bluuebunny/crossref_metadata_2025 huggingface dataset:
Speech referenced equal loudness contours for pure tones
Authors: Rigo Thomas G. , Chari Nallan C. A.
Published: October 2005

Equal loudness contours for pure tones with speech as the reference stimulus were established through an alternate monaural loudness balance procedure. Untrained subjects compared the loudness of a nonmeaningful sentence presented at 10, 30, 50, 70, and 85 dB sensation levels (re: speech detection threshold) to the loudness of six pure tones in the octave test frequency range, 250–8000 Hz. The speech levels and the pure tone frequencies were randomized during the presentation. The results suggest: (1) a similar shape for the contours plotted in terms of sensation level and hearing threshold level in contrast to the contours based on sound pressure level (SPL), (2) a different shape for SPL based contours when compared to the classical pure tone equal loudness contours, and (3) a spread of loudness matches which varied with pure tone frequency and speech presentation level. A discussion of the results will be presented.
Modulation of loudness by environmental visual information
Authors: Mulligan B. E. , Goodman L. S. , Faupel M. , Lewis S. , Anderson L. M.
Published: October 2005

Loudness of sounds heard in outdoor settings is reportedly subject to visual influences, viz., the visibility of sound sources [D. E. Aylor and L. E. Marks, J. Acoust. Soc. Am. 59, 397–400 (1976)] and the visibility of vegetation [B. E. Mulligan et al., J. Acoust. Soc. Am. Suppl. 1 67, S22 (1980)]. The latter finding, however, was considered to be questionable due to the possibility of differential masking by ambient noise in the outdoor sites investigated. To assess this possibility, a second experiment was conducted at the original five sites with equalized ambient noise levels. As in the first experiment, observers estimated loudness magnitudes of 500 Hz tones presented through headphones. Evidence of masking was apparent at all sites, but loudness again was found to increase as a function of the proportion of visual vegetation. This finding does not appear to be attributable to differential masking. A third experiment conducted in the laboratory relied upon photographic projections of the same sites and failed to obtain any visual influence on loudness. It thus appears that the mere sight of vegetation is insufficient to alter an observer's loudness criterion in the absence of other contextual information. [Work supported by USDA-USFS.]
Estimating hearing protector attenuation for the second percentile using parametric statistics
Authors: Berger E. H. , Kerivan J. E.
Published: October 2005

One method for reducing hearing protector attenuation data for multiple frequencies is a single number method such as the Noise Reduction Rating (NRR). Averaged data from ten subjects, three replications per subject, are combined with a subtractive two standard deviation (σ) correction in order to predict the 98% protection rate (second percentile). This study examined the errors incurred by assuming that the distribution of attenuation data is sufficiently normal to equate a −2σ correction to the protection achieved by the second percentile. Attenuation for a foam earplug was measured on 92 subjects of varying experience, according to ASA STD 1-1975, with one replication per subject for both a “subject” and “experimenter” fit. The second percentile single number attenuation was calculated from the actual distribution, and estimated by using a −2σ correction, as in the NRR. For the subject fit, the NRR underpredicted the second percentile attenuation by 1.6 dB. For the experimenter fit, it overpredicted protection by 2.2 dB. The skewness and kurtosis of the distributions were also evaluated. Typical values for subject fit were g1 = 1.65, g2 = 0.37 al 500 Hz, and g1 = 1.18, g2 = 0.03 at 1 kHz. These findings indicate that for adequate sample sizes and subject selection criteria, parametric statistics may be used to describe the attenuation distributions.
Wearing conditions of personal hearing protectors in a steel plant
Authors: Hétu Raymond
Published: October 2005

All workers from a steel mill answered a questionnaire on their use of personal hearing protectors. As many as 225 out of 327 workers were using protectors daily (Regular Users: RU), while 74 never wore them (Non Users: NU). Three types of protection were employed among the RU: foam inserts (N = 128), earmuffs (n = 73) and foam inserts with earmuffs (N = 24). Nearly half of the RU have been wearing a protector during 3 h or more daily, some up to 8 h. The protector was said to be removed and fitted again seven times or more daily among at least 28% of the users. RU considered they were normally working with their hands soiled with oil, grease or dust in a proportion of 83%. One out of four reported having suffered at one time or another from serious discomfort or pain in or around their ears because of the protector. RU also stated in a proportion of 86% that verbal communication was essential to the fulfillment of their work while communication was said by 62% among them to be more difficult when wearing the protector. Some workers further asserted that they had to remove their protector when they had to communicate verbally. Motives for not using any protector among NU are also analyzed in relation with the noise exposure conditions, the nature of the work performed and reported physical intolerances. Implications for hygiene standards, effective protector insertion or placement, workload and work organization are discussed.
The effects of frequency response smoothness and high-frequency range on speech intelligibility in noise
Authors: Bornstein Steven P. , Randolph Kenneth J. , Maxon Antonia , Giolas Thomas
Published: October 2005

