bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic propagation in shallow water
Authors: Bradley D. L. , Tulko T. J. , Gregory W. R.
Published: October 2005

Acoustic transmission loss measurements using an airborne technique developed by Urick were made on the East Coast of the United States and in the North Sea. In addition to effect of site on transmission characteristics, the effect of season, sound frequency, source depth, and direction of propagation with respect to the bathymetry were also investigated. Generally, a correlation between transmission loss and the sound velocity profiles were observed; the more negative the sound speed gradient, the higher the transmission loss. Specifically, transmission loss in the summer season was consistently higher than in the winter season. The variation from site to site was large and water column dependent. The effect of direction (bathymetry) indicated sound traveling upslope suffers the highest loss; sound traveling downslope the lowest, and in constant water depth, an intermediate value. The effect of short time intervals on transmission loss was found to be negligible, with the observed variation fitting very closely the expected variation in source level due to explosive source charge variation. There was no apparent dependence on source depth and the frequency effect was a monotonic one, with higher losses occurring at higher frequencies. [Work supported by the Naval Air Systems Command.]
Anechoic chamber having the columnlike sound-absorbing block
Authors: Fujii S. , Suzuki N. , Nagaoka T.
Published: October 2005

We have constructed many anechoic chambers for acoustical studies. Special features of these anechoic chambers are the use of the columnlike sound-absorbing block having both absorbing performance and economical merit. The columnlike sound-absorbing block is arranged with two kind of lengths and different densities of glass wool boards. The cutoff frequency of this sound-absorbing block is 190 Hz with 400 mm length and 220 Hz with 300 mm length, respectively, and their sound-absorbing performances are almost same as the usual sound-absorbing wedge. Sound field characteristics in the anechoic chamber finished by the above-mentioned sound-absorbing blocks are nearly equal to those in the chamber with the usual sound absorbing wedge. In the case of the anechoic chamber finished by the 400 mm length columnlike sound-absorbing blocks, of which inside dimensions are 5.2 m long by 6.6 m wide by 4.7 m high, the inverse square characteristics are satisfied at frequencies above 160 Hz as far as 1.6 m from the sound source situated in the center of the chamber (0.7 m from the wall surface). In addition, this columnlike sound-absorbing block has merits in economy and easiness of repair.
Pure-tone measurements in a reverberation room
Authors: Chu W. T.
Published: October 2005

Recent experimental results obtained at the National Research Council of Canada confirmed the theoretical prediction that the standard deviation of levels for pure-tone excitation in a room without moving elements is 5.57 dB. However, contrary to the general belief, the reverberant field created here is not random. Two-point space-time cross-correlation measurements reveal that the field is definitely coherent. This experimental finding is supported by a theoretical analysis based on the modal theory of room acoustics. Some comments and recommendations for the present standards concerning pure-tone power measurements in reverberation chambers will be given.
A microcomputer-controlled system for laboratory reverberation measurements
Authors: Carlson J. David
Published: October 2005

In the Lord Corporation 423 cubic meter reverberation room, a microcomputer-controlled instrumentation system has been implemented to measure sound absorption and to determine sound power. The kernel of the system is a Cromemco Z-2D microcomputer (Z-80 microprocessor) with dual disk drives and a seven-channel A/D converter. Amplified and filtered microphone signals are taken directly from the parallel outputs of a General Radio 1/3-octave multifilter and fed to an in-house built interface. The interface consists of 28 parallel true rms detectors (Analog Devices ♯536) and seven 4X-multiplexers (RCA ♯CD4151). An important feature of the AD536 converter is the availability of a decibel output with a useful dynamic range of 60 dB. Separate averaging time constants can be selected for each channel. The overall system is quite inexpensive yet extremely flexible and powerful; both Fortran IV and 16K Extended Basic software are available. A description of the system and its performance are given.
Accuracies on pressure calibration of 12-in. condenser microphones
Authors: Takahashi T. , Miura H.
Published: October 2005

The accuracy of coupler calibration of 12-in. condenser microphones, such as MR112 and B&K4134, was tested. The coupler used was a new 1-cm3 coupler [A. Suzuki and S. Yoshikawa, J. Acoust. Soc. Jpn. 28, 475–484 (1972)], as well as the 20-cm3 a coupler attached with B&K adaptor DB0225. Calibrations were carried out at the frequencies 50–12 500 Hz by the 20-cm3 a coupler and 50–30 000 Hz by the 1-cm3 coupler. Pressure response levels calibrated by the reciprocity technique using both couplers showed very good agreement. If the theoretically calculated correction values [H. Miura and E. Matsui, J. Acoust. Soc. Jpn. 30, 639–646 (1974)] are applied to measured values, the differences of the response levels calibrated by both couplers are within 0.05 dB in the frequency range 100–10 000 Hz. It can be said that the method of precise coupler calibration of 12-in. condenser microphones has been achieved.
A method to determine changes in sound levels by analytical and experimental simulation techniques
Authors: Mehta A. V.
Published: October 2005

