bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustics of the Binyanei Ha'Oomah Jerusalem Congress Hall
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 10 years. The original primary design goal was to provide a place for large assemblies the most important of which was the biennial meeting of the World Zionist Congress. During construction, the repeated use of the partially completed “unroofed” structure for out door concerts led to the reconsideration of the original design goals to give primary emphasis to music. The hall now has become the Jerusalem 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.
Resonant Displacement of Nickel and Permendur Magnetostrictors under Static Compressive Stress
Authors: Whymark Roy R. , Witting James M.
Published: September 2005

Relative resonant displacement of bar magnetostrictors as a function of polarization at atmospheric stress and at a compressional, axial stress of 230 atm is measured. Laminated bars of nickel and 2V-permendur are driven at frequencies both at and well below the resonant frequency of the bars, about 23 kc. Measurements of the Q and the reversible permeability enable one to compare the magnetostrictive constants and the coupling at the two stress levels for both materials.

The resonant displacement was found to change only slightly upon application of the compressive stress, for polarizing fields up to 100 oe. The compressive stress increased the maximum coupling for permendur by about 10%, the stress decreased the maximum coupling for nickel by about 10%.
Phonetic Typewriter
Authors: Olson Harry F. , Belar Herbert
Published: September 2005

The important factors involved in the development of a phonetic typewriter are as follows. The particular form in which the words are typed. The means for analyzing the sounds of speech. The identification of the analyzed sounds. The encoding, coding, and decoding of the sounds for the operation of the actuating mechanism. The design of the mechanism for actuating the typewriter. A study has been made of these problems. As a result of this study a simplified model of a phonetic typewriter has been developed incorporating all of these aspects. This model serves to illustrate the principles involved and provides means for further study towards a complete system.
Propagation of Acoustic Pulses from a Circular Cylinder
Authors: Barakat Richard G.
Published: September 2005

In two-dimensional linear acoustic theory Huygens' principle fails; the failure of Huygens' principle being manifested by the existence of a tail to the acoustic pulse. A two-dimensional problem of importance is the radiation of acoustic pulses of various shapes by an infinitely long circular cylinder. The problem is attacked directly via the use of the Laplace transform. In the inversion of the Laplace transform, relatively new function called the Nielsen W0 function is encountered. Exponential, sine, and rectangular pulses are studied and their shape determined at various distances from the cylinder. Finally the passage to the steady state of a semi infinite sine wave train is outlined.
Some Notes on the Reflection of Sound from a Rigid Corrugated Surface
Authors: LaCasce E. O.
Published: September 2005

The Rayleigh solution for reflection from a corrugated surface, and some possible modifications, are examined. For small slopes these methods produce similar analytical expressions and almost identical numerical results. When the first nonradiating term is included in the computations, the magnitude of the scattered amplitudes is essentially the same, but an estimate of the phase change as a function of frequency is provided. For larger slopes, differences appear in the analytical form as well as in the numerical results. The Rayleigh expression has advantages above cutoff, while a new approach seems better before and just after cutoff.
'Twixt Earth and Sky with Rod and Tube; the Mobility and Classical Impedance Analogies
Authors: Firestone Floyd A.
Published: September 2005

The techniques which comprise the mobility analogy have been introduced into the classical impedance analogy. The mobility and impedance analogies are set forth in form for practical use. The completely dual character of these two analogies is rendered evident by placing the elements of the mobility analogy on a series of left-hand pages and the dual elements of the impedance analogy on the facing right-hand pages. In each analogy a set of mechanical and acoustical symbols is provided so that mechanical and acoustical schematic diagrams can be drawn without the necessity of drawing either of the analogous electrical schematic diagrams. These mechanical and acoustical symbols resemble somewhat their analogous electrical symbols so as to indicate to anyone familiar with circuit theory the algebraic operations which are to be performed in the analysis.

Whereas in an electrical schematic straight line represents an ideal wire, in a mobility schematic a straight line represents an ideal incompressible massless rod; in an impedance schematic a line represents a hydraulic tube filled with ideal massless incompressible liquid which can sustain either tension or compression.