The effects of the electroacoustic parameters of frequency response smoothness and high-frequency range on speech intelligibility in noise were examined. Two major questions were asked: (1) Does a smooth frequency response provide better speech intelligibility in noise than an irregular frequency response? (2) Does speech intelligibility increase as high-frequency range is increased? The irregular response consisted of 3–5 peaks, one-third octave wide and 10 dB in amplitude. The high-frequency range conditions were low-pass filtered at 4000, 6000, and 9000 Hz. Two different measures of speech intelligibility, the Tri-Word Test of Intelligibility [Sergeant et al., J. Acoust. Soc. Am. 65, 218–223 (1979)], and The Nonsense Syllable Test [Levitt et al., Commun. Sci. Lab. Res. Rep. 11, C.U.N.Y. (1978)] were processed through a master hearing aid and then presented at 80 dB SPL, with noise competition 5 dB lower, to 18 normal hearing subjects listening in the sound field at zero degrees azimuth. Best speech intelligibility occurred when providing a smooth frequency response with the widest high-frequency range. The effects of providing a smooth frequency response and high-frequency spectral information will be discussed both in terms of basic speech communication processes and regarding application to persons with impaired hearing.
Speech intelligibility as a function of hearing aid microphone location
Authors: Seewald Richard C. , Bornstein Steven P. , Randolph Kenneth J.
Published: October 2005

The contribution to speech intelligibility of the resonance effects of the ear canal and pinna has been of recent research interest. The present study investigated these effects by comparing monaural and binaural speech intelligibility between over-the-ear and in-the-ear microphone locations, utilizing a master hearing aid which controlled for other electroacoustic effects, The experimental design also allowed examination of the effects of azimuth on both monaural and binaural aided speech intelligibility. Items of the Tri-Word Test of Intelligibility [Sergeant et al., J. Acoust. Soc. Am. 65, 218–223 (1979)] were presented randomly from five loudspeakers equally separated on the front semicircle against an uncorrelated multiple-talker background. The results generally favored the in-the-ear microphone location. Binaural squelch was demonstrated.
A comparative evaluation of multiple-choice word intelligibility tests
Authors: Chari Nallan C. A. , Price Lloyd L. , Williams Thomas F. , Kernaghan Jean F.
Published: October 2005

Intelligibility scores obtained with the Modified Rhyme Test (MRT), Oklahoma University Closed-Response Test (OUCRT), and the California Consonant Test (CCT) were compared. The word lists were recorded by a male speaker with general American English dialect. Twenty-four normal-hearing subjects heard the three lists monaurally at most comfortable loudness level. Four listening conditions, namely, lowband (100–1500 Hz), highband (2000–6000 Hz), speech-in-noise (S/N ratio = 0 dB), and wideband (100–6000 Hz) were employed. The mean intelligibility scores for the three lists across the four listening conditions ranged from 99.2% through 45.3%. An analysis of these findings from practical considerations will be discussed.
Dispersion relations for simultaneous antisymmetric and symmetric waves in a fluid-loaded plate solved by a new numerical technique
Authors: Dubbelday Pieter S.
Published: October 2005

Straight-crested waves propagating freely in a fluid-loaded plate undergo attenuation as a consequence of radiation of sound into the fluid. If the two sides of the plate are loaded by different fluids, both antisymmetric and symmetric waves are present. To find the complex roots of the dispersion relations, a new numerical technique was developed. The basic algorithm indicates the location of a root relative to a line situated close to the root (determined by the real wave speed for an unloaded plate). By successively decreasing the spacing of two mutually perpendicular pairs of lines, the root is enclosed within a square of arbitrarily small size. This routine is applied to the above problem, for exact and thick-plate theory. Exact theory predicts a noticeable effect on attenuation if both wave types are included, for wavelengths small compared with the plate thickness. Thick plate theory gives results close to exact theory for longer wavelengths, but fails to reproduce the effect of including both wave types. [Work supported by NSF.]
Structure-fluid coupling for two parallel transversely vibrating beams in compressible fluid
Authors: Yousri Gerges Samir N.
Published: October 2005

Structure-fluid coupling problems have become significant as structures have become lighter and more slender due to the use of high strength materials as in the case of offshore structures and water-cooled nuclear reactor components. The fluid compressibility affects structural vibration modes due to structure-fluid coupling in which structure motion and fluid motions are coupled and hence the in-vacua free vibration frequencies of the structure change as well as the damping. This effect is usually accounted for with the added mass and radiation damping concepts. Results have been obtained for the radiation damping of a single beam [S. N. Yousri Gerges and F. J. Fahy, J. Sound Vib. 26, 437–439 (1973); 40, 299–306 (1975)], a single shell [S. N. Yousri Gerges and J. C. S. Pinto, Brasil Offshore 81, Rio de Janeiro, September 1981, Brazil], and also for multiple spheres [R. New and T. J. Fisher, J. Sound Vib. 22, 1–17 (1972)]. This current investigation deals with the added mass of a beam vibrating transversely parallel to a similar one. Results are obtained for a separation distance from 2.5 to 12.5 beam radii, these results complement those previously published for the radiation damping [S. N. Yousri Gerges and F. J. Fahy, Acústica 29, 278–287 (1973); 31, 178–180 (1974)]. The results obtained show that the proximity of other similar, parallel, vibrating beams is found to increase or decrease the added mass depending on the phase relationship of the motion of the adjacent beam. In-phase vibration at low frequency increases the added mass due to the constructive interference field. [The financial support of CNPq, FINEP, BID, and CNEN, and the help of Vilson Wronsky with the computer terminal at UFSC are gratefully acknowledged.]
Sound radiation of heated metal cylinder under impulsive loading
Authors: Dreiman Nelik I.
Published: October 2005