A method is described to determine changes in the sound levels of an acoustical system due to changes in the variables internal to the system as well as external to the system. The method involves analytical and experimental simulation techniques to determine various partial factors which are then superimposed to estimate the resultant sound levels as a function of a desired variable. A practical approach is suggested for the applications of the method by approximations to save time, effort, materials, etc.
Utilization of fiber optics in the evaluation of the dynamical constants of a loudspeaker
Authors: Cuomo F. W.
Published: October 2005

The dynamical characteristics of a loudspeaker have been obtained utilizing a fiber-optic displacement transducer and a sound level meter. The diaphragm behavior below and in the vicinity of resonance readily demonstrates the analogy to a series RLC resonant circuit where the loudspeaker cone can be treated as a vibrating piston in an infinite baffle. Invoking the properties of a damped, driven harmonic oscillator the amplitude maxima of displacement and velocity at resonance are defined in terms of their respective frequencies. The results provide a convenient method for the determination of the mechanical resistance, stiffness constant, and quality factor.
Finite element simulation of acoustic transmission systems
Authors: Kagawa Y. , Yamabuchi T.
Published: October 2005

An axisymmetric transmission system is often used for acoustic duct and filter configurations, as a model of vocal tract system, and as acoustic horns for radiation. The finite element approach has successfully been applied to a transmission system with a cavity of complex cross-sectional profile. In the present approach, the finite element technique is applied to the hollow internal space, while the analytical approach is utilized for the open semi-infinite space. Compatibility conditions are then introduced for the interface boundary. A velocity potential in the semi-infinite space can be expressed as an integral of the product of the velocity potential and Green's function with respect to the opening interface boundary. The integration is numerically carried out. With this approach, computation time is greatly reduced at the expense of the additional numerical integration over the opening surface. Numerical examples are shown for both the conical and exponential horn. The throat impedance is calculated and the analytical and the measured results are compared. The axial farfield sound pressure and phase characteristics, the acoustic center, the internal sound pressure distribution, and the directional characteristics are also demonstrated.
Comparison of measured Concorde supersonic transport aircraft noise levels to regulatory levels and health and welfare criteria
Authors: Lane S. R.
Published: October 2005

A considerable quantity of measured noise level data has been collected for approach and take-off operations of the Anglo-French Concorde Supersonic Transport (SST) aircraft. The largest body of SST noise data has been obtained by the FAA at Dulles International Airport in Virginia and is generally in the form of maximum A-weighted noise level and Effective Perceived Noise Level. However, during test flight operations at various airports in the U. S. (in Alaska, California, Texas, and other states) noise data in the form of various noise rating scales including maximum A-weighted and C-weighted level, single event noise exposure level (SENEL), perceived noise level (PNL), effective perceived noise level (EPNL), and others have been obtained. There is a requirement to compare the corresponding values of the various noise rating scales to determine ff there are consistent relationships (differences) between them so the noise levels in terms of one rating scale can be predicted from noise levels in the form of another rating scale. This is particularly important since most of the SST data collected is in terms of PNL or EPNL, and the proposal in Congressman Glen Anderson's bill (HR 8729) to standardize all noise data to the average day-night level (Ldn) will require converting to the SENEL scale. Therefore the available SST data were evaluated and summarized to provide a comparison to the FAA FAR 36 noise limits, and to establish conversion factors for transferring from one noise rating scale to another.
Optimal discrimination against a convecting and exponentially decaying noise field and against all-pole stochastic processes
Authors: Chandiramani K. L.
Published: October 2005

A closed-form solution is presented for optimal discrimination against a spatially homogeneous, convecting, and exponentially decaying random field. The optimal procedure requires modification to the conventional processing only for the two end sensors of a line array of equispaced sensors. The same feature, i.e., confinement of the modification to sensors at the two ends of the array, applies for a class of noise fields. These noise fields are discrete in space, defined only at equispaced locations in space and are modeled by what is called purely autoregressive or all-pole processes. Relevance of the above work for measurement of low wave-number and acoustic contents of a low-speed turbulent boundary layer wall pressure field is discussed.
Forward and backward masking in the goldfish
Authors: Popper A. N. , Clarke N. L.
Published: October 2005

Auditory thresholds for the goldfish were determined for 15, 25, and 50 ms long pulses that were presented before, after, or simultaneously with a pulsed noise masker. The masking noise had a substantial effect on pure tone thresholds, particularly when the two signals were presented simultaneously. The effects of the masker on sensitivity decreased as the interval between the two signals increased, with the greatest effects on sensitivity occurring when the silent period was 50 ms or less. When the silent period increased beyond 50 ms there were less profound changes in sensitivity. While the effects of the masker differed for the three different pure tone signals, the individual pure tones had the same amount of forward as backward masking. It is suggested that the single most significant factor affecting sensitivity to the pure tone was the duration of the silent period between noise and masker and not the duration of the noise or pure tone signals. Further, these data, along with other physiological and behavioral data, lead us to suggest that forward and backward masking in the goldfish occurs in the central nervous system rather than in the peripheral auditory system. [Supported by NIH.]
Single unit responses in the auditory cortex of Rhesus monkeys during a sound localization task
Authors: Benson D. A. , Hienz R. D. , Goldstein M. H.
Published: October 2005

