bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of a Rod Subjected to a Rectangular Input Pulse
Authors: Rose Joseph L. , Schaller Richard , Mortimer Richard W.
Published: October 2005

The Mindlin-Herrmann and modified Mindlin-McNiven bar theories are used to analyze longitudinal impact problems. Solutions, obtained by the method of characteristics, are compared with experimental data and with a two-dimensional finite difference solution by Bertholf. In particular, the elastic response of a 34-in. diam cylindrical steel rod subjected to longitudinal impact is studied experimentally and analytically. Excitation in the bar is produced by impacting the specimen with an impacter bar of similar cross-sectional geometry and material properties. Velocity of the impacter bar at time of impact as well as the longitudinal and circumferential strain histories along the specimen are experimentally obtained. Knowing the impacter velocity, the velocity input pulse is determined and used as the boundary condition for the solutions of the two theories. Comparison of experimental and theoretical results indicate the following: (1) The longitudinal velocity of the pulse initiation (or head) travels with the theoretical bar velocity. (2) The magnitude, shape, and width of the longitudinal and circumferential strain pulses as measured agree quite well with results obtained by both theories. Techniques for evaluating the Mindlin-Herrmann, Mindlin-McNiven, and other bar theories for certain applications are included in the paper. For example, it is shown that for certain ranges of input pulse durations, the strain predications from the Mindlin-Herrmann and Mindlin-McNiven theories give strain magnitudes that differ by at least 15%.
Critical Response of Some Multidegree of Freedom Mechanoacoustical Systems
Authors: Rajagopal Ganesh , Seshadri T. V. , Lowery R. L.
Published: October 2005

The maximum amplitude of response to a pulse of a plate window in combination with a room and a doorway is shown to be considerably more than that of the plate alone. Two pulse shapes are considered: sine and N wave. Analytical solutions are derived for the linear systems. For large amplitudes of plate vibration, the governing differential equations are nonlinear and the maximum response is obtained by numerical techniques. Results are presented for the maximum deflections and stresses for different modes of application of the pressure pulses. [Work supported by the National Aeronautics and Space Administration.]
Development of an Equation for Defining the Acoustics of Office Landscape
Authors: Krishnan P. V. , Sulewsky James E.
Published: October 2005

Acoustical conditions under which speech communication and speech privacy may be achieved in open-plan office landscape spaces are discussed from a signal-to-noise ratio concept. Based on this concept and assuming free field conditions, a simple design equation relating speech level, speaker orientation, speaker-listener distance, masking background level, and barrier (screen) attenuation with signal-to-noise ratio is developed. Methods of establishing design parameters for speech communication and speech privacy are illustrated, based on this equation.
The Class Circle—an Acoustical Design Concept for Open-Plan Schools
Authors: Pirn Rein
Published: October 2005

The acoustical acceptability of many academic spaces depends upon the ease of speech communication within groups of students and upon the degree of speech privacy between such groups. The acoustical variables that govern these relationships in terms of the articulation index (AI) were demonstrated in earlier work [R. Pirn, J. Acoust. Soc. Amer. 48, 98(A) (1970)]. The present concept prescribes the arrangement of the students and teacher of any one class in a circle defined by a reflective floor in an otherwise absorptive space, which takes advantage of the variations in the value of AI due to speaker orientation and speaker-to-listener distance. For design values of AI>0.50 (intraclass) and AI<0.20 (interclass) this paper demonstrates (1) the relationship between circle size and the required ambient noise, (2) the required separation between circles with and without space dividers, and (3) the implications on floor area utilization. It is shown that the concept is compatible with conventional school designs for class capacities of up to 35 students.
Cochlear Potentials and Electrolyte Contents in Endolymph in Experimentally Induced Endolymphatic Hydrops
Authors: Konishi T. , Kelsey E.
Published: October 2005

It has been reported that surgical obliteration of the endolymphatic duct and sac brought about the endolymphatic hydrops in guinea pigs [R. S. Kimura, Ann. Otol. Rhinol. Laryngol. 76, 665 (1967)]. In order to reveal functional disturbances in endolymphatic hydrops, we undertook measurements of cochlear potentials and sodium and potassium contents in the endolymph in guinea pigs with obstruction of the endolymphatic duct. The sodium and potassium contents in the endolymph were determined in 19 cases of endolymphatic hydrops and the cochlear potentials were measured in 12 animals. The endocochlear potential (EP) and the cochlear microphonics (CM) were recorded from the scala media of the basal and third turns. The results obtained were compared with those obtained in sham operations. In all guinea pigs in which the endolymphatic duct and sac were obliterated successfully, endolymphatic hydrops were observed 5 to 10 weeks postoperatively. In these animals EP was markedly decreased (62.9±14.0 mV). The average EP was 86.4±8.2 mV in the sham operation group. In addition, the endolymphatic hydrops resulted in significant loss of CM in the third turn and, to a lesser degree, in the basal turn. A slight rise in sodium content (1.7±1.9 mEq/L) was observed, compared with 0.9±0.6 mEq/L in the sham operation group. The average potassium content was 162.1 mEq/L in the endolymphatic hydrops and 161.5 mEq/L in the sham operation. The relationship between morphological and functional changes was discussed.
Homomorphic Analysis—Synthesis System for Wind Instrument Tones
Authors: Strong William J. , Plitnik George R.
Published: October 2005