In experimental work reported in this paper, the sound radiation of heated metal (medium alloy steel) cylinder subjected to longitudinal impact load has been studied in some detail. The data show that the attenuation rate and spectra of sound radiation from metal cylinder at elevated temperature (100°–250°C) are different from one at normal temperature (20°C). The attenuation rate first decreases with increasing temperature, has a minimum value of about 160°C and increases rapidly on the high temperature side (180°–250°C). The experimental data also showed that increased temperature caused a shift in the spectra. Effects of various parameters on sound radiation of metal cylinder are discussed.
Distinction between boundary and distributed damping in a waveguide near cutoff
Authors: Smith P. W.
Published: October 2005

Recent analyses consider the spatial concentration of random response that occurs near the source in a point-excited, one-dimensional waveguide which has both a cutoff frequency and distributed damping. They use a modal expansion [J. Appl. Mech. 46, 417 (1979)] and a scattering expansion [J. Acoust. Soc. Am. 69, 1337 (1981)]. Now, the exact closed-form solution is examined for a problem having both distributed and boundary damping as well as a cutoff frequency. (For simplicity, a string on an elastic foundation is taken as the canonical problem.) With the exception of quasi-static, forced response at frequencies below the cutoff, no marked spatial concentration is apparent if the distributed damping is small enough, regardless of the amount of boundary damping. The criterion of “small” distributed damping is that the field radiated directly from the source be not significantly attenuated when it reaches the boundaries.
Interaction between pitch control and articulatory mechanisms
Authors: Honda Kiyoshi , Baer Thomas
Published: October 2005

Movements of articulatory organs influence laryngeal function in various ways and may change vocal fold tension, and movements of the articulators may also result from pitch control. Since the mechanisms for pitch control and articulation use some of the same structures, they interact. In a previous report, we noted that forward movement of the hyoid bone, produced by genioglossus activity for a high vowel and geniohyoid activity for high pitch, participated in increasing fundamental frequency. Hyoid bone movement during speech influences vocal fold tension and provides a supplementary tensor mechanism. In this study, we report cinefluorographic observations on two American English speakers with simultaneous EMG measurements from the genioglossus. The vowels /a/, /i/, and /u/ were pronounced in /kaCVC/ utterances with different stress patterns. Hyoid bone position, epiglottis position, and genioglossus muscle activity were compared across changes in vowel identity, consonant environment, and stress pattern. The relationship between these measures and fundamental frequency variations were used to further explore the nature of interaction between pitch control and speech articulation. [Work supported by NINCDS.]
Auditory feedback during the acquisition of new sounds
Authors: Manning Walter H. , Hein Sally L.
Published: October 2005

Two foreign sounds were taught to nine normal speaking young adults during ten training sessions. During each session the speaker's ability to correctly produce the test sounds was assessed using two 25-word test lists in four experimental conditions: no masking, monaural right-ear, monaural left-ear, and binaural masking. As subjects repeated the test words a switching device presented multitalker masking to the speaker at 100 dB (A). The accuracy of each subject's articulation was determined using a 1–5 equal appearing interval scale. Accuracy of articulation significantly improved over the training sessions. The sounds were produced significantly better during the no masking than during the binaural masking condition. Binaural masking became less disruptive to correct articulation as the speakers acquired the correct production of the sounds. These data support the possibility that information carried via auditory feedback becomes less important as adult speakers learn to articulate new sounds. Skill acquisition appears to influence the role of auditory feedback during the acquisition of speech sounds in adults.
Neutralization of obstruent voicing in german is incomplete
Authors: Port Robert , Mitleb Fares , O'Dell Michael
Published: October 2005

A familiar phonological neutralization rule is the merger of voiced and voiceless obstruents in syllable-final position in German. Thus, the /d/ in Leid ‘sorrow’ is pronounced [-voice] like the /t/ in leit ‘lead.’ A spectrographic test of minimal pairs by nine Germans, however, revealed (1) vowels before underlying voiced consonants were 10% longer than before underlying voiceless ones, (2) there was a slightly longer interval of glottal pulsing into the consonant closure for the underlying voiced consonants, yet (3) consonant closure durations were the same. Since these consonants all sounded voiceless to us, a listening test was performed. Native speakers of German listened to these utterances and indicated which word of the minimal pair was heard. Subjects were able to guess the intended word about 70% correct—significantly better than chance. This “semicontrast” must be nearly useless in conversation. These results show that voicing neutralization is only partially achieved in German and disprove any analysis of the form [+voice] → [−voice]. Instead we propose that Germans employ a “motor implementation rule” of final devoicing that simulates the voiceless feature but is distinct from it. [Research supported by NIH grant HD12511.]
Blocking of alveolar flapping: A prosodic phenomenon
Authors: Parker Frank , Walsh Thomas
Published: October 2005

In many dialects of English, intervocalic /t, d/ are realized as a flap [f]. Under appropriate stress conditions, this occurs invariably within words (e.g., “water”), and sometimes between words (e.g., “hit it”). Egido and Cooper [J. Phon. (1979)] carried out studies which they claim show that sentence boundaries and syntactic deletion sites inhibit flapping. They conclude that flapping is blocked because the speaker is unable to “look ahead” across such locations. This account is inaccurate in two respects: (1) not all sentence boundaries and deletion sites block flapping; (2) “look ahead” is irrelevant since speakers must have access to information across such boundaries in order to perform other syntactic operations. Instead, we suggest flapping is blocked at sites following fronted adverbials and at deletion sites that create ambiguous surface strings. The blocking effect is explained by the presence of a final intonation contour (FIC), which can be shown to precede both of these locations. A FIC causes phrase-final lengthening [Lieberman (1967); Klatt, J. Phon. (1975)], which in turn lengthens phrase-final /l, d/. Lengthened /t, d/ cannot, in turn, be flapped. Thus, flapping is blocked not because of the speaker's inability to “look ahead,” but rather because the structural description of flapping is not met. The rule must specify the absence of a FIC.
Transglottal pressure during the laryngeal vibratory cycle
Authors: Löfqvist Anders , Kitzing Peter , Carlborg Björn
Published: October 2005

Understanding of the laryngeal vibrations requires knowledge both of the properties of the vocal fold tissues and the aerodynamic forces interacting with the myoelastic ones during each vibratory cycle of the glottis. This paper reports measurements of pressure variations below and above the vocal folds during individual vibratory cycles. Pressure was recorded using miniature transducers placed in the trachea and in the pharyngeal cavity. Information on laryngeal vibratory movements was obtained by simultaneous trans-illumination and electrical glottography. Egressive airflow was recorded using a pneumotach screen. Results indicate variations in transglottal pressure associated with changes in glottal opening. Subglottal pressure may vary 20%–40% above and below the mean pressure during each cycle, depending on phonation type and intensity level. Pressure variations showed a lag of 0.5-1 ms in relation to glottal vibratory movements. Influences of vocal tract resonances on subglottal pressure were sometimes observed during the open part of the glottal cycle.
Prediction of articulatory movement from phonetic input
Authors: Vaissiere Jacqueline
Published: October 2005

Data obtained by a computer-controlled x-ray microbeam system are being analyzed [Kiritani et al., J. Acoust. Soc. Am. 57, 1516–1520 (1975)] in the form of predicting the movements of three pellets located along the tongue surface, and three other pellets located on the velum, the jaw, and the lower lip. The analyzed data include a set of isolated words and sentences spoken by two native speakers of American English. This communication describes the rules necessary for reconstructing with accuracy the position of the six pellets during the sequence /Cae(N)C/, where C represents an alveolar consonant. The high intraspeaker consistency makes it feasible to predict, for each speaker, the behavior of each of the pellets. The large interspeaker differences result in a set of speaker dependent rules. For example, the jaw pellet position and the tongue pellet position (located at about 1 cm behind the tongue tip) for an alveolar consonant depends mainly on the feature “tense-lax,” for one speaker, and on the syllabic position of the alveolar consonant for the second speaker. The rules governing the articulators not directly involved in the production of the alveolar consonants generally show large interspeaker differences.
The evaluation of speech intelligibility for acoustical variables in the open plan office
Authors: Webster Michael P.
Published: October 2005

There are several acoustical variables to be considered when designing an open plan office. These variables are identified and measured with mock-ups in a semi-anechoic test chamber. Articulation index is used as an analysis technique to evaluate each variable's impact on speech intelligibility. The affect of the panel, ceiling, and vertical wall sound absorption is evaluated. The speech level, speaker directivity, panel height, and ambient noise level are also considered. The laboratory measurements and the utilization of articulation index provide a meaningful method to evaluate and compare acoustical variables in the open plan office.
The acoustics of the new Changi International Airport in Singapore
Authors: Heng Raymond B. W.
Published: October 2005

A previous paper has described the general acoustic design of the new international airport in Singapore and some of the noise control measures adopted. This paper reports on some of the subsequent field tests and measurements carried out in the main areas of the airport since the completion of the actual construction works and prior to the opening of the airport to the public. Sound transmission measurements were made following ISO/R140 involving field tests of both the facade as well as the internal partitions. Special sound generating equipment providing up to 110 dB of white noise was used in some of the measurements. This was necessary in view of the high sound insulation values designed in some parts of the building facade. Reverberation time measurements were obtained following the recommendations of ISO/R354 and room absorption values obtained using Sabines' formula. Background noise levels were measured both prior to the opening of the airport to the general public as well as afterwards to study the achievement of the designed values. Comparison of the results of the measurements with the original design values as well as special techniques devised and developed during the tests are discussed and evaluated.
Sonar discrimination and classification of underwater targets by a bottlenosed dolphin
Authors: Chun Norman K. W.
Published: October 2005