Correct mobility schematics are obtained by inspection through considering each mass as having one terminal fixed in a frame of reference called the earth which has zero mobility and infinite mass and is analogous to electrical ground; correct impedance schematics are obtained by inspection through considering each spring as having one terminal fixed in a force of reference (P0, etc.) called the sky which has zero impedance and infinite compliance (in both cases the analogous electrical element is a conducting sphere in free space, not a condenser). Although it is recommended that analogous electrical circuits not be used in routine analysis, they can be copied directly from a mobility schematic by considering mechanical earth analogous to electrical ground, or copied directly from an impedance schematic by considering mechanical sky analogous to electrical ground.
Equivalent Circuit of a Resonant, Finite, Isotropic Elastic Circular Disk
Authors: Sharma Roshan Lal
Published: September 2005

The equivalent circuit of a finite circular disk resonant at any frequency corresponding to the first three axially symmetric flexural modes is obtained from a function of two dynamic variables; (1) the kinetic energy in the disk, (2) velocity of the mechanical motion. This function, called the equivalent mass, is computed over a domain of arguments which is of practical interest. The results indicate fairly good agreement between theory and practice.
Differential Effect of Instructions upon the Rate of Oral Reading
Authors: Schwartz Martin F.
Published: September 2005

A study was designed which considered the effects of two sets of printed instructions upon oral reading rate. The first set explicitly required one group of subjects to attempt to read a series of sentences naturally, while the second set explicitly required another group of subjects to attempt to communicate the meaning of the sentences to the experimenter as they read them. Statistical treatment of the data revealed that those subjects instructed to “read to communicate” required significantly more time to read a series of sentences than those subjects instructed to “read naturally.”
Determination of the Elastic Constants of Optical Glasses by an Ultrasonic Method
Authors: Barnes James M. , Hiedemann E. A.
Published: September 2005

The values of the elastic constants of twelve samples of optical glass commercially produced in the United States and a sample of fused silica were calculated from the results of measurements made on these samples. The method used was a combination of the ultrasonic method developed by Schaefer-Bergmann with that of Hiedemann.

The accuracies of the experimentally determined values of the longitudinal and shear wave velocities were 0.13% and 0.25%, respectively, while the accuracies in determining the elastic constants were 0.5% for the shear modulus, Lame's modulus, and the bulk modulus, 0.7% for Poisson's ratio, and 0.8% for Young's modulus. The values of the surface tensions of the samples were calculated using the results of the measurements and Auerbach's equation.
Binaural Interaction of Clicks of Different Frequency Content
Authors: Deatherage Bruce H.
Published: September 2005

Results from previous experiments have suggested the notion that the neural information for the lateralization of brief sounds comes largely from the basal turn of the cochlea. An examination of that notion which uses stimuli at the two ears of different frequency content shows that the relation is not so simple. When stimulus clicks to the two ears are identical, then approximate simultaneity places a unitary click-image in the center of the head; and when the stimulus click to one ear differs only moderately in frequency content from the click to the other, then a single click-image is still heard but the stimulus click of high-frequency content must be delivered later than the low-frequency click in order to place the image in the center of the head. If the frequency difference is great, however, a unitary click-image is no longer heard. Instead, the sound breaks up into two images, one of high and one of low pitch, which may be independently brought to the median plane of the head by appropriate adjustment of the interaural temporal relation of the dichotic stimuli. Current auditory theory about localization and pitch neither predicts nor accounts for the presence of two such images.
Network Model of the Middle Ear
Authors: Møller Aage R.
Published: September 2005

The fine-structure acoustic-impedance curve of the ear obtained from normal humans in vivo is used to develop a network model of the middle ear. First a model representing the middle ear during stapedius muscle contraction is constructed, representing the middle ear with the stapes blocked. A further development adds a circuit corresponding to the input impedance of the cochlea as seen from the stapes. To decrease the influence of the eardrum itself, the eardrum was coated with collodion. Good agreement is found between the input impedance measured at the ear and calculated from the model over the range investigated, from 200 to 1800 cps. The effect of the collodion coating is investigated and the earlier model is modified to fit the input impedance of the uncoated ear. The agreement is not so good as in the case of coated drum. The reason is suggested to lie in the complicated motion of the uncoated eardrum, which could not be represented by the simple circuit of the model.
Speech Communications in Noise: Some Equipment Problems
Authors: Hawley Mones E.
Published: September 2005

The design of a speech communication system begins with an operations analysis of the communication problem. When speech has been chosen as the means and when the needed linkages have been determined, the designer chooses the best compromises among the frequently conflicting factors of intelligibility, safety, comfort, quality, reliability, and economy. It is particularly important to provide good quality as well as adequate intelligibility. The latter may be predicted with reasonable accuracy if the noise and signal levels and the transfer characteristics throughout the system are known. Pressure gradient microphones, especially with noise shields, noise attenuating earcaps, and earplugs, are the primary acoustical devices that can be used to obtain high intelligibility through improvement of signal-to-noise ratios. If the listeners are in intense noise, headsets presently pose the major systems limitation. Automatic volume control and peak clipping are the audio techniques most frequently used to complement the transducers. Typical values and limitations for these kinds of processing are given. Optiomum results can be obtained only if the whole system is designed together.
Theory of Ultrasonic Attenuation in Cylindrical and Rectangular Waveguides
Authors: Carome E. F. , Witting J. M.
Published: September 2005