A homomorphic filtering system similar to one described by Oppenheim [J. Acoust. Soc. Amer. 45, 458 (1969)] for speech was applied to the analysis and synthesis of wind instrument tones. The input signals were sampled 10 000 times per second and multiplied by a 25-msec time window. New analyses were made at 10-msec intervals. A minimum phase characteristic was used in the synthesis process. Evolution of the spectral envelope was observed by comparing smoothed spectra from the attack, steady-state, and decay parts of the waveform. The relative stability of the spectral envelope for different tones from the same instrument was observed by comparing the corresponding smoothed spectra. The scheme produces “intelligible” tones in the sense that synthetic tones of one instrument can be identified as belonging to that instrument. However, the quality of the synthetic tones is often inadequate. The relative merits of this scheme as applied to music and speech will be discussed. Examples of the synthetic tones will be presented.
Electroacoustic Teaching Aids to Music Education
Authors: Martin Daniel W.
Published: October 2005

A variety of electroacoustic musical instruments, electroacoustic accessories for traditional musical instruments, and audio recording and playback devices have been developed and adapted through headset listening for (a) private home practice, (b) monitored practice, (c) individual instruction within a group or classroom of musical instruments, (d) prerecorded instruction of individuals or groups, (e) multi-group instruction, and (f) multi-ensemble rehearsals within the same room. Special electronic and electroacoustically controlled instruments are provided, including Electropianos, electronic organs, electronic rhythm generators, electronic synthesizers, solid-body guitars, brass instruments with natural attenuators, and an Electroconsort table of six individually voiced electronic keyboards for elementary students. Integral modular music education systems allow mixing groups of different instruments for versatile teachers or mixed prerecorded tape instruction. Two-way speech communication is provided through microphones built into either instruments or music stands.
Sounds of the Mongoose Herpestes auropunctatus
Authors: Mulligan B. E. , Nellis D. W.
Published: October 2005

The vocal repertoire of Herpestes auropunctatus consists of about 12 basic sounds that may be isolated by the human ear. Physical analyses of a large sample of recorded mongoose sounds also indicate 12 types of vocalization and these sound categories correlate nearly perfectly with those distinguishable by the human ear. The mongoose modulates its sounds intensively, spectrally, and temporally. Distinctive features of these sound types are their onset-offset transients, and their patterns of variation in amplitude and spectral content. The extensive vocal repertoire of Herpestes auropunctatus provides a means of interspecific and intraspecific communication under the conditions of limited visibility that exist in its favored habitat of dense grass and brush.
ATF3 Jet Noise: Uniquely Low, Uniquely Distributed
Authors: Gray L.
Published: October 2005

Measured ATF3 jet noise is analyzed and compared with that of a small turbojet and turbofan operating at comparable engine conditions. Shown by the data/analysis is (1) the ATF3's absence of the dramatic lobing of jet noise energy characteristic of other jet engines, (2) ATF3 jet noise levels 24 dB and 31 dB lower than the turbofan and turbojet, respectively, for operation at comparable thrust, (3) ATF3 jet noise 8 dB lower than the turbofan for operation at comparable jet efflux velocity, and (4) a jet noise variance between engines of ten times the logarithm to the base ten of the product of the ratio of the primary jet efflux velocity raised to the sixth power and the ratio of the primary jet nozzle diameter raised to the third power; i.e., 10 log10[(V2/V1)6(D2/D1)3].
Some Frequently Recurring Phonological Processes in English
Authors: Shockey Linda
Published: October 2005

If automatic recognition is ever to deal with any except the most formal of speech styles, it will have to consider at least a few very common phonological rules which apply in non-maximally-differentiated speech. Phonological literature on the whole treats all rules or processes equally, offering no way to discriminate between processes which are reflected rarely in practice and those which are relatively frequent and which, therefore, if incorporated into a recognition strategy, might result in greater success. This paper presents some of the most dominant processes found through analysis of recordings of reading and conversational speech from Midwestern and Eastern U. S. subjects. The acoustical properties of speech sequences showing evidence of these rules are also discussed.
Circular Lenses for Longitudinal Acoustical Viewing Systems
Authors: Clark J. A.
Published: October 2005

An acoustical viewing system employing a circular lens operates as follows: Waves scattered at an oblique angle by insonified objects on the ocean bottom are intercepted by a thin plate suspended horizontally above the bottom. Transverse plate waves, excited by the intercepted waves, are focused by a circular lens fastened integrally to the plate. One simple means for constructing a circular lens is to decrease the thickness of the plate (and thereby decrease the wave propagation velocity) in a region bounded by two circular arcs. The acoustical image formed on the plate, consisting of local transverse vibrations, provides a longitudinal view of the ocean bottom. The acoustical image can be detected optically or electronically. Three important advantages of an acoustical viewing system employing a circular lens over alternative designs are (1) inherent system rigidity, (2) elimination of image degradation due to multipath propagation phenomena, and (3) possibility of achieving direct acousto-optic image conversion even under such adverse conditions as must be anticipated at sea. An analysis of several factors influencing circular lens performance is given, including field of view, resolution, dispersion, boundary reflection, aberration, and sensitivity. [This work supported by ARPA and monitored by ONR.]
The Diffraction of Sound by a Finite Circular Baffle with a Monopole on Its Surface
Authors: Lauchle Gerald C.
Published: October 2005

The theory for the diffraction of sound from a point source located on the surface of a rigid finite circular disk is presented. Oblate spheroidal wave functions are used to formulate an exact solution for a very thin disk of elliptic profile. For the case of the point source at the axis of symmetry, directivity curves are computed. Also included are the directivity curves for a positive monopole on one side of the baffle and a negative one exactly opposite on the other side. The model represents a loudspeaker in a free circular baffle. It is shown that the resulting sound field can be approximated by a dipole of finite dipole axis at low frequencies. The equivalent dipole axis is computed for this range of frequencies. At higher frequencies the field can be approximated by a ring source and point source combination. They are both of equal, but opposite, strength and shifted in phase by π/2. The frequency response curve for the pressure along the axis of the baffle is computed and compared to experimental results. The agreement is excellent. The low-frequency asymptotic solutions are also derived and compared to the exact computations.
Automatic Formant Extraction Using Linear Prediction
Authors: McCandless Stephanie
Published: October 2005

An algorithm is presented for automatically extracting the first three formant frequencies and amplitudes during voiced segments of continuous speech. It uses as input the linear prediction spectra and a segmentation parameter to indicate voicing and volume. A linear prediction spectrum is a smooth curve whose peaks correspond to pole positions, and therefore, in general, to formants. Complications arise, however, during the following situations: (a) Two formants may merge into one peak (as in r and w). (b) One formant may disappear, legitimately (as in n and m). (c) Spurious peaks may appear (as in nasalized vowels). (d) F4 may be present to confuse the issue. The algorithm chooses the middle of each high-volume voiced region as an anchor point, and branches out from there in both directions in time. At each frame, formant slots are filled with available peaks on the basis of frequency position relative to an educated guess. After some special routines to check for unused peaks and/or unfilled slots (including a formant enhancement program to separate merged peaks) the educated guess is updated with the formant frequencies decided in the current frame, to be used in evaluating the next frame. The algorithm has been implemented on the UNIVAC 1219 and the Fast Digital Processor, a fast special-purpose computer, and has proven successful with a large number of unrestricted sentences.
Translation between Different Community Noise Exposure Measures
Authors: Copley Lawrence G.
Published: October 2005

In current widespread use there are about eight different measures of community noise exposure. These can be divided into two categories: discrete and random. The “discrete” measures are most applicable to distinct intrusive noises such as aircraft overflights or train passages. Included amongst these “discrete” measures are NEF, CNR, NNI, and CNEL. The “random” measures are most applicable to general fluctuating community noise. Included amongst these “random” measures are the statistical measures (L1, L10, L50, etc). and also such “noise pollution” measures as NPL and TNI. There is a practical need for a methodology to translate between “discrete” measures and “random” measures. The reason for this is that the noise climate in many urban neighborhoods is determined by both randomly fluctuating noises as well as discrete intrusions. The relationships between the two types of measure are partly mathematical and partly empirical. This paper is a progress report on a research effort to develop a translation methodology that will permit the evaluation of noise exposure from both randomly fluctuating and discrete intrusive sources. [Research supported in part by U. S. Department of Transportation].
The Effects of Distance and Topography in Highway Noise Attenuation
Authors: Goff Richard J. , Tsui Chung Y.
Published: October 2005

The attenuation of highway noise was studied at three sites each having a different topography. Site 1 is a flat field level to the highway while site 2 is a steep incline. The highway is elevated above the adjacent field at site 3. At each site, sound-pressure readings were taken for 5-min intervals at different distances from the edge of the road and compared with simultaneous readings taken at a reference distance. An analytical expression for the sound intensity at a point as a function of the distance to the highway and the traffic density was derived. The expression reveals that the individual noise sources approach a line source as the traffic becomes denser. Based on the line source assumption, multilane highway traffic can be combined into a single lane from which experimental results can be treated for the estimation of highway noise attenuation. The influence of the measurement location with respect to the traffic density is discussed.
Community Noise Impact from Military Helicopter Operations
Authors: Goldstein Jeffrey , Heymann Roger , Bragdon Clifford R.
Published: October 2005

Helicopter deployment and operations throughout the United States have mandated concern by the Army for studies of the environmental impact resulting from military helicopter operations. Federal and Department of Army guidelines for evaluation of helicopter noise were employed. Noise measurement stations were located throughout residential areas adjacent to bases having helicopter operations. Composite Noise Ratings (CNR) establishing zones of noise sensitivity were used complying with HUD guidelines. Although discretionary and unacceptable CNR zones were confined to the installations investigated or adjacent nonresidential tracts of land, operational recommendations were made to minimize possible community annoyance due to noise. It was concluded that the areas impacted from helicopters are not as widespread as those from jet aircraft due to the lower magnitude of noise levels. Community response is expected if pilots deviate from established noise-abatement flight patterns and procedures. There is a definite need to establish minimum altitudes for helicopter overflight. Runways utilized should be selected carefully to minimize noise levels intruding into residential areas. These conclusions are in agreement with other helicopter impact investigations. Special problem areas with respect to psychoacoustic response, blade slap, spectral content, meteorological effects, and multiple flights were encountered.
Parametric Acoustic Waveform Generation from Spherical Primary Fields
Authors: Hamilton Robert , Mello Peter , Moffett Mark B.
Published: October 2005

Parametric acoustic secondary signals which are generated largely within the nearfield of the primary sound beam exhibit a waveform proportional to ∂2F2/∂t2, where F is the envelope of the primary waveform and t is the time. However, the secondary waveform can be expected to tend toward ∂F2/∂t as more of the parametric generation occurs in the farfield of the primary beam. In an experiment conducted at the Millstone Quarry facility of the Naval Underwater Systems Center, the latter waveform has been produced by the modulation of a 330-kHz primary pulse from a 1.5-in.-diam underwater sound projector. [This work was supported in part by the National Science Foundation.]
Perception of Coarticulation in English VCV Sequences
Authors: Shockey L. , Lehiste I.
Published: October 2005

Öhman's 1966 investigation of the acoustic correlates of coarticulation in Swedish and English VCV sequences [J. Acoust. Soc. Amer. 39, 151–168 (1966)] indicates that terminal formant transition frequency values are strongly influenced by the nature of the transconsonantal vowel. However, the literature reflects no attempts to discover whether these coarticulation effects are perceptible, e.g., whether in a VCV sequence the initial VC carries significant perceptual cues as to the quality of the following V. The present experiment was designed to investigate the latter question. Forty-eight VCV utterances involving the vowels /i æ a u/ and the consonants /p t k/ were recorded and either the initial or final vowel removed by splicing techniques. The resulting tapes were played to listeners who were asked to indicate which vowel had been deleted. Results were random indicating that coarticulation effects are not sufficient cues to the perception of the vowels which occasion them. These results are counterevidence for the claim by Wickelgren [Psychol. Rev. 76, No. 1, 1–15 (1969)] that the “context sensitive” allophone may be a basic cue in speech recognition. The results also suggest that some coarticulation effects may not have to be taken into consideration in speech synthesis.
Loss in Cochlear Microphonic Sensitivity in Young Cat Ears Exposed to Intense Sound
Authors: Price G. Richard
Published: October 2005

Almost no data exist regarding the relative susceptibility of young ears to damage from high-intensity sound. If age is a factor in determining susceptibility to hearing loss, then damage-risk criteria should reflect it. Use of children in an investigation of this type is out of the question, however; therefore an animal model had to be substituted. As a preliminary step in this direction, anesthetized kittens were exposed to 5.0-kHz stimulation at 10 dB above that intensity necessary to produce a maximum cochlear microphonic (CM) output at 5.0 kHz (max+10) for periods totaling 50 min. Round-window CM sensitivity was measured before, during, and after exposure. Losses were compared with adult cats similarly stimulated. At max+10 the young ears showed significantly more loss than the adult ears (18-dB average loss as opposed to 9 dB).
Acoustic Antennas for Atmospheric Echo Sounding
Authors: Hall F. F. , Wescott J. W.
Published: October 2005

The successful utilization of acoustic waves for atmospheric echo sounding requires an efficient antenna, with high on-axis gain and suppressed sidelobes. Existing microwave antennas and optical searchlights have been adapted for acoustic use, and their performance measured. A conical horn reflector antenna made of fiberglass has given excellent performance at 1–5 kHz after being coated with a viscous damping tar to keep reverberation time short for the reception of weak echoes with minimum delay following the transmission of 20 acoustic watts from the antenna. Septum dampers have been used successfully on parabolic dish antennas. Antenna beam patterns have been measured on an outdoor range, across a canyon, and the results agree closely with predictions from diffraction theory. Absorbing, cylindrical antenna enclosures have been found effective in reducing sidelobe reception by 10 to 20 dB, also in agreement with predictions. Attention to antenna design should provide unimpaired echo sounder operation in an urban environment, and keep noise pollution from the sounder pulses below the annoyance threshold.
Signal Fluctuations in the BIFI Range
Authors: Kanabis W. G. , Sussman B.
Published: October 2005

Short-term and long-term fluctuation studies have been made in the BIFI Shallow X, Water Acoustic Range, which is 37 kyd in length. It is shown how time-smear analysis may be used to predict the extent of short-term signal fluctuation by taking into account the energy content of the “front” and “tail” of the received signal. The method is applied to an actual received signal with good results. Long-term fluctuation, such as that due to tide, is considered in terms of normal mode theory, using the results of the time smear analysis to provide an estimate of the relative strengths of the modes. When applied to the BIFI range this method predicts that tidal effects will cause negligible fluctuations in the received signal, due to the absence of modes other than the fundamental at this large range. This prediction was verified by experiment. At shorter ranges, the interaction of several modes will cause relatively large fluctuations in the signal as the water depth changes during the tidal cycle.
Earthquake Effects on Earth Dams
Authors: Bolton Seed H.
Published: October 2005

Possible effects of earthquakes on earth dams are outlined and illustrated by descriptions of the performance of the Hebgen Dam in the Hebgen Lake earthquake of 1959, the Sheffield Dam in the Santa Barbara earthquake of 1925 and the San Fernando Dams in the San Fernando earthquake of 9 Feb. 1971. Methods of analyzing the stability of earth dams during earthquakes are reviewed and dynamic analysis procedures for this purpose are illustrated by means of recent studies for specific projects.
Noise in Buildings
Authors: Tichy Jiri
Published: October 2005

This paper reviews the papers presented in the session on Noise in Buildings at the Conference on Noise Control, held and organized in July 1971 by Purdue University. The invited papers presented covered developments in sound transmission loss theory and practice (Vér and Ostergaard), and an extensive report on a noise abatement research program (Winzer). Contributed papers covered comparisons between field and laboratory evaluations of the sound transmission loss of several partitions (Grantham and Heebink), acoustical flanking in structures (Shiner), acoustically rated windows (Smith), and new wall constructions for high transmission loss (Sharp). Two other papers reported on recent theoretical developments in England of sound absorbers as sound insulators (Mulholland) and attenuation of sound in lined ducts (Bokor).
Ray Sweep-Out Method
Authors: Bucker Homer P.
Published: October 2005

To calculate the ray intensity field at a point (a receiver point) in range and depth one must locate all possible ray paths from the source to the receiver. When there is a large number of receiver points it is desirable to use a method in which all receiver points are considered as the rays are tested to see which ones travel from source to receiver. Consider the receivers to be located at depths z1, z2, z3, ⋯zN. Then two neighboring rays are traced out and 2N tables are set up that contain the intersection ranges of the two rays with the N receiver depths. By comparing the entries in the two tables for the same depth one can quickly determine which receivers have been bracketed by the neighboring rays. After one sweep of the vertical beam pattern of the source, all rays that can travel from the source to all receivers have been located; hence the name, ray sweep-out method. Special treatment is required in two cases: when only one ray crosses a receiver depth and when the source and a receiver depth are at an axis of minimum sound speed.
Stochastic Analysis of Ocean Microfluctuations for Ray Theory Intensity Calculations
Authors: Neubert J. A.
Published: October 2005

To facilitate a stochastic treatment of sound propagation in the random ocean, the rapid, small-scale microfluctuations are separated from the slow, large scale macrovariations in the Lagrangian form of the ray-intensity relation. The Lagrangian ensemble expectation of this expression yields an extension of the conventional ray theory intensity relation which permits consideration of partial coherence in multipath problems and a practical estimate for the standard deviation σI of the intensity about its expected value. The partial coherence factor is shown to be a function of the curvilinear range, the frequency and the oceanographic conditions while σI depends on the partial coherence factor and appears to saturate as this factor approaches zero.
Kelvin-Helmholtz Instability—A Mechanism for Bottom Loss
Authors: Polak J. A. , Stickler D. C.
Published: October 2005

The interface between two fluids in relative motion is unstable to disturbances having a frequency greater than a critical frequency. This is the Kelvin-Helmholtz instability. The hypothesis is put forward that this instability can be excited at locations where the sea floor is composed of unconsolidated sediments, and thereby provides a mechanism for an acoustic bottom loss. For currents of 0.1 kt the critical frequency is less than 15 Hz, and for a 0.001-kt current the critical frequency is less than 1.5 kHz. As a consequence of this hypothesis, it follows that two geologically similar regions can have different loss characteristics depending on bottom currents. Furthermore, bottom currents will induce an additional frequency dependence in the acoustic bottom-loss characteristics. It is speculated that the Kelvin-Helmholtz instability is responsible for sediment transport on the continental shelf as well as the spectacular turbidity currents which sometimes occur in canyons. It is also suggested that in ocean regions where there are sharp density and current gradients, for example at the thermocline, absorption of acoustic energy can take place. [This work was supported by Contract N00039-71-C-0307.]
Intensity Discrimination of Pulsed Sinusoids: The Effects of Filtered Noise
Authors: Viemeister N. F.
Published: October 2005

It has been shown repeatedly that Weber's law does not hold for intensity discrimination of pulsed tones. The masking function for such waveforms (10 logΔI vs 10 logI, for constant performance) typically is linear with a slope of 0.9 over a range in I of at least 60 dB. The present experiment indicates that the slope of the masking function increases from 0.9 to 1.0 as regions above the signal frequency are masked by filtered noise. A necessary and sufficient condition for a slope of one is a high-pass noise which masks regions at and above the second harmonic of the signal. This suggests that the “near-miss” to Weber's law observed in the absence of an intense noise reflects the observer's use of information at aural harmonics. A model based upon this notion gives a good quantitative account of the data. The amount of distortion assumed in the model is in reasonable agreement with other data. [This research was supported by the Information Sciences Directorate, Air Force Office of Scientific Research and by an NINDS Special Fellowship.]
Atmospheric Infrasound, 10 to 0.1 Hz
Authors: Donn William L. , Balachandran N. K.
Published: October 2005

Two tripartite arrays of capacitor microphones operating continuously in 10 to 1 and 1 to 0.1 Hz passbands are maintained at Lamont. Natural infrasound (about 0.2 Hz) which is radiated by ocean waves is multiply reflected between the surface and the 100-km level in the winter, and the 50-km level in the summer atmosphere. Periodic diurnal variations in amplitudes is shown to be related to the rotation of high velocity tidal winds in the upper atmosphere. Seasonal variations are shown to be controlled primarily by stratospheric winds (about 50-km elevation). Natural infrasound of about 6 Hz, detected over an interval of several years, is more common in winter but the source is not yet resolved. Infrasound from large rockets launched at Cape Kennedy is shown to be generated aerodynamically by the ascending and descending first stage booster at speeds greater than Mach I. Frequencies observed at long range are from 2 to 0.1 Hz. The seasonal variations in rocket infrasound from maximum in winter to nearly nil in summer are controlled by variations in the stratospheric sound channel caused by variations in stratospheric winds from westerly in winter to easterly in summer. Infrasonic waves are shown to generate seismic waves in low-veclocity sediments by means of resonant coupling. Shock waves generated by Apollo rockets when passing at orbital elevations have been detected with great clarity on Bermuda and have been shown to generate seismic waves in the ground. Propagation details of both natural and artificial sound are determined by the application of three-dimensional ray tracing.
Infrasound Radiation from Severe Storms
Authors: Young Jessie M. , Greene Gary E. , Craine Lloyd B.
Published: October 2005

A review of experimental evidence over the last two decades leads to the conclusion that 1 to 100 MW of low-frequency acoustic energy is radiated from the immediate neighborhood of many severe meteorological storms. The most convincing evidence is from simultaneous observations of space-time correlated pressure fluctuations on widely separated microphone arrays in the United States, together with National Weather Service meteorological data on the occurrence of midcontinent storms. Presence of sound in the ionosphere above some of the same storms has been inferred from Doppler phase fluctuations where the ionospheric reflection points are located above the storm area. A broad frequency spectrum with periods from a few seconds to a few minutes has been found, and asymmetric propagation is probably due to stratospheric winds. Direction and directional changes of sound from nearby thunderstors, together with weather radar results, indicate that funnels, tornados, and hail need not be present but that the radiation occurs from very high clouds that often penetrate the tropopause. The radiating mechanism from these storm systems is not yet completely understood.
Musicians' Learning Perceptual Skills Using a Computer-Based Teaching Machine
Authors: Dowling W. J.
Published: October 2005

As part of a university program in innovation in instruction, music students in an introductory ear training course learn to reproduce tonal patterns using a computer-based teaching machine. The kinds of patterns involved are intervals of two tones, brief melodies, simultaneous combinations of tones in chords, and chord progressions. The basic procedure involves presentation of a stimulus pattern by the computer. The student then attempts to reproduce the pattern on a keyboard. The computer provides feedback and presents another pattern. Problems can be graded for difficulty and are designed to complement classroom experience in the course. The computer, a Hewlett-Packard 2116B, produces tone patterns directly through a digital-to-analog converter using a 3-kHz sampling rate. This sampling rate was chosen to provide sufficient frequency resolution and bandwidth for the musical pitches employed, while at the same time leaving the computer able to attend to other users in a time-sharing system. The advantage of digital synthesis of tones lies in flexibility in choice of waveform and pitch scale. Students respond on an electronic organ keyboard monitored by the computer. The computer keeps a complete record of stimuli presented and students' performances. It is expected that this tool will prove to be of great value to both the teaching of perceptual skills of music and for studying the psychology of learning those skills.
Diffraction of Light by Two Adjacent Parallel Ultrasonic Waves
Authors: Leroy O.
Published: October 2005

We study the diffraction of light by two parallel adjacent ultrasonic waves, with equal frequencies but different ultrasonic pressure and widths, and showing a phase-difference δ. Expressing the refractive index of the disturbed medium, by means of Heaviside's step function, we deduce a system of difference-differential equations for the amplitudes of the diffracted lightwaves, using the method of Raman's and Nath's generalized theory [Proc. Indian Acad. Sci. 3A, 119 (1936)]. Applying the NOA method (Nth-order approximation method) for sufficiently large values of ρ = λ2/μ0μ1λ*2, we approximately solve the obtained system up to the orders ±1, and calculate the general expressions for the intensities of the diffracted lightwaves. We may conclude that (1) if δ = kπ (k being an integer), there is always a symmetrical diffraction pattern; (2) in the special case where both ultrasonics have the same pressure and equal widths, but δ = π, the intensities of the orders ±1 are given by J±1(2ζ1) = [16ρ2/(ρ2+8)2] sin4(ρ2+8)−1ζ1/4 (ζ1 = 2πμ1L1/λ), showing that J±1 is not negligible for ρ⪆1. This result is not in accordance with the assumption of Pande, Paneholy, and Parthasarathy [J. Sci. Indian Res. 3, 2 (1944)], that the diffraction of light by adjacent and superposed ultrasorties is equivalent.
Intensities of Rays Reflecting from Curved and Inclined Surfaces in Inhomogeneous Media
Authors: Spofford C. W.
Published: October 2005

Two approaches have traditionally been used for computing intensities along rays: the analytic technique wherein a range derivative is calculated along the ray trajectory; and the analog technique which uses a slightly separated companion ray to estimate the geometrical divergence [e.g., C. B. Moler and L. P. Solomon, J. Acoust. Soc. Amer. 48, 739–;744 (1970)]. The analytic approach has been difficult to implement for rays reflecting off sloping let alone curved surfaces, and both approaches obscure the relative importance of the various factors influencing intensity. A new analytic approach for computing intensities along rays is presented which avoids computing the range derivative. While quite general, it is appropriate for implementation in ray-tracing programs. In addition, by providing an effective chain rule for intensities, this technique permits isolation of the effects of each of the relevant parameters. [Work supported by Office of Naval Research.]
Automobile Passby Noise Variability
Authors: Bettis R. A.
Published: October 2005

Passby noise levels were repeatedly measured for two cars under different environmental conditions; measurements were made according to the SAE J986a procedure. The level produced by each car was found to be affected significantly by ambient temperature, temperature gradients, wind velocity, and wind gradients. The magnitudes of these effects varied between the cars.
Aerodynamic Noise Sources Associated with the Tracked Air Cushion Vehicle (TACV)
Authors: Hayden R. E.
Published: October 2005

Of the many potentially troublesome noise sources associated with the TACV, the most difficult to reduce are the aerodynamic sources, due to the inherent speed of the vehicle and the relatively high-cushion pressures which induce high-speed air flows from beneath the vehicle. This study analyzes various aerodynamic noise sources of the TACV including noise from the lip of the air cushion, sound radiation from the interaction of the escaping air jet with various track configurations, flow over rough surfaces, and direct radiation from the turbulent boundary layer on the vehicle. Results of wind-tunnel experiments are presented and predictions are made for the aerodynamic noise of the full-scale vehicle. [This study was performed under contract to the Department of Transportation, Transportation Systems Center, Cambridge, Massachusetts.]
Propagation of Complex Waves in Ducts Having Discontinuous Cross Section
Authors: Oslac M. J. , Richards R. T.
Published: October 2005

A spinning mode synthesizer has been developed to study the propagation of complex higher order modes in cylindrical ducts. This device has been shown (“The Design, Development, and Use of a Spinning Mode Synthesizer,” M. J. Oslac, and J. M. Seiner, Proc. Purdue Noise Conf.) to be very useful in studying the behavior of spinning waves which are believed to be the principle component of the noise generated by fans, compressors, and jet engines. In this investigation, the spinning mode synthesizer was coupled to a 12-in.-diam cylindrical duct 8 ft long, which was in turn coupled to an 8-ft-long, 18-in.-diam cylindrical duct having an anechoic termination. Single higher-order modes were then propagated down the infinite duct having at its center an abrupt cross-sectional change. Radial, axial, and circumferential measurements were made in both the 12 and 18-in. ducts. Transmission, reflection, and generation of modes at the discontinuity are compared with a mathematical model. [This research is being conducted under a NASA grant.]
Very Brief Short-Term Memory in Speech Perception
Authors: Pisoni D. B.
Published: October 2005

The distinction between categorical and continuous modes of perception has played a central role in discussions of speech perception. Recent findings of Fujisaki and Kawashima [J. Acoust. Soc. Amer. 47, 57 (1970)] suggest that these two modes are not necessarily dichotomous but may be related to the degree to which some brief auditory short-term memory store is employed during discrimination. The present experiment examined discrimination performance within and between phoneme boundaries using a delayed comparison AX same-different task. The delay interval between presentations of the standard and comparison sounds varied over a range from 0–2.0 sec for each of four types of synthetic speech stimuli. For steady-state vowels accuracy of discrimination both within and between boundaries was related to changes in the delay interval. Discrimination of stop consonants remained relatively stable both within and between boundaries. The results suggest that vowels (even as short as 50 msec in duration) are stored differently than stop consonants in auditory short-term memory. [Research supported in part by grant to Haskins Laboratories from NICHD.]
Immediate Recall of Conversational Speech
Authors: Jarvella R. J.
Published: October 2005

