bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal order identification thresholds: Some parameter dependencies
Authors: Pastore Richard E. , Kaplan Jody K. , Harris Laura B.
Published: October 2005

Temporal order identification thresholds (TOT) for sinusoidal stimuli were measured under a variety of conditions with practiced observers using a Levitt up-down adaptive procedure. TOT was not altered by contralateral timing cues which had previously been found to be effective in counteracting backward masking. However, TOT was found to be a function of the duration of the temporally simultaneous portion of the two stimuli prior to their simultaneous offset. Average thresholds ranged from 5.7 ms for the shorter stimulus duration of 10 ms (i.e., the stimuli were 15.7 and 10.0 ms with simultaneous offset) to 23.1 ms for the shorter stimulus duration of 300 ms. This dependency is in contrast with the typical finding of a constant 17 ms TOT independent of the stimulus parameters. The nature of stimulus uncertainty in TOT will be discussed.
Sensitivity of cross-sensor beamforming to random errors in amplitude and phase
Authors: Ramsdale Dan J. , Howerton Roger A.
Published: October 2005

Cross-sensor beamforming offers the potential of providing good side-lobe suppression for sparse acoustic arrays or filled arrays which develop faulty elements during exercises at sea. To determine the sensitivity of this technique to random errors in amplitude and phase we computed the cross-sensor beam pattern with each element in the array subject to a random amplitude and phase error. For a line array with 32 equally spaced elements, the beam pattern from the cross-sensor method was nearly identical to that of the conventional beamformer with both subject to the same set of random errors. Repeating the same computation with four inoperative elements showed that the cross-sensor method maintained good side-lobe suppression while the side lobes of the conventional beamformer were elevated corresponding to the amplitude weights of the faulty elements. The mean beam pattern for the cross-sensor method was computed analytically assuming the errors were random, independent, and uniformly distributed. The result can be expressed as the sum of the error-free pattern and an additional angle-independent term due to the random errors. Comparison of this expression with the corresponding one for the conventional beamformer reveals that for a filled array the two results are identical. [Work supported by NAVMAT.]
Reverberation time in occupied concert halls calculated from measured reverberation time in unoccupied halls
Authors: Schultz Theodore J.
Published: October 2005

Beranek's book Music Acoustics and Architecture (pages 550– 551) gives three curves that allow one to predict the reverberation time for an occupied concert hall from the measured reverberation time for the unoccupied hall. Beranek fitted these curves by eye to his tabulated data (Appendix 2) on the reverberation times measured (at 125, 500, 1000, and 2000 Hz) in approximately 50 unoccupied and occupied halls, built before 1960. This paper presents least-squares regression curves fitted to Beranek's data, establishes the probable reliability of the revised prediction (in terms of correlation coefficients and standard errors of estimates), and extends the prediction to other frequency bands of interest. Comparison with measured data from unoccupied and occupied halls shows good agreement with the predicted values.
An evaluation of acoustical measurements and analysis procedures as applied to open-plan office spaces of the conventional screen-desk and modular furniture types
Authors: Spalding G. Robert , Niedzielski Joseph
Published: October 2005

Objective and subjective procedures have been employed in a testing program to evaluate the intermodule speech-privacy potential of contiguous open-plan work stations under laboratory conditions. Interzone sound-attenuation measurements were made to determine such single-number performance ratings as Speech Privacy Noise Isolation Class (NIC'), Articulation Index (AI) and A-weighted sound level difference (ΔdBA). These ratings were compared to subjective jury judgment of speech privacy. Agreement between the objective ratings and the subjective rating was found to be good for both conventional and modular furniture types of open-plan spaces when vertical surfaces were highly absorbent. This agreement deteriorated when vertical panel surfaces were sound reflective. The sound-absