bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering of Acoustic Waves by a Periodic Thermal Field
Authors: Salant Richard F.
Published: October 2005

One-dimensional scattering of acoustic waves by the thermal field, produced by a sinusoidal spatial distribution of heat sources in a perfect gas, is examined analytically. The scattered field is found to consist of a transmitted acoustic wave, a reflected wave, and an entropy wave. When the thermal-field wavenumber is near the entropy wavenumber or twice the acoustic wavenumber, a resonance-like phenomenon occurs, resulting in large-amplitude scattered waves.
Vibrational and Rotational Relaxation in Sulphur Dioxide
Authors: Winter T. G. , Bass H. E. , Evans L. B.
Published: October 2005

Ultrasonic-absorption measurements have been used to study the vibrational and rotational relaxation in SO2 from 290° to 1090°K. This work extends the temperature range of earlier investigations by 500°K and is in agreement with the other studies in the low-temperature region. The vibrational data has been analyzed by assuming that the 518-cm−1 mode exhibits a relaxation time τ1, that the 1151- and the 1361-cm−1 modes relax together with a relaxation time τ2,3, and that the two relaxations occur in parallel. It is found that τ1 increases with increasing temperature while τ2,3 decreases with increasing temperature in the normal manner. The two vibrational collision numbers are a factor of 10 apart at room temperature but approach each other at high temperature. This is the first ultrasonic measurement of rotational relaxation in SO2, and the results confirm those of a previous thermal-transpiration measurement but conflict with an earlier thermal-conductivity measurement.
Medial Geniculate Units of Squirrel Monkey Sensitive to Binaural Time and Intensity Cues
Authors: Starr Arnold , Don Manuel
Published: October 2005

We wish to define neural events correlated with binaural discrimination abilities of squirrel monkeys. Single units in medial geniculate of pentobarbital-anesthetized squirrel monkeys were studied during presentation of binaural clicks. The signals were square-wave pulses (250 μsec) transduced by 12-in. Brüel & Kjær condensor microphones located at the external auditory meati. We studied unit responses to monaural clicks, and to binaural clicks with varying time (Δt) or intensity (ΔI) differences between ears. Eighty-three of the 143 units studied were inhibited by monaural clicks presented to either ear and no binaural sensitivity was found. Fifteen units, activated by monaural clicks, also showed no sensitivity to binaural signals. The remaining 45 units (31% of the population studied) were clearly sensitive to the binaural signals discharging differentially as a function of the Δt and ΔI parameters of the click pairs. The most common type of binaural interaction was a linear change in the unit's response probability as a function of Δt and ΔI parameters. The portion of the Δt or ΔI range over which the unit was sensitive varied with click intensity. The data is discussed in relationship to binaural click discrimination of squirrel monkeys.
Cellular Activity in the Auditory Cortex of the Awake, Behaving Monkey
Authors: Miller Josef M. , Sutton Dwight , Gourevitch George
Published: October 2005

The characteristics of single cells in the auditory cortex of unanesthetized monkeys were studied in response to pure tones, clicks, white noise, and complex sounds. Cellular activity was evaluated at the same time as the monkey was responding to acoustic stimuli in a simple reaction-time task. Single-cell activity was observed in animals prior to training and in the barbiturized animal. Cells isolated in the anesthetized animal exhibited minimal responsiveness to acoustic stimulation. In the untrained awake animal, responsiveness was found to be quite variable, and consistent cellular responding could be maintained only by novel acoustic stimuli. By contrast, in the trained animal, simple repetitive stimulation evoked consistent sustained patterns of activity. The responsiveness of cells in trained animals performing the required task were observed to change with frequency and with intensity of the pure-tone stimuli. Excitatory firing patterns were observed in some cells while inhibitory patterns were seen in others. In some cases, frequency-dependent excitatory and inhibitory response patterns could be elicited in the same cell. The present observations of different neural response patterns in anesthetized, inactive-awake, and actively responding animals suggest that interpretations of neural mechanisms observed in one state may not be applicable to other states. [Research supported by two grants from the Public Health Service.]
Tentative Classification for Auditory-Nerve Fibers
Authors: Teas D. C. , Konishi T. , Nielsen D. W.
Published: October 2005

The distribution of spontaneous discharge rates for auditory-nerve fibers recorded from the guinea pig modiolus suggests that there is a greater number of fibers in the 10–30 discharges/sec range than in the cat. Some tentative groupings on the basis of discharge rates has been possible from an inspection of the cumulative frequency distribution. Three groups are suggested, with means of 10, 24, and 71 discharges/sec. The standard deviations are 2.8, 2.3 and 2.7 discharges/sec, respectively. The spontaneous discharges are reduced by COCB stimulation. The “high-rate” group shows less reduction by COCB than the two “low-rate” groups. For nerve fibers with best frequencies above 1 kHz, the effect of the COCB on spontaneous discharges varies as Δu varies with frequency. Below 1 kHz, there is more COCB effect on spontaneous discharges than would be expected from Δu.
Penn State Manpower Needs Survey
Authors: Johnson John C. , Reethof Gerhard
Published: October 2005

Current and projected manpower needs in acoustics have been deduced from data obtained through a recent survey. Based upon responses from more than 500 organizations, there are currently openings for employment as follows: technicians, 190; two-year technical graduates, 60; baccalaureate, 194; master's, 152; doctorate, 199. The data have been analyzed and results will be presented in a manner designed to delineate the needs in the physical sciences, engineering, speech and hearing, psychology, and other fields, for each of the above levels of education. The results will encompass projected estimated requirements in addition to current new position needs for one, two, and five years hence. The results also delineate the current and projected needs in accordance with types of organization, including industrial, government laboratory, government administrative, university, consulting firm, and foundation. Although the data obtained, and consequently the resulting analyses, of such an undertaking can never be completely accurate, the results presented here are considered to be the most comprehensive and accurate obtained to date for the field of acoustics.
Needs of Industry for the Acoustically Educated
Authors: Groeining James A.
Published: October 2005

In hiring engineers and scientists to do acoustical work, industry must consider qualifications for growth opportunities in other areas, as well as in acoustics; most hirees eventually shift to other work. However, the more intensely trained and more theoretically inclined can provide long-term stability in specialty areas such as acoustics in staff research and development. Thus, the major need of industry is for pragmatical broadly trained individuals. A minor need is for the more specially educated and more theoretically inclined.
Household Noise, Can Anything Be Done About It?
Authors: Newman Robert B.
Published: October 2005

Noise control is often considered in the design and construction of first-class buildings. Why not in houses? The techniques for the control of the quality of the acoustical environment are available. But, until users, designers, and builders realize that equipment noise, lack of privacy, and nerves-jangling reverberance are unnecessary, it is not likely that matters will improve. Conventional building materials can be used more effectively, and existing techniques can often be adapted to the solution of household noise problems.
Household Noise Problems—Appliances
Authors: Wald B. G. , Tope P. H.
Published: October 2005

The noise history of appliances is reviewed, including designs, installations, and customer expectations from early developments to the present. An outline of our noise-control efforts is presented, with their relationship to other factors: safety, performance, appearance, cost, weight, size, serviceability, life, etc. Consumers, individually at the time of purchase and collectively by way of noise legislation and codes, decide what they want. We are striving to supply their wants. We are working with appliance industry organizations, ARI and AHAM, to develop and adopt noise measurement and application standards that will permit noise comparisons and determine compliance with codes. With this information, the consumer will be able to make more objective decisions regarding noise. A specific case history for the automatic clothes washer outlines the problems, approaches, materials, results, etc.
Sound Rating of Outdoor Unitary Air-Conditioning Equipment
Authors: Ramsey Robert W.
Published: October 2005

The Air-Conditioning & Refrigeration Institute and member companies have developed a single-number sound-rating standard for outdoor unitary air-conditioners and heat pumps. It is intended to allow air-conditioning manufacturers to publish certified sound-rating numbers. This rating can then be used to predict sound-pressure levels in typical installations. The rating system calls for an acoustic test to be conducted in a reverberant-type sound room according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., standard on “Measurement of Sound Power Radiated from Heating, Refrigerating & Air-Conditioning Equipment.” These tests are conducted at standard rating conditions of temperatures and refrigerant pressures. The measurements are taken in 13-oct bands in the frequency range of 100–10 000 Hz, and the values are corrected for frequency distribution and pure-tone content before the calculation of the single-sound rating number. The sound-rating number can be used to select the quieter type air-conditioning and to predict an expected annoyance level or sound-pressure level. An example calculation of the expected sound-pressure level in a neighbor's home is shown through the use of slides.
Sound Field of a Parametric Acoustic Array
Authors: Muir T. G. , Gruber G. J.
Published: October 2005

The interaction of two collinear high-frequency carrier waves in water to produce a difference-frequency radiation is considered in terms of the farfield amplitudes, beam patterns, and transient characteristics of the carrier waves. The growth and decay of difference-frequency sound with increasing range in the volume of interaction are predicted by means of a numerical integration of the source-strength density for steady-state conditions. The azimuthal response of the parametric array is also predicted by this method. The results were borne out by several experiments done in a fresh-water lake at carrier frequencies of 415 and 482 kHz with a difference frequency of 64 kHz. Measurements were also made in the transient stage of the difference frequency pulse using 0.5-msec pulses centered at 432 and 442 kHz. The 10-kHz difference-frequency radiation appeared as a 0.5-msec pulse with spikes on the leading and trailing edges. A spectral analysis of this pulse shows a weighting of sidelobe energy toward higher frequencies. This effect is predicted by a convolution method. [This work sponsored by the U. S. Navy Office of Naval Research.]
Propagation Laws and Shock Profile for N Waves from Sparks
Authors: Wright Wayne M.
Published: October 2005

Weak sparks in air can serve to generate intense short-duration acoustic transients that resemble N waves. Using an improved wide-band capacitor microphone and preamplifier, we have repeated our earlier measurements [W. M. Wright, J. Acoust. Soc. Amer. 36, 1032(A) (1964)] of amplitude decay and waveform elongation for N waves from sparks of about 0.1-J discharge energy. At propagation distances for which the initial compression phase of the N wave was completely formed, the duration of this phase T and amplitude Ps were found to satisfy the theoretical relations T ∝ [1+k ln(r/r0)]12 and Ps ∝ r−1[1+k ln(r/r0)]−12, where k is a parameter that depends upon the values of Ps and T at the reference distance r = r0. The observed rise time of the head shock (5%–95%) increased from about 0.45–2.5 μsec as the wave traveled outward to 2 m and its amplitude decreased. The rise time became considerably shorter than predicted by weak-shock theory for situations in which it exceeded about 10% of the half-duration of the N wave. [This work was supported in part by the Office of Naval Research.]
Diffraction of a Gaussian Light Beam by Cylindrical Ultrasonic Standing Waves
Authors: Hargrove L. E.
Published: October 2005

This paper presents some results of theoretical and experimental examination of the farfield diffraction of a Gaussian light beam that has passed axially through a cylindrical ultrasonic standing wave. The range of parameters within which the light-beam diameter and sound wavelength are comparable is particularly emphasized. The theoretical approach is appropriate to the range of parameters for which the ultrasonic perturbation of refractive index may be characterized as an axially symmetric phase grating. Although the diffraction integral was not completely integrated in terms of familiar functions, some potentially useful expressions for the average and the time-dependent light intensities were obtained. Theoretical and experimental results are in good agreement.
Acoustical Holography Using Liquid Crystals
Authors: Werchan Ronald , Cook Bill D.
Published: October 2005

We have previously reported [J. Acoust. Soc. Amer. 47, 74 (1970)] that cholesteric liquid crystals can be used to visualize ultrasonic fields. Liquid crystals provide a spatially continuous display of the radiation field in a plane. Photographing the patterns of interfering coherent acoustic fields retains sufficient phase information for image reconstruction. Thermal diffusion is found to be a limiting factor.
The Position-Dependent Power Spectrum of Reflected Noise
Authors: Lusted Dean
Published: October 2005

Noise appears grossly to shift the power spectrum as a function of distance from the reflecting surface with source and observer static (e.g., the nearer the ear to the reflecting surface, the higher the predominant pitch of the noise appears to be). The predominant pitch similarly appears to be dependent on the angle of reflection (e.g., in contrast to the Doppler effect, the pitch of the noise of an overhead moving source appears to decrease on approaching but appears to increase on passing the observer). Analysis of tape recordings of a ventilating fan noise over a clay floor in a large building demonstrate the variation of the power spectrum as a function of elevation above the clay floor and the angle of reflection.
Cochlear-Microphonic Phase Characteristics
Authors: Dallos P. , Schoeny Z. G. , Cheatham M. A.
Published: October 2005

The interscala phase of the cochlear microphonic (CM) was measured in turns two and three in guinea pig cochleas, and at two locations in turn one of guinea pig and cat cochleas. Phase measurements were made at a wide range of stimulus frequency and intensity. The relative phase between CM in scalae vestibuli and tympani of a given turn appears to be a sensitive indicator of the contributions to the recorded CM of local and remote potential generators. It appears that in guinea pig and cat the local response can be measured up to 10 000 Hz in the first turn, and in guinea pig up to 3000 Hz in the second turn and up to only 500 Hz in the third turn. In the round-window region, complex phase patterns are demonstrated in both species.
Automatic System for Synthesis-by-Ruale
Authors: Browman C. P. , Coker C. H. , McMahon L. E. , Umeda N.
Published: October 2005

A fully automatic system for conversion of printed text into speech sounds is described. The system is divided into two parts: one part generates prosodic information from programmed rules, and the second part synthesizes the sounds. The sound synthesizer is realized by a programmed articulatory model of the vocal tract [C. H. Coker, J. Acoust. Soc. Amer. 47, 49 (1969)]. This paper focuses mainly on details of prosodic-feature assignment. This part of the system contains a syntax analyzer and a dictionary. Using information from the dictionary, the syntax analyzer assigns a phrase category to each word (subject, verb, object, etc.) and a potential for a pause at every phrase boundary. Each word is then assigned a stress and pitch contour using the pause potentials obtained from the syntax analyzer. In the last stage of the prosody generation, each phoneme is assigned duration, pitch, and intensity controls, compatible with the articulatory model program. In the articulatory model, coarticulation which depends upon phoneme duration is automatically treated. The prosodic-rule program is implemented for time sharing on an on-premises GE-635 computer. This program is linked via a data-communications set to the synthesizer implemented on a DDP-516 laboratory computer.
Speech Synthesis by Concatenation of Formant-Coded Words
Authors: Rabiner Lawrence R. , Schafer Ronald W. , Flanagan James L.
Published: October 2005