Spoken dialogue was systematically interrupted to prompt listeners' recall for one of the final two sentences which they had just heard. Besides change of speaker, three experimental conditions were defined, based on the more immediate speech. These were overt recurrence, implied but linguistically deleted recurrence, and lack of recurrence of critical phrases from the sentences to be recalled. Shared linguistic information in immediate memory by speakers and listeners as they talk is proposed to account for facilitation of recall in the implied recurrence condition. This information is coded to permit the deletion and recovery of linguistic segments in the production and perception of speech. Implications for regulation of the flow of information in conversational speech are noted.
Memory Effects in Auditory Presentation of Digit Sequences Related to Presentation of Verbal Material
Authors: Bronell Carl E.
Published: October 2005

Two experiments investigated accuracy of recall for digit sequences of length 7 and 10 which were presented with other verbal material. In study 1, subjects listened to a complete recorded message before attempting to recall the digit sequence imbedded in the message. Study 2 required that subjects only “listen to as much of the message as you need….” More errors were made when recall was delayed by additional verbal material. When 10 digits were presented, but only 7 were required to be recalled, error rates were higher than when 7 digits were presented. Requiring the subjects to reorder the digit sequence before recall increased error rate. Systematic effects of alternative message phrasings were observed on both error rate and listeners' subjective evaluation of relative difficulty. Error rates in the two studies were generally similar.
The Verbal Transformation Effect: Consistency of Subjects' Reported Verbal Transformation
Authors: Lass Norman J. , Tekieli Mary E.
Published: October 2005

Continued listening to recorded repetitions of a stimulus has been found to produce perceptual illusory changes in normal listeners. This phenomenon was labeled by Warren [Brit. J. Psychol. 52, 249–258 (1961)] as the verbal transformation effect. The purpose of the present investigation was to study the consistency of subjects' reported verbal transformations in terms of the number of forms and transitions elicited, number of repetitions of the stimulus prior to the subjects' first verbal transformations, types of transformations reported, exact forms employed, and order of reported transformations. Six stimuli, representing variations in meaningfulness and phonetic complexity, were individually presented via headphones to 24 subjects in each of three listening sessions. Results indicate that consistency of subjects' transformations is not equivalent for all measures investigated. Subjects were consistent in the number of forms and transitions and types of transformations that they reported, but inconsistent in the number of repetitions of the stimulus that they required before reporting their first transformations, in the exact forms which they used, and in the order of reported transformations. Consistency as a function of the meaningfulness and phonetic complexity of the stimuli, and the implications of these findings for future research on this phenomenon, are discussed.
Weak-Shock Solution for Initially Distorted Sinusoidal Waves
Authors: Lockwood J. C.
Published: October 2005

A theoretical application of Blackstock's weak-shock solution [J. Acoust. Soc. Amer. 39, 1019–1026 (1966)] for the case when a distorted sine wave is assumed as the boundary condition is presented. In Blackstock's analysis, the waveform of an initially sinusoidal wave is expressed as a Fourier series, and the harmonic components are evaluated for ranges up to and including the formation of a decaying sawtooth wave. This paper represents a first step in applying Blackstock's solution for more general boundary conditions. A boundary condition is assumed that consists of a sine wave to which we have added the second-harmonic component of a distortion that is supposed to have taken place prior to the point of application of the boundary condition. The solution is obtained by evaluating the Fourier components of this two-frequency wave as it distorts. [This work was sponsored by the Office of Naval Research.]
Impact Noise on Floors
Authors: Ford R. D. , Warnock A. C. C.
Published: October 2005

A study was made of impulses created by an instrumented standard ISO tapping machine hammer when it strikes various resilient coverings placed on a concrete floor to test the premise that the improvement obtained by using the resilent covering is additive to the basic nature of the floor. In spite of some discrepancies, more marked with carpets than with vinyl, to a close approximation this turned out to be the case. The second part of this study was subjective and was a preliminary attempt to define the parameters of footstep noise upon which subjects base their evaluation. Recordings of footsteps were made in a reverberant room both in its usual condition with a reverberation time of 2–4 sec and with absorbent material added to reduce the reverberation time to about 0.5 sec, which is more typical of domestic conditions. Subjects were asked to adjust the level of a masking noise until the footsteps were no longer intrusive. A better correlation was found with peak levels of the sound than the long-term rms levels. This suggests that the usual method of normalizing for room absorption may be inappropriate for impact noise problems.
Introduction to Electrets
Authors: Wintle H. J.
Published: October 2005

A short review will be given of the types of electret in terms of their electrostatic configuration: dipolar, internal space charge (heteropolar), injected space charge (homopolar), and deposited charge (monopolar). The methods used to make thermo-, photo-, electro-, and surface-charged electrets will be described. The internal fields, short-circuiting effect, stability, limitation due to air breakdown, charge measurement, charge storage, and trapping levels will be discussed.