A four-alternative, forced-choice response paradigm was used to test the ability of an Atlantic bottlenosed dolphin (Tursiops truncatus) to discriminate among and classify underwater targets by echolocation. The dolphin was required to differentiate among three cylindrical targets which had slight size differences. The targets were fabricated of various materials and differed in peak amplitude by at least 0.6 dB, and in echo duration by a minimum of 0.05 ms. Each target was identified by a response to its corresponding manipulandum. An additional response manipulandum was used by the dolphin to specify a “target-absent” condition. The results of the experiment show that the dolphin was able to perform fine sonar discriminations of targets by echolocation, and that it could select the appropriate response from four different alternatives at an accuracy level above 95% correct.
Further study of the space and time stability of a narrow-band acoustic signal in the ocean: Short range results
Authors: Koenigs P. D. , Herstein P. D. , Browning D. G.
Published: October 2005

In the last of a three paper series on the space and time stability of a narrow-band acoustic signal, results from short (15–50 km) ranges are presented. In contrast to the data obtained at longer ranges [Herstein et al., J. Acoust. Soc. Am. Suppl. 1 69, S33 (1981)] an increased frequency spread was found in the received signal due to the greater number of possible raypaths at short ranges. A marked change in the character of the received signal was observed at ranges less than 30 km. Space and time variability are given for percentage Doppler shift, bandwidth, and intensity. Comparison is made to data reported in the two previous papers and with predictions of the Multipath Expansion Option of the Generic Sonar Model. [Work supported by DARPA and ELEX PME 124.]
Generalized window synthesis for optimum time-delay detection
Authors: Hassab Joseph C.
Published: October 2005

Correlation techniques have been widely used for estimating time delays in signal arrival at spatially separated sensors. The time-delay estimation process in the presence of noise has been enhanced through design of windows or filters [J. C. Hassab, IEEE Trans. ASSP-27, 373–380 (1979)] based on signal-to-noise maximization, least-square minimization, maximum likelihood, and ad-hoc techniques. The resulting windows are usually limited to situations that obey the condition of Gaussian random processes, uncorrelated signal and noise, uncorrelated noise across sensors, and zero mean noise. This paper extends the consideration process to many other situations and synthesizes a generalized window under very open conditions. This generalized detection window is then simplified under a series of assumptions that accommodate decreasingly complicated situations. Five windows are obtained presuming respectively the following conditions: (a) open conditions; (b) Gaussian random processes; (c) condition (b) plus uncorrelation between signal and noise; (d) conditions (b) and (c) plus zero mean noise; and (e) conditions (b), (c), and (d) plus uncorrelation of noise between sensors. Relationships between the present windows and those previously proposed in the literature are established. Sensitivity of the windowing functions to the presumed conditions is evaluated.
O-ring loss data for quantizers followed by an O-ring device and an accumulator
Authors: Struzinski William A.
Published: October 2005

A mathematical model is developed to compute the O-ring loss for quantizers followed by an O-ring device and an accumulator. A 3-bit (8 level) quantizer is selected as an example. The O-ring loss is then computed using Gaussian input statistics for a detection probability of 0.5 and false alarm probabilities of 10−2, 10−3, 10−4, and 10−6. The O-ring loss is computed as a function of the number of channels O red and the number of samples in the accumulator. It is concluded that there will be a large signal-to-noise ratio loss if integration is performed following O ring.
Beamformer quantization error analysis and dynamic range considerations
Authors: Mucci Ronald A.
Published: October 2005

A methodology is presented which can be used to analyze the effects of inaccuracies caused by finite precision arithmetic and finite precision data representation on beamformer performance. The random errors associated with quantization are of primary concern. For the baseband beamformer with interpolation analyzed, quantization errors occur in the A/D conversion process, the basebanding and interpolation functions, and in the shade, delay, and sum beamforming operations. These errors contribute to a noise floor which interferes with the detection of low-level signals. Hence, quantization errors can have an impact on the dynamic range, i.e., the ratio of the peak signal level to minimum detectable signal level. A brief description of the noise model commonly used to characterize the quantization errors is presented. The sources of error are identified for the digital baseband beamformer with interpolation, and expressions are presented for the variances of the individual sources. A procedure is presented for determining the total effect of the combination of the individual sources of error on the beamforming process.
Sampled data reconstruction of bandpass signals using multi-channel processing
Authors: Brown J. L.
Published: October 2005