One technique for synthesis of limited-context messages is to concatenate individual words. Previously, this has been accomplished by concatenating the acoustic waveforms of isolated words. The synthetic output is intelligible but sounds irregular. One difficulty is that the word waveforms can not easily be adjusted in duration. Also, no simple means exists for making smooth acoustic transitions from one word to the next. Formant-coded speech, on the other hand, is exceedingly flexible. Words can be lengthened or shortened, formants can be manipulated, and pitch contours can be superimposed on the formant data to simulate normal inflection. A speech-synthesis system based on concatenating formant-coded words has therefore been implemented on the Honeywell DDP-516 computer. Using interactive computational techniques, a model for synthesizing strings of seven digits (as in a telephone number) has been studied. For such a limited-context message, simple rules for timing and for generation of a pitch contour have been used. Interpolating functions, based upon spectral derivatives, enable the formant contours to make smooth transitions between words. In its preliminary form, the system has been used to synthesize seven-digit number strings in a carrier sentence automatically. Recordings of the synthetic output will be demonstrated.
A Large Multipurpose Hall and Electroacoustics
Authors: Ditamore J. W.
Published: October 2005

A theatre having a seating capacity of 6080, a volume of 1 320 000 ft3, and a midrange reverberation time of 1.4 sec has a demand for presentation of events requiring both reinforcement and considerable variation in reverberant character. A system of distributed loudspeakers and delayed sound, modified by a reverberation chamber, is deployed over the ceiling surfaces. The reverberation time can be instantly varied between 1.4 and 2 sec. Operational techniques have been studied to determine a method for the most effective application. A closed monitoring booth with communicable access by a sound director is provided. The control console function provides for independent channel equalization and a group-mastering arrangement to provide for proper accenting of multimicrophone pickup. Stage playback is used for performer support. The types of programs include symphony orchestras, variety shows, singers, instrumentalists, and lecturers. The system has been in operation for about ten years. It has been observed that the audience appears to reflect approval of the sound they hear in the form of more enthusiastic applause and standing ovations than was previously noted for the same type of program material performed without the aid of electroacoustics.
Acoustics of St. Peter's Basilica, Rome
Authors: Shankland R. S. , Shankland H. K.
Published: October 2005

With Vatican permission, we made acoustical measurements in St. Peter's Basilica in May 1970. The reverberation times for this largest church in the world (20 000 000 ft3) are much shorter than expected; those for the empty Basilica at midfrequencies being about 7.5 sec. This unexpectedly low value results because St. Peter's is a group of five large churches and a number of smaller spaces weakly coupled acoustically. Analysis by standard reverberation theory and simple considerations of acoustical coupling between the spaces agrees with the observations. Measurements made in 1966 with a large congregation gave reverberation times of about 5 sec. In 1964, when the Basilica was filled with highly absorbing seating for the Ecumenical Congress, the reverberation times were about 312 sec. For the 200th anniversary Beethoven celebration on May 23, 1970, a complete concert-hall stage was installed in the rotunda and the acoustics for Miss Solemnis were judged excellent by critical musicians. The exceptional acoustical properties are due to the multiple coupled air spaces into which the Basilica is divided, and to the diffusion produced by the wealth of architectural detail and sculptural ornament.
Tubular Microphone Windscreen for In-Duct Fan Sound-Power Measurements
Authors: Bolleter Ulrich , Crocker Malcolm J. , Baade Peter K.
Published: October 2005

The design of a porous tabular windscreen for in-duct fan sound-power measurements is described. Such a windscreen tends to cancel out turbulent pressure fluctuations. The windscreen also modifies the response of a microphone to acoustic waves, since it effectively converts an omnidirectional microphone into a line microphone with a pronounced directivity. This directivity can be used with advantage in both the plane-wave and cross-mode frequency regions, since the microphone sensitivity to reflected waves is reduced. However, in the cross-mode region, this directivity is a complication, since the acoustic power carried depends upon the angles at which the cross modes propagate. The ideal directivity in this region for estimation of sound power from pressure measurements is (cosθ)12. The directivity has been made to approximate this. Experimental data of the frequency response, directivity, and signal-to-noise ratio are presented. [Work done partly at Herrick Laboratories, supported by Air Conditioning and Refrigeration Institute, and partly at Carrier Corporation.]
Supervision of Heat and Power Machinery by a Telemetric Electroacoustic Method
Authors: Schaudinischky L. H. , Schwartz A.
Published: October 2005

A telemetric electroacoustic method is explained, enabling the discovery of irregularities in the machinery noise, by hearing, after the general noise level has been reduced to a low level, eliminating the masking effect of the original high noise intensity. In addition, an objective system is proposed, using transducers for vibration as well as for airborne sound. Continuous recording, the introduction of electric filters, and the comparative observation of standard vibration and noise curves with those produced by the machinery (applying double beam oscillographs, spectral line analysis, etc.) are also analyzed.
Noise Analysis of Sources in Data-Processing Equipment
Authors: Peterson R. H. , Smith W. C. , Zelenski R. E.
Published: October 2005