A theoretical study is made of attenuation of ultrasound in cylindrical and rectangular waveguides. The systems treated consist of a piston source radiating into a bounded, inviscid fluid and a receiver of the same size as the source. Expressions for receiver output are derived, and acoustic loss as a function of path length is computed for various source and waveguide configurations. Boundary conditions corresponding to both perfectly rigid and perfectly free walls are considered. The waveguide approach is extended to the limiting case of radiation into an unbounded medium, and results are given for both square and circular systems. In the latter case the curve of loss versus path length agrees well with that previously obtained using more conventional diffraction theory.
Effect of Visual Factors on the Intelligibility of Speech
Authors: Neely Keith K.
Published: September 2005

Research has indicated the important role that vision plays in face-to-face voice communication. This study was an attempt to quantify further the visual contribution to speech intelligibility in a high intensity noise environment in terms of the angle and distance from the listener to the speaker.

Results indicated that (1) visual cues resulted in a significant increase in listener-intelligibility scores, (2) the angle at which the listeners observed the speaker influenced their listener-intelligibility scores, and (3) the distance of the listener from the speaker did not have a significant effect on listener-intelligibility scores within three to nine-foot limits.

The importance of speech-reading training and the use of visual cues is evident where face-to-face voice communication has to be conducted in high intensity noise environment.
Acoustic Radiation from a Stationary Cylinder in a Fluid Stream (Aeolian Tones)
Authors: Etkin B. , Korbacher G. K. , Keefe R. T.
Published: September 2005

The equation for the radiated sound associated with body forces in a fluid is applied to the flow past a circular cylinder. The sound field is found to be related to the oscillating lift and drag forces which act on the cylinder. Quantitative predictions are made of the directionality and intensity of the field. Some experiments were conducted in a subsonic wind tunnel, in order to test the theory. The microphone was located both inside and outside the tunnel. Over-all sound pressure levels and sound spectra were measured with various cylinders mounted in the test section. There is qualitative agreement between the theory and the experimental results.
Some New Measurements on Sonically Induced Cavitation
Authors: Meyer Erwin
Published: September 2005

This paper reports experimental investigations of the behavior of single cavitation bubbles produced in water. In the first set high intensity sound of frequency 14.6 kilocycles is focused on a hydrophone. Oscillograms were made of the natural oscillations of the cavitation bubbles. In the second series of observations motion pictures were made of cavitation bubbles at the rate of 105 000 frames a second. This enables the actual oscillations of the bubbles to be observed visually.
Reciprocity Calibration of Microphones in a Diffuse Sound Field
Authors: Diestel H. G.
Published: September 2005

Microphones can be calibrated by a primary technique in a diffuse sound field. The formula for the diffuse-field voltage response is derived from the well-known relationship for a reciprocal transducer in free space. It is shown that the reciprocity parameter for a diffuse-sound field follows from that for free space by replacing the distance by the “diffuse-field distance” of a point source. This distance depends only on the total absorption in the reverberation room. The experimental procedure is described in some detail and the results of the diffuse-field calibration of a Western Electric 640 AA condenser microphone are presented.
On the Transmission of a Spherical Sound Wave through a Stretched Membrane
Authors: Lamb George L.
Published: September 2005

The transmission of a spherical sound wave through a homogeneous stretched membrane of infinite extent is investigated theoretically. An integral representation of the transmitted sound field is initially derived. The path of integration is then transformed into the complex plane and the integration carried out in an approximate manner by the method of stationary phase.

The transmitted sound field is found to be composed of two parts, an outgoing spherical wave modified by an amplitude factor containing angular dependence and a surface wave. The surface wave, which results from the free flexural vibration of the membrane itself, exhibits an interesting “zone of silence” in the transmitted sound field.
Hypersonic Resonance of Quartz at 3500 Mc
Authors: Stewart James L. , Stewart Ellen S.
Published: September 2005

The hypersonic resonance of X cut quartz crystals 0.1 mm thick has been observed at room temperature. Six to twelve odd harmonics in the region 2950 3600 Mc have been excited in several crystals. Hypersonic radiation into water was detected.
Response Spectra by Means of Oscillograph Galvanometers
Authors: Conrad Robert W. , Vigness Irwin
Published: September 2005

A response spectrum (shock spectrum) is the response of a series of single-degree-of-freedom systems of given damping to a shock or vibratory motion, as a function of the frequencies of the simple systems. An oscillographic galvanometer is a single-degree-of-freedom system having a rotational response to an exciting current. If the exciting current is made proportional to the amplitude of the motion, the response of the galvanometer to the current will be proportional to that of a single-degree-of-freedom system to the motion, provided their natural frequencies and damping properties are the same. A commercial galvanometer-type oscillograph has been obtained having twelve undamped galvanometer elements with natural frequencies in the range between 10 and 2500 cps. Damping, by electrical means, has been made adjustable between about 3 and 50% of critical. Associated circuitry has been constructed so that electrical playback of recordings of shock and vibratory motions can be conveniently analyzed. Calibration techniques are described and examples are given for analysis of simple and complex shock motions.
Panoramic Representation of the Sound Field
Authors: Sacerdote Gino G. , Bordone-Sacerdote Cesarina
Published: September 2005

