bluuebunny/crossref_metadata_2025 huggingface dataset:
Model-based shaping of vibroacoustic properties of gears
Authors: Radkowski Stanislaw
Published: July 2002

The work undertakes an issue of estimating and predicting the level and structure of the vibroacoustic signal generated by a pair of toothed wheels and propagated by the structure of the gear’s housing. Assuming that the basic role in transmission of such diagnostic information is played by the phenomena of amplitude and phase modulation of the vibroacoustic signal, it is pointed to the significance of the signal’s nonlinear components. For that reason in this work a model of a signal in the form of a Volterra series is assumed, which enables examination of the influence that disturb nonlinear components. On the basis of exemplary analysis of the contact conditions disturbances, the possibility of the generation of a bilinear component is presented. What serves this purpose is the model of nonlinear and instantaneous contact. Simultaneously problems of selection of signal analysis methods that enable realization of assumed aims are presented. Emphasizing the fact that defect development does not always lead to a significant growth of the vibroacoustic signal’s power, the importance of methods of higher-order spectral analysis like bispectrum and bicepstrum has been shown. June or ftp.aip.org.
Metal and composite aircraft panels: Selection of parameters optimal from the viewpoint of acoustic fatigue lifetime
Authors: Baranov Nikolay I. , Baranov Sergey N. , Kuravsky Lev S. , Zhukov Konstantin P.
Published: July 2002

Optimization techniques to ensure synthesis of stiffened and laminated composite panels subjected to acoustic excitation are presented. The criteria for optimization are established to balance the structure weight and fatigue life. Test spectrum of loading pressure fluctuations is in use, with the parameters of pressure correlation ensuring the greatest response. For stiffened structures, stress spectra and corresponding root-mean-square values in points of maximum response are computed by means of special software to draw the special final diagrams that connect nondimensional structure parameters and optimization criteria. These diagrams are then used to select optimal parameters of reinforcement. For composite structures, correlation of the nondimensional parameters representing structure stress level, acoustic load level, dominant frequency of vibration, and panel anisotropy is computed by the same technique. The functions computed are later used to estimate how the criterion for optimization depends on the number of layers, lay-up sequence, and the directions of fibers. The approach proposed allows aerospace designers to select and motivate their decisions having increased confidence in the development and modifications of these structures.
Perception of synthesized Hindi geminate and cluster sounds
Authors: Shrotriya Nisheeth , Agrawal Shyam S.
Published: July 2002

This paper describes the various differences in acoustic parameters of geminate, nongeminate, and cluster sounds of Hindi, which can be used for their perceptual distinction. Words containing these sounds were synthesized using a PC-based Klatt synthesizer, which uses a set of about 60 parameters. For distinction between geminate and nongeminate sounds, the parameters such as duration of the plosive gap and preceding vowel, and the formant frequencies and intensity of the burst are important but the closure duration plays the most significant role. This difference is of the order of 1:1.5. However, if the closure duration is reduced to 50% or less, the unvoiced sounds are perceived as voiced sounds. In the case of the cluster (-C1C2-) words containing stop consonants, when C1 and C2 have the different places of articulation, a burst is observed in the middle of the closure. It was found that this burst has no perceptual effect when it was moved to the left and right positions adjacent to the vowels. Even the removal of the burst has no perceptual effect.
A perceptual experiment on Thai consonant types and tones
Authors: Roengpitya Rungpat
Published: July 2002

Tonogenesis in Thai arose historically from neutralization of voicing contrast prevocalic consonants: new higher tonal variants after what had been voiceless consonants and new lower variants after the earlier voiced consonants. Today, Thai has again acquired a series of voiced stops and the same allophonic variation in F0 may be observed on the tones following voiced and voiceless stops. How important are these F0 cues to Thai listeners? Can one stage of the tonal multiplication process that shaped Thai tonal systems be demonstrated in the lab? A perceptual experiment was conducted. Six pairs of Thai words with voiced and voiceless initial stops were recorded, spliced at six different points of time, and put into contexts. These tokens were played to 11 native-Thai subjects for judgment as voiced or voiceless. The result showed that listeners tended to identify those syllables with gated-out bursts and closures as voiceless. However, there was a significant success at differentiating voiced and voiceless stops at gates past these points. It remains to be determined whether the cues that facilitate this are F0, vowel amplitude, or voice quality. If F0 plays a role, then this result mirrors the rise of distinctive tones in the Thai history.
Acoustic correlates of ‘‘devoiced’’ vowels in standard modern Japanese
Authors: Varden J. Kevin
Published: July 2002

