bluuebunny/crossref_metadata_2025 huggingface dataset:
Interior noise measurements on the MBTA Green Line
Authors: Wolfe Steven L.
Published: October 2005

Measurements were made inside a PCC car with steel wheels, a PCC car with Acousta-Flex wheels and a new Standard Light Rail Vehicle (SLRV) simulating a typical revenue trip over the entire Massachusetts Bay Transit Authority Green Line from Riverside to Lechmere Stations and return. The results indicated peak noise levels from wheel squeal of 106 dBA and an average noise level of 82 dBA in the steel-wheel PCC car. These levels were reduced 10 and 4 dBA, respectively, in the PCC car with Acousta-Flex wheels; and 20 and 10 dBA, respectively, in the SLRV. Statistical distribution charts of the entire runs are presented along with 13-octave band analyses of selected events showing the relative levels and predominant frequencies of wheel squeal, general running noise, and stationary noise.
Elevated measurement of traffic noise above an ideal reverberant city
Authors: Froseth S. E. , Lambert R. F.
Published: October 2005

Aerial noise measurement methods may be well suited to the determination of spatially averaged traffic noise exposure levels, and could possibly be used as a means of assessing the long-term effectiveness of motor vehicle noise regulations. In this study two theoretical models are developed for some specific aerial measurement situations. Several characteristics of the models are examined. Limited experimental measurements agree well with theoretically predicted results; elevated measured noise levels are nearly proportional to the density of the traffic (in vehicles per unit area) on the city streets.
Echo reduction in low-frequency calibration using complex cepstrum
Authors: Poche Lynn B. , Rogers Peter H.
Published: October 2005

The complex cepstrum technique was investigated for possible use in removing echoes caused by early reflections when low-frequency, peaked-response transducers are calibrated using transient signals. Synthetic measurement data produced by a J9 projector driven with a damped sinusoidal pulse and a pressure release reflection are shown. Real measurement data from a low-frequency line array driven by a single-cycle sinusoid with complex surface and bottom reflections are also shown. In both cases, the echoes were successfully removed using the complex cepstrum technique. Data were digitized directly and stored on digital magnetic tape. Oversampling was reduced by sifting to achieve the correct sampling rate required by the complex cepstrum method. [Supported in part by the Naval Electronic Systems Command.]
On designing an optimum sonar window
Authors: Brigham G.
Published: October 2005

Acoustic transmission through sonar windows can be a serious problem for electrically scanned receiving systems with narrow beams, low side lobes, and very wide bandwidth/field of view. An optimum sonar window for most systems can be designed by simultaneously considering (a) the three-dimensional model of acoustic transmissitivity for a thick, uniform panel [R. D. Fay, J. Acoust. Soc. Am. 25, 220–223 (1953)] and (b) the acoustic transmissitivity of free-flooded, elastic, uniform gratings [G. Brigham et al., J. Acoust. Soc. Am. 59, 505(P) (1976)]. Since an optimized uniform panel would probably not take impact loading a trussed paneling is likely. By choosing materials that will be free of lateral coincidence in the sonar bandwidth/field of view, the transmissitivity can be held to within 90% or better with a phase distortion due only to panel inertia. The trussing can be designed rugged but small relative to an acoustic wavelength, with a cross-sectional deformation compliance equal to the compressibility of sea water to eliminate the Rayleigh scattering in the omnidirectional mode and a weight ratio calculated to eliminate the Rayleigh dipole scattering.
Temporal patterns of syllables
Authors: Shockey Linda R. , Mattingly Ignatius G.
Published: October 2005

Comparisons of the temporal patterns of pairs of syllables differing only as to presence versus absence of a particular consonant suggests that the temporal effect of the consonantal articulation is not necessarily either additive or simply related to the duration of the acoustic segment conventionally associated with the consonant. In a study of such temporal effects, various monosyllables were embedded in turn in a short carrier sentence, and each version of the sentence was read 30 times at a carefully controlled tempo by one speaker. Durations of segments, syllables and breath-groups were measured from oscillograms, and least pairs, e.g., say versus slay, compared. It appears that final stop or final nasal lengthens both syllable and breath group by an amount roughly equal to the durations of the corresponding acoustic segment; an initial stop, liquid or aspirate induces no appreciable lengthening, other segments in the syllable being sharply reduced; and initial /s/ lengthens the syllable breath group by an amount approaching the duration of the fricative segment the durations of the other acoustic segments being slightly reduced. It is hoped that these results will contribute to more adequate synthesis by rule. [Work supported by NIH and VA.]
Use of nonsense-syllable mimicry in the study of prosodic phenomena
Authors: Liberman Mark Y. , Streeter Lynn A.
Published: October 2005