Recording, by means of a sonagraph, the sound pressure generated by a turning loudspeaker, fed by white noise, one can give a synthetic representation of the directional behavior of the loudspeaker. One can study the behavior of reflecting surfaces and the directivity of a microphone by the same method.
Psychophysical Comparison of Just Tuning and Equal Temperament in Sequences of Individual Tones
Authors: Ward W. D. , Martin D. W.
Published: September 2005

Two experiments were performed to investigate one facet of the question of discriminability of melodic sequences in just intonation and equal temperament. First an ABX test was given to 20 listeners, in which prerecorded ascending diatonic scales of each type were used. Two widely different timbres were used, one flutelike and the other spectrally complex. Only three subjects gave results significantly different from chance. A second experiment employed scales deviating from equal temperament in a manner similar to the just scale, but varying in amount from −6 to −30 cents on the third, sixth, and seventh steps (mi, la, and li). These were compared to equally tempered scales by both ABX and AX procedures. Results showed that the maximum difference between the just and equally tempered scales (16 cents) lies just below the “ABX threshold,” but above the “AX threshold.” It is significant that music students used here (admittedly well conditioned to equal temperament) said that when they. were certain of a discrimination, it was because one of the scales contained tones which were “too flat.”
Liveness Effects on the Intelligibility of Noise-Masked Speech
Authors: Thompson P. O. , Webster J. C. , Gales R. S.
Published: September 2005

Liveness is a quality of sound correlated with room volume, reverberation time, and distance between the sound source and listener (or pick-up device). In this study, speech samples of varied liveness were obtained by mixing, in controlled ratios, the direct output of the talker's microphone and an output passed through a 9×7.5×6 ft reverberation chamber. In preliminary laboratory tests, the materials consisted of PB words, short phrases, and connected discourse; and varied from very low to high liveness values. The main tests were of an applied nature. Lists of sentences of low and zero (dead) liveness were transmitted over VHF radio and presented over earphones to 19 listeners in a series of intelligibility and preference tests. These lists were also presented to listeners in 105 db SPL helicopter cabin noise. The results indicated that the live speech was less intelligible and less preferred.
Ultrasonic Pulse Technique for Measuring Acoustic Losses and Velocities of Propagation in Liquids as a Function of Temperature and Hydrostatic Pressure
Authors: McSkimin H. J.
Published: September 2005

A fixed path ultrasonic unit operating in the frequency range of 20–200 mcps is described which can be used for measuring acoustic wave velocities and losses in liquids as a function of temperature and hydrostatic pressure. A simple phase balance technique insures a high order of accuracy for velocity determinations,

Illustrative data for carbon tetrachloride, Dow Corning DC-703 and DC-200 silicone fluids, and water are shown. Determination of freezing points of liquids using ultrasonic waves for indication is also discussed briefly.
Wave Propagation on Beam-Plate Systems
Authors: Heckl Manfred
Published: September 2005

Formulas for the attenuation of bending waves that travel over a beam-plate system, containing one or several beams, are derived and compared with measurements. It is found that one beam gives an attenuation which is very small near the resonances of the beam and rather high elsewhere, but in the average over wide frequency bands the attenuation appears to go nearly like the square root of frequency. The addition of beams of the same material and dimensions does not give an appreciable increase in attenuation. Formulas for the force impedance and mean-square velocity of beam-plate systems are also given. Finally, the damping of a beam by a plate attached to it is discussed.
Acoustical Field at Normal Modes in Rooms
Authors: Korn T. S. , Van de Plas R.
Published: September 2005

The physical form of the acoustical field at normal complex modes in rooms can be represented as a set of elementary curvilinear ducts, each carrying a single stationary wave, satisfying individually the boundary conditions at the walls. In spite of the differences in their lengths, all the ducts resonate at the same nominal frequency, the differences in their flares adjusting the phase velocity along their axes.