This paper documents the acoustic characteristics of what have been called devoiced vowels in Tokyo Japanese, traditionally attributed to the phonological rule of high vowel devoicing [T. J. Vance, Introduction to Japanese Phonology (1987)]. More recently they have been attributed to articulatory gesture overlap [S-A. Jun and M. E. Beckman, Paper, Annual Meeting of the LSA (1993)]. Current research by the author indicates both processes are consistent with the data. The vowels which have undergone phonological processing, however, are not simply devoiced; they have undergone a process of obstruentization similar to that found in the Turkish language of Uyghur discussed both pedologically [R. F. Hahn, Spoken Uyghur (1991)] and phonologically [E. M. Kaisse, Language 68, 313–332 (1992)]. Specifically, the vowel sites surface as voiceless fricatives at the place of articulation of the preceding voiceless consonant. This is evidenced acoustically by high-frequency frication in spectrograms and a high number of zero crossings. Additionally, formant frequency information is preserved, as evidenced by formant bars in spectrograms and spectral sections, allowing the perception of the original vowels in the face of heavy loss of vocality.
Nasal vibration spectra in vowels
Authors: Tronnier Mechtild
Published: July 2002

An accelerometer microphone attached to the upper part of the nose for measuring pathological nasality has been applied. The advantage of this technique is the easy application, the minor degree of invasiveness, and the minimal speaker distraction. The analysis of the obtained signal has been subject to discussion. Some researchers judged from signal intensity whether speech was produced on a hypernasal level or not. Others calculated the intensity ratio of the accelerometer signal to a voice source signal to eliminate intensity variation. The analysis of the spectral pattern of the accelerometer signal is suggested here. Spectral information in such a signal is a good indicator to reflect the velar port opening, which results in nasal resonance and nasal vibration at the nasal surface. Different vowels induce a different degree of velar opening, which does not necessarily reflect the degree of perceived nasality and measured acoustic resonance. This is due to different nasal and oral impedance of the vowels. Therefore, the spectral patterns of individual vowels in the accelerometer signal are described here. Simultaneously, a fiberendoscopic film has been recorded, showing the velar opening to confirm visually the presence or absence of velopharyngeal coupling.
Isolating the critical segment of AE /r/ and /l/ to enhance non-native perception
Authors: Kubo Rieko , Pruitt John S. , Akahane-Yamada Reiko
Published: July 2002

Brief synthetic stop-consonant+vowel syllables as short as 20 ms are reliably identified for place of articulation. Further, removal of the steady-state vowel in synthetic stop-consonant+vowel series improves discrimination performance, but does not affect identification. Subsequently, vowel truncation of consonant-vowel syllables has been used to improve native English speaker’s perception of Hindi dental and retroflex stop-consonants. Whether such truncation techniques are effective for native speakers of Japanese on the AE liquids /r/ and /l/ was examined. The /r/ or /l/ segment from 50 minimal word pairs, produced in five phonemic positions, was isolated by truncating the surrounding phonemic environment. Six durations of the segment were created: 60, 100, 140, 180, 220 ms, and full-length (unedited productions). Native Japanese speakers were asked to identify the target phoneme for each segment, which was presented in a random sequence but blocked by speaker and segment duration. Segment duration significantly affected performance. Interestingly, while longer segments were perceived better than full-length stimuli, shorter segments were not perceived as well. Identification training with these stimuli confirmed the effectiveness of such manipulations. The implications of these findings are discussed with regard to theories of cross-language speech perception and methods of training non-native contrasts.
The relationship between non-native phoneme perception and the MMN
Authors: Stack Janet W. , Dalebout Susan D.
Published: July 2002

The mismatch negativity (MMN) auditory-evoked potential reflects the detection of minimal stimulus differences at a preattentive level. It has been reported that the MMN reflects acoustic, rather than phonetic processing of speech stimuli. The purpose of the present study was to examine the relationship between discrimination at a neurophysiologic level, as reflected by the MMN, and the behavioral ability of native speakers of American English to discriminate and label pairs of Hindi stop consonants that are contrasted by a place of articulation feature that is not phonemic in English. These pairs were the voiceless unaspirated Hindi stop consonants, dental and retroflex /t/, and the voiced unaspirated Hindi stops, dental and retroflex /d/. The present study addressed two questions: (1) whether the MMN response would be evoked by acoustic differences resulting from differences in place of articulation, even though behavioral discrimination ability was poor; and (2) whether there would be a difference in the presence/absence or other parameters (latency, duration, amplitude, and area) of the MMN response depending on which voicing contrast was presented.
The effects of postvocalic voicing on the duration of high front vowels in Swedish and American English: Developmental data
Authors: Stoel-Gammon Carol , Buder Eugene H.
Published: July 2002

In most languages of the world, a vowel preceding a voiced obstruent is longer than the same vowel preceding a voiceless obstruent. Although the effect of postvocalic voicing on vowel duration is often considered to be phonetically driven, the extent of influence differs considerably across languages. In English, for example, vowels preceding voiced obstruents are nearly twice as long as those preceding voiceless obstruents, whereas in Swedish, the influence is minimal, perhaps because vowel length is phonemically contrastive in this language. The present study examines acquisition data from Swedish and American children, aged 24 and 30 months, to determine developmental patterns of vowel duration associated with context-sensitive voicing. It was hypothesized that the 24-month-old children from both language backgrounds would exhibit the phonetically based tendency for vowels to be significantly longer in the voiced context, but that at 30 months of age, the effects of final consonant voicing would be much stronger in English than in Swedish. Durational measures of high front vowels (tense/long /i/ and its short/lax counterpart) supported the proposed hypothesis. [Work supported by NICHD.]
Comparison of American English vowel production and identification by native speakers of Russian
Authors: Bell-Berti Fredericka , Romano Lisa Jayne , Lorin Eugenia
Published: July 2002

Learning a new language requires mastering the phonetic as well as lexical and syntactical aspects of the new language. As part of a larger study of second-language learning, the identification of American English vowels by speakers of Russian and the identification of those speakers’ productions by native speakers of American English were explored. Four adult bilingual Russian/English speakers (two women and two men) participated in this study. The subjects performed two tasks. First, they identified ten English words (ten repetitions of each, presented in random order, of: heed, hid, head, had, hod, hawed, hood, who’d, hud, heard) produced by a native speaker of American English. Then recordings were made of the subjects as they produced four repetitions each, in random order, of these ten English words. These recordings were digitized using SoundDesigner II software with an audiomedia board on a Macintosh Quadra 800 computer. Listening tapes will be prepared, using SoundDesigner II software, for identification of the Russian speakers’ vowels by native American English speakers. The results of the identification of the Russian speaker’s vowels will be compared with the identification of American English vowels by the native Russian speakers. [Work supported by St. John’s University.]
The Kirchhoff approximation: A new iterative solution
Authors: McDaniel Suzanne T.
Published: July 2002

A new iterative solution to the problem of sea surface scattering is obtained which has the Kirchhoff approximation as its leading term. This solution is obtained by transforming an integral equation of the first kind for the surface potential to one of the second kind, and applying the method of successive approximations. The advantages of this method are that the conditions under which this solution converges may be readily established and the solution may be iterated to sufficiently high order in the interaction to examine the rate at which it converges. A numerical example of scattering from an echelette grating is considered, and the regime of convergence established. It is found that the new iterative solution converges only for such surfaces on which kσσ′<π><π where k is the wave number of the scattered radiation and σ and σ′ are, respectively, the rms surface height and slope. This finding raises doubts concerning the regime in which the Kirchhoff approximation is traditionally deemed applicable. Finally, numerical studies are presented to illustrate the convergence of the iterative solution.
Time dependence in forward scattering: Experimental results and model comparisons derived from sea surface and seabed bistatic cross sections
Authors: Dahl Peter H. , Williams Kevin L.
Published: July 2002

In shallow, littoral regions the acoustic transmission channel can often be governed by the process of forward scattering from both the sea surface and seabed. In this paper, measurements of the intensity time dependence of high-frequency O(10) kHz sound that has been forward scattered from both the sea surface and seabed are discussed along with simulated time series for this process. The data are from an experiment conducted near Key West, Florida in waters 25-m deep, for which the seabed was characterized by a carbonate sand-silt-clay mixture. The simulated time series are derived from the bistatic cross sections for sea surface and seabed by convolving the bistatic scattering impulse response with the waveform emitted from the transmitter. For the seabed in situ estimates of sediment properties were used as inputs to a model described in Williams and Jackson [J. Acoust. Soc. Am. (submitted)]. For the sea surface, the necessary representation of the two-dimensional surface wave correlation function was derived from estimates of the directional wave spectrum. The latter were measured with a directional wave buoy that operated in the immediate vicinity of the acoustic measurements. [Work supported by ONR Code 321OA.]
Shallow-water in-plane bistatic scattering experiment
Authors: Crowe D. Vance , Hines Paul C. , Barry Patrick J.
Published: July 2002

Every reverberation experiment done in shallow water is by its nature, bistatic at long ranges. That is to say, in addition to simple monostatic returns, the received signal is composed of energy arriving along bottom bounce paths for which incident and scattered angles are different. Therefore, it is possible to measure in-plane bistatic scattering strength using a monostatic geometry [Hines, Crowe, and Ellis, J. Acoust. Soc. Am. (in review)]. Noting this, a simple array consisting of a pair of free-flooding-ring projectors and two hydrophones was used to measure monostatic and bistatic scatter in 100 m of water on the Scotian Shelf. A series of linear FM (LFM) pulses was transmitted in four frequency bands over the range 900 to 2100 Hz. The reverberation data between the first bottom return and the first surface return provided estimates of monostatic backscatter strength for grazing angles down to 10°. Data arriving after the first-bottom–first-surface interaction provided estimates of in-plane bistatic scattering strength for pairs of incident and scattered grazing angles (φi, φs) down to (7°, 57°). In this paper, the experiment and data are described in light of the monostatic and bistatic arrivals.
Estimation of contrast agent concentration using spectrum analysis
Authors: Deng Cheri X. , Lizzi Frederic L. , Silverman Ronald H. , Coleman D. Jackson
Published: July 2002

A theoretical scattering model was formulated to calculate the calibrated power spectrum of ultrasound contrast agents. The analysis incorporates the scattering coefficient from an encapsulated contrast agent bubble and includes the effects of realistic focused beams. The results relate specific spectral features to the characteristics of contrast agents, including their concentration and size distribution. Analytical calculations and experimental studies were conducted to analyze the calibrated power spectra of backscatter data using Albunex® and AerosomesTM over frequency bands employed in typical medical ultrasound (3–12 MHz) and very-high-frequency ultrasound (VHFU, 15–50 MHz). The results showed that contrast agent concentration can be estimated from the spectral features such as the spectral slope and intercept values, which are measured using linear regression analysis. These studies also demonstrated the feasibility of employing contrast agent with VHFU, using wide-band transducers with center frequencies near 40 MHz. The VHFU scans of in vivo rabbit eyes showed the time history of contrast agent activity and revealed increased backscatter (as much as 8 dB) within subsegments of the ciliary body. Estimation of contrast agent concentration as a function of time promises to provide key information about perfusion in a contrast agent perfused organ.
Effect of spectral distance on vowel height perception
Authors: Wong Patrick C. M. , Diehl Randy L.
Published: July 2002

Perceived vowel height has been reported to vary inversely with the distance (in Bark) between the first formant frequency (F1) and the fundamental frequency (F0) [H. Traunmueller, J. Acoust. Soc. Am. 69, 1465–1475 (1981)]. However, in a study using back vowels, Fahey et al. [J. Acoust. Soc. Am. 99, 2350–2357 (1996)] found that phonetic quality was not only determined by the F1−F0 distance, but also by the tonotopic distances between any adjacent spectral peaks (e.g., F3−F2, F2−F1, and F1−F0), with greater weight accorded to smaller distances. The present study further tested this possibility by using front vowels. Listeners identified three sets of synthetic vowels varying orthogonally in F1 and F0 and ranging from /i/–/ɪ/, /ɪ/–/ε/, or /ε/–/æ/. The results allowed this possibility to be rejected. Furthermore, they supported the study of Hoemeke and Diehl [J. Acoust. Soc. Am. 96, 661–674 (1994)] that F1−F0 was the best predictor of perceived vowel height for the phonological distinction [+/−high] (i.e., the /ɪ/–/ε/ distinction), while F1 alone was the best predictor for the two other vowel set distinctions. [Work supported by NIDCD.]
Integration of small transducers in commercial products
Authors: Hietanen Jarmo
Published: July 2002

Miniaturization of electronic devices requires smaller components as well as a higher level of integration. Whenever audio acoustics is involved, as in mobile phones, it is exactly the acoustics components that offer the largest challenge in this respect. There are physical limitations to how small those components can be made, and with present methods of integration, even the smallest acceptable size is still too large. Progress in material research is expected to offer new possibilities for solving problems in further integration of components, e.g., microphones. In the development of silicon microphones, new materials and processes are utilized already. Decreasing the size of components and systems makes the problem of vibration coupling through structures more severe. Furthermore, in smaller components there are a number of physical effects to be accounted for, not only in practice but also in numerical simulation models of these systems. An example of this is the effect of viscosity when predicting acoustic performance of the system. Normally viscosity is neglected, but in very narrow ducts, for example, viscosity causes significant effects. Very small components and systems cannot be expected to operate physically, as do their larger predecessors.
Power flow to a cylindrical shell with an attached structure
Authors: McDaniel J. Gregory
Published: July 2002

This paper presents an analytical framework for understanding and controlling the physical mechanisms which govern power flow to infinitely long cylindrical shells from applied point forces. It has been observed by others that the power flow to an empty shell peaks dramatically when the excitation frequency is near the cutoff frequency of a wave in the shell. In this paper, these observations are explained and generalized by a new analytical expression for power flow based on classic analyses of a shell’s response to an applied point force. This expression quantifies the partition of power among propagating waves excited by an applied force. Furthermore, the expression confirms that power flow increases dramatically as a propagating wave is excited in the vicinity of its cutoff frequency. In the context of this understanding, the attachment of a passive structure to the shell is explored as a means of controlling power flow. The nonlinear problem of designing a structure which satisfies practical constraints and minimizes power flow is formulated in such a way as to be solvable by a variety of optimization techniques. The formulation, which can be extended to other structures, is based on an expression for power flow in which the impedance of the attached structure acts in mechanical parallel with the shell’s impedance at the points of attachment. An example indicates that a significant reduction in power flow can be achieved by the attachment of a passive structure whose parameters have been optimized by a genetic algorithm.
Motor equivalence in the production of /∫/
Authors: Perkell Joseph S. , Matthies Melanie L. , Zandipour Majid
Published: July 2002