A critical step in mechanism noise reduction for data-processing equipment is identification of sources. Techniques such as disabling mechanisms, microphone probing, and frequency analysis are useful here. We have discussed procedures based on noise-time analysis within machine cycles at past Acoustical Society of America meetings as being particularly useful for this work. For high-speed impacting machinery, normally used analog acoustical instruments are inadequate for noise-time analysis. Procedures have been devised using a high-speed electronic switch attenuator in a “stroboscopic” mode to overcome these limitations. This technique has been useful for source identification and examples are presented. Digital procedures have considerable potential for these applications. Fast Fourier transform digital filtering, and related techniques are useful and we have used these procedures where applicable in noise-time analysis using an IBM 1130 computer system. The practical limit here is in processing time and/or computer size (and cost). Our present direction is combining the best of both digital and analog techniques in a hybrid system. The resulting approaches will be discussed as more nearly optimum than other approaches and most usable for mechanism noise identification.
Theoretical and Experimental Results for Coaxial-Flow Jet Noise
Authors: Mason V. , Eldred K. M.
Published: October 2005

A simple theory has been developed for the prediction of the noise reduction due to the interaction between a primary jet and a slower coaxial secondary jet. The theory is compared with the results of a series of more than 300 model coaxial jet experiments in which area ratio, velocity ratio, primary-nozzle Mach number, primary-flow total temperature, and relative axial position of the primary and secondary nozzles were varied over the ranges typical of existing and projected fan-jet engines. The agreement between theory and experiment was found to be very good, considering the simplicity of the theory. The noise output of the model jets was scaled to give the noise output of full-sized jets. The over-all sound-power level and perceived noise level on a 1500-ft sideline were calculated. For constant thrust, the greatest noise reductions occurred for coplanar nozzles with area ratio of 10 and velocity ratio of 0.5. This configuration yielded a 9-dB decrease in over-all sound power and a 10-dB decrease in maximum perceived noise level. The experimental results were also reinterpreted to indicate the acoustically optimum configuration for a practical bypass engine and the acoustic penalty that results from slight deviations from this optimum configuration determined. [Research supported by the Federal Aviation Administration.]
Auditory Flutter Fusion as a Measure of Environment on Mental Stress
Authors: Hale Paul N. , Mayyasi Adil M.
Published: October 2005

This research was conducted to evaluate the feasibility of utilizing the deviation in auditory flutter fusion as a predictor of induced mental stress resulting from variations in environmental temperature and illumination. Auditory flutter fusion is a sensory effect tantamount to visual flicker fusion in the auditory sense. The experiment involved the performance of a mental-stress task consisting of solving arithmetic problems. This task, which depends on prior learned information, was selected as the mental task representative of the types performed by office personnel. Six college male students 20–23 years of age were used. Judgments were made of two thresholds (i.e., fusion and flutter) in the prestress and poststress periods. The deviations due to the mental stress induced during the 1-h stress period were determined. The experiment was conducted under the combined environmental effects of three levels of environmental temperature (60°, 75°, and 90°F) and three levels of illumination (20, 50, and 100 fc) with repeated measures. There was no noise induced in the stress period. A completely randomized design, using a factorial arrangement, was employed for treatment by analysis of variance. The results indicate that, regardless of the threshold utilized, temperature (i.e., 60°–90°F) and illumination (i.e., 20–100 fc) have no statistically significant effect on the deviation in auditory flutter fusion.
Evaluating the Over-all Acoustical Performance of Flight Helmets and Headsets
Authors: Greene J. W. , Williams C. E. , Forstall J. R.
Published: October 2005

The objective of this study was to obtain data which would be helpful in developing a standardized test procedure for evaluating Navy flight helmets and headsets with respect to both noise attenuation and the reception of auditory signals. Masked threshold measurements for pure tones and speech, and intelligibility measurements in noise, were obtained from subjects wearing various helmets and headsets while in a noise field of 100 dB. In addition, tape recordings were obtained of intelligibility word lists presented to a manikin head fitted with the same flight helmets and headsets while situated in the noise field. These recordings were then presented to groups of listeners. Data obtained for the various helmets and headsets are presented and discussed.
Noise Levels inside Diving Chambers during Compression and Decompression
Authors: Murry Thomas
Published: October 2005

The noise levels inside diving chambers and submarines have been suggested as a possible contributer to the hearing losses of Navy divers and submariners. In this experiment, sound-pressure levels of the noise in a diving chamber were measured during compression and decompression. Several men were situated in a diving chamber which was pressurized to a depth equal to 100 ft of sea water. Two dives were made. In the first, measurements were taken during compression with a piezoelectric microphone oriented so that it was approximately in a horizontal line with the diver's ear and facing away from the intake valve; during the ascent stage, the microphone was at the same position in the chamber but hanging downward at the diver's ear level. The microphone was previously calibrated under pressure, using the reciprocity calibration technique. Measurements were taken with an octave-band noise analyzer located outside the chamber. The results indicate that the noise levels were highest in the frequency range between 300 and 4800 Hz. The results are discussed with relationship to proposed damage-risk criteria for Navy personnel.
Glottal Parameters and Some Acoustic Measures in Patients with Laryngeal Pathology
Authors: Koike Y. , Takahashi H.
Published: October 2005

High-speed motion pictures of larynges with different pathologies were taken simultaneously with recordings of the acoustic signals picked up by a contact microphone coupled to the neck. The acoustic signals were displayed on an oscilloscope and photographed onto the same film as the laryngeal images. A semiautomated digital reduction system was employed to reduce the acoustic data and glottal dimensions into digital information. The amplitude of the pressure signal and laryngeal parameters such as glottal area, glottal width, and excursion contours of both folds were calculated and displayed by computer programs. A good agreement was observed between the periodicity of the contact-microphone signal and that of glottal area, though the phase relation between the two parameters varied considerably from patient to patient. Relations among the glottal area and other laryngeal parameters mentioned above were considered. It is pointed out that the glottal-width function does not represent the glottal-area function in many cases with pathologic larynges. The validity of the contact-microphone technique for extraction of the fundamental periods of speech is discussed in reference to the acoustic approach to detection of laryngeal pathology. [This study was supported by two U. S. Public Health Service grants.]
Phonation During Glottal Stops
Authors: Hamlet S. L.
Published: October 2005

The presence of glottal closure during phonation was determined by transmitting continuous-wave ultrasound through the larynx and detecting it on the opposite side. In a series of glottal stops, vocal-fold vibration does not always completely cease during the glottal stop, although the pitch drops rapidly at that time, the vocal intensity is reduced, and the closed phase of the vocal-fold vibratory cycle is proportionately long. Phonation of this sort may be similar to vocal fry. [Supported in part by a U. S. Public Health Service grant.]
Is Your Measure of Speech Level Valid … or Even Reliable?
Authors: Brady Paul T.
Published: October 2005

The equivalent peak level (epl) of a speech sample is an estimate of the peak of the instantaneous level distribution, based on a power measurement [J. Acoust. Soc. Amer. 44, 695–699 (1968)]. It is an objective precisely defined measure that can be immediately instrumented by anyone having a computer with an A to D converter. In this study, the epl is compared with traditional speech-level measures, and the following conclusions are drawn: (1) epls tend to be normally distributed among many talkers; (2) during continuous speech, the epl is about 10 dB higher than the average power; (3) during telephone calls on a particular circuit studied here, epls average 14.7 dB higher than average power; (4) In estimating peaks on telephone calls, 5.2% of the instantaneous-speech waveform exceeds the epl, and 1.5% exceeds the epl plus 3 dB; and (5) subtracting 11 dB from the epl yields a rough conversion to VU (volume unit), though the VU is highly variable among observers and correlates poorly with any of the above objective measures.
Interference Filtering in Hydrophone Calibrations
Authors: Poché Lynn B. , Sabin Gerald A.
Published: October 2005

A method is suggested for filtering the interference signal that is superimposed upon the direct signal when low-frequency sound is transmitted between a projector and a hydrophone closely spaced in shallow water. The simple digital technique of a running mean is remarkably effective, within certain limitations, if the span or “window” of the mean is chosen carefully. The method lends itself to machine processing of data from automated calibration systems. Fourier analysis of typical data samples confirms the method of choosing the smoothing window.
Frequency, Amplitude, and Waveform Modulation in the Vocal Vibrato
Authors: Oncley P. B.
Published: October 2005

Various observers have noted that the fluctuation of pitch in the normal vocal vibrato is accompanied by a fluctuation of loudness and of timbre. Although this coupling is an implicit outgrowth of the formant principle, the point does not appear to have been explicitly pointed out in the literature, and seems to have been missed by some. Consider any single partial lying on the slope of a resonance peak, such as a vowel formant. If the slope is positive, an increase in frequency leads to an increase in intensity; if negative, the converse is true. Since the voice has many partials randomly located with respect to the formants, the loudness may be expected to vary with pitch, but with sometimes a positive and sometimes a negative phase relation. The overtone structure will also vary though the vibrato cycle. This timbre vibrato is clearly shown in a motion picture made some years ago at Bell Telephone Laboratories. Several other interesting points concerning the practical utility of the vibrato in singing are also mentioned.
Aerodynamic Study of Vibrato and Voluntary “Straight Tone” Pairs in Singing
Authors: Iwata Shigenobu , Large John
Published: October 2005

Vibrato and voluntary “straight tone” were juxtaposed in a task in which fundamental frequency and intensity were kept constant. The vowel /ɑ/ (“ah”) was sung by advanced student female singers in three different registers: chest register at 220 Hz, middle register at 440 Hz, and head register at 880 Hz. Air flow was recorded by a pneumotachographic system. It was found that fluctuations of air flow in vibrato were synchronous with the amplitude vibrato. These fluctuations were more obvious in middle and head registers than in chest register, probably because of changes in glottal resistance. The air-flow rate for vibrato is usually 10% higher than that for straight tone in all registers. This relationship may be expressed in the formula: AFR(v) = 1.11×AFR(st)+7.1 cm3/sec. Such a result can be explained on the basis of the greater average glottal resistance resulting from the constantly working musculature necessary to inhibit the vibrato. The results of this study suggest that the physiological control of vocal vibrato is a combined laryngeal and respiratory mechanism, with the laryngeal factor predominating. [This research was supported by a U. S. Public Health Service Research grant from the National Institute of Neurological Diseases and Stroke.]
Speaker Recognition: Basic Considerations and Methodology
Authors: Hecker Michael H. L.
Published: October 2005

