bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereo Geometry Measurements
Authors: Klipsch Paul W.
Published: September 2005

Methods of evaluating accuracy of geometry of stereophonic sound reproductions involve generating sounds—such as speech or clicks—over a systematic array and then having observers attempt to locate the virtual sources of such sounds on playback over a stereo system. Multiple-row sound source arrays previously have been used. Distance and vertical localizations are poor so lateralization was evaluated with a single row of sound sources. Using the root-mean-square error divided by the array spread as a “criterion of error,” Table I evaluates direct listening (“live”) and the various reproducing systems indicated.

TABLE I.

Conditions Abbreviation Criterion of error

1. Direct listening Live 0.042

2. Stereo-directional microphone, 2 sound

tracks, 3 speakers SD-2-3 0.11

3. 3 Spaced microphones, 3 electrically

independent channels 3-3-3 0.123

4. 2 Spaced microphones, 2 sound tracks,

3 speakers 2-2-3 0.137

5. 2 Spaced microphones, 2 sound tracks,

2 speakers 2-2-2 0 30

Playback array subtended nearly 90 deg at the observer. For condition 5, errors increased grossly as the observer moved away from the axis of symmetry, only slightly for the other reproducing systems, and none for the “live” condition.
Subjective Evaluation of Factors Affecting 2-Channel Stereophony
Authors: Harvey F. K. , Schroeder M. R.
Published: September 2005

In transmitting and reproducing 2-channel stereophonic signals, the original program material may be modified deliberately or unintentionally. A study was made of many of the subjective aspects associated with these modifications. Three of the more important modifying parameters, involving channel separation, were evaluated in a formal test program using 10 critical observers. Musical selections in groups of four were suitably chosen for each parameter and played through a stereo system with and without modification. Questions were asked for detection of a spatial difference, preservation of the spatial resemblance, and listener preference. Composite results indicate that approximately 90% of the observers say that the spatial resemblance is good if (1) full channel separation is maintained out to 8 kc with no separation above this frequency, (2) full channel separation is maintained down to 100 cycles with no separation below this frequency, (3) a channel separation of 16 db is maintained over the whole band. The results for detection and listener preference are presented graphically along with resemblance data both for individual musical selections and selections in groups of four. In tests using white Gaussian noise radiated from the loudspeakers, it was found that in-phase and out-phase noise as well as two uncorrelated noises have approximately the same loudness (for equal powers). In addition, pertinent observations on other subjective aspects are reported.
Some Notes on the Measurement of Microphone Wind Noise and on the Use of Wind Screens
Authors: Doelling N.
Published: September 2005

Microphone wind noise measurements have been obtained by a technique involving a microphone attached to the end of a long pendulum. These data are compared with measurements obtained in a duct. Subsequent experiments indicate that the level of the microphone wind noise depends, in some cases, on the level of turbulence in the air stream. It appears, however, that the reduction of noise afforded by the wind screen is independent of turbulence level. A useful method for separating wind noise from acoustic signals is implied by this tentative result.
Attenuation and Amplification of Sound in Absorbing Ducts with Superimposed Airstream
Authors: Mechel Fr.
Published: September 2005

Sound propagation has been investigated in absorbing ducts with superimposed airstreams up to 80 m/sec (a) for dissipative absorbers (rockwool) and (b) for reactive absorbers (resonators). With the dissipative absorbers the attenuation is sensibly altered by the flow. The reasons are: variation of the wavelength, turbulence-induced variation of the absorber's flow resistance, and variation of the sound phase profile by the flow profile in the duct (sound propagation downstream or upstream, respectively). With the reactive absorbers distributed periodically along the duct, the acoustic input signal may be amplified. if there is a coincidence between flow speed and phase velocity of the first Hartree harmonic. This sound amplification is phenomenologically analogous to the amplification in traveling-wave tubes. Anemometric measurements show under conditions of amplification a stabilization of turbulence by sound.
Generation of Sound in Ducts by Flow Rate Changes
Authors: Franken Peter A.
Published: September 2005

The introduction of mass or heat into a system acts as a source of sound. In the present case, the system consists of a long cylindrical duct, and the duct cross section is much larger than the cross section of the source volume. An expression relating sound pressure, source characteristics, and duct dimensions is obtained from the work of Ingard and others. Sound pressure is directly proportional to the time rate-of-change of mass or heat flow. The special case of a source associated with a high-pressure-ratio orifice is considered. Experimental results are shown to be in good agreement with predicted values.
Expansion Chamber Filters for Liquid Piping Systems
Authors: Mikeska E. E. , Bohls F. O.
Published: September 2005

Measurements of the effectiveness of simple expansion chamber filters in reducing low-frequency fluid-borne noise transmission in a water-filled piping system are presented and compared with theoretical design curves. Values of attenuation comparable to or greater than those predicted by plane wave theory for gaseous flow mufflers were found. The configurations tested included single chambers with lengths from 2 to 10 ft and double-section filters with chamber lengths of 5 and 7 ft. An area expansion ratio of 14 was used for all the tests in a piping system built of 2.73-in. i.d. tubing. Maximum attenuations of 20 db or more were measured for single chambers and 30 to 40 db for double-section filters. The effects of standing waves in the piping at either end of the filter are considered. Measurements were made both with and without water flow in the system.
Malfunction of Electronics in Acoustic Noise Fields
Authors: Noiseux D. U. , Doelling N. , Coles J. J.
Published: September 2005

Malfunction of electronic systems operating in acoustic noise fields may arise from one or more of several possible sources. Electrical noise may be generated by the direct action of the acoustic pressure field on electronic components or by the mechanical vibration induced in supporting structures by the indirect action of the acoustic pressure fields. A third source of malfunction is mechanical failure of the component or of its supporting structure as a result of sound-induced vibration. Some particular experimental results are given that illustrate each of these types of malfunction. The vibration response of printed circuit boards to sound fields has been studied for boards with boundary conditions similar to those found in electronic equipment. Some of the boards were loaded with components, others were not. Vibration response, electrical noise, and mechanical modes of failure of some typical systems have been studied. Data have been obtained that allow comparison of the relative importance of the probable sources of malfunction. Brief consideration is given to an approximate method for comparing the magnitude of the accelerations induced by sonic excitation with those induced by a standard vibration test. A short film strip will be used to illustrate vibration response and mechanical failure of a component-loaded circuit board. (Supported by Wright Air Development Division.)
Anti-Noise Ordinance for a Residential Community
Authors: Hunter J. L. , Carome Edward F.
Published: September 2005

An anti-noise ordinance has been proposed for the City of Shaker Heights, Ohio, a suburb of Cleveland which is wholly residential. The call for an improved ordinance was stimulated chiefly by complaints by residents of excessive noise from neighbors' air conditioners. Octave-band analyses were made in each case. The survey showed several instances in which the levels were such as to cause “strong complaint” reactions, as estimated by Rosenblith and Stevens. Further study and discussions indicate that a noise ordinance based on the NC-45 curve at the property line of the resident should be a realistic limit for noise from stationary sources at night. Daytime levels are 5 db higher in each band.
Loudness and Noisiness of Sounds of Different Bandwidth
Authors: Kryter K. D. , Williams Carl
Published: September 2005

Experiments were conducted in which approximately two hundred subjects judged the relative loudness and noisiness of sounds (primarily filtered “white” noise) that varied in bandwidth and location on the frequency scale. In addition, to some of these sounds was added a pure tone, the level of which was varied with respect to the level of the broader band sound in which the tone was placed. Also, estimates were obtained for some of these sounds of the sound pressure levels that the subjects felt would be tolerable in their homes. The data obtained will be presented in terms of (1) equal loudness and equal noisiness contours as functions of frequency, (2) the effects of pure tone components in a broader band background sound upon judgments of loudness and noisiness, and (3) estimates of acceptable levels for environmental noise. (This study was conducted in part under a grant from the National Institutes of Health.)
Measurements of the Threshold of Hearing in Water and in Air and the Effect of Foam Neoprene Hoods on the Underwater Threshold
Authors: Montague W. E. , Strickland J. F.
Published: September 2005

Increasing interest in and use of SCUBA (Self Contained Underwater Breathing Apparatus) for sport, military use, and scientific use in geology and oceanography raises numerous problems involving auditory communication under water. A few studies, starting with Sivian's in 1947, have explored listener sensitivity under water. However, discrepancies exist of the order of 15 to 30 db between the data of various experimenters. The present experiment was undertaken to attempt to resolve these differences and to obtain a more accurate estimate of the loss of pressure sensitivity of the water-immersed ear. In addition, data were obtained measuring the attenuation of auditory signals by diver's foam neoprene hoods. Different thicknesses and configurations of hoods were tested. The thresholds were measured in a calibrated underwater sound field and in air using the Békésy audiometric technique.
Comparative Attenuation Characteristics of the Acoustic Reflex and the V-51R Earplug
Authors: Fletcher John L.
Published: September 2005

Previous research has shown that temporary threshold shifts of individuals exposed to impulse noise were significantly smaller when they were presumably protected by having the acoustic reflex activated prior to exposure as compared to exposure without such activation. However, no inference could be drawn from those data concerning the actual attenuation value of the reflex action. In order to investigate the attenuation of the acoustic reflex, pre- and post-exposure thresholds were obtained for 13 subjects exposed under two conditions to 100 rounds of machine-gun fire (fired singly). In condition I the acoustic reflex was activated to protect the listener; in condition II protection was afforded by V-51R earplugs. Results show that protection by the acoustic reflex is superior to that of V-51R plugs up to 1000 cps, while the plugs provide more protection at and above 2000 cps.
Acoustic Resonators for Sound Attenuation at the Ear
Authors: Zwislocki J.
Published: September 2005