This theory is confirmed by the analysis derived from the theory of horns. An experiment on the computed model of the duct yielded with good accuracy the calculated frequency of resonance.
Design and Performance of a New Reverberation Room at Armour Research Foundation, Chicago, Illinois
Authors: McAuliffe D. R.
Published: September 2005

During the last year the ARF Acoustics Section has been moved into new quarters. In these new facilities a reverberation room has been built for use in the acoustic research of that group. The room has a volume of approximately 3000 cu ft and a reverberation time of about 5 sec. The four walls and ceiling of the room have been splayed. Measurements indicate that the room has a relatively uniform reverberation time with respect to frequency. Data are presented to show the ambient noise level in the room, the steady-state sound energy distribution within the room, and the reverberation time as a function of frequency and location within the room.
Pulse Compression in an Acoustic Waveguide
Authors: Walther Klaus
Published: September 2005

Experiments on propagation and compression of pulses in an acoustic waveguide are described. A water filled channel of 32 ft length with pressure release surfaces is used as an acoustic waveguide with a cutoff frequency fc=13.5 kc. Measurements on transient waveforms and on the dispersion curve of the guide in the frequency range between 13.5 and 26 kc are reported. In the pulse compression experiments the wave-guide is used as a “matched filter” with a frequency-dependent delay time. A frequency modulated input pulse of 12.6 msec length is compressed into an output pulse of shorter duration and of higher peak amplitude. The frequencies in the input pulse vary from 14 to 22 kc. A time compression ratio of 52.5:1 and a peak amplitude gain of 18.6 db are achieved experimentally. The detection of a pulse in the presence of noise for an input signal to noise ratio of −20 db is illustrated.
Remarks on Birdsall's “Detection of a Signal Specified Exactly with a Noisy Stored Reference Signal”
Authors: Gundy Richard F.
Published: September 2005

The existence of an optimum decision procedure for a signal specified exactly with reference to a noisy stored reference signal is re-examined. It is shown that, within the framework of the theory of signal detectability, no such procedure exists.
Volume Per Seat and Variation of the Reverberation Time with the Size of the Audience
Authors: Carbonell Jaime R. , Zuccoli José L.
Published: September 2005

A maximum relative variation of the reverberation time according to the size of the audience must be stated as a design condition for a hall together with the value of the reverberation time itself (for instance, 1.3 sec at 500 cps, ±10%). It is interesting and very useful to compute, quantitatively, how a change in the type of seats, the volume of the hall, or the number of seats would affect the relative variation in the reverberation time according to the number of occupied seats. The present work gives, in the form of equations and charts, an easy way to do this.
Interval of Time Uncertainty in Auditory Detection
Authors: Egan James P. , Greenberg Gordon Z. , Schulman Arthur I.
Published: September 2005

Three experiments were conducted to measure the decrement in performance that results from uncertainty in the time of onset of a signal presented against a continuous background of noise. The fixed-interval observation experiment was employed. A light defined an observation interval for the listener during which the signal, a tone of 1000 cps, either was or was not presented [p(SN)=0.5]. The signal, when presented, started at an instant randomly selected within the observation interval. Thus, the listener was uncertain as to (1) whether or not the signal would occur in the observation interval, and (2) the onset time of the signal, if in fact the signal occurred. The interval of time uncertainty (ITU) during which the tone might start was systematically varied from one series of trials to the next, and the listener knew the duration of ITU in each series. After each observation interval, the listener indicated his confidence that a tone was presented by using a rating scale. Operating characteristics [p(y|SN) against p(y|N)] were plotted on normal-normal coordinates, and measures of detectability were computed. The functional relation between the detectability index d, and the interval of time uncertainty is presented for each experiment.
Array Steering in a Layered Waveguide
Authors: Clay C. S.
Published: September 2005

The usual way to determine the direction of a radiating source with an array is to steer the array for maximum output. The steering can be done by time delays or by mechanically turning the array. The output of the array can be expressed as the sum of the time average of the products of the pressure 〈PmPn〉, observed at detectors m and n. The value of 〈Pm(τm)Pn(τn)〉 can be maximized by a proper choice of time delays τm, τn. This procedure is straightforward in an infinite homogeneous medium. If the medium is a layered waveguide, there are many more possibilities for submaxima of the PmPn terms.

The normal mode solution of the radiation field of a band limited noise point source is used to calculate the acoustical pressures Pm and Pn. The value of 〈Pm(τm)Pn(τn)〉 as a function of time delay is compared with the value of PnPm obtained with mechanical steering. For these calculations, the noise source is assumed to have a bandwidth of one fifteenth of the center frequency, and the depth of the water is assumed to be about 2λ over a thick layer of unconsolidated sediment. The number of maxima of the 〈Pm(τm)Pn(τn)〉 is related to the number of modes propagating in the waveguide if the steering is done with time delays. Mechanical steering yields one maximum that corresponds to the source direction.
Plane Waves in a Thermoelastic Solid
Authors: Deresiewicz H.
Published: September 2005

In an isotropic, thermoelastic solid shear waves are unaltered by thermal effects. However, two distinct dilatational waves exist, both of which are dispersed and attenuated by the medium. One of the waves (denoted the E wave) is close in character to the pure elastic wave, the other wave (denoted the T wave) is similar in nature to the pure thermal wave.

The properties of the two dilatational motions are studied and relations are given expressing the variation, in each, of phase velocity, amplitude attenuation, and specific loss with impressed frequency. For the E wave the result is verified that this disturbance propagates at the adiabatic velocity at low frequencies and at the isothermal velocity at very high frequencies. An explanation based on physical considerations is offered to account for this generally overlooked phenomenon. It is further found that the amplitude is attenuated exponentially as the square of the frequency at relatively low frequencies, but approaches finite value as the frequency increases without limit. The specific loss reaches maximum for the E wave, a minimum for the T wave, near the frequency whose period is equal to the relaxation time due to thermal currents.

Finally, the ratios are computed of the amplitude of the temperature to the amplitude of the displacement in each of the two modes of motion. Numerical work indicates that, for metals at room temperature, the effect of coupling between elastic and thermal motions is very small.
Theoretical and Experimental Study of Underwater Sound Reverberation
Authors: Cron Benjamin F. , Schumacher William R.
Published: September 2005

A theoretical study of the fluctuation of the amplitude and phase associated with the return of a single frequency pulse was made. A vectorial representation was used. From this model the conditions necessary for first-order Rayleigh distribution of amplitudes are given. Experimental tests were conducted in the Bermuda area. Data on volume reverberation, as well as surface return and surface plus bottom return, were obtained. The data were processed via the USL Datrac-Datatron system. Analog as well as digital processing was used. An analog electronic circuit was used to generate the Hilbert transform of the returned signal. The return signal and the Hilbert transform were both sampled by the “Datrac” system at a rate of the reciprocal of the bandwidth. The analog values thus obtained were then converted to digital form by the “Datrac” system. From the digital values of the original time function and the Hilbert transform of the time function, the Datatron 205 was programmed to compute the corresponding values of the envelope and the phase of the carrier frequency. Experimental histograms were obtained by the computer for these values. The experimental histograms were compared with the expected theoretical distributions. Statistical tests of goodness of fit were conducted on these data. The results showed the theoretical assumptions to be valid.
Detection of Auditory Sinusoids of Uncertain Frequency
Authors: Green David M.
Published: September 2005

The decrease in the detectability of a gated sinusoidal signal in noise caused by deliberately introducing uncertainty about the signal's frequency is no greater than 3 db, even in an extreme condition of uncertainty. In this extreme condition the signal duration is 0.1 sec, and the signal frequency is varied between 500 and 4000 cps. This effect is not critically dependent on signal duration. Moreover, the observers not only detect the signal but display at least gross information about the frequency of the signal in the uncertain frequency conditions.

Several models, suggested in previous studies, are considered. The magnitude of the decrease observed in the data falls far short of the predictions of these models. An interpretation suggested by the data is that the observers in a detection task, even when a signal of fixed frequency is used, are highly uncertain as to the exact physical parameters of the signal. Another way of stating this assumption is to say that the observer never tests for the presence or absence of a signal on the basis of one simple hypothesis. From this assumption we should expect little decrease in detectability from deliberately introducing frequency uncertainty. This interpretation would suggest the same result would be obtained if time were the major experimental variable.
Modes of Vibration of the Indian Drum Dugga or Left-Hand Thabala
Authors: Ramakrishna B. S.
Published: September 2005

The dugga or the left-hand thabala is a companion drum to the right-hand thabala and the two together are widely used in India. The vibration characteristics of the latter which has a symmetrically loaded membrane were discussed previously where it was shown how this drum produces harmonic overtones.

The left-hand thabala also has a loaded drumhead, but the loading is here eccentric. The boundary value problem of this drumhead is not separable, and hence there is no readily available method for computing its characteristic frequencies. An approximate theory for computing the frequencies of the lower modes is here developed under the assumption that for these modes the effect of the (unloaded) annular region on the loaded region may be replaced by a suitably determined elastic support around its boundary. This leads to the boundary value problem of a membrane with an elastic boundary support whose stiffness constant per unit length is a function of the polar angle. The problem is still unseparable, but the eigenvalues can be now computed by a boundary perturbation technique from those of a membrane with a boundary support of constant stiffness. Computed and measured frequency ratios agree within seven percent or better.
Note on the Design of “Terminal-Analog” Speech Synthesizers
Authors: Flanagan James L.
Published: September 2005

The synthesis of vowel sounds by lumped-constant electrical networks having transfer functions similar to the transmission properties of the vocal tract is considered. A comparison is made between cascade and parallel connections of simple electrical resonators for producing vowel sounds. The cascade arrangement of resonators is shown to yield vowel sounds having formants of proper amplitude when information specifying the formant frequencies only is known.
Measurement of Loudness: An Addendum
Authors: Semeonoff B.
Published: September 2005

