extended theoretical calculation. It is shown that the extended theory together with reasonable modifications in the parameters describing the turbulent flow leads to better agreement between experiment and theory.
Successful Method of Attack on Plane Progressive Finite Waves
Authors: Fay R. D.
Published: September 2005

The characteristic feature of the method is that at any point in the sound field the conservation criteria are expressed in terms of the instantaneous values of the speed of propagation, the particle velocity, the excess pressure, and excess density. These criteria, together with the adiabatic assumption, determine explicit relations between any two of these quantities. Excess pressure and excess densities are here defined as departures from the equilibrium values that exist at the instant when the particle velocity is zero.

For waves of finite amplitude these equilibrium values, as well as the speed of propagation, are found to depend on the intensity. The increment in the speed of propagation does not agree with that obtained by classical methods of analysis. The discrepancy found to be due to the omission in the classical forms of the continuity criterion of a term that specifies the effect of the rate of change in the speed of propagation.
Simple Form of the “Sing-Around” Method for the Determination of Sound Velocities
Authors: Ficken George W. , Hiedemann E. A.
Published: September 2005

An arrangement for the determination of sound velocities in liquids by means of measuring pulse repetition rates is described which, although very simple, allows an accuracy of better than 1%.
Higher Modes of Radial Vibrations in Short, Hollow Cylinders of Barium Titanate
Authors: Stephenson C. V.
Published: September 2005

This paper discusses the forbidden and allowed modes of radial vibrations in hollow cylinders of barium titanate. Theoretically, for a given ratio of outside diameter to inside diameter, it is possible to predict which of these higher modes will be observed. The theory has been checked experimentally and, within the limits of the experiment, has been found to be true.
Ultrasonic Stroboscopes for the Study of Ultrasonic Fields
Authors: Gessert W. L. , Hiedemann E. A.
Published: September 2005

The possibilities and limitations of different ultrasonic stroboscopes described by Bär for the special purpose of studying ultrasonic phenomena were investigated in greater detail. One type is appropriate for the measurement of the velocity of propagation of progressive ultrasonic waves. A modified setup offers special advantages for the precise determination of the sound velocity in a liquid relative to a standard liquid. Another optical arrangement is best suited for the study of ultrasonic fields; it was used for direct measurements of the Rayleigh phase shift at a liquid-liquid interface and for photography of the phase field before an ultrasonic tranducer.
New Method for the Calibration of a Plane Hydrophone
Authors: Laufer Arthur R. , Thomas Garland L.
Published: September 2005

The high-frequency calibration of a plane disk hydrophone of large diameter by the usual plane-wave reciprocity method is a difficult task, requiring a large anechoic tank and precise mechanical alignment gear. A new and absolute calibration technique utilizing the radiation pressure of a standing wave system is described. The calibration curve of a barium titanate hydrophone of diameter 1.5 in. and of resonant frequency 1.0 mc is presented over the frequency range of 300 to 5000 kc.
Sawtooth Shock as a Component Test
Authors: Morrow Charles T. , Sargeant Homer I.
Published: September 2005

The shock effect of a terminal-peak sawtooth of acceleration obtained by a drop onto a lead pellet has been investigated experimentally using the shock spectrum as the criterion of severity. It is shown that this spectrum obtained by analysis of the acceleration-time data can be made to approximate closely over a wide frequency range that obtained theoretically for an ideal sawtooth. The smoothness of the spectrum which results from the extreme asymmetry. of the pulse shape makes the sawtooth particularly attractive standard pulse shape for shock test in the laboratory.
Optimum Hydrophone Design for Low Frequencies
Authors: Hueter T. F. , Moose P. H.
Published: September 2005

In a recent paper, P. M. Kendig emphasizes the importance of efficiency in the design of an optimum hydrophone. However, in most applications, the threshold of signals that may be measured is determined essentially by the self-noise of the associated preamplifier. Therefore, in practice, the highest sensitivity hydrophone will result in the best signal-to-noise ratio.

Because of the availability of high-grade ceramics and high-impedance preamplifiers. the significant problem facing the designer is which physical configuration to employ. The comparative equations of Table I of the reference paper may be misleading in the selection of the optimum physical shape, which, as demonstrated by a practical example, should be dependent on consideration of sensitivity and impedance.
Electronic Control of Noise, Vibration, and Reverberation
Authors: Olson Harry F.
Published: September 2005

Existing passive materials are inadequate to cope with many problems in the control of noise, vibration and reverberation. It is only within quite recent times that active systems have been given consideration for the control of sound. The electronic sound absorber is an example of an active-type sound absorber. The electronic sound absorber consists of a microphone, amplifier, and loudspeaker connected in an inverse feedback manner. The electronic system reduces the effective acoustical impedance in the vicinity of the absorber. As a consequence, the electronic sound absorber may be used in the manner of a conventional sound absorber or as a zone-type sound reducer. The electronic vibration reducer consists of a sensor, amplifier, and driver connected either in negative or positive feedback fashion. The electronic vibration reducer may be used to isolate vibrating machines or to reduce the vibration of machines.
Role of Equivalent Noise Pressure and Sensitivity in Determining Signal-to-Noise Ratio
Authors: Kendig Paul M.
Published: September 2005