During a study of bone conduction in a free sound field, it has been observed that small Helmholtz resonators attached to perforated earplugs can considerably increase the sound attenuation in the vicinity of their resonance frequency. Some improvement is also present at lower frequencies. Unfortunately, above the resonance frequency the sound attenuation is usually decreased because of an anti-resonance effect. Recently, using the results of impedance measurements at the entrance to the ear canal, it became possible to eliminate the negative effect without diminishing the positive one. This development has opened the way for practical applications in the areas of ear protection, communication, and hearing testing. Earplugs and semi-inserts have been designed with an attenuation characteristic equivalent to that of some of the best earmuffs available commercially. The paper discusses some experimental results as well as the underlying theory. (Work supported by a contract between the Office of Naval Research and Syracuse University.)
Time-Intensity Frequency Analysis of Prolonged Noise Samples Aboard the U.S.S. Saratoga
Authors: Tolhurst G. C. , Morrill S. N. , Camp R. T. , Ades Harlow W.
Published: September 2005

Adequate description of noise environment, as related to human exposure and hearing conservation, requires detailed information not only on spectrum and SPL, but also on temporal duration of SPL above hazardous levels with due regard for spectrum. Continuous magnetic tape recordings were made at six different microphone positions, four on the flight deck and two on the hangar deck, approximately 6 continuous hours per microphone position, totaling 35.7 hr. These recordings include all of the noise occurring during the time sampled, regardless of the type of ship's operation. The ship was under fully operational conditions, and the time samples were taken during the normal working day which included air operations. The recordings were analyzed in the laboratory by a Noise Cumulator to yield the time in minutes that the noise exceeded 7–11 pre-set sound pressure levels above 80 db in each of three frequency bands; i.e., 30–17 500 cps, 300–1200 cps, and 1200–17 500 cps. The results of these analyses were plotted as a function of percent of accumulated time. Other analyses, employing more limited time samples were made but with greater frequency-intensity detail.
Operational Evaluation of an Audiometric Test Room and Three Audiometers Aboard the U.S.S. Saratoga
Authors: Harbold G. J. , Greene J. W. , Tolhurst G. C. , Ades Harlow W.
Published: September 2005

In order to evaluate the feasibility of conducting a hearing testing program under various conditions of an operational cruise aboard a CVA type aircraft carrier, an audiometric test room (modified 1AC Model 1203) was installed aboard the USS Saratoga. The audiometric test equipment that was placed in the test room consisted of one individual and two group audiometers—namely, (a) the Rudmose ARJ-3, (b) the Maico Group Audiometer R-4 (a pure tone pulse test with single descent feature in 10-db intensity steps), and (c) the Ampex Group Audiometer Model S-3510 (reported as the NMRL Group Monitoring and Screening Audiometer). Two groups of subjects were tested to obtain hearing levels as determined by each audiometer during three conditions—namely, (1) in port, (2) underway, and (3) during catapult operations. The general effectiveness of the test room will be discussed in terms of ambient noise in the room and the measured noise reduction. The hearing data will be presented so as to show comparisons among the three audiometers as well as among the three conditions of testing.
Articulation Testing in Moderate Sized Rooms, I
Authors: D'Eustachio D.
Published: September 2005

Difficulties are experienced in using articulation tests for comparing high-quality systems because the scores are too high for good sensitivity. In a series of experiments using air transmission tests in rooms with volumes under 10 000 cu ft it was possible to increase the difficulty of the task so that scores did not exceed 85% under optimum listening conditions. The scores were lowered by training the listening crew to take down ten speech sounds (read as a group of three nonsense syllables in about 112-sec) in less than 6 sec. Score stabilities were such that, with a total of 54 or 108 tests using nine listeners and six readers, differences in mean scores of a few per cent were significant at the 1% level. Details of training program, experimental design, and test material used will be presented.
Measurements of Forward and Back Scatter from Cylinders in an Anechoic Chamber
Authors: Beckerle John C.
Published: September 2005

Measurements were made in air of the amplitude and phase characteristics of forward and back echoes from hollow phenol fiber circular cylinders. Data were obtained at frequencies varying from 4 to 20 kc with cylinders of radius a ranging from 2.54 cm to 7.62 cm (0.3 < a/λ < 5.0). The target cylinders were permitted to swing in pendulum fashion with respect to a fixed source and receiver. Three receiver distances were used: 3.90, 5.57, and 7.14 m, all large compared to a2/λ. The ratio of forward to back scatter intensity was found to be 10 log (8a/λ) db, in agreement with first-order theory for an infinitely long rigid cylinder. Within the limits of experimental accuracy, the forward scatter data agree with the theory of diffraction by an opaque strip of width 2a, while the back echo indicates a dependence on the geometrical shape of the scattering surface. When the hard surface cylinders were wrapped in soft Plycel packing material, no change in the forward echo was observed. The back echo was reduced by approximately 10 db. (This work was supported by the Office of Naval Research, U. S. Navy Department.)
Some Results of Missile Vibration Measurements
Authors: Franken Peter A. , Keast David N.
Published: September 2005

Measurements of skin vibration have been obtained on three different missile structures. Spectra of vibration due principally to rocket engine noise are reported for structures ranging from 3 ft to 10 ft in diameter. The data cover the frequency range from approximately 15 cps to 10 000 cps and have been analyzed in 13 octave bands of frequency. The effects of the structural differences between the missiles are empirically evaluated. (This work has been supported in part by the U. S. Army and the U. S. Air Force.)
Free Oscillations of Edge-Connected Simply Supported Two-Plate Systems
Authors: Ungar Eric E.
Published: September 2005

A simple semigraphical method is developed for calculating the natural frequencies of systems made up of two plates rigidly joined to each other at a common edge. The mode shapes are discussed, and the modes for which coupling is most severe are indicated. It is demonstrated that at higher modes the component plates become effectively uncoupled, as one would expect intuitively. Charts for easy determination of the natural frequencies are presented. One of these gives, as a by-product, the natural frequencies of rectangular plates (of any dimensions) having one edge clamped and the remaining three simply supported. (Supported by the Office of Naval Research-Acoustic Branch.)
Impedance Measurements on Beam-Plate Systems
Authors: Heckl Manfred
Published: September 2005

Measurements made on point driven beams, which are attached over their entire length to plates, show that in most cases the impedances are only slightly different from the impedances of the beams alone. These results agree with calculations. The differences that do appear are in the form of added damping, which is caused by the bending wave radiation into the plate, and in the form of a small increase of mass, which is caused by local motion of the plate. If two beams are attached to a plate and the plate is driven at a point somewhere in between, resonances occur which change the plate impedance. Measurements are also reported on this system and are compared with calculations. (Supported by the Office of Naval Research.)
Damping of Composite Structures by Viscoelastic Interlayers
Authors: Ungar Eric E. , Kerwin Edward M.
Published: September 2005

Previous work on damping of plate flexural vibrations by constrained viscoelastic layers is generalized to apply to beam-like structures. A previously presented “structural parameter” is redefined so as to permit a unified analysis of damping obtained in systems consisting of two elastic structures with a viscoelastic interlayer. Such systems include: sandwich plates, plates with attached damping tapes, beams with inserts, and two beams mounted flange-to-flange. Design optimization with respect to this structural parameter is discussed in conjunction with other design considerations. Some of the effects of end constraints and discontinuities of the main structure or the constraining member are presented. (Results presented in part grew out of studies supported by the U. S. Air Force, Wright Air Development Division, and the U. S. Navy, Bureau of Ships.)
Concept of Rheological Models with Acoustical Applications
Authors: Sperry William C.
Published: September 2005

The theory of rheological models considers series and parallel combinations of lumped elements which are assumed to behave mechanically like the constituent phases of a material, but which, apart from this mechanical behavior, have nothing in common with the real medium. Usually the elements are elastic springs, viscous dashpots, and dry-friction bodies. The behavior of real materials can be described only approximately by models. However, in principle any degree of approximation can be achieved by an indefinite number of model constants. A number of models, both linear and nonlinear, are investigated in detail for impressed harmonic forces. Model constants for linear models are simply mechanical impedances, dependent upon frequency, with the element characteristics as parameters. The nonlinear models result from the inclusion of dry-friction bodies which are approximated by viscous dashpots which absorb the same energy per cycle. For these cases. the model constants are again defined as mechanical impedances but differ from those for linear models in the sense that they are dependent upon driving force amplitude as well as frequency. The use of a generalized model constant gives equations of motion generality and adds no complications to the mathematics. Applications are given for lumped and continuous media, both solid and gaseous. (This research was supported by Armour Research Foundation.)
An Attempt to Persuade the IBM 704 Computer to Identify Vowel Types
Authors: Foulkes J. D.
Published: September 2005

In a classical study of the vowel sounds of English, G. E. Peterson and H. L. Barney collected a large body of experimental data which related perceived vowel quality to measurements of the first three formant frequencies and the voice pitch. If these data are used to make scatter diagrams of vowel types plotted on coordinates representing the physical measurements, it is seen that a particular vowel tends to cluster in a region whose boundary has a complicated shape. The complicated form of these vowel regions makes it difficult for a computer to use the raw data to interpret vowel quality. This paper describes a coordinate transformation which simplifies the boundaries of the vowel regions into simple rectangular blocks. The technique used to find the transformation involved programming the computer to plot scatter diagrams directly on the printer. These snapshots then were used by a human observer in a guided search for a simple transformation. The coordinate system found has been used in speech recognition studies.
How to Make an Ambient Noise in the Ocean
Authors: Frosch R. A.
Published: September 2005

A number of possible sources of ambient noise in the ocean will be examined with regard to their reasonableness in comparison with the general characteristics of measured ambient noise. Among these will be biological sources, seismic noise, shipping, sea surface waves, lightning, and instrumental error. (This work was supported by, the Office of Naval Research.)
Effect of Wind on Shallow Water Ambient Noise
Authors: Dietz F. T. , Kahn J. S. , Birch W. B.
Published: September 2005

With the support of the Office of Naval Research, a year's measurement program of shallow water ambient noise recently has been completed. The results of a study of over 600 spectra show that the sound pressure spectrum level is linearly correlated with the logarithm of wind speed in the frequency range 80 cps-10 kcps. The effect is frequency dependent with the largest increase in sound pressure due to wind speed occurring in the 500 cps–1500 cps frequency band. No correlation between wind speed and sound pressure level has been found for wind speeds less than 6 mph or at frequencies below 80 cps.
Nonrandom Associations between Shallow Water Ambient Noise and Tidal Phase
Authors: Dietz F. T. , Kahn J. S. , Birch W. R.
Published: September 2005

A one year's measurement program of shallow water ambient noise, supported by the Office of Naval Research, recently has been completed. For each ambient noise spectrum determination (40 cps-10 kcps), a record was kept of the time of the measurement with respect to the time of the previous high water. The tidal period was divided into 25 one-half hour classes and the data sorted into these classes. A measure of central tendency and spread for the sound pressure level was computed for each time class and these values plotted at the midpoint of the tidal phase classes. These results, for over 600 spectra, indicate a nonrandom distribution of ambient noise for frequencies in the band from 40 cps-100 cps and a random distribution for frequencies above 100 cps.
“Surfseisms”—Elastic Waves Generated in the Bottom by Pounding Surf
Authors: Saenger R. Alfred
Published: September 2005

The following experiment was performed on the beach at Fire Island in an area whose geophysical structure is well known: vertical component geophones were planted in the sand near the surf, and recordings were made of particle velocities in the surface sand layer. At the same time motion pictures were taken of the breaking water waves. The pattern of signal bursts and relative silences found in these surfsesims correlates well with surf behavior. Spectrum analyses of surfseisms have been obtained over a frequency range from 10 to 50 cps. An analysis of the dispersive wave train produced by a simulated shot source shows very low group velocities of the order of several hundred ft/sec. A qualitative theory of surfseism phenomena will be presented. (This work was supported by the Office of Naval Research.)
Resonance Effects in the Measurement of the Complex Modulus
Authors: Bodner S. R.
Published: September 2005

Various mechanisms by which resonances may be introduced into systems for the measurement of the complex modulus of materials are discussed from the physical viewpoint and are formulated mathematically. The mechanisms under consideration arise primarily from second-order elasticity effects that may be a consequence of the testing technique or of the microstructure behavior of the material. Some comparisons are made between experimental results and mathematical predictions.
Observations of the Audio-Frequency Resonant Dispersion Phenomena in Some Materials
Authors: Tomboulian Roger
Published: September 2005

The apparent resonant behavior of the elastic constants of certain materials have been observed and measured on a device which exerts axial dynamic compressional stresses in small samples. The effects of temperature and original internal stress condition on the resonant phenomena in samples of salts, metals, and polymers have been studied. Experiments to determine the nature of the stress pattern in the samples at resonance will be discussed. A theory based upon the motion of pinned dislocations in prestressed samples will be suggested as a possible explanation of this phenomenon.
Sound Absorption Coefficients Determined by Acoustic Pulses
Authors: Rogers C. L. , Watson R. B.
Published: September 2005

Earlier measurements on the sound absorption coefficient of acoustical materials using a pulse technique, and therefore allowing the measurements to be made in all ordinary laboratory, have been extended to take further account of the actual pulse shape. Apparatus has been constructed to give an indication of the average pressure of the acoustic pulse. Measurements have been carried out on a relatively reflective sample to give a vigorous test of the method. Comparison is made with data from reverberation chamber measurements and from impedance tube measurements for one-pulse frequency.
On the Accuracy of Transmission Loss Measurements
Authors: Heckl Manfred , Watters Bill G.
Published: September 2005

One of the authors [M. Heckl and K. Seifert, Acustica 8, 212–220 (1958)] recently has described the performance of a wall between two, one-dimensional rooms (tubes). It was found that the TL was influenced by the relative lengths of the two rooms and by the sound absorption of the rooms. When the lengths are the same and when the sound absorption is low, the TL of the wall may drop 10 or so decibels below its normal value over a wide frequency range. This effect, which results from the matching of normal modes of vibration in the two rooms, also can occur with three-dimensional rooms. Theoretical and experimental results will be given. Also, the effect of damping, mismatching the rooms, and adding diffusing objects will be considered. Some other effects that influence the accuracy of TL measurements will be discussed briefly.
Case History of Office Privacy with Lightweight Construction
Authors: Farrell William R.
Published: September 2005

The increasing use of lightweight, movable partition systems and ceiling systems in office building construction has led to the conclusion that, in order to achieve adequate speech privacy and freedom from annoyance and distraction between adjacent offices, even more consideration than usual must be given to the actual background sound levels that will exist in the finished offices. A recent case history of such an office privacy situation is discussed, including a summary of the acoustical design analysis, measurements made at a mock-up installation, and some preliminary follow-up measurements in the completed building. A discussion of practical methods for achieving the required background sound levels is included.
Recognition of “Verbal Expression” over Communications Systems
Authors: Pollack Irwin , Rubenstein Herbert , Horowitz Arnold
Published: September 2005

Communication systems which involve extensive speech processing may yield relatively high intelligibility scores but may fail to transmit other characteristics normally associated with voice communication systems. Among these other characteristics are features associated with the talker: his identity, his vocal effort, his expressive state, etc. A series of exploratory studies was designed to determine whether previously untrained listeners could identity the “verbal expression” of untrained talkers. Talkers were instructed to read neutral sentences, e.g., “The lamp is on the desk,” under instructions to “sound happy,” “sound pedantic,” etc. High recognition scores are obtained after a preliminary indoctrination period by some talkers with eight alternative expressions. The effects of background noise, whispering, and temporal sampling also will be discussed.
Speaker's Scale of Vocal Effort
Authors: Lane H. L. , Catania A. C. , Stevens S. S.
Published: September 2005

When a speaker judges the subjective magnitude of his own vocal effort, a power function describes the relation between perceived magnitude and the actual sound pressure produced. Speakers were asked to give numerical estimates of the apparent strength of their own vocal productions, or, conversely, to produce vocal levels in response to numerical criteria stated by the experimenter. The combined evidence from both procedures indicates that the speaker's impression of his own vocal level grows approximately as the 1.1 power of the sound pressure he produces. The power laws governing vocal effort (exponent 1.1) and loudness (exponent 0.6) call be used to predict successfully the outcome of cross-modality comparisons in which subjects try to match their vocal level to criterion sounds of various intensities presented either by loudspeaker or by earphone. The slope of the matching function relating the criterion SPL to the vocal SPL is given by the ratio of the two exponents. What this means is that speakers do not judge their vocal level by listening to themselves, for the sound pressure they produce when they try to match a criterion sound does not grow as fast as the sound pressure of the criterion sound.
On the Relative Loudness Levels of Synthesized Vowels
Authors: von Redlich Jean , Wendahl Ronald W.
Published: September 2005

A three-formant parallel resonant synthesizer, stimulated by a quasi-periodic source, was used to produce ten vowel-like stimuli. These stimuli were recorded in a sequence dictated by a paired comparison design. The formant frequency positions and their relative amplitudes were calibrated to the data provided by Peterson and Barney. Formant amplitudes were independently controlled within plus or minus 0.5 db of their stated values. The temporal presentation of items was accomplished by use of a sequential timer with the duration of the stimuli set at approximately 350 msec. The intra-pair interval was about 200 msec, and the inter-pair judgment time was approximately 5 sec. The stimuli were presented to each subject individually in an anechoic chamber with a sound pressure level, as measured at the subject's head, of 60 db. With the over-all sound pressure held constant, predictions were made about the loudness using formant frequency positions and their relative amplitudes. Comparisons of the predicted loudness levels with those obtained show close agreement.
Effect of Duration upon the Intelligibility of Synthetic Vowels
Authors: Wendahl Ronald W. , Case Agnes Lashlee , Stream Richard W.
Published: September 2005

A series-resonant synthesizer was used to tape-record ten vowels, replicated once at five durations ranging from 80 msec to 1.3 sec. Growth and decay, inflection rate, fundamental frequency, and intensity were held constant. The recorded stimuli were presented to 16 judges who transcribed them in phonetic script. The results indicate the importance of duration of synthesized vowels upon intelligibility and indicate optimal values for programming a synthesizer. Also, it was found that vowel duration is a less significant factor in determining the intelligibility of synthetic vowels than it is for the human speech mechanism.
Speech Communication in Churches
Authors: Balachandran C. G. , Northwood T. D.
Published: September 2005

Churches of medium size frequently are satisfactory for music but are marginal or unsatisfactory for speech. Usually the congregation will try to solve matters in one of two ways: a public address system (which, chances are, merely will increase the level of chaos) or sound absorption treatment (which may spoil the church for music). A more satisfactory approach is to concentrate on the specific problem of speech originating at the pulpit or lectern and to solve it by improving the ratio of direct to reverberant sound. Various methods of doing this have been examined in typical churches, using pulse studies and speech articulation tests.
Directional Distribution of Ambient Noise in the Ocean
Authors: Becken Bradford A.
Published: September 2005

The directional distribution of ambient noise in the ocean has not been measured previously. The conventional, trainable, searchlight transducer is unsuitable for measurements; observations in several directions in succession are inadequate owing to the required assumption of a stationary process. In addition, the single transducer fails to permit investigation of the correlation of envelope fluctuations in several directions. Accordingly, the system employed is based upon a 32-element receiving array employing 32 beams, simultaneously distributed uniformly over all space [V. C. Anderson, J. Acoust. Soc. Am. 30, 470 (1958)]. The signal reception and processing system is described briefly. Because of the finite beam widths (low resolving power) and beam side lobe structure, an analysis technique converting observed relative beam responses to the true field distribution has been developed. Data obtained at depths to 1000 ft are discussed in light of departures of ambient noise from an isotropic distribution. Preliminary deductions concerning the sources of sea ambient noise found in the distribution are presented. (This work represents one of the results of research carried out under contract with the Office of Naval Research.)
Interdependence of Space and Time Parameters in Acoustic Measurements
Authors: Gardner S.
Published: September 2005

A study has been made of the effects of finite averaging time on observations made of spatial characteristics of acoustic fields. Ordinarily, directional properties of observational devices and of the associated observables are computed and measured in terms of steady-state conditions. However, there is an interdependence among spatial and temporal parameters. Calculations will be discussed showing the quantitative nature of this interdependence between space and time domains; for example, when finite averaging times are employed and when pulse signals are used with elementary array configurations.
Studies of the Mechanism for the Flow-Induced Cavity Resonance
Authors: Harrington M. C. , Dunham W. H.
Published: September 2005

Investigations of the excitation of cavity resonance by air flow [M. C. Harrington, J. Acoust. Soc. Am. 29, 187 (1957)] have been extended. Oscillations induced by flow across the mouth of box-shaped cavities, with and without lips, have been studied in water and air. This device consists of a box with a flexible side upon which a sinusoidal variation in volume of the box is imposed, thus inducing velocities normal to the flow in the mouth of the box. Motion pictures of dye, injected upstream of the mouth, indicate that vortex formations are caused by the fluctuating velocity fields normal and tangential to the mouth. This vortex formation causes the turbulent mixing zone, containing free stream kinetic energy, to curve into and out of the box. The instability of the mixing zone causes alternating pressures in the box, which in turn may provide the excitation mechanism for resonance. Flexibility of the structure in water, and the compressibility of air, provide energy storage between cycles. In either case the amplitude of the peak-to-peak pressure changes determine the magnitude of the velocity variations normal to the flow in the mouth of the box.
Determination of Fermi Surfaces of Metals Using Ultrasonics
Authors: Morse R. W.
Published: September 2005

In metals the conduction electrons form a Fermi-Dirac system in which all states are occupied up to the neighborhood of a characteristic energy EF (the “Fermi energy”). In general the momentum of an electron (P) of given energy is a function of direction in the crystal, the surface P space defined by E(P) = EF being the “Fermi surface.” The function E(P) may not be single valued in P and the Fermi surface may be formed of several branches in more than one Brillouin zone. This paper describes a recent low-temperature ultrasonic technique from which the shape and dimensions of Fermi surfaces can be obtained. The method is based on observing the attenuation as a function of magnetic field (H) at helium temperatures in pure metals where the electron mean free path is much longer than the ultrasonic wavelength. The attenuation varies periodically in H−1, the period being determined by the Fermi momentum perpendicular to H and the direction of propagation. The Fermi surfaces of copper and gold as determined ultrasonically will be discussed. The surfaces in these metals make contact with zone boundaries, which leads to a wide variety of orbit types which have been observed ultrasonically.
Ultrasonic Attenuation in Metals at Low Temperatures
Authors: Bhatia A. B. , Moore R. A.
Published: September 2005

Firstly, Pippard's expressions [Phil. Mag. 46, 1104 (1955)] for the attenuation are derived by considering that the forces on the ions determining wave propagation in a metal arise from (1) the electric field set up by the sound wave, (2) the transfer of momentum to the ions in electron-ion collisions, and (3) an elastic restoring force independent of the electron-ion interaction. Secondly, a method for solving the Boltzmann transport equation at low temperatures will be given when the collision integral is due to the interaction of electrons with phonons and impurities. Although, in principle, the method is applicable for all relevant wavelengths λ of the sound waves, explicit solutions have been obtained only for the limiting cases λ >> l and λ << l; here l is the mean free path of the electrons. For λ >> l, it is found that the relaxation time τ2 appropriate for attenuation is the same for both shear and dilatational waves; however, τ2 is different from τc, the relaxation time for the electrical conductivity σ Further, it is found that the τ in Pippard's expression for the attenuation of extremely high-frequency shear waves is to be interpreted as τc. Lastly, it is shown that, where electron-electron collisions are not unimportant, their relaxation time may be deduced from the observed temperature variation of σ and attenuation.
On the Measurement of Ultrasonic Shear Fields in Fused Silica
Authors: Weeks Richard F.
Published: September 2005