Some early but hitherto unpublished work on the measurement of loudness is reported, primarily for its relevance to Stevens' recent survey of this subject. Experiments using methods of magnitude estimation and of constant stimuli were carried out with a 512-cps tone from an electrically-driven tuning-fork at levels of approximately 60 to 100 db. Fairly marked differences were found between estimates of half and double loudness made by 3 subjects, each of whom showed individual consistency. On the whole greater decibel change was needed for double than for half-loudness. Experiments on bisection of loudness intervals were also carried out, the results showing discrepancies from predicted values.
Supra-Aural Cushions in Audiometry
Authors: Sergeant Russell L. , Harris J. Donald
Published: September 2005

Differences in median audiometric thresholds for 20 subjects resulting from embedding earphones in the standard MX-41/AR muff and in the Willson “Sound Barrier” supra-aural muff are presented. Applying these corrections to the Willson muff with its much superior sound-attenuation properties makes possible threshold audiometry in much noisier workspaces than heretofore.
Practical Production and Use of Multitones
Authors: Raes A. C.
Published: September 2005

Advantages of multitones over warble tones and random noise are discussed. Three methods for producing multitones with simple apparatus and a tape recorder are described. Satisfactory decay curves have been obtained using only two components. A simple “duotone” generator, continuously adjustable over a single range from 80 to 3500 cps is described.
Auditory Detection of an Unspecified Signal
Authors: Gundy Richard F.
Published: September 2005

Listeners were required to detect an auditory signal against a background of “white noise.” The effects (1) of giving trial-by-trial information as to whether or not a signal was delivered, and (2) of giving the subject an opportunity to hear the signal before the test sequence began, were studied at two levels of signal energy. The results were analyzed within the context of the theory of signal detectability. Subjects who were given an opportunity to hear the signal before the test sequence began maintained a stable level of performance throughout the experimental session. On the other hand, subjects who were given no opportunity to hear the signal performed near chance level at the beginning of the session but showed gradual improvement as trials progressed. The effect of trial-by-trial feedback was surprisingly small in all groups. Near the end of the session, the signal was demonstrated to all subjects and the differences between the groups vanished.
Pitch Shifts of Periodic Stimuli with Changes in Sound Level
Authors: Small Arnold M. , Campbell Richard A.
Published: September 2005

Pitch shifts with changes in sound level were investigated for two types of stimuli, one whose pitch was hypothesized to be analyzed on the basis of “place” and the other whose pitch was presumed to be related to “periodicity.” Eight subjects made alternate monaural pitch matches with four stimuli; pure-tone, dc pulses (both with energy at the fundamental frequency-place pitch), and two varieties of ac pulses (with little energy at the fundamental frequency-periodicity pitch). The fundamental in all cases was approximately 100 cps. Generally, pitch shifts were small, although there were marked differences in the extent and in the variability of the pitch matches as a function of the type of stimulus. Partly because of large differences between subjects, statistically significant shifts were found for only two of the stimuli, one “place” and one “periodicity” stimulus. These shifts were similar in direction, with the pitch shifting downward as level is first increased, then upward with a further increase. Although there appears to be little in the data to support duality of pitch analysis, it is possible that all stimuli were perceived on the basis of periodicity. However, it seems difficult to handle pitch shifts with changes in level within the confines of “periodicity” analysis.
Elastic Constants of Staurolite
Authors: Bhimasenachar J. , Rao G. Venkata
Published: September 2005

The elastic constants of Staurolite have been determined using the ultrasonic wedge method. The values of the constants are: c11 = 34.3; c22 = 18.5; c33 = 14.7; c44 = 4.6; c55 = 7.0; c66 = 9.2; c23 = 12.8; c31 = 6.1; c12 = 6.7 in units of 1011 dynes/cm2. The value of compressibility is 7.58×10−13 cm2/dyne.
Improved Quasi-Stereophony and “Colorless” Artificial Reverberation
Authors: Schroeder M. R.
Published: September 2005

“Quasi stereophony” is defined as the reproduction over two or more loudspeakers (or binaural earphones) of different sound signals derived from a single audio signal. The purpose of quasi-stereophony is to create (from a single audio signal) an illusion of spatially distributed sound sources. Quasi-stereophonic reproduction does not permit correct localization but does share with true stereophony the properties of “depth” and “ambience” which are important attributes of stereophony (for the casual listener perhaps even more important than correct localization).