The relative importance of the receiving sensitivity, impedance, efficiency, and equivalent noise pressure of a hydrophone in determining signal-to noise ratio is discussed. It is concluded that even when the threshold is determined by the self-noise of the preamplifier, it is the equivalent noise pressure, or rather the efficiency, that ultimately determines the signal-to-noise ratio, provided the hydrophone impedance is taken into account.
Measured Absorption Characteristics of Resonant Absorbers Employing Perforated Panel Facings
Authors: Mikeska E. E. , Lane R. N.
Published: September 2005

Reverberation chamber measurements are presented for resonant absorber constructions covering a range of resonant frequencies. Types of constructions tested were (1) thick layers of porous material covered by the facing and backed by a hard wall and (2) facings covered with a resistive cloth layer and mounted with air space backing. Measurements were made with thicknesses up to 1412 in. behind the panel to secure high absorption at low frequencies.
Ultrasonic Relaxation in Freon Vapors
Authors: Miyahara Y. , Richardson E. G.
Published: September 2005

From the point of view of their use in supersonic wind tunnels in which it is desired to obtain a high Mach number without great expenditure of power, the substitution of the air by vapors having a low velocity of sound is of interest. The freons (halogen-substituted methanes) suggest themselves for this. It is shown that these vapors have ultrasonic relaxation times in the neighborhood of 10−7 sec coupled with high absorption coefficients in the ultrasonic range, a fact which may limit their usefulness in wind tunnels. The relation between relaxation times measured by other methods and by the present one are discussed.
Backscattering of Sound from the Sea Surface: Its Measurement, Causes, and Application to the Prediction of Reverberation Levels
Authors: Urick R. J. , Hoover R. M.
Published: September 2005

In many applications of underwater sound, the “reverberation,” or backscattered return, from the sea surface is the limiting background in which the desired echo appears. Little has been known about sea-surface backscattering in spite of its importance to the prediction of reverberation levels in practical applications.

Using two transducers—one for transmitting, one for receiving—mounted so as to be rotatable in a vertical plane and suspended from a buoy, measurements have been made of the backscattering of sound pulses from the surface of the sea as a function of grazing angle between 5 and 90 degrees, wind speed between 3 and 18 knots, and pulse length. When converted to a scattering coefficient per unit area, the results provide some hints as to the processes by which sound is scattered by the ocean surface, and give the basic data for computing the reverberation to be expected with transducers of arbitrary beam width and orientation.
Reduction of Speech Spectra by Analysis-by-Synthesis Techniques
Authors: Bell C. G. , Fujisaki H. , Heinz J. M. , Stevens K. N. , House A. S.
Published: September 2005

Procedures are described for reducing the speech wave to a specification in terms of the time-varying vocal-tract resonances and source characteristics. The basic method, which has been called analysis by synthesis, involves the comparison of speech spectra with a series of spectra that are synthesized within the analyzer. Each comparison spectrum is generated according to a set of rules based on an acoustical theory of speech production. The result of the analysis of each input spectrum is a set of parameters that describes the synthesized spectrum providing the best match. In one version of the method convergence, towards the best match is controlled by the experimenter; in another version convergence to a match is accomplished automatically without the intervention of the experimenter. All the operations have been programmed on a general-purpose digital computer and have been applied to the analysis of vowels and some consonants. The advantages of the analysis techniques are discussed.
Methods of Measuring Vowel Formant Bandwidths
Authors: Dunn H. K.
Published: September 2005

The damping constants of vowel formants, as expressed in the half-power bandwidths, have been studied from the reports of several investigators. The accuracies of methods of measurement used have been estimated through application of the same methods to an electrical analog of the vocal tract. Two new sets of measurements are presented, one on spectrograms of real speech, the other making use of an artificial larynx, applied to real subjects. It is concluded that, while wide individual variations occur, the average bandwidths for male voices probably lie in the lower range of those which have been reported.
Axisymmetric Modes of Vibration of Thin Spherical Shell
Authors: Baker Wilfred E.
Published: September 2005

In this paper we present a detailed study of the theory of free, axisymmetric vibrations of thin elastic spherical shell and demonstrate by experiment that the normal modes of vibration predicted by theory do exist. The theory, which is an expansion of an ancient study by Lamb, predicts the existence of two infinite sets of normal modes, one of which is bounded in frequency and the other unbounded. The first four modes in each set are identified by experiments on a small steel shell.