Behavioral studies have suggested that the auditory cortex plays an essential role in the localization of sound in space. The present study investigated how single units in the auditory cortex (koniocortex and adjacent belt areas) respond to sound sources that an animal is required to localize. Sound stimuli 100 ms in duration were presented randomly from one of five speaker locations within arm's reach of the monkey. In the localization condition animals were trained to press a key on the speaker which had presented the sound. Unit activity in the localization condition was compared to that recorded in another condition, the detection condition, in which the animals pressed a single key whenever a stimulus was presented regardless of its location. Approximately 5% of the units had significantly greater evoked activity in the localization condition than in the detection condition. The type of response pattern and spontaneous activity remained the same. Most of the recorded units were differently responsive to sound location. Generally there was a gradual increase in evoked activity as the sound source was changed from ipsilateral to contralateral speaker locations.
Underwater repetitive mammal sound sequences in the Bering Strait
Authors: Thompson Paul O.
Published: October 2005

Much attention has been directed in the last eight years to the “songs” of the humpback whale, Megaptera novaeangliae, the only known cetacean to produce a complex sequence of sounds that is repeated substantially unchanged for hours at a time. Mammal sounds in similar (but simpler) “song” sequences were tape recorded by the Naval Ocean Systems Center in the ice-covered Bering Strait on two occasions separated by several months. Although the sounds and sequences in the two recordings were clearly different, they are believed to be from the same species. Among possible sources of the sounds are the walrus, Odobenus rosmarus, and the bowhead whale, Balaena mysticetus. Analyses of the sound patterns and arguments on sound source identification will be presented.
Larynx height and word accent distinction in Japanese
Authors: Simada Z. , Nümi S. , Hasegawa K. , Tanakadate A. , Shitara T.
Published: October 2005

The larynx by and large takes a higher position at the high voice fundamental frequency (F0) and moves downwards again with the lowering of F0. This paper focuses on the question whether variations in larynx height are correlated systematically with the different patterns of Japanese word accent. One male native speaker of standard Japanese pronounced phrases containing two-mora test words of the form /VmV/ (where V stands for the vowel /a/ or /i/) while distinguishing among the three possible accent patterns for such sequences. Together with the speech sounds, lateral motion pictures of the subject's anterior neck were taken with a 16-mm cinecamera. The differences in larynx height estimated from these pictures are discussed with respect to the physiological mechanisms for F0 control.
The radiation impedance and radiation directivity of conical nozzles
Authors: Plumblee Harry E. , Salikuddin M. , Dean P. D. , Ahuja K. K.
Published: October 2005

An impulse technique for determining radiation impedance and radiation directivity of jet nozzles is discussed. Results for an unflanged pipe are compared with the theoretical results of Levine and Schwinger [Phys. Rev. 73, 383–406 (1948)] for the purpose of justifying the technique. Data are then presented to show the effect of nozzle size and jet velocity on both nozzle transmission and radiation impedance and radiation directivity. Conical nozzles are used and the results for 2- and 1-in. diameter nozzles are compared with those for the 4-in. diameter straight unflanged pipe. Effects of jet exit velocity up to 1300 ft/s are displayed and discussed in the light of available theory. Spectral energy is determined for the incident and reflected wave signals in the pipe, and the transmitted wave in the farfield and energy conservation for the system is discussed. Finally, it is shown that the test method can be usefully applied at frequencies above the plane mode regime.
Predicting vocal frequency from selected physiologic measures
Authors: Shipp Thomas , Doherty E. Thomas
Published: October 2005

Measures of intrinsic laryngeal muscle activity, subglottal air pressure and vertical laryngeal position were obtained simultaneously on four adult male subjects while they sustained vocalization at frequencies between 100 and 400 Hz. A stepwise multiple regression analysis of the physiologic data showed that the only significant term for any one subject in predicting his vocal frequency was cricothyroid muscle activity. This single term explained over 90% of the variability in the vocal frequency produced. Pooled data from the group showed that three terms contributed significantly to vocal frequency: Cricothyroid activity alone resulted in an R2 of 67%, while adding subglottal air pressure measures increased R2 to 71% and adding the final term of cricothyroid times thyroarytenoid muscle activity increased R2 to 73%. For these subjects, intrinsic laryngeal muscle activity overshadowed any of the other forces thought to influence the frequency of sustained phonation. [Work supported by NIH.]
Speaking fundamental frequency (SFF) characteristics of children
Authors: Hollien Patricia A. , Brown W. S. , Hollien Harry
Published: October 2005