The technique of nonsense-syllable mimicry of natural utterances [used by Lindbloom and Rapp, Publ. No. 21, Institute of Linguistics, University of Stockholm (1973) (unpublished)] has many advantages in the study of prosodic phenomena, especially duration. In analytic studies, the elimination of segmental effects as a factor makes data collection much more efficient, and requires only one segmentation criterion. In perceptual studies, the technique eliminates lexical information without unnatural distortions of the signal. In a series of validation experiments, we have found that: (a) the patterns of duration obtained by using this technique were stable and reproducible within and across speakers; (b) mimicry of different natural models with identical stress patterns and constituent structures produced indistinguishable nonsense-syllable duration patterns; (c) obtained duration patterns correspond closely to results of work on natural speech by ourselves and others.
Reading speed as a clue to text structure
Authors: Harris M. O.
Published: October 2005

Text consists of structured content. Do readers reflect that structure in their production? A system is under design to map the content pattern of a given text, sentence by sentence, thus locating major and lesser topic boundaries. The system depends on word frequency and distribution in that text, and on the recognition of synonyms and other forms of reference, which establish links betwen text segments. Acoustic tools help to identify significant variations in reading performance, and these can then be interpreted in terms of the text structure. Material for the present paper consists primarily of four passages, each read by three speakers; about an hours' reading in all. The passages are structurally independent excerpts from much larger works. All of the sentences were randomized together and read as one list, and then each passage was read in original form. A study based on duration measurements, indicates clear agreement among speakers as to the locations where reading speed changes occur: e.g., in sentences of transition between major topics, and at points of salient semantic shift. However, the nature of the change increase or decrease in speed is highly speaker dependent.
Perceptual phonetics of coarticulation
Authors: Martin J. G. , Meltzer R. H. , Mills C. B.
Published: October 2005

In experiments reported earlier at ASA meetings (November, 1975) and elsewhere, reaction time (RT) of subjects monitoring stop-consonant phoneme targets in tape-recorded sentences was observed. RT was compared when the target (a) was carried by the normal, intact sentence version or (b) was temporally displaced by experimental intervention, that is, separated from prior sentence context by addition of 200 msec to the normal pre-stop-consonant silent interval. Faster RT to temporally displaced than to normal targets was interpreted in terms of coarticulatory cues to target existing in the speech interval preceding the intervention which were used to anticipate the target across the intervention interval. In further analysis, data were separated on the basis of four classes of pretarget phonetic context: stop, fricative, sonorant, and vowel. All classes produced coarticulatory effects (relatively faster RT to displaced compared to normal targets), some more than others. Additional analysis indicated similar effects in the normal sentence versions also. Discussion concerns the mapping of perceptual results onto acoustic and articulatory data. [Work supported by NIMH, ARIBSS.]
Word-letter phenomenon with speech stimuli: a word-segment effect
Authors: Rogers Joseph , Thistle Anne B. , Neilson Brooke
Published: October 2005

Single speech segments excised from natural speech were significantly better identified when embedded in words than when embedded in incomplete words or presented alone. This held true, however, only when a pre- and post-exposure mask designed to contain a randomly ordered selection of the features of speech segments was employed. Under no-mask or white-noise-mask conditions, segments showed a slight advantage over words. These findings parallel those previously reported for visual stimuli: single letters in word context are significantly better identified than single letters alone, but only with random letter-feature masking. Without such masking there is a slight advantage for letters alone. This “word-letter phenomenon” has been offered as evidence for heirachical processing in vision. Likewise, a word-segment effect suggests at least some form of heirarchical processing in speech perception. Further, the parallel results of both visual and auditory studies indicate that auditory and visual language processing channels are either remarkably similar or converge at a relatively early stage. [Work supported by a UCSD Academic Senate Grant to James L. McClelland.]
Test of speech intelligibility in noise using sentences with controlled word predictability
Authors: Kalikow D. N. , Stevens K. N. , Elliott L. L.
Published: October 2005

This paper describes a test of everyday speech reception, in which a listener's utilization of the linguistic-situational information of speech is assessed, and is compared with the utilization of acoustic-phonetic information. The test items are sentences which are presented in babble-type noise, and the listener response is the final word in the sentence (the key word) which is always a monosyllabic noun. Two types of sentences are used: high-predictability items for which the key word is somewhat predictable from the context, and low-predictability items for which the final word cannot be predicted from the context. Both types are included in several 50-item forms of the test, which are balanced for intelligibility, key-word familiarity and predictability, phonetic content, and length. Performance of normally-hearing listeners for various signal-to-noise ratios shows significantly different functions for low- and high-predictability items. The potential application of this test to assessment of speech reception in the hearing impaired is discussed. [Work supported by NINCDS.]
Perceptual determinants of phrase boundary placement
Authors: Streeter Lynn A.
Published: October 2005

In speech production many acoustic cues are correlated with the presence of a major syntactic boundary. Here the relative contribution of three acoustic cues, fundamental frequency contour, duration, and amplitude to perceptual segmentation process was evaluated. The stimuli were ambiguous algebraic expressions, such as “A times E plus 0,” in which the middle term E could be a member of either the first or the second phrase. Two levels (appropriate and neutral) of each of the three cues were varied in a complete factorial design. The results indicated that while all three cues significantly influenced the placement of a phrase boundary, duration was more potent than either amplitude or the fundamental frequency contour.
Automated vibration signature analysis
Authors: Frarey J. L.
Published: October 2005

Diagnosing the condition of a machine by its vibration signature has a great deal of appeal. The problems that have been encountered in its widespread use involve the availability of analysis equipment and the skill of the data analyst. Combining a real time analyzer with a computer can process a great amount of data quickly and reduce the drudgery of analysis. Single-frequency Fourier component calculation may easily be made in the computer and can take the place of tracking filters and phase meters. This ability to process, store, and recall data quickly, coupled with the ability to program a computer to recognize basic problem symptoms, is making automated signature analysis for machine diagnostics possible, Hardware and software examples demonstrating this capability are presented to support the conclusions.
Use of time waveform characteristics and phase measurements for vibration signal analysis
Authors: Catlin J. B.
Published: October 2005

Comparisons are made betwen amplitude versus frequency and amplitude versus time analyses for typical machinery generated vibrations such as unbalance, misalignment, oil whirl, and aerodynamic/hydraulic pulsations. The information provided in each case shows the extent to which the amplitude versus time supplements the amplitude versus frequency analysis. Transient and non-steady-state vibrations are shown to be particularly well suited to amplitude versus time analysis; providing considerably more information than amplitude versus frequency. In particular, examples include machine criticals, beat frequencies, and electrical unbalance. Various combinations of basic vibration waveforms are used to suggest standardized techniques which can aid in simplifying interpretation of actual vibration data. The use of phase measurements, as obtained from time wave forms and as a direct measurement, is described for balancing and detection of machine defects.
Parameters to be considered in machinery vibration monitoring systems
Authors: Gorman R. M. , Bowen K. A.
Published: October 2005

Vibration monitoring systems are being used in many applications to aid in predicting incipient machinery failure. This presentation addresses the significant choices which have to be made in the selection of such a system. The number of vibration transducers to be monitored and their locations on particular machines are discussed. A comparison is made of various frequency ranges and filter bandwidths which can be used in analysis of the monitored signals. Other areas discussed are the determination of the time interval between measurements, the allowable increases in vibration levels before repair is required, and the applications of trend analysis in monitoring systems.
Measurement of the rate of dissipation of turbulent kinetic energy in convective conditions by acoustic sounding
Authors: Caughey S. J. , Crease B. A. , Asimakopoulos D. N. , Cole R. S.
Published: October 2005

In the bistatic configuration acoustic sounding offers a remote method for determining CV2, the structure parameter of the wind field and hence (assuming a value for the inertial subrange constant α of 0.5) for estimating the rate of dissipation of turbulent kinetic energy ε, since [see, e.g., Kaimal Boundary Layer Meteorol. 4, 298–309 (1973)] CV2 = 4αε2/>3 ≈ 2ε2/3. Direct estimates of ε and CT2 (the structure parameter for temperature) were made using turbulence probes [see Readings and Butler, Meteorol. Mag. 100, 286–298 (1972)] attached to the tethering cable of a large (1300 m3) balloon. Sounder derived values were obtained using two carefully calibrated acoustic arrays. The second array was oriented at 45° to the vertical and positioned to record the off-axis (135°) scattered sound from the transmission of the first at 100 m height. In applying the bistatic radar equation the term involving CT2 was found negligible and excellent agreement was obtained between the sounder and directly measured ε values.
Pibal/acoustic radar examination of Arctic boundary-layer winds
Authors: Carsey F. D.
Published: October 2005

Pibal balloon wind data taken over Arctic pack ice is normalized using the acoustic radar derived boundary layer thickness. The resulting winds can be averaged to yield a well behaved profile reflective of seasonal stability and heat flux. Examination of the original and the constructed mean profiles gives information on the character of the transport and the nature of the eddies in the planetary boundary layer. In particular, regimes of constant stress and of secondary flow are identifiable. A technique for using acoustic radar derived heights and synoptic meteorological data to obtain air stress profiles is developed. [Work supported by NSF and NOAA.]
Laboratory measurements of atmospheric absorption in air
Authors: Lee M. C. , Sutherland L. C.
Published: October 2005

Laboratory measurements of atmospheric absorption in moist air are reported at frequencies from about 4 to 400 Hz/atm. These measurements provided data for frequencies below the range of any previously published results. They were observed in a resonance tube apparatus at pressures up to 100 atm. Initial measurements of boundary losses in the tube, measured with argon, agreed closely with predicted values based on current theory. This accounted for finite acoustic propagation through the tube wall and “real gas” effects, as well as viscous and thermal losses. The measured values of absorption in air and the corresponding molecular relaxation frequencies provided new validation at very low frequencies for a standard prediction model on air absorption in preparation by the S1-57 Committee on Sound Propagation. [The research was supported in part by the U. S. Army Research Office, Research Triangle Park, NC.]
Coherent ray propagation through a Gulf Stream Ring
Authors: Weinberg N. L. , Zabalgogeazcoa X.
Published: October 2005

Coherent ray-tracing techniques were applied to describe acoustic propagation through a Gulf Stream Ring 320 km in diameter as measured in 1973. Rays were traced from a fixed source to a fixed receiver 445 km distant incorporating the profile variations of the Ring which had a forward movement of 4 km a day. This anomaly shifted the deep sound channel axis about 400 m and also decreased the minimum sound velocity. These profile variations caused significant changes in the arrival pattern of the ray types and number of cycles. A time history is presented of the relationships between the received signal variations and the passage of the Ring including the effects of the changes in multipath structure.
Exact relation between the solutions of the Helmholtz and parabolic equations
Authors: DeSanto J. A.
Published: October 2005

Given that the velocity potential Ψ satisfies the Helmholtz equation describing sound propagation in a waveguide with a depth and range dependent sound speed. Given that the function p satisfies a parabolic partial differential equation (which can be “derived” from the Ψ equation). What is the relation between Ψ and p? It is shown that Ψ can be expressed as an integral transform in range of p. For sound speeds which are only a function of depth, the integral transform is exact. This is explicitly shown using the normal mode expansion. For sound speeds which depend on both depth and range, the transform involves the solution of an auxiliary partial differential equation. In either case, a stationary phase approximation of the integral transform yields the usual parabolic approximation. Corrections to this stationary phase approximation will be discussed.
Initial field for the parabolic equation method
Authors: Palmer D. R.
Published: October 2005

One of the practical problems which anyone interested in using the parabolic equation method must face is the proper choice for an initial field. In this paper we propose the use of an initial field which is more physical than a Gaussian, far easier to construct numerically than a coherent sum of normal modes, and for which a detailed error analysis is possible.
Future time prediction of transient signals from limited time measurements using the Prony method
Authors: Beatty L. G. , Robinson A. Z.
Published: October 2005

Reflection interference associated with the reception of acoustic signals imposes low frequency limitations on the information which can be derived from the spectrum of the direct signal if the usual steady-state or Fourier-type processing is employed. To eliminate this interference it would be desirable to be able to predict the future of the direct signal from the measurement of a small number of time samples taken before the arrival of the unwanted echo. One approach to this problem is to seek a closed form solution of the transient wave form in terms of the poles told zeros of its Laplace transform from the time sample measurements. This procedure which is tantamount to expanding the waveform in a series of complex exponentials is called the Prony method. Theoretically this expansion should be possible for signals whose transforms have a finite number of poles and zeros. Results of a computer simulation of this process and its implication for underwater sound calibration are discussed. [Work supported in part by the Naval Electronic Systems Command.]
Sound transmission through the sea surface
Authors: Barger J. E. , Sachs D. A. , Nitsche J. R.
Published: October 2005

Under conditions of sea state 2.5–3 with significant swell, cw-tone bursts from a helicopter-borne calibrated acoustic horn were received by a vertical string of hydrophones, and the effect of the rough air—water interface on the acoustic transmission was measured. The experiments covered a range of parameters comparable to those previously reported at the 90th Meeting of the Acoustical Society for experiments with scaled sea surfaces [J. Acoust. Soc. Am. 58, S86(A) (1975)]; namely: acoustic source frequencies of 220, 450, and 1000 Hz, grazing angles from ∼3°–5° to ∼20°, and source heights from 50 to 4000 ft. The sound path was oriented parallel and antiparallel to the sea direction. Transmission losses relative to smooth surface transmission from 2 to 8 dB were observed at 220 and 450 Hz at heights up to 1000 ft. At 1000 Hz, transmission was generally close to or better than flat surface for source altitudes below 4000 ft. The transmission at all frequencies generally improved at the highest altitude. The data were found to compare well with the results of the scaled experiments under similar conditions. [Work supported by DARPA and monitored by ONR.]
Noise on dredging ships and auxiliary vessels
Authors: Heymann R. W. , Sachs F. Z. , Fortino E. P.
Published: October 2005

High noise aboard dredges and auxiliary vessels is for the most part attributable to diesel engines. Diesels are used in dredges for propulsion, dredging pump operation, and electrical generation. High diesel noise is as a rule confined to the diesel compartments. Other potentially high-noise sources are the ventilation system; and various mechanical equipment such as conventional and hydraulic pumps, motors, and compressors. Sources other than diesel and ventilation systems produce high noise only in their immediate vicinity. With personnel confined to dredges, hearing conservation criteria must account for 24-hour-per-day exposure as well as an 8-hour-per-day workspace exposure. Approaches for noise control depend on whether a ship is being retrofitted or newly designed. Costs are important. For new designs, isolation of diesels and personnel within separate compartments and judicious location of noise-producing equipment with respect to quarters are effective control methods. For existing dredges, personnel boothes are an effective solution. Ventilation noise is reduced with conventional building industry approaches of duct linings and silencers. Sealed passenger compartments and acoustically treated engine compartments are utilized on launches and auxiliary vessels.
Analytic techniques for shipboard structure-borne noise control
Authors: Feit D.
Published: October 2005

Ships like many other modern forms of transportation have become noisier through the years. This is in no small part due to propulsion equipment working at higher horsepowers and pressures and oftentimes packaged more densely into lighter, more efficient structures which can unfortunately be acoustically more transparent. The primary path of sound transmission through ships is via structural waves which propagate throughout the ship's structure. These waves are first generated by the acoustic energy of the machinery source coupling with the adjacent structure or directly via vibrations generated by forces transmitted through the machinery bearings. The ship's structure then provides an efficient transmission medium for sound energy to propagate from one part of the ship to another. The present paper describes the analytical tools that are available to the shipboard noise-control engineer to deal with the structure-borne noise and vibration isolation design problems.
Noise control in boats and small ships
Authors: Smullin J. I.
Published: October 2005

Noise-control problems in boats and small ships are shown to differ from those of other ship classes due to geometrical scaling laws for person occupied spaces, and by high power to displacement ratios common to them. For the fastest boats, noise sources from propeller cavitation, flow, and spray noise have pronounced importance. Obstacles to noise-reduction techniques outlined are sensitivity of boat performance to weight, expected seaway induced acceleration loads, and corrosive effects of salt environment. Criteria for noise control are presented based on ship function: pleasure/work and continuous running/intermittent operation. Examples illustrating the general problem include measured machinery foundation impedance and vibration mount effectiveness, measured transfer functions for structure-borne noise. Examples of noise-control techniques include measured results with lightweight joiner-work partitions, isolation of interior trim from hull shell, and successful use of structural damping materials.
Noise exposure and control on fixed marine structures
Authors: Judd S. H.
Published: October 2005

Machinery noise sources on drilling and producing platforms include engines, turbines, gears, generators, pumps, and compressors. Noise transmission is both structure borne and airborne. Exposure evaluation requires consideration of work shifts ranging up to 12 hours per day, seven days in a row, as contrasted to the typical on-shore 40-hour work week. Exposure time is not limited to the work shift for those who must live on the structure. The design problem is to avoid or eliminate excessive noise levels. If this is not feasible, noise levels are minimized both as to intensity and the physical area affected by use of quiet machinery. Enclosure and/or other acoustical treatment is then used to bring exposure within acceptable limits. Off-duty areas and crew quarters are placed in the quietest available location, and isolated from structure-borne and airborne noise. Examples of noise sources and control measures are illustrated by case histories.
Permeability of fluid flow through outer hair cell cilia
Authors: Frommer G. H. , Steele C. R.
Published: October 2005

A 400× scale model of the reticular lamina with three rows of w-shaped obstacles simulating the outer hair cell cilia bundles was constructed. The pressure required to produce a given low rate of fluid volume flow through the lamina was measured. The results are highly repeatable and show a non-linear effect with the following properties: (1) A sharply defined threshold, (2) increasing permeability for flow rate from threshold to about 40 dB over threshold, and (3) asymmetry in permeability. For the 40-dB range of flow rate above the threshold of nonlinearity, the outward flow from the spiral sulcus to the scala media encounters some 15% less resistance than the inward flow. Although such a nonlinearity is intriguing, a tentative calculation with physiological parameters places the nonlinearity threshold at about 80 dB SPL. So at present, it seems unlikely that the phenomenon is related to any significant cochlear mechanism. [Work supported by NIH.]
Comparison of one- and two-dimensional cochlear models
Authors: Sondhi Man Mohan
Published: October 2005

A technique will be described for solving a two-dimensional cochlear model proposed by Lesser and Berkley [J. Fluid Mech. 51, 497–512 (1972)] and developed further by Allen [J. Acoust. Soc. Am. 59, S31 (A) (1976)]. It will be shown that the two-dimensional model is well represented by a pair of second-order differential equations. Several functions (e.g., basilar membrane velocity versus frequency and distance, driving point impedance at the stapes versus frequency, etc.) will be derived from the two-dimensional model and compared to the corresponding functions derived from the one-dimensional model.
Cochlear nonlinearity and second filter; psychophysical estimation of model parameters
Authors: Duifhuis H.
Published: October 2005

Recently we proposed a theoretical model for cochlear nonlinearity and second filter [J. Acoust. Soc. Am. 59, 408–423 (1971)]. From psychophysical two-tone suppression data we attempted to estimate characteristics of the two filters and of the compressive nonlinearity y = xν. In our first experiments probe frequency (suppressee as well as test probe) was 1 kHz. Masker (suppressor) frequency was a parameter. We used the pulsation-threshold method, where masker plus suppressee and test probe alternated. The pulsation threshold of the test probe was measured as a function of masker level, suppressee level being a fixed parameter. Data curves typically are characterized by a horizontal part, a descending part, and an ascending part. The descending part, reflecting suppression contains the wanted information. Insofar as our interpretation of the data is valid, we estimate for ν a value from 0.25 to 0.8, depending on musket frequency. The low-frequency part of the second-filter characteristic levels off at approximately 10-dB attenuation. The first-filter characteristic depends on level. Thus, the data show more nonlinearity than the model accounts for. Possible modifications will be discussed.
Detailed evaluation of monostatic acoustical sounder determinations of urban atmospheric boundary layer structure
Authors: McElroy J. L. , Pitchford A. M.
Published: October 2005

Field programs for the development and evaluation of air quality simulation models and for the design of optimum air monitoring networks are being conducted over Metropolitan St. Louis, Missouri, and Las Vega Nevada, respectively. As part of these programs, urban boundary layer structure (principally mixing depth) is monitored using monostatic acoustical sounders; free, tethered, and radio-controlled radiosonde flights; aerometric measurements from vertical spirals with helicopter and fixed wing aircraft; and, return signatures from ground-based and airborne downlooking LIDAR. In this paper, extensive comparisons are made between acoustical sounder information and that using the conventional in situ and other remote techniques. Stratification of data is made according to distinctive segments of the diurnal boundary layer cycle, overall synoptic weather situation, sounder pattern recognition type, and site location (i.e., climatic region). In general, the data sets compare well and the overall results are similar to previous limited studies. Differences are largely relatable to the underlying physical principles of operation and to the response-resolution properties of the various techniques.
Detection of acoustic backscatter from falling snow by acoustic Doppler sounding
Authors: Melling H. , List R.
Published: October 2005

Acoustic echoes have been detected during medium intensity snowfall by a vertically directed acoustic Doppler sounder. The echo was observed at a level in excess of 30 dB above noise. When displayed on a facsimile recorder the signal was mottled and diffuse in character, showing a decrease in intensity with height. When compensation was made for atmospheric attenuation the echo intensity was quite uniform with height. Vertical velocities measured by the sounder were downward and averaged 1–1.5 msec−1. The standard deviation was 0.8–1 msec−1. These values agree with concurrent optical estimates of snow fallspeed. A computation of the scattering cross section from the echo intensity is in agreement with empirical relationships deduced for electromagnetic radars. Statistics of “instantaneous” echo frequency and power were also computed. Only the probability density function of power did not agree with the predictions of Srivastava and Carbone [Radio Science 4, 381–393 (1969)]. These authors predict an exponential probability density for power whereas the observations statisfy a log—normal function. This result suggests that multiple scattering may be of significance in acoustic sounding.
Echosonde detection of the abrupt transition from a laminar to a turbulent planetary boundary layer
Authors: Schubert J. F.
Published: October 2005

Echosonde measurements of the abrupt transition from a laminar to a turbulent planetary boundary layer are compared with meteorological measurements from a 300-m TV tower and a network of seven 61-m towers located near the echosonde site. Preliminary data show that the conditions necessary for early nighttime transition from laminar to turbulent flow exist during clear afternoons wren the heat flux changes sign, the planetary surface begins to cool, and the surface wind dies. [Work done under USERDA Contract No. AT(07-2)-1.]
Model study of nonlinear response to paired clicks
Authors: Hall J. L. , Schroeder M. R.
Published: October 2005

T. J. Goblick, Jr. and R. R. Pfeiffer [J. Acoust. Soc. Am. 46, 924–938 (1969)] found various nonlinear effects in auditory-nerve responses of cats to paired clicks. We have been able to reproduce these effects in a nonlinear model of the basilar membrane [M. R. Schroeder, Proc. IEEE 63 (9), 1332–1350 (1975); J. L. Hall, J. Acoust. Soc. Am.56, 1818–1828 (1974)] in greater detail than has been possible in previous studies [D. O. Kim, C. E. Molnar, and R. R. Pfeiffer, J. Acoust. Soc. Am. 54, 1517–1524 (1973)]. To investigate the origin of these nonlinear effects, selected portions of the membrane model were made linear. In this manner it was found that the effects arise in two regions of the membrane model. The strongest contribution occurs just basal to the place of observation (characteristic frequency f=fc). A weaker contribution occurs just basal to the place with characteristic frequency f=2fc.
Nonexponential integrator in an energy-detection model for auditory perception
Authors: Hall J. L. , Sondhi Man Mohan
Published: October 2005

In a continuation of a study described at the 88th Meeting of the Acoustical Society of America [M. M. Sondhi and J. L. Hall, J. Acoust. Soc. Am. 56, S37 (1974)], the absolute threshold for two-component tone bursts of 500-msec and 1-sec duration was measured as a function of the frequency spacing between the two components. The average frequency of the two components was 700 Hz, and the frequency difference between the two components ranged from 0 to 8 Hz. When interpreted in terms of an energy-detection model (peripheral filter followed by squarer, integrator, and threshold detector), the measurements give an estimate of the window shape of the integrator. Experimental results are fit poorly with an exponential window. A better fit is obtained with a window decreasing initially more rapidly than exponentially. A nonexponential window is also suggested by psychophysical data on detection of pulse trains [J. Zwislocki, J. Acoust. Soc. Am. 32, 1046–1060 (1960)].
Recursively generated combination tones
Authors: Russek Shelley J. , MacLeod Donald I. A.
Published: October 2005

When a presented stimulus includes three pure-tone primaries of frequencies f1, f2, and f3, a combination tone generated by two of the primaries may combine with the third primary in generating further combination tones: for instance, 2f1 − (2f2 minus; f3) = 2f1 minus; 2f2 + f3. If the parent combination tone (in this case, 2f2−f3) is eliminated by canceling it with a pure tone of appropriate frequency, the “second-generation” tone (2f1 − f2 + f3) disappears along with it. The process of combination-tone generation thus appears to be a recursive one in which a combination tone, once generated, may participate in the generation of other combination tones. This suggests that distortion products in the ear are coupled back to the input of the distorting stage and themselves undergo distortion. Similar experiments using only two primaries suggest that all combination tones of odd order arise mainly from the recursive generation of cubic distortion products. The combination tone 2f2−f1, as well as the tone 2f1−f2 may be an important contributor to higher-order tones.
Masking effects at cubic intermodulation product frequencies
Authors: Erdreich John
Published: October 2005

When in the presence of two monaural phase synchronized tones fh and f1 a third tone of frequency 2f1+fh or 2f1 − fh (a pair of intermodulation distortion products) is varied in phase relative to itself, the amplitude to which the tone must be raised to exceed threshold changes. These phase-related masked threshold shifts may be attributable to the time structure of the tones, to interaction between nonlinear distortion products and the maskee tone, or to changes in the detection criterion for the maskee. The form of this monaural phase effect may be either sinusoidal and of a single period, or it may exhibit a double peak. The single-peak monaural phase effect is produced with a maskee of 2f1−fh if the distortion product is made inaudible by either narrow-band masking centered at 2f1−fh or by reducing the level of the primaries and therefore the level of the intermodulation product. With a maskee of 2f1+fh the phase effect is sinusoidal until the distortion product exceeds threshold levels. This suggests that the double-peak form of the monaural phase effect is the result of suprathreshold ambiguities of vector summation between maskee and the intermodulation distortion product. Furthermore, the demonstration of phase effects with added narrow-band noise indicates that the sinusoidal threshold effects with long-duration (greater than the maskee period) maskee tones is not a function of fine time structure [E. Zwicker, Acustica 34, 139–146 (1976)] but of vector summation between distortion product and maskee.
Nonlinear distortion in listeners with sensorineural hearing loss
Authors: Lindstrom R. , Leshowitz B.
Published: October 2005

Evidence suggesting that combination tones are not a result of middle-ear or basilar-membrane mechanics has been presented in the literature. It has been proposed that the sensory cells in the cochlea are the site of the site of the nonlinearity. However, the precise location of the sensory region responsible for the generation of the combination tones is not known. This important theoretical problem was explored using a tonal masking paradigm with listeners having a localized region of sensorineural hearing loss. Psychoacoustical tuning curves were measured in order to delineate the frequency region of combination tone audibility. By manipulating the frequency of the fixed probe with respect to the listener's hearing loss, the sensory region over which the nonlinear distortion product is generated was determined. Results of this study showed that when the fixed probe was just lower in frequency than the region of the threshold elevation and Fm < Fp, combination tones were not detected. However, with the probe just higher in frequency than the region of threshold elevation, audible combination tones were produced. The conclusion was drawn that the nonlinearity resides in the cochlear region basal to that of the primaries.
Disruption of categorical processing in music
Authors: Siegel J. A.
Published: October 2005

Musicians judged 13 tonal intervals under magnitude estimation instructions. The intervals were spaced in 20-cent steps and covered a range of three semitone categories. In experiment I, the subjects were naive with respect to the exact nature of the stimulus set, and under these conditions, evidence for categorical perception was obtained. The psychometric functions were well predicted by these subjects identification of the same stimuli. Stimuli in different categories were judged as perceptually distinct, but the judgment of intonation within a category was poor. That is, these subjects were unable to distinguish among sharp, in-tune, and flat stimuli with the same interval name. In Experiment II, subjects were given specific information concerning the nature of the stimuli. Their judgment of within-category differences failed to improve, and their assignment of the stimuli to the three interval categories became more variable. It appears that musicians are poor at judging within-category differences in intonation, and that attempting to do so disrupts the processing of categorical information.
Perception of musical-interval tuning
Authors: Hall Donald E.
Published: October 2005

When two musical tones are heard together, there is a perception of whether or not they are “appropriately” spaced in pitch. This judgment is dependent on musical training and/or aptitude, as well as on several physical variables. Terminology must be used with care, because such words as “consonant,” “dissonant,” or “fused” already have other meanings. It would be of real interest to musicians to establish more quantitative information about tuning perception. Some experiments currently in progress will be briefly described.
Scaling the perceived width of vibrato tones
Authors: Shonle John I. , Simmons William R.
Published: October 2005