Photographs of transducer radiation patterns in solids often exhibit many of the features predicted by diffraction theory for the radiation from a uniformly illuminated aperture in an infinite black plane. A comparison of quantitative measurements of these radiation patterns with those predicted by theory offers the most direct method of determining the applicability of diffraction theory to the radiation from bonded transducers. We shall discuss the experimental considerations and apparatus to measure ultrasonic shear fields in fused silica. Our technique makes use of the stress-induced rotation of the plane of polarization light passing through an ultrasonic field. Fields are generated by transducers bonded to a polished fused silica test sample. The sample is placed between crossed polaroids. A narrow beam of light passing through the sample and polaroids is detected by a photomultiplier. The output of the photomultiplier is displayed on an oscilloscope while the light beam is slowly moved across the ultrasonic field. By driving the transducer from a pulsed rather than a continuous oscillator and suitably gating the photomultiplier signals, it will be possible to extend measurements to very small shear field strengths with an amplitude range of well over 100. A few preliminary measurements of the radiation patterns from thickness shear mode ceramic transducers will be presented.
Propagation of Transverse Elastic Waves in Polyisobutylene under Various Pressures
Authors: Nolle A. W.
Published: September 2005

The velocity and the absorption coefficient of 2-Mc transverse elastic waves in polyisobutylene (molecular weight, 1.35 × 106) have been measured at pressures up to 1400 atm for temperatures of 10°C and 20°C. Pulsed signals are conducted into and out of a thin sample via Y-cut cylinders of crystalline quartz to which the sample is bonded. The object of the measurements is to determine δT/δP for constant behavior—in this case, for constant dynamic mechanical properties in shear. Closely similar derivatives are already known on the basis of (1) the behavior of the absorption maximum for bulk waves; (2) dynamic mechanical properties in compression; (3) hydrogen nuclear magnetic resonance absorption line width; (4) calculations based on a theory due to F. Bueche. All of these results, as well as the present measurement, yield values in the neighborhood of 0.02 C°/atm for δT/δP. (Assisted by the Office of Naval Research.)
Generation of Intense Audio Sound Fields Utilizing Arrays of Multiple-Driver Horns
Authors: Levy Sidney E. , Carlisle Richard W.
Published: September 2005

There are several major applications for intense audio sound fields: the outdoor propagation of speech and of warning signals, and the sonic fatigue testing of missile and aircraft components. In these applications, several factors combine to make it necessary to limit the portion of the frequency spectrum covered by any one loudspeaker unit. In order to provide adequate power capacity, selection is required between the alternatives of (a) using a large number of identical drivers, (b) using a plurality of drivers each especially designed for a selected portion of the frequency range, and (c) using combinations of these arrangements. In an array currently being used for sonic fatigue testing, a plurality of large open-cone woofers is used for low frequencies, and a plurality of horns is used for middle and high frequencies. Each horn is driven by several drivers. The driver voice coil and diaphragm proportions have been optimized to withstand fatigue stresses under the thermal conditions encountered. The driver is rated at 50-w input for program material. Horn assemblies are available having throat arrays for mounting 6, 12, or 24 drivers. Various applications will be illustrated.
Hand-Held Calibrator for Pressure-Measuring Systems
Authors: Rule Eric , Perls Thomas A.
Published: September 2005

The problems involved in laboratory and field calibrations of high-amplitude dynamic-pressure-measuring systems are discussed. A novel method is described which utilizes the vibration sensitivity of the transducer for the generation of high-amplitude dynamic pressures at a frequency suitable for calibration. The design, construction, and evaluation are described for a simple hand-held calibrator based on this principle and providing over-all system calibrations at ±12.5 psi and ±5 psi, at 60 cps.
Cylindrical-Wave Reciprocity Parameter
Authors: Bobber Robert J. , Sabin Gerald A.
Published: September 2005

It cylindrical waves are propagated between the projector and the hydrophone in a reciprocity calibration, a cylindrical-wave reciprocity parameter Jc is needed for the hydrophone sensitivity computation. The parameter Jc would be used, for example, when the projector and hydrophone are both long lines and are closely spaced or in a self-reciprocity calibration where a line transducer is placed near a totally reflecting plane. It is the cylindrical equivalent at the spherical-wave reciprocity parameter 2r/ρf for spherical waves between two point transducers or the plane-wave reciprocity parameter 2A/ρc for plane waves between two plane transducers. Two different derivations. one based on four-terminal network theory and the other on wave propagation theory, lead to the expression Jc =2l(rλ)12/ρc, where l is the length of the line transducer, r is the radial distance between transducers, and λ, ρ, and c are the usual wavelength, density, and speed of sound.
Effect of High Static Pressure upon a Magnetostrictive Ferrite
Authors: Wilson G. L.
Published: September 2005

A double-dumbbell transducer element of a commercial nickel-copper-cobalt-ferrous ferrite (Ferroxcube 7AI) with acoustic “pressure-release” material at each end was placed between the jaws of a hydraulic pressure testing machine. The effective electro-mechanical 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. the resonant frequency increased by 8%. and the clamped inductance (which is proportional to the incremental permeability) decreased by 40%.