While some information is available concerning the SFF characteristics of children, these data are based on relatively small groups of preschool and school-aged (but prepubescent) subjects. Moreover, it has been suggested [AAPS Newsletter 3, 5 (1976)] that prepubescent girls actually may exhibit lower SFF levels than similar groups of boys. Accordingly, a standard reading passage was recorded for four groups of 30 boys and 30 girls each (N = 240) for the ages of 7, 8, 9, and 10 years; all subjects were drawn from the Gainesville, Florida public schools. Mean SFF levels were obtained via processing by the IASCP Fundamental Frequency Indicator (FFI-8). The resultant data demonstrate a systematic—and expected—lowering of SFF through the ages 7–10 years. Further, the postulation that average f0 for girls is lower than that for boys was verified; however, the trend was slight and not statistically significant. Variability within the obtained data will be discussed—as will the findings when contrasted to similar (previous) studies of a like nature. [Research supported by NIH.]
Disturbance of the rhythmic structure of speech in the dysarthrias
Authors: Hirose H. , Sawashima M.
Published: October 2005

Disturbance of rhythm in the speech flow process is one of the important factors in prosodic abnormalities. The rhythmic structure of Japanese is considered to depend, to a considerable extent, on regularity in syllable (mora) length, which is often affected in dysarthric cases of cerebellar dysfunction or Parkinsonism. In the present study, the dynamic patterns of the articulatory movements in the repetition of Japanese monosyllables were observed in dysarthric cases by means of a pellet tracking technique using an X-ray microbeam system. It was found that in the case of ataxic dysarthria of cerebellar origin, the breakdown of speech rhythm is related to inconsistency in the velocity, range, and rate of repetitive articulatory movements. In Parkinsonian dysarthria, so-called hastening phenomena were observed in terms of a gradual decrease in the velocity, range, and interval of repetitive movements. An analysis of the dynamic aspects of the dysarthrias will be a promising approach for elucidating the nature of central problems in the production of speech. [Work supported by a Grant-in-Aid for Scientific Research (No. 149271), Ministry of Education.]
A model for estimating distributions of fish school target strengths
Authors: Love Richard H.
Published: October 2005

A model has been developed to estimate the distribution of fish school target strengths for any schooling species. The model has both biological and acoustic components. The biological component estimates distributions of school size and density for a given species. A discrete spectrum of nondimensionalized school densitites, developed by combining and synthesizing the results of experimental studies on intraschool spacing, is utilized to estimate school density distributions. Discrete spectra of school sizes based on empirical knowledge and assumptions of school growth and reduction are utilized to estimate school size distributions. The acoustic component combines estimates of target strengths of individual fish with numbers of fish insonified to calculate school target strengths at any aspect for a school of given size and density. Multiple scattering is neglected, but attenuation through the school is accounted for by the use of shadowing factors. Provision is made for schools which are not totally insonified due to limitations of sonar beamwidth or pulse length. Comparison to available experimental data indicates that the model produces a reasonable estimate of target strength distributions.
Tuning curves of auditory-nerve fibers
Authors: Kiang N. Y. S. , Liberman M. C. , Baer T.
Published: October 2005

The tuning curves of single fibers in the auditory nerve of cats have a sharp, low-threshold portion (tip) and a broader, high-threshold portion (tail). The relationship of tip to tail changes as a function of characteristic frequency (CF). Fibers with high CF have tails extending to much lower frequencies. For units with CF around 1 kHz, the tip and tail merge to form a V-shaped curve. For units with lower CF, the tail can be seen on the high-frequency side of the tuning curve. The “seams” in the tuning curves that represent the merging of tip and tail occur at frequencies for which there is a change in slope of the phase versus frequency function. Under certain pathological conditions such as ototoxic poisoning or acoustic trauma, the tip and tail may be affected differently. The relationship of the tip and tail to discharge rate versus SPL functions will be discussed. [Work supported in part by NIH.]
Masking near the edge of a high pass noise
Authors: Small Arnold M.
Published: October 2005

The simultaneous ipsilateral masking of a sinusoid of frequency fs located near the infinitely steep edge, fc, of a high passed noise was examined as a function of the level of a background noise, L1, and that of the high-passed masker. Lh. The performance of each of three listeners was virtually identical in a 4 IFC adaptive psychophysical procedure. When fs≪fc masking was determined solely by L1 and when fs≫fc masking was influenced only by Lh. However, when fs≈fc masking appeared to be related to the sum of the sound pressures contributed by L1 and Lh within a critical band, CB. Variation in Lh yielded no change in the shape of the masking function as long as Lh−L1 was constant. The frequency region below fc within which Lh influenced masking increased as L1 decreased relative to Lh. This could be interpreted as a widening of the CB or perhaps a manifestation of Greenwood's [J. Acoust. Soc. Am. 50, 502–543 (1971)] combinational aggregate.
Narrow-band noise masking in the parakeet
Authors: Fahrbach S. E. , Saunders J. C. , Bock G. R.
Published: October 2005

Narrow-band noise masking was studied in the parakeet, Melopsittacus undulatus, using a modified method of limits and an instrumental avoidance conditioning procedure. Masked thresholds were obtained from five subjects at ten frequencies between 0.5 and 5.0 kHz for each of four intensity levels (26, 46, 66, and 86 dB SPL) of a 1/3-octave-band noise masker centered at 1.6 kHz. The amount of masking was found to be linearly related to noise level, and the shape of the masking curve was symmetrical on both sides of the center frequency of the masker. In all cases, the greatest threshold shift occurred at the masker center frequency. Narrow-band noise masking has been studied in other species, most of them mammalian. The realitive symmetry of the parakeet narrow-band masking curves contrast with the results already obtained in mammals. [Work supported by NSF.]
Cochlear-distortion products: inconsistency with linear motion of the cochlear partition
Authors: Kim D. O. , Siegel J. H. , Molnar C. E.
Published: October 2005

Under two-tone stimulation at frequencies f1 and f2 (f1<f2), the phase-locked response of a cochlear nerve fiber is composed predominantly of distortion-products (f2−f1) or (2f1−f2) when these distortion frequencies are near the characteristic frequency of the nerve fiber. We have concluded (H1) that the distortion-product is generated in a more basal region and propagated apically to the characteristic place of the distortion frequency. An alternative hypothesis (H2) postulates that the distortion-product is generated locally near the characteristic place of the distortion frequency, and that a “second filter” passes the distortion frequency but blocks frequencies f1 and f2. With f1=3680 Hz and f2=4000 Hz, at 50 dB SPL, we have found strong (f2−f1) from fibers with characteristic frequencies near 320 Hz. In noise-damaged cochleas [Siegel et al., Abs. No. B1], where histological and physiological examinations show damage in the basal region but no damage in the 320-Hz region, interpretation of the absence of the (f2−f1) response in accordance with H2 would require that (1) in normal cochleas, the stimulus frequencies f1 and f2 must propagate to the 320-Hz region; and (2) noise damage to the organ of Corti in the basal region must interfere with this propagation f1 and f2 to the 320-Hz region. Accepted theories of cochlear mechanics support the propagation of distortion-products as required by H1 but do not support the above two requirements needed for H2. [Work supported by NIH Grants NS07498, NS00162, RR00396, and NS07057.]
Flapping rule in American English: an acoustic study
Authors: Laferriere Martha , Zue Victor W.
Published: October 2005

This study presents a detailed acoustic description of the /t, d/ flaps in American English, and the implications of this description for the formulation of phonological rules. The data base, a subset of the utterances described in the previous paper, contains minimal pairs of the types metal/medal, and polysyllabic words such as critical/medical. Our results show that dentals commonly labeled “flaps” fall into more than one category. For example, the durations and onset spectra of the /t/'s in waited and seating are measurably different, indicating a possible difference in the underlying production mechanisms. Our quantitative results suggest a reevaluation of the so-called flapping rule and its interaction with other phonological processes such as nasal deletion (as in winter) and vowel lengthing (as in waited/waded).
Observation of personal characteristics of lingual articulation by use of electro-palatography
Authors: Itoh H. , Hiki S.
Published: October 2005

Lingual contact to palate was observed utilizing electro-palatography in the utterances of Japanese monosyllables, words and sentences by fifteen adult subjects (nine males and six females). Based on the palatograms recorded with sixty-four electrodes at every 20 msec and the measurements of the three-dimensional shape of the plaster cast of the subjects' palates, personal characteristics of the lingual articulations of Japanese vowels and consonants and their coarticulatory effects were analyzed. Changes in the characteristics of lingual articulations of children caused by the growth of their palates were also observed, and the points to be considered for making the artificial palates in the application of the electro-palatography to the speech training of hearing-impaired children were discussed as well.
Lip and mandible coordination during the production of bilabial and labiodental consonants in English
Authors: Hasegawa Akira , McCutcheon Martin J. , Fletcher Samuel G.
Published: October 2005

The production of bilabial and labiodental consonants requires a major articulatory constriction in the most anterior part of the vocal tract. This constriction is formed by the movements of the lips and mandible. Experiments were conducted to examine lip and mandible movements during the production of /p, b, m, f, v, w/ in a VCV context (V = /a/). Reflectors (< 1.3 mm in diameter) were placed on the subject's lips and on rigid wires attached to a mandibular tooth and the head. Reflector displacements on the midsagittal plane together with voice spectra were digitized and recorded every 10 msec. The locations of the reflectors with respect to the maxillary incisors were analyzed after correcting for head movements. Inter- and intrasound production characteristics of these consonants will be discussed according to the displacement and velocity values of lip and mandibular movements. [Supported by NIR Grant NS-11852-01A from NINDCDS.]
Simulation and classification of glottal waveforms
Authors: Titze I. R. , Talkin D. T.
Published: October 2005

Glottal volume velocity and glottal transconductance are simulated with a computer model of the vocal folds. The simulated glottal transconductance is shown to be a facsimile of electroglottographic and ultrasonic waveforms recorded by other investigators. The control parameters of the model are cricothyroid contraction, thyroarytenoid contraction, subglottal pressure, and contraction of the primary adductor-abductors. A variety of glottal waveforms are generated by different combinations of these control parameters, demonstrating quantitatively the effects of contracting laryngeal muscles on voice production. We note that the primary mechanical links between neuromuscular control and acoustic out-put are laryngeal configuration and viscoelastic tissue properties. Qualitative (perceptual) effects of simulated phonation bear this out.
Sibilant production: three-dimensional reconstruction of normal articulatory constriction using dental impression material
Authors: Allen George D.
Published: October 2005

Theoretical models of airway constriction for sibilants make assumptions which may or may not be justified and which are difficult to extend to pathological cases such as malocclusion. In an attempt to determine the exact shape of the constriction, fast-setting dental impression material was placed in the mouths of normal English speaking adults, who then attained and held articulatory positions for /s/ and /æ/. The impressions thus formed were then sectioned to obtain successive cross-sectional areas. There is wide variability among normal speakers in the observed cross-sectional area patterns, and an attempt will be made to relate these differences to variations in air flow and pressure and the resulting acoustic signal. [Supported by NIH Grant No. 1 R01 DE04267.]
Precision of reference sound source measurements
Authors: Voorhees C. R. , Pallett D. S.
Published: October 2005

The precision of sound power determinations from typical reference sound sources has been the topic of a recent study at the National Bureau of Standards. The 425 m3 reverberation room was qualified for measurements on pure tone sources in the 100–2500 Hz frequency range, according to the procedures of ANS S1.21–1972 [see Noise Control Engineering 7(2), 71–80 (1976)]. The sources which were studied included those manufactured by B & K, Electricite de France, and ILG. The study involved numerous one-third octave band sound power determinations of each source at each of three source positions. The experiment was designed such that variance due to changes in source output with time or position might be identified and that sound power would be determinable to within ± 0.5 dB at the 95% confidence level. The results to be presented include the estimation of the source sound power level and associated variance over numerous repetitions at single source positions as well as the mean source sound power levels and variance over three source positions.
Laboratory in sound and music, for a general-education course in descriptive acoustics
Authors: Ayers R. Dean
Published: October 2005

An optional, one-unit laboratory course to accompany a three-unit general-education course in descriptive acoustics has been designed to utilize some fairly sophisticated equipment available in our electronics laboratory. In the very first experiment, students become familiar with the use of the oscilloscope by following a literal cookbook to get a stable display on the screen, then systematically varying the individual controls to observe their effects on the instrument's operation. In later experiments they get to use stroboscopes, frequency counters, digital multimeters and tuneable filters to investigate pitch intervals, sound spectra, resonance, standing waves and other important concepts that they are studying in the lecture course. Typically about half the students taking the lecture will also take this lab; currently we are filling two lab sections to their enrollment limits of 24 students each. The experiments are quite demanding for the students (and the instructor!), but morale and performance are noticeably stronger than is typical for more traditional laboratory classes.
Wind instrument very-nearfield and room-average spectra
Authors: Benade A. H. , Greenberg P. S. , Hoekje P. L. , Suttle R. M.
Published: October 2005

Woodwind and brass instruments radiate their lower-frequency components isotropically. At higher frequencies (above the tone-hole or bell-propagation cut-off frequency) each component is radiated in its own highly directional pattern which complicates measurement of overall spectral envelopes, even in a reverberant room. A microphone placed at the first open hole of a woodwind receives a rapidly convergent series of contributions from the lower holes. It is shown that both above and below the tone-hole cut-off frequency (≃ 1500 Hz for clarinet or oboe) the spectrum recorded by this microphone is very nearly the same as that obtained by spectral averaging of sounds recorded at many points in the room. Similar results are obtained for spectra obtained with a microphone placed one bell radius in front of a brass instrument bell. Despite the spectral match, the perceived tore color of nearfield recordings differ from those based on simple room averages, and from ordinary room listening. The auditory mechanism appears to be sensitive to early-echo spectral subtleties associated with the differing angular distribution of low and high frequency components. Implications for psychoacoustics, for recorded conventional music, and for electronically generated music will be discussed.
Cycloramic stereotone positioners for weaving streams in space
Authors: Goldsmith David S.
Published: October 2005

The introduction of spatiality as an integral dimension of musical tone exerts an influence upon the net character of the music produced that is so profound as to make such music generically distinct from the prior art. After briefly introducing plastic music by means of discussing fundamental aspects of chord connection obtained by the continuous rearrangement through space of stereotones among stereostreams as seen in an harmonic kaleidoscope, for example, the relative merits of overt and covert circumradial pickup embodiments are reviewed. An overt embodiment represents the earphone-conveyed subjective disposition of the listener in the audience in relation to the players surrounding the pickup observably in that a microphones and baffle assembly is seen to be oriented as the score is executed. A covert embodiment operates by means of electronic switching among stationary microphones in a circular array and thus eludes mechanical problems but at the same time denies the spectacle of a motional presentation that promotes comprehension and emphasis by the correspondence perceived in visual and auditory cues.
Regge pole character of resonances in sound scattering from elastic bodies
Authors: Dragonette L. R. , Flax L. , Überall H.
Published: October 2005

Previous work [R. D. Doolittle, H. Überall, and Peter Ugincuis, J. Acoust. Soc. Am. 43, 1 (1968)] on the scattering of acoustic waves from submerged elastic cylinders has analyzed the creeping-wave contributions to the scattered field, determined from the residues of poles of the scattered amplitude in the complex angular momentum plane. In a recent publication [L. R. Dragonette, L. Flax, and H. Überall, J. Acoust. Soc. Am. (in press)] we have established the connection between the creeping waves and the resonances corresponding to the eigenvibrations of the elastic body. Further studies are reported here which show the analogy of the resonances with the “Regge Poles” of the nuclear-physics literature. The passage of a given resonance may be followed through a series of individual partial waves in the scattering amplitude, where it is seen to move up in frequency. [Supported by the Office of Naval Research, Code 421 (HÜ).]
Frequency dependence of bottom reverberation
Authors: Steiner G. R. , Au L. W. , Floyd R. W.
Published: October 2005

During October 1976, reverberation measurements using wide-band bionic signals were made in shallow coastal waters (30 m) off Oahu, Hawaii. These measurements were made to help assess the acoustical environment in which porpoises are known to perform effectively. The areas of these experiments were selected to provide a range of bottom types which included sandy, rocky, and a combination of the two. The projector and receiver bandwidths and wide-band transmitted signal permitted the estimation of bottom backscattering strength over a range of grazing angles (5–40°) and frequencies (20–80 kHz). [Work supported by Naval Sea Systems Command.]
Effect of absorption of sound in the sea on the estimation of target coefficients
Authors: Moravan K. Y. , Sienkiewicz C. G.
Published: October 2005

The detection and classification capability of animal sonar systems may depend on relatively invariant target-echo characteristics compared to reverberation interference. A numerical calculation of the effect of frequency-dependent absorption of sound on target coefficients [R. A. Altes, J. Acoust. Soc. Am. 59, 97–105 (1976)] has been made for several classical targets. The variation of target coefficients have been calculated as a function of range, ocean temperature, and center frequency for several bionic signal wave-forms. It was found that the target coefficients change without any simple recognizable pattern. However, when the cross-correlation coefficient of two sets of normalized energy-weighted target coefficients corresponding to different ranges and ocean temperatures at the same center frequency is calculated, it is found to be less sensitive to absorption than the individual target coefficients. [Work supported by the Naval Sea Systems Command.]
On the input acoustic admittance of the human middle-ear
Authors: Rabinowitz W. M.
Published: October 2005

A method for obtaining the acoustic admittance (or impedance) at the eardrum of normal human ears is discussed. Its validity is demonstrated for frequencies up to 4 kHz. Special attention is given to estimating the earcanal space between the eardrum and the tip of the electroacoustic probe hermetically sealed in the earcanal; admittance measurements with earcanal static pressures of +40 and −40 cm H2O (re ambient) are used. However, in contrast to the usual assumption applied in clinical measurements, we do not assume that these static pressures reduce the (middle-ear) admittance at the eardrum to zero. Results are reported for four subjects. Below 500 Hz, the eardrum admittance is compliance dominated. From 1 to 4 kHz, the resistive component of the eardrum impedance exceeds the reactive component. Furthermore, a local increase in eardrum resistance is observed near 2 kHz; this may reflect the influence of the middle-ear cavity resonance [J.J. Zwislocki, J. Acoust. Soc. Am. 34, 1514–1523 (1962)]. Implications of the results for earphone couplers are discussed. [Work supported by NIH.]
Health and welfare benefits of existing and proposed Federal noise-emission standards for newly manufactured construction equipment
Authors: Goldstein Jeffrey , Gray Larry , Newman Frederick M.
Published: October 2005

The U. S. Environmental Protection Agency (EPA) has undertaken a coordinated approach to lessen construction-site noise through the promulgation of noise-emission standards applicable to newly manufactured construction equipment. An integral component of this approach is the assessment of the contribution of construction equipment to the attendent health and welfare impact upon the nation's population. To date, EPA has promulgated final noise-emission standards for portable air compressors and medium and heavy trucks. An additional noise-emission regulation has been proposed for wheel and crawler tractors. This paper will examine the benefits afforded to the public in terms the reduction of the extensiveness and severity of construction-site noise impact attributable to the lessening of construction equipment noise emissions. Specifically, information in the form of time-streamed benefits for typical scenarios of construction-site activity, as developed during EPA wheel and crawler tractor studies, will be presented.
Principles of group audio teleconferencing
Authors: Stockbridge C. D. , Curtis T. H. , Mitchell O. M. M.
Published: October 2005

Group teleconferencing is a viable alternative to face-to-face meetings especially when staff time or travel funding is limited. To be effective, an audio teleconference system must provide natural speaking and listening conditions for any participant in any location; constraints must be minimized. This paper discusses the principles underlying the choice of

(1) meeting tasks for teleconferencing,

(2) meeting room size and location,

(3) noise level and reverberation treatment,

(4) equipment, including microphone type and placement,

(5) two- and four-wire transmission facilities, and

(6) conference bridges.

Once installed, utilization of the system depends on how potential users perceive the system in terms of their own requirements. Factors which have been found to affect user perception and use of group audio teleconference systems will be reviewed.
Near noise-field characteristics of Nike rocket motors for application to space-vehicle payload environmental testing
Authors: Hilton D. A.
Published: October 2005

During the launch and ascent flight phases for large space vehicles such as the Space Shuttle, the vehicle itself and the payload it carries can be subjected to high-level acoustic energy produced by the first-stage rocket motors. It is highly desirable that certain vehicle and payload components be environmentally qualified before flight and considerable effort has been expended in the search for suitable noise sources that could be used conveniently for the proof testing of space-vehicle structures and payloads. It had been suggested that the exhaust noise of a Nike solid propellent rocket motor might be suitable to reproduce the interior noise environment that had been predicted for the Shuttle Orbiter cargo bay during lift off. The Nike motor is easy to handle, readily available in reasonable quantity, and relatively low in cost. In order to document the noise field of a typical Nike motor during static firing, noise measurements were recently accomplished at the NASA Wallops Flight Center during the firing of two Nike boosters. The boosters were mounted vertically with the exhaust nozzle up and an array of 16 microphones was located around the test stand. Two boosters of different ages were fired in order to determine the degree of correlation between noise measurements made on motors having different loading dates. This paper presents the results of these measurements in octave and 1/3-octave form along with appropriate overall noise-level listings. There was very good agreement between the data as measured for the two Nike motors tested although the first motor was loaded in 1955, and the second motor was loaded in the early 1970's. As applied to the specific case of the Space Shuttle; the noise field of the Nike motor provided a reasonable reproduction of the estimated interior noise levels for the cargo bay in the frequency range of 63–1000 Hz.
Computer generated wave-front reconstructions
Authors: Lang M. S.
Published: October 2005

Studies conducted at the Pennsylvania State University have shown that acoustical holography is useful in determining which portions of a large vibrating surface generate farfield sound. Recently, digital computer techniques have been introduced for the reconstruction process because they provide more information; however, analysis of the large amounts of information can be laborious. This problem was solved by displaying the wave-front reconstructed in the plane of the object on an interactive computer graphics system as a three-dimensional surface with the relief representing intensity. Given the capability to rotate, window, and threshold the data in real time, a real time, a researcher can quickly analyze the relative radiation from different locations on the object under study. A motion picture illustrating the technique and showing experimental applications will be shown.
Generalized beamforming
Authors: Vasholz David P.
Published: October 2005

A general formulation of the problem of extracting information about random wave sources is presented. The formulation places no restrictions upon the complexity of the propagation and applies to any situation where the propagation may be adequately described by a deterministic Green's function. It is shown that the general problem may be cast into the form of an integral equation, the kernel of which contains the physics of the propagation and the solution of which describes the location and spectral content of all sources. For the special case of a homogeneous medium it is shown that conventional processing techniques may be viewed as attempts to solve an approximate version of the integral equation. A technique for treating the general case is derived. This procedure, which is a generalized version of beamforming, may then be used to investigate limitations on the performance of hypothetical systems imposed by only approximate knowledge of the propagation and by observation of the transmitted wave field over only a limited spatial domain.
Predicting and improving array beam patterns
Authors: Kesner J. W.
Published: October 2005

Measured beam patterns of transducer arrays often differ somewhat from computer predictions of what the beam patterns should look like. Some of the differences may be due to housing and baffle effects, mutual coupling, and element to element variations in sensitivity and resonant frequency. Optimization techniques for improving the directional response of transducer arrays are limited in their success by these variations and characteristics, which are unique for every array. If both the amplitude and the phase far field patterns for each element in an array are measured, a more accurate prediction can be made of the total array pattern by using superposition due to the linearity of the medium. This paper presents experimental results verifying the accuracy of this technique and its usefulness in troubleshooting and optimizing the amplitude and phase shading on an array.