This paper is based on an interpretive survey of the literature. Speaker recognition is defined as any decision-making process that uses speaker-dependent features of the speech signal. The origin and nature of these features are discussed, and three general methods of speaker recognition (aural, visual, and automatic) are described. Each method is illustrated by several experimental studies. Speaker recognition by listening appears to be the most accurate and reliable method at the present time. Speaker recognition by visual comparison of spectrograms is coming into use in criminology, but the validity of this method is still in question. Speaker recognition by machine is limited by various design shortcomings, both of concept and implementation.
The Noise of Melting Icebergs
Authors: Urick R. J. , Colvin G. M. , Tulko T. J.
Published: October 2005

Icebergs seem to have escaped serious attention as sources of underwater sound. We have measured the noise of icebergs by using sonobuoys dropped by an aircraft at distances between 200 and 10 000 yd. Two isolated icebergs 130–150 ft high were measured at a location northeast of Newfoundland. Noise apparently originated by the bergs was found to have a spectrum flat to about 8 kHz, with spectrum levels of −37 and −42 dB re 1 dyn/1 cm2 at 200 yd from the two bergs. In the laboratory, we have observed the noise of ice melting in a small pressure vessel containing a hydrophone. Two kinds of noise were heard. One was an impulsive noise apparently due to thermal cracking that disappeared under an applied pressure. The other was a sizzling frying sound that became louder as the pressure increased but occurred only with cloudy milky ice and not with clear ice free of air. We surmise that this noise is caused by the implosion of tiny air bubbles trapped in the ice as their walls become broached during the melting process. Alternatively, the noise of real icebergs may be due to tiny explosions of trapped air bubbles having high internal pressures. Iceberg noise should therefore depend on size, depth, air content, rate of melting, and origin of the berg.
Maximum Eigenvalue (Vector) Beamforming with an Adaptive Antenna Array
Authors: Owsley N. L.
Published: October 2005

An adaptive array beamforming technique based on an eigenvector interpretation of the conventional (i.e., time delay and sum) single-frequency array directional response pattern is presented. In particular, the directional response pattern of a K-element antenna array can be expressed in terms of the spectral density matrix of the spatially received data. This directional response pattern can, in turn, be expressed as a sum of K terms, each involving a single eigenvector of the spatial spectral density matrix where each term in the sum is weighted by the corresponding eigenvalue. The array beamforming technique presented exploits the fact that positional information regarding the spatially coherent, source-like components of the array's environment concentrates in the larger spatial eigenvalues and related eigenvectors. This “clustering” effect allows the conventional directional response pattern to be approximated by a truncation of the eigenvalue-weighted sum. A single-term approximation to the conventional bearing response pattern is the subject of this paper. An adaptive array processing technique is proposed which recursively obtains the single-term truncation approximation to the bearing response pattern. The potential of this array processing technique for automatic multiple source location and tracking is examined.
Applications of Acoustics to Oil Well Surveying
Authors: Gollwitzer Lee H.
Published: October 2005

Oil well surveying is comprised of lowering an instrument by means of an electrical cable into the borehole to obtain measurements of physical parameters of the formations. The velocity-logging tool provides a continuous measurement of compressional velocity of the rock strata. Under certain conditions, shear velocity can also be obtained. These measurements provide data on lithology, porosity, and type of fluid in the pores. The design of the acoustical portion of these tools is unique because of the wide range of pressures and temperatures encountered, and the special mechanical requirements of oil field equipment. Other acoustical tools have been developed to determine sizes of caverns and provide an acoustic image of the borehole wall.
Nonmetric Scaling of Loudness-Ratio Data
Authors: Richards Alan M. , Levitt Harry
Published: October 2005

Loudness scales for 1-kHz tones, as determined by conventional scaling procedures, have yielded conventional loudness functions which grow as approximately the 0.50 power of the sound pressure. That is, a 10-dB increase in intensity corresponds roughly to a doubling of loudness. By plotting the loudness as a unidimensional logarithmic function of intensity, we imply that if A is twice as loud as B, which, in turn, is twice as loud as C, then A is four times as loud as C. In order to test this prediction loudness ratio estimates were obtained from 10 subjects on four 7×7 matrices of stimuli at 1 kHz with differing interstimulus spacings (30–90 dB SL in 10-dB steps; 40–70 dB SL in 5-dB steps; 40–55 dB SL in 2.5-dB steps; and 30–90 dB SL in irregular intervals). Using a multidimensional representation of the data based upon Shepard's analysis of proximities [R. N. Shepard, Psychometrika 27, 125–140, 210–246 (1962)], a simple two-dimensional configuration was found which adequately represented the data. If the diagram is projected on only one dimension, an approximation is obtained that is locally accurate, i.e., the loudness-ratio data are accurately represented over a limited range.
Radiation of Flexible Piston in Spherical Baffle
Authors: Lubell Alan H.
Published: October 2005

This problem is a natural continuation of the works of Morse on the rigid piston in a rigid spherical housing. Its solution is made possible by the little known but widely applicable method of Botman. A free circular disk driven at its center is assumed as the dynamic model. The method of Kirchhoff as given by Rayleigh is used to find the values of ka for the first two axisymmetric modes. These together with the rigid piston mode give an adequate representation for the range of ka of interest (ka<8). Botman's method is used in conjunction with an IBM 7090 computer. Machine limitations dictated the use of only 10 spherical harmonics: close fits to vibrational modes were not possible in spite of the choice of θ = 30° for the angle subtended by the piston. No significant error in the integrated radiation reaction is expected, however,owing to the cutoff properties of spherical wave impedances. Computed graphs of X, R, directivity, and source level with comparison to Morse's results are given. Computed patterns are also shown. Some inferences with regard to the design of practical underwater radiators characterized by wide frequency range and omnidirectional patterns are made.
Thin Fluid-Loaded Plates
Authors: Nayak P. Ranganath
Published: October 2005

The admittance of thin plates with a heavy fluid on one side, excited by spatially and temporally harmonic line forces and moments, is obtained. The forcing frequency f is assumed to be below the critical frequency fc. These line admittances are then used to analyze the non-normal incidence of plate bending waves on simple and clamped line supports. Numerical results are presented for (a) the acoustic radiation from the support, and (b) the transmission of the bending wave past the support. Significant differences are found from the in-vacuo results. The results for the transmission of plate waves past supports are of particular importance in the calculation of vibration transmission along fluid-load beam-plate arrays, such as ship hulls. Neglect of the fluid-loading effects may lead to serious underestimation of the transmitted vibration in such structures.
Sonic Boom Induced Building Structure Responses Including Damage
Authors: Clarkson Brian L. , Mayes William H.
Published: October 2005

Concepts of sonic boom pressure loading of building structures and the associated responses are reviewed and results of pertinent theoretical and experimental research programs are summarized. The significance of sonic boom load time histories, including waveshape effects, are illustrated with the aid of simple structural elements such as beams and plates. Also included are discussions of the significance of other such phenomena as three-dimensional loading effects, air cavity coupling, multimodal responses, and structural nonlinearities. Measured deflection, acceleration, and strain data, from laboratory models and full-scale building tests are summarized, and these data are compared where possible with predicted values. Damage complaint and claim experience due both to controlled and uncontrolled supersonic flights over communities are summarized with particular reference to residential, commercial, and historic buildings. Sonic boom induced building responses are compared with those from other impulsive loadings due to natural and cultural events and from laboratory simulation tests.
Animal Response to Sonic Boom
Authors: Bell Wilson B.
Published: October 2005

Experiments and observations have been made to test the effects of sonic booms (real or simulated) on mink, horses, dairy and beef cattle, sheep, turkeys, pheasants, and chickens. Several of these tests were carried out under field conditions. Results of some of these trials are considered similar to the sensory effects of sonic booms on humans. In one controlled experiment, there were no adverse effects on the hatchability of chicken eggs exposed to sonic booms on each of the 21 days of incubation. In another experiment, three groups of mink exposed to simulated sonic booms showed only slight differences in total kit mortality, at 10 days of age, between boomed and control groups. A current field trial involving the effect of sonic boom startle on pregnant and whelping mink is discussed. Field observations of other species of domestic animals are presented. The need for fundamental research on physiological responses of animals to impulse noise patterns is emphasized. Following further analysis of data now available, additional facts may be needed on selected domestic and wild animals and marine life.
Discrimination of Minimum- and Maximum-Phase Waveforms
Authors: Leshowitz Barry
Published: October 2005

Observers were asked to discriminate between a pair of computer-synthesized waveforms having identical long-time energy spectra but different short-time spectra. One member of the pair was constructed by passing a time waveform, called an excitation function, through a simple resonant circuit. We call this waveform “minimum phase.” “Maximum-phase” waveforms were constructed by passing the same excitation function through a filter whose impulse response is reversed in time. The pairs of signals thus generated have identical energy spectra but differ in their phase spectra. Within the duration of the impulse response, the effect of time-reversing the impulse response is to produce what is called local time reversals in the output waveform. Three excitation waveforms were used: a noise burst, a sinusoid, and a pulse. The effects of duration of the impulse response and bandwidth of the filter were examined. In agreement with phase discrimination of transients, observers can discriminate local time reversals within sustained stimuli down to about 2 msec. For a given excitation function, the discrimination was maintained so long as the bandwidth of the filter was between 250 Hz and 30 Hz. [Research supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]