To explore the idea that speech motor goals are acoustic targets, upper lip protrusion and tongue blade fronting were examined in the sibilant /∫/ for evidence of motor equivalence in eight speakers of American English. Positive correlations across multiple repetitions of /∫/ (motor equivalence) would occur if the upper lip compensated with more protrusion when the tongue blade was further forward and vice versa. This motor equivalence would serve to maintain an adequate front cavity size for good acoustic separation from /s/ and enhance the acoustic stability of /∫/. It was hypothesized that motor equivalence would be found among less prototypical tokens, as elicited in a ‘‘clear+fast’’ speaking condition. Acoustic spectral analyses indicated excellent acoustic separation between the two sibilants, even in the ‘‘clear+fast’’ condition. There were significant positive correlations of the tongue-blade and upper lip movements for 28% of all possible cases, with considerable individual variation. When motor equivalence could be compared across the speaking condition, the tokens produced with the motor equivalent pattern were acoustically less prototypical. No occurrences of negative movement correlations were found. One possible source of individual variation may be the use of saturation (quantal) effects, which could also enhance acoustic stability. [Work supported by NIH.]
Aerodynamic characteristics of trills
Authors: Sole Maria-Josep , Ohala John J. , Ying S. Goangshiuan
Published: July 2002

What are the aerodynamic conditions required for trills? To find out we had two subjects produce steady-state voiced, voiceless, and ejective alveolar trills. The backpressure during trills was intermittently bled with a tube of varying diameter (and thus impedance) inserted in the speaker’s mouth via the buccal sulcus and gap behind the back molars. Intraoral pressure was measured via a catheter inserted into the pharynx through the nose. The variation, impairment, or extinction of trilling as a function of gradual decrease in intraoral pressure was analyzed acoustically. It was found that (1) bleeding the oro-pharyngeal pressure by 2 cm H2O impaired sustained trilling; (2) the minimum Po required to sustain tongue-tip vibration is lower than that required to initiate it; (3) extinction (and reinitiation) of trilling generally results in a fricative; (4) the range of Po variation for trills is narrower than that for fricatives; (5) voiceless and ejective trills are significantly less affected by venting the backpressure than voiced trills. The behavior of trills in varying aerodynamic conditions accounts for observed phonological patterns: final trill devoicing, alternation between trills and fricatives, co-occurrence of trilling and frication, and limited distribution of trills. [Work supported by DGICYT, Spain, PB 96-1158, and by Committee on Research, UCB.]
Further results on the perception of place coarticulation in Taiwanese stops
Authors: Peng Shu-hui , Nearey Terrance
Published: July 2002

Previous study of place coarticulation using logistic discrimination [Peng and Nearey, J. Acoust. Soc. Am. 101, 3110(A) (1997)] showed that 87% of Taiwanese word-final dental or velar stops in stop consonant clusters [CVstop1-stop2V(C)] spoken in various speech rates were correctly classified based on formant transitions from the preceding vowel. This automatic classification was sigificantly (though only moderately) correlated with categorization by Taiwanese speakers in a concept formation test. An earlier study [Peng (1996)] also showed that there was not a consistent correlation between Taiwanese listeners’ categorization of the stops and patterns of gestural overlapping shown in EPG measurements. To avoid complication involving listeners’ difficulty with the concept formation task and the influence of native speakers’ lexical knowledge, the present study examined the perception of the stops by phonetically trained listeners in a different experimental paradigm. Listeners were asked to identify the consonant clusters (tt, kk, tk, kt) from the excised first word in a four-way forced choice identification test. The phonetic judgments of these listeners will be compared with the categorization by Taiwanese speakers, the results of discriminant analysis, and EPG measurements.
An approximation to the planar harmonic Green’s function at branch points in wave-number domain
Authors: Danicki Eugene J.
Published: July 2002

An arbitrary anisotropic piezoelectric half-space is considered, and harmonic wave field in both time and space on its surface. A planar harmonic Green’s function, dependent on the wave number, is involved in the matrix relation between complex amplitudes of the applied traction and the resulting particle displacement on the surface of the half-space. An approximation to this function is derived, being valid in the vicinity of the cutoff slownesses of bulk waves, for certain cases of the shape of the slowness curves at the cutoffs. The Stroh formalism is adopted and a new theorem is proved for this purpose. This approximation is useful in any analysis of the wave field carried out by means of the methods of complex variable, for example in finding the singular points or determining the type of branch points (at the cutoff wave numbers of bulk waves) on the complex plane of a wave number. The branch points of square and cubic root type are discussed. The approximation parameters are derived from the matrix dependences at a given branch point. The computed examples are presented for effective surface dielectric permittivity of quartz substrate.
Ultrasonic pulse propagation in inhomogeneous one-dimensional media
Authors: Cretu N. , Delsanto P. P. , Nita G. , Rosca C. , Scalerandi M. , Sturzu I.
Published: July 2002

The propagation of acoustic or ultrasonic pulses and waves in 1-D media with continuous inhomogeneities due to spatial variations in density, Young modulus, and/or cross section of the propagation medium is discussed. A semianalytical approach leads to a general form of the solution, which can be described by a function, whose Taylor expansion is absolutely convergent. The special case of a periodic inhomogeneity is studied in detail and the dispersion law is found. It is also shown that a finite width pulse is generally not broken down by the inhomogeneity, even though its law of motion is perturbed. A numerical treatment based on the Local Interaction Simulation Approach (LISA) is also considered, and the results of the simulations compared with the semianalytical ones.
Response to “Comments on ‘Acoustic dispersion and attenuation in many spherical scatterer systems and the Kramers–Kronig relations’ ” [J. Acoust. Soc. Am. 104, 1111–1114 (1998)]
Authors: Ye Zhen
Published: July 2002

This communication replies to some comments in “Comments on ‘Acoustic dispersion and attenuation in many spherical scatterer systems and the Kramers–Kronig relations.’ ”
Experimental determination of the total vibratory power transmission in an elastic beam
Authors: Pan Jie , Ming Ruisen , Hansen Colin H. , Clark Robert L.
Published: July 2002

A structure can simultaneously support different types of structural waves. For active control of vibration in a beam structure, it is necessary to consider all wave types simultaneously. Thus it is necessary to be able to measure the vibration amplitude associated with all wave types at any beam cross section as well as the total vibratory power transmission associated with all wave types. In this paper, the theoretical basis is outlined for a new method which allows measurement of all the required quantities using appropriately oriented and located accelerometers. Experimental results are also provided to illustrate the usefulness of this method.
Directivity of noise radiated by a vortex ring
Authors: Kopiev Victor F. , Zaitsev Mikhail Yu. , Chernyshev Sergey A.
Published: July 2002

It is shown theoretically that the vortex ring noise is to consist of three quadrupoles with axis along the ring velocity vector. These are axisymmetrical modes and two-mode families with dependency on the azimuthal angle ‘‘fi’’ of exp(i*fi) and exp(2i*fi) kind. Each family consists of an infinite number of closely disposed modes with an identical accumulation point. This fact does not allow the separation of the quadrupoles from the spectrum analysis since all the modes are disposed in a coinciding narrow frequency interval. To reveal the noise directivity, the noise generated by a freely flying vortex ring in the anechoic chamber is measured with the use of an array of six microphones set around the movement axis. A special analysis of six measured signals which account simultaneously for azimuthal and transversal directivity of acoustic signals has allowed the separation of each quadrupole component and has proven that the vortex ring noise really consists of three equally excited quadrupoles perceived in the far field as narrow-band random noise. [The investigations were partly realized with support of CRDF according to award RE2-134.]
The effect of intrasentence pause on the articulation rate of prepausal and postpausal utterances
Authors: Kakita Kuniko
Published: July 2002

This study examined the effect of intrasentence pause on the temporal organization of the utterances both preceding and following the pause. Japanese sentences, consisting of six phrases (‘‘bunsetsu’’) with a possible pause location after the third phrase, were produced (1) without any intrasentence pause (NoP condition), (2) with a short pause (ShP condition), and (3) with a normal-length pause (NrP condition). The articulation rate (mora/s) for each phrase in the ShP and NrP conditions was normalized with respect to the articulation rate for the corresponding phrase in the NoP condition for the purpose of comparison. For the ShP and NrP conditions, the phrase immediately preceding the intrasentence pause showed a notable decrease in articulation rate compared with the NoP condition (approx. 10%), while the sentence initial and final phrases showed slight increase in articulation rate (approx. 5%), suggesting that pause insertion is not a localized speech event but that it involves the temporal reorganization of the utterance as a whole. The difference in pause conditions was reflected consistently in the amount of articulation rate decrease in the prepausal phrase, the normal-length pause accompanying a greater articulation rate decrease than the short pause.
The effect of speaking rate on lingual behavior for a transconsonantal vocalic gesture: An x-ray microbeam study
Authors: Bunton Kate , Weismer Gary
Published: July 2002

The purpose of the present study was to further explore the relationship between speaking rate and articulatory movements. A good deal of evidence suggests that speaking rate variation is accompanied by changes in the extent of overlap for successive articulatory gestures, however, previous work has shown that a simple model of gestural sliding is inadequate to explain changes in acoustic measures across speaking rates [Weismer et al. (in submission)]. Therefore, a more descriptive study of movement may be one step toward developing an acoustic model of changes in articulatory processes across speaking rate. Exploration of lingual movement across speaking rate was carried out using data from the x-ray microbeam data base. Ten speakers produced multiple tokens of the sentence ‘‘The other one is too big’’ at different speaking rates. Plots of the changing tongue contour through the VCV sequence /ubI/ from ‘‘too big’’ were examined to determine if the pattern of tongue movement was similar across speaking rates but with more or less overlap, or if the behaviors looked qualitatively different. Preliminary results show at least two different variations in lingual movement underlying changes in speaking rate. [Work supported by DC00820 and DC00319.]
Design criteria for organ performance halls and concern halls with organs
Authors: Kirkegaard Dana L.
Published: July 2002

While it is generally understood that reverberation time is an important criterion in designing an organ performance hall, little has been written on the importance of the organ’s transient response or its unique distribution in space. Whereas an orchestra is generally confined to a stage platform, the organ pipe chests may rise to different levels at heights 15–40 ft or more above the stage. As a result, EDT, C50, C80, IACC and other parameters sensitive to placement of the source may vary significantly between the stage platform and various divisions in the organ. This spatial differentiation is an important element in the design of an organ performance hall. Integration of an organ in the design of either a concert hall or recital hall presents several design challenges. The physical height of the organ is often in conflict with the need to provide early reflections for ensemble support. Optimal criteria for RT, G, C50, C80, and other acoustical parameters may also be at odds, paticularly in a University recital hall. The spatial distribution of the organ may play an important role in meeting these design challenges.
Considering the pipe organ from a scientific and engineering perspective
Authors: Noack Fritz
Published: July 2002

Acoustics of the pipe organ as a musical instrument will be discussed, both with and without the effects of the surrounding architecture (i.e., in and out of the acoustical context of a performance space). For the theoretical condition of the organ removed from its acoustic environment, the paper will examine key elements which contribute to, or otherwise affect, sound produced by the pipes. These include key action, windchest design and pipe-interval layout, wind pressure(s), scaling and voicing decisions, arrangement of divisions, casework or enclosure (fully encased or unencased, open or behind a facade, solid or resonant case panels), facade pipe and pipe shade details, etc. This theory will be contrasted with the real-world condition of the organ directly affected by its acoustic environment, including location in the room, free-standing case or fully/partially chambered installation, etc. The author will conclude with general guidelines for planning a new organ in a variety of architectural spaces and acoustic conditions (existing and known, or on paper and merely predicted), including location, layout of manual and pedal divisions, tonal design, pipe scaling, and voicing.
Bowhead whale call detection rates versus distance from airguns operating in the Alaskan Beaufort Sea during fall migration, 1996
Authors: Greene Charles R. , Richardson W. John , Altman Naomi S.
Published: July 2002

Four autonomous seafloor recorders stored sounds continuously for 15–22 days in September 1996 off Prudhoe Bay. Three recorders were 31, 44, and 62 km offshore (water depths 25 to 44 m), transecting the normal fall westward migration path of bowhead whales. The fourth recorder was 45 km southeast (‘‘upstream’’) of the other three and 72 km east of the airguns. Each record was transcribed to note times whale calls and airgun pulses were heard. Call detection rates at the four recorders were compared for times with and without airgun pulses at the recorder nearest to the airguns. At the recorder closest to the airguns, call detection rates were lower (P<0.02) at times with pulses than without them. At the recorder farthest offshore, call detection rates were higher when airgun pulses were evident close to shore than without pulses. These results imply that either some whales swam an indeterminate distance farther offshore, or changed their calling behavior, or both when the airguns were operating close to shore. [Work supported by BP Exploration (Alaska), Inc., Anchorage, AK.]
The effect of load conditions on the design and performance of actuators
Authors: Johnson Marty E. , Fuller Chris R.
Published: July 2002

This paper demonstrates the effect of dynamic load conditions on the design and performance of actuators. Actuators have both active and passive properties that determine their overall performance. The interaction between the active and passive components of an actuator, and hence the performance, will depend on both the objective (i.e., the actuator used in a control system or as a source) and the dynamics of the structure to which the actuator is attached. It is shown that it is mainly the active properties of an actuator which are affected by the load conditions of the structure. Changes in the active properties due to varying load conditions are demonstrated for various actuator types. By altering the passive properties of an actuator (i.e., mass and stiffness) it is possible to enhance the performance of the actuator used in a particular application. It is shown that the optimal actuator design depends on both the dynamics of the structure to which the actuator is attached and the performance objective. It will be demonstrated that actively changing the passive properties of an actuator allows significant enhancement of performance.
Comparison between sound transmission measurements made in working offices and in the laboratory
Authors: Brown Steven M.
Published: July 2002

Field and laboratory sound transmission measurements on office partitions are compared. The measurements were carried out both in working offices and in a laboratory setting on virtually identical full partition constructions. The effects of various performance-enhancing construction details are examined in both settings. The effects of these details are also compared to expectations based on the architectural acoustics ‘‘folklore.’’ Implications are noted for using laboratory sound transmission data in predicting field performance and in guiding the design and specification of partitions intended for use in offices.
Measurements and modeling of sound propagating into unconsolidated water-saturated porous media in a laboratory environment
Authors: Simpson Harry J. , Houston Brian H. , Couchman Luise S.
Published: July 2002