This paper describes a new filtering method for producing quasi-stereophony. In contrast to earlier proposals, the new filtering method leaves the amplitude spectrum of the sound intact. The same kind of filter has also been used for generating “colorless” artificial reverberation. Experimental results indicate that both quasi-stereophony and artificial reverberation can be achieved without spectral distortion.
Noise Measurements Around a Subsonic Air Jet Impinging on a Plane, Rigid Surface
Authors: Marsh Alan H.
Published: September 2005

Measurements are presented of the noise produced by a 1.5 in. diameter air jet, with an exit Mach number of 0.66, impinging perpendicularly on a plane, rigid plate. The over-all sound power output increased rapidly, as the nozzle-to-plate separation distance was decreased. The over-all sound power generated, when the plate was 2 diam from the nozzle, was 10 db greater than that produced with the plate removed. For a 2-diam plate separation the over-all sound-pressure levels (SPL's) (measured at a radius of 24 nozzle diameters from the center of the jet exit in the horizontal plane through the jet centerline) were 15 to 18 db greater than those produced at corresponding positions with the plate removed, while for a 20-diam separation, the increase varied between 2 and 7 db. The spectrum of the noise changed as follows as the separation distance was increased: (a) the peak frequency decreased, (b) the pronounced peak changed to a broad one, and (c) the magnitude of the peak decreased.
Effect of a Longitudinal Static Pressure upon a Magnetostrictive Ferrite
Authors: Wilson Geoffrey L.
Published: September 2005

Double-dumbbell transducer elements of two commercial nickel-copper-cobalt-ferrous ferrites (Ferroxcube 7A1 and 7A2) with acoustic “pressure-release” material at each end were placed between the jaws of a hydraulic pressure testing machine. The effective electromechanical coupling coefficient for the sample was measured for various magnetizing currents and static loads. As the load was increased to 5600 lb, corresponding to 4600 psi in the narrow “limbs” of the element, the effective coupling coefficient at optimum bias decreased from 0.21 to 0.05, and the clamped inductance (which is proportional to the incremental permeability) decreased by 40 per cent.
On the Combination of Intensity and Frequency Differences in Auditory Discrimination
Authors: Pollack Irwin
Published: September 2005

The results of Harris and collaborators on the discrimination of combinations of auditory intensity and frequency differences were examined with reference to four models of auditory discrimination. Of the four, the most successful prediction of the effect of combinations of intensity and frequency differences assumes a recognizable threshold for each of the stimulus variables.
Dependence of Successive Judgments in Detection Tasks: Correctness of the Response
Authors: Shipley Elizabeth F.
Published: September 2005

Forced choice and yes-no auditory detection data were examined for single-trial dependencies of the correctness of the response. In both procedures a correct response is more likely when the previous response was correct than when it was wrong. The effect of various characteristics of the signal were studied in the forced-choice procedure: the dependence is more pronounced for higher-intensity signals and for signals of a pure tone rather than for an increment in background noise. An attempt is made to relate these findings to a criterion-correction explanation of the sequential dependence.
Equal Beating Chromatic Scale
Authors: Leigh Silver A. L.
Published: September 2005

An unequal temperament is described in which the fifths and fourths of the tuning chain have the same beat rate. No Wolf intervals are produced and all intervals can be described by ratios of integers. The equal heating chromatic scale is an excellent approximation to equal temperament; moreover it may well represent a closer approximation to Bach's “well-tempered tuning” than does equal temperament. Circulation of a kind is complete and this tends to restore in some degree the feature of key color. Inasmuch as there is only one beat rate to observe (very nearly one per second) the procedure for tuning keyboard instruments to this temperament is simpler than that nominally required for equal temperament. Tuning notes are appended.
Operating Characteristics, Signal Detectability, and the Method of Free Response
Authors: Egan James P. , Greenberg Gordon Z. , Schulman Arthur I.
Published: September 2005

The method of free response refers to the following listening situation. Against a background of noise, a weak signal is presented several times in a long (2-min) observation interval. The temporal intervals between the presentations of the tones are randomly distributed; consequently, the listener does not know when a tone will occur, and he does not know how many tones will be presented. From one series of observation intervals to the next, the listener is instructed to adopt various criteria and to press the single response-key each time he “hears a tone.” The problem consists in the determination of a procedure that allows the total number of yes responses to be partitioned meaningfully between “hits” and “false alarms.” A model is developed in which the measurable quantity, rate of response, is related to the “hit rate” and to the “false-alarm rate.” Although the criterion adopted by the listener cannot be directly evaluated, the use of a wide range of criteria makes it possible to estimate the detectability ds of the signal. Two experiments are described, and the results support the model.
Impedance of Tapered Structures
Authors: Young Frederick J. , Young Beverly H.
Published: September 2005

A general expression for the impedance of acoustical horns and analogous devices is derived by considering a manifold of uniform structures. The impedance of the manifold is obtained by complete mathematical induction and the impedance of a smoothly varying tapered structure is obtained by a limiting process. With the expressions established here the impedances of acoustical horns having mouth to throat area ratios ranging from 0.125 to 8 can be calculated with less than 10% error at zero frequency.