We have investigated the psychological magnitude of the width of vibrato tones. In the experiments reported here, the signal was a modulated 440-Hz sine wave. The method of magnitude estimation was used with 14 subjects, who heard the vibrato tones produced by a speaker in a room, resulting in a power-law exponent of 0.80. Then eight subjects using the method of magnitude production and listening with headphones set widths for both “twice as wide” and “ half as wide,” yielding an exponent of 1.85. The third experiment investigated whether the difference was attributable to differences in psychophysical method or in method of presentation. Five subjects performed magnitude estimation listening with headphones, with a resultant exponent of 1.70. An experiment on the detection of the presence of vibrate confirmed that there is a significant difference between perceiving vibrato with headphones and from a speaker in a room. Sixteen subjects in a room were performing in a 2AFC task at the 83% correct level at a width of ± 2 cent, whereas ten subjects with headphones were able to score only 68% correct at a width of ± 10 cent.
Preliminary analysis of vocal chant
Authors: Large John , Murry Thomas
Published: October 2005

The use of chanting as a mode of voice production has been generally limited to religious ceremonies, theatrical performances, or classroom exercises such as memorizing the multiplication tables. It has been suggested that chanting of the type done by Tibetian lamas resembles the production of vocal fry. The purpose of this study was to compare vocal chant, vocal fry, and normal phonation on the parameters of mean air-flow rate, fundamental frequency of spectrum. Three males and two females produced samples of vocal chant, vocal fry, and normal phonation. The samples were produced in pairs (i.e., chant normal) with no break between the pairs. The subjects produced two sets of samples, one in a sound-treated room and one in a respiratory mask. The first set was used to obtain the acoustic measures; the second to obtain the air-flow values. The results indicate that vocal chant, vocal fry, and normal phonation are produced at three different ranges of air-flow rate. It was also possible to different late vocal fry and vocal chant on the basis of voice fundamental frequency.
Imitation of synthesized vowels by children and adults
Authors: Kent R. D.
Published: October 2005

Imitations of 15 synthesized vowels, some English vowels and some not, were obtained from ten adults (five men and five women) and ten six-year-old children (five boys and five girls). Estimates of the first three formant frequencies, F1, F2, and F3, were made from spectrograms of the vowel imitations. The reliability of reproduction was assessed by calculating standard deviations for five imitations each of ten of the synthesized vowels. Generally, both the intra- and intersubject variabilities of the formant frequencies were great for children than adults, but the differences in intra-subject variability were not much greater than the differences in measurement error associated with different fundamental frequencies. Subjects tended to reproduce non-English vowels less reliably than English vowels, although adults were influenced less by phonetic familiarity than were the children. Vowel familiarity appeared to be especially important for reliable reproduction of the F2 frequency. Plotting of the data for English vowels in a F1−F2 plane with linear dimensions revealed an almost linear clustering for the four subject groups, but the group clustering was not as linear for the non-English vowels. [Work supported by NIH.]
Control of vocal tract length in speech
Authors: Riordan Carol
Published: October 2005

Accurate control of vocal tract length is essential for the correct production of vowels. Vertical larynx movement and lip spreading/protrusion, often acting together, are important determinants of vocal tract length. The present study was designed to determine whether constraining lip spreading/protrusion will induce compensatory vertical larynx displacements, particularly on rounded vowels. Upper lip and larynx movement were monitored photoelectrically while French and Mandarin native speakers produced the vowels /i, y, u/ first under normal speech conditions and then with lip activity constrained. In agreement with the findings of Sundberg (1969), Benguerel (1974), and Ewan (1976), there were significant differences during normal speech in upper lip protrusion and larynx position as a function of the vowel and tone uttered, in particular a difference in lip protrusion between /u/ and /y/. Results further reveal that the generally low larynx position of rounded vowels becomes even lower than lip protrusion is constrained. This data has implications for the role of a contrast-preserving strategy in speech production. [Supported in part by the National Science Foundation. ] Also, Department of Languages and Linguistics, University of Essex, Colchester, England.
Some perceptual experiments on the Mandarin tones
Authors: Zue Victor W.
Published: October 2005

A series of experiments, using both natural and synthetic speech materials, were conducted to investigate the perception of the four different tones in Standard Peking Mandarin. In the initial experiment, all stimuli were of the same duration and differ only in the fundamental frequency (F0) contour. It was found that the “averaged F0 contours of these tones possess some essential features for absolute identification. It was also found that the frequency range spanned by the four F0 contours can be reduced by an order of magnitude without seriously impairing performance. In an extention of the above experiment, the intrinsic differences in duration among the four tones were taken into account, and native as well as naive subjects were used. The remarkable performance of these experiments has led us into an investigation of the categorical boundaries in the perception of some simple F0 contours. Some preliminary results of these experiments will also be presented. [Work supported by NINCDS.]