If a deterministic bandpass signal having an angular bandwidth of σ on the positive frequency axis is used as a common input to an even number m of “independent” linear time-invariant filters, then it is shown that the input signal may be completely reconstructed from sampled values of the filter outputs, each output being sampled at the uniform rate of σ/π m samples/second. Since direct sampling of the original bandpass signal requires a sampling rate of from σ/π to 2 σ/π samples/second (depending on band orientation) for its specification, the multi-channel processing alternative reduces the sampling rate on a per-channel basis by a factor of at least l/m. Quantitative differences are encountered in the bandpass case when the number of processing channels is odd; in general, a per-channel reduction of l/m in sampling rate is no longer possible unless a particular relation holds between the center frequency and bandwidth of the signal.
A rapidly converging algorithm for adaptive noise-canceling filters
Authors: Ozeki Kazuhiko , Umeda Tetsuo
Published: October 2005

A new training algorithm for adaptive noise-canceling filters was proposed and its convergence property was investigated. The well-known algorithms for adaptive filters such as the LMS algorithm [Widrow et al., Proc. IEEE 63, 1692–1716 (1975)] and its improved version [Nagumo et al., IEEE Trans. AC-12, 282–287 (1967)] have a common problem in that the convergence becomes very slow when the value of the 1st order autocorrelation coefficient R1 of the input signal approaches unity or minus unity. The reason for this phenomenon was made clear geometrically. The proposed algorithm is based on this geometrical investigation, and is so devised as to make the speed of convergence independent of R1 of the input signal. The result of a numerical experiment showed that, when the order of the filter is 16 for example, as R1 is changed from 0.00 to 0.99, the convergence time increases only 20% ∼ 30% in the new algorithm, while in Nagumo's algorithm it rises more than 10 times. This confirms the effectiveness of the new algorithm.
On the parallel interconnection of quadrature receivers to improve detection performance in a multipath environment
Authors: Higgins Robert C.
Published: October 2005

In this paper, the probability of detection formulas along with the corresponding receiver operating characteristic curves are derived for a parallel quadrature receiver structure where the integration times of the component receivers correspond to successive coherence intervals within the signal duration. The results are compared with a single quadrature receiver structure where the integration is performed once over the signal duration. For this analysis, the received signal model is assumed to be piecewise constant with Rayleigh amplitude fluctuations and uniform phase fluctuations. The background noise is white Gaussian with zero mean. For tractability, the signal duration is divided into two equal time intervals with signal correlation characteristics between intervals specified by the correlation coefficient p. The performance curves of the two receivers are compared for p = 0 and p = 1. The results demonstrate that when the two signal-parts are not correlated (p = 0), the parallel quadrature receiver structure provides a substantial improvement in detection performance; however, when the two signal parts are completely correlated (i.e., coherent signal), this receiver suffers only a slight loss in performance compared with the convential quadrature receiver. [Work supported by NUSC's independent research/independent exploratory development program.]
A comparison of methods for controlling side-lobe level in uniformly-spaced arrays with faulty elements
Authors: Ramsdale Dan J. , Lawrence Mimi Zebrick , Ioup George E.
Published: October 2005

Many of the arrays used for underwater acoustics research consist of hydrophones which are uniformly spaced. Standard weighting techniques are available for side-lobe control in these arrays, e.g., Chebyshev or Harm weighting. When one or more elements fail, however, these standard methods in general are not effective. We have considered three methods for regaining side-lobe control for such perturbed arrays. In the first method, the weights of the faulty elements are distributed among the remaining functional elements in the array according to a Lagrange interpolation scheme. In the second method, angularly spread narrow-band interferences are inserted on both sides of the main lobe and an optimal beamforming algorithm used to compute a new set of weights. In the third method, the new weights are determined by minimizing the power in the side-lobe region in the presence of an isotropic noise field. We have compared the side-lobe control attainable with each method for both 16- and 32-element arrays which have one or more faulty elements. Preliminary results show that both the second and third methods can restore a certain amount of the side-lobe suppression lost but at the expense of a wider main lobe and the use of negative weights. The interpolation scheme yields near perfect restoration of the original side-lobe levels within approximately ±30 degrees of the main beam but produces markedly elevated levels for larger angles. [Work supported by NORDA and the Naval Electronic System Command.]
Radiation of low-frequency sound
Authors: Van Buren A. L.
Published: October 2005

The fundamentals and problems of low-frequency sound radiation are reviewed. Emphasis is on the constraints that physics imposes on the development of high-power, low-frequency, underwater sound sources. Included are discussions of such constraints as a highly reactive radiation impedance, the requirement of large displacements of the radiating surfaces, strong radiation coupling between elements in an array, and the possibility of cavitation.
Eigenvalue analysis of matrix methods for the parabolic equation
Authors: Gilbert Kenneth E. , White DeWayne
Published: October 2005

Several new methods which handle sound speed and density discontinuities have recently been used to solve parabolic equations for underwater sound propagation. The methods are similar in that each involves a matrix whose eigenvalues are, for horizontally stratified media, the usual eigenvalues found by normal mode programs. This paper compares the accuracy of the eigenvalues computed by four different matrix methods currently in use: (1) a finite difference method, (2) a cubic spline method, (3) a linear finite element method, and (4) a cubic finite element method. Some implications of using these matrix methods to calculate sound propagation via the parabolic approximation will be discussed.
Dipole characteristics of a magnetostrictive rare earth iron “square-ring” transducer
Authors: Cohick S. M. , Butler J. L.
Published: October 2005

A magnetostrictive transducer has been constructed of rare earth Terfenol D (Tb0.3Dy0.7Fe2) rods in a “square-ring” configuration, which is essentially cylindrical. The transducer, 6 in. in diameter and 2 in. high, is resonant at 2.0 kHz in the omnidirectional mode. Some underwater detection systems also require directional information. A means of operating the “square-ring” in a dipole mode is developed. The physical mechanism of the dipole transducer behavior is described. The modification to the transducer and the driving circuit are presented. The acoustic calibration of the transducer in the dipole mode shows acceptable performance from 1.5 to 5 kHz. The dipole resonance is 2.4 kHz. [Work supported by NSWC in cooperation with NADC.]
Diffraction of sound by an infinite rigid cylinder to small forward angles: A calculation using methods of physical optics
Authors: George Jacob
Published: October 2005

We have used the Kirchhoff method of physical optics to calculate the acoustic intensity diffracted by an infinite rigid cylinder to small forward angles and have compared the results with those of exact calculations. The intensities predicted by the two methods are in excellent agreement. Kirchhoff predictions of a phase angle seem to be unreliable.
Pressure patterns in the nearfield of a diffracting object
Authors: Waterhouse R. V.
Published: October 2005

A steady train of plane waves impinges normally on a tight circular cylinder of infinite extent. The nearfield diffraction patterns for the normalized rms pressure were computed for values of ka from 1.5 to 6, where k is the wavenumber and a is the radius of the cylinder. Charts are given, showing the contours of rms pressure for ka = 1.5, 2, 3, 4, and 6, for each of two boundary conditions, pressure reflecting, and pressure release. Each chart shows the contour pattern out to a distance of 5 radii. The computed expressions are infinite series containing Bessel functions and their gradients. In some cases more than 30 terms in the series must be evaluated to get convergence to within 1%. The charts show that there are substantial areas where the pressure differs from the undisturbed value by 6 dB or more.
Acoustic spectroscopy
Authors: Brill D. , Gaunaurd G. C. , Überall H.
Published: October 2005

The resonances of elastic objects imbedded in a fluid medium have been shown to play an important role in the acoustic response of the object. We have previously discussed aspects of the inverse scattering problem, i.e., how to gain information regarding the material composition of the target from a determination of the resonance peaks. [J. Appl. Phys. 52, 3205–3214 (1981)]. Nuclear physics has shown that information on the shape of nonspherical objects may be obtained from analysis of the splitting of the giant (nuclear) resonances. We have used this idea to study the acoustically excited mechanical resonances of liquid targets by plotting the resonance spectral levels of liquid spheres. We have further studied the splitting of these resonances as the sphere deforms into spheroids of increasing eccentricity. These spectra are compared with those of cylinders of similar length/diameter ratios b/a, towards which they converge as b/a ≫ 1. The use of such an “acoustic spectroscopy” scheme for shape identification of acoustic targets is emphasized. [H. Überall is also at the Physics Department, Catholic University of America, additionally supported by Code 421 of ONR. D. Brill was supported by Code 2842 of DTNSRDC, Annapolis, MD 21402.]
Anomalous behavior of a clarinetlike system
Authors: Backus John
Published: October 2005

Some preliminary work has been done on the problem of understanding in detail the interaction between the vibrating clarinet reed and its associated vibrating air column. In the course of the work, a configuration of brass tubing with tone holes was found which is rather difficult to sound with a clarinet mouthpiece and reed and which produces a poor “stuffy” tone. The input impedance curve of the configuration does not appear to be sufficiently different from that of a conventional clarinet to explain this behavior. Measurements with an impedance tube showed that at the amplitudes associated with playing, nonlinear effects at the tone holes produce an increase in the acoustic resistance that lowers the Q of the system by about a factor of two. However, this also does not appear to explain the difficulty of sounding the configuration; it was found that the Q of a piece of tubing could be lowered by about a factor of two by lining the wall with an insert of emery cloth, yet the rough wall tube could be sounded about as easily as a smooth tube. It is hoped that understanding this configuration will help in understanding the behavior of the clarinet, so work is continuing. [Work supported by the National Science Foundation.]
Oboe and bassoon perturbation weight function measurements
Authors: Benade A. H. , Carman J. C.
Published: October 2005

The adjustment of woodwind air columns for proper tuning and intermode cooperation requires knowledge of the fractional mode frequency shifts (Δf/f)n produced by air column cross-section perturbations Sp(x), as represented by the formula (Δf/f)n = −∫0LWnSpdx. In the conical woodwinds direct measurement of the weight function Wn(x) via a movable perturbing volume is not practicable. Instead, closely spaced probe microphone measurements of the modal pressure wavefunctions permit calculation via Wn = [pn2 − (∂pn/∂x)2(1/kn)2]⧸ ∫ 0L S0(x)[pn2] + (∂pn/∂x)2(1/kn)2]dx. We have measured the set of Wn's of several representative fingerings on the Triebert system 6A (conservatory), system 3, and Vienna Academy system oboes, and on the German system bassoon. Effects of nonuniform taper, tone holes, etc. are in agreement with theoretical expectation. Overall the patterns of inter-instrument similarity and of departure from simple-cone behavior are quite parallel to what we reported earlier for the clarinet family. [Work supported by NSF.]
Coupling of violin string vibrations to the acoustic field
Authors: Weinreich Gabriel , Arnold Eric B.
Published: October 2005

We have developed a method for determining the monopole and dipole moments of a violin resulting from unit force amplitude applied at the string, at any frequency corresponding to a string resonance, that is, at a frequency at which the instrument would be bowed. What is actually measured is the quantity related to this by a reciprocity theorem, namely, the amplitude of string displacement produced by a controlled acoustic pressure and pressure gradient. The violin is immersed in turn in acoustic fields produced by each of four independent speakers and the string displacements (for both string polarizations) are measured; in each of the four cases, we also determine the acoustic pressure and the three components of pressure gradient at the position of the violin. By a computer superposition, fields that have unit pressure amplitude and zero gradient, and fields that have unit gradient component in each direction but zero pressure, are simulated. From this the moments can be calculated. Results on a number of violins will be reported. [Work supported by NSF.]
Piano training system using a micro-computer and the characteristic extraction of the learners' playing a fundamental etude
Authors: Kitagaki Ikuo , Suetake Kunihiro
Published: October 2005

A computerized piano training system is discussed here. It consists of a keyboard adaptor quasi-fixed in a piano, a micro-computer, and a TV monitor fitted with it. The system permits detecting time when a learner depresses a keyboard, processes the data, and evaluates the playing. The data and the evaluated information are displayed graphically on a TV monitor. Considering that a fundamental etude is essential as an educational material and that physical measure of the playing of an etude is considered to be more significant than that of popular musical compositions, we designed the system focusing on the playing of fundamental etudes such as “Hanon.” With the system, we obtained data on about three hundred learners. Thus, it became clear that the playing of the Hanon Etude can be classified into three kinds of typical patterns.
Absolute tonality and absolute pitch
Authors: Ward W. Dixon , Terhardt Ernst
Published: October 2005

The initial 5 s of each of the 12 major-key preludes from Bach's Well-Tempered Clavichord was recorded as written and also shifted by ±1, 4, 6, or 7 semitones, and a randomized tape consisting of two repetitions of each of the 108 items was prepared. Twenty musicians, mostly pianists, decided whether each item was played in the correct key, transposed up, or transposed down; a simplified version of the original (correct) score was printed on the answer sheet. Only two subjects failed to discriminate, at the 5% confidence level, the correct rendition from the transposed ones, even when only the ±1-semitone transpositions are considered. The four subjects claiming to possess absolute pitch performed slightly better than the rest, but it is clear that absolute identification of tonality is an ability that is more widespread than commonly supposed. The results support the “unlearning” theory of Abraham and Watt: an inborn potential for developing absolute pitch is relatively common, but it tends to become atrophied or suppressed because of the far greater importance of relative pitch in our musical environment. [Research supported by the Bryng Bryngelson Communication Disorders Research Fund.]
The use of resonators to silence centrifugal fans
Authors: Koopmann G. H. , Neise W.
Published: October 2005

In this paper, we present the latest results of a continuing study directed to reducing the noise of centrifugal fans by altering the noise source mechanisms. Basically, our method involves replacing the cutoff section of a fan casing with a quarter-wavelength resonator. The mouth of the resonator is formed from a perforated plate which has the same curvature as the original cutoff section. By tuning the resonator to the blade passing frequency, significant reductions in the noise level of the blade passing frequency tones in both the inlet and outlet ducts are possible under varying, aerodynamic loading conditions. Previous studies were performed on fans which had backwardly curved blades. In the present study, we extended the method to a noisier, less aerodynamically stable class of fans which have impellers constructed of flat, radial blades. As in the previous studies, substantial noise reductions in both inlet and outlet ducts are achieved when the resonator is optimally tuned. An additional part of the study included the measurement of the impedance of the resonator as a function of aerodynamic load and rotational speed of the fan. [Work supported by EPRI.]
Centrifugal fan V-Notch cutoff
Authors: Strong Walter F.
Published: October 2005

The sound from two 5600 HP induced draft fans at a 500-MW coal-fired power plant was a source of community annoyance. Each fan was retrofitted with a V-notch cutoff designed to reduce the noise generated at the blade passage frequency and its harmonics. The cutoff is the part of the fan casing at the discharge which is closest to the impeller blade tips. A conventional cutoff has a straight edge parallel to the blade tips, while the edges of a V-notch are askew to the blade tips. The V-notch design was based on aerodynamic tests of a 116 scale model fan with inlet and discharge ducts. In order to evaluate the performance of the V-notch cutoff, detailed sound measurements were taken in the community, near the fan cases and inside the stack (in 330°F hot flue gas) both before and after the fan modifications. In addition, the in-stack measurements were coincident with fan performance measurements and were taken for several operating conditions. A 5- to 7-dB reduction of the tones was achieved which significantly reduced complaints.