Three models of sound propagating into and within a water-saturated sandy bottom are compared to measurements made in the NRL shallow water laboratories. An initial set of measurements was made in a manufactured 212-μm mean diameter sand, which was washed and filtered, to quantify sound penetration as a function of incident angle and interface roughness, as well as to identify the wave types generated within a water-saturated sandy bottom. Measurements have also been made of sound propagation within a water-saturated sandy bottom, which employed a specialized set of transducers to generate and measure compressional waves and a second set of transducers to generate and measure shear waves. Measurements have also been made in a 525-μm mean diameter water-saturated sand. All of the above measurements are compared to a fluid bottom model and a Biot media model, both of which characterize the sound propagating within a water-saturated sandy bottom. In addition, the measurements of sound penetration into the standy bottom are compared to roughened interface scattering models. [Work supported by NRL and ONR.]
Measurements of acoustic velocity in granular media
Authors: Kimura Masao
Published: July 2002

The frame bulk and shear moduli are important in analyzing the acoustic propagation in marine sediments. However, the studies on these moduli are not considered to be sufficient. The frame bulk and shear moduli of marine sediments are related to the longitudinal and shear wave velocities in dry marine sediments. In this paper, the longitudinal and shear wave velocities in dry glass beads with five different grain sizes are measured to investigate the effect of grain size. The grain sizes are 0.05, 0.1, 0.2, 0.4, and 0.8 mm. The longitudinal wave velocities are measured using piezoelectric transducers with the operating frequency of 11.8 kHz. The shear wave velocities are measured using bimorph-type piezoelectiric transducers with an operating frequency of 3.5 kHz. The measured results show that the longitudinal wave velocity largely increases and the shear wave velocity slightly increases as the grain size increases.
Structural damage identification using free decays
Authors: Burkhardt John
Published: July 2002

A new nondestructive technique is proposed for the identification of structural damage which exploits the unique, nonexponential decay characteristics of locally damaged systems. By statistically modeling both mode shapes and damage characteristics a power-law decay model is derived and advanced as the basis for the newly proposed technique. Theoretical predictions indicate that both the presence and extent of structural damage can be determined by the observation of free structural decays. Numerically simulated structural decays are presented which support the proposed technique.
Air column resonance demonstrations
Authors: Hansen Uwe J. , Hoekje Peter
Published: July 2002

An impedance head designed and constructed at the Physikalisch Technische Bundesanstalt in Braunschweig, Germany is used to illustrate the pattern of resonances in an air column confined to a cylindrical tube closed on one end and open on the other. This is compared to the pattern observed for a tube closed on both ends. The effect observed when adding a mouthpiece is demonstrated, as is the effect when adding a bell. Finally the resonance patterns associated with a number of brass instruments will be demonstrated.
A simple apparatus for demonstrating linear and parametrically excited vibrations in strings
Authors: Brown David A. , Lavoie Bruce
Published: July 2002

A simple apparatus for inducing vibrations in strings is presented. The apparatus can be used to excite linear vibrations as well as parametric oscillations in a string under tension. The apparatus consists of an inductive transducer which can be arranged to induce transverse vibrations or to modulate the tension in the string which causes parametrically excited waves. Resonance phenomena in the drive transducer can also be demonstrated.
Interactive experiences in acoustics
Authors: Feth Lawrence , Gillman Martin
Published: July 2002

Interactive experiences (IEs) are more than classroom demonstrations because they permit the student to change selected parameters as a means for understanding the acoustical principles being demonstrated. Using the LabView programming language, IEs have been developed to aid in teaching acoustics to nontechnical undergraduates. The IEs run on most Windows 95 PCs. A hands-on demonstration will be given during the presentation. [Work supported by a grant from the Battelle Endowment for Technology and Human Affairs.]
Across-frequency gap duration discrimination
Authors: Grose John H. , Hall Joseph W. , Buss Emily
Published: July 2002

Gap detection performance declines as the two markers defining the gap are shifted apart in frequency. The purpose of this study was to determine whether this frequency dependence is also seen for gap duration discrimination, where an increase in the duration of a base silent interval is discriminated. Two standard gap durations were employed: 35 and 250 ms. The two markers defining the gap were either isofrequency (1035 Hz) or were separated by 3 or 6 ERBs above and below 1035 Hz (1519/685 Hz, 2188/432 Hz). In another condition the marker frequencies were randomly chosen. The nominal duration of the second marker was always 300 ms but the nominal duration of the first marker was either 12.5, 50, or 300 ms. Irrespective of nominal duration, the actual duration of each marker was randomized over a range of ±20% on each interval of a trial to prevent overall duration of the stimulus complex serving as a viable cue. Results from listeners with normal hearing indicated that gap duration discrimination generally declined when the markers were separated in frequency. The effect of varying the duration of the first marker was not constant across listeners. [Work supported by NIH NIDCD R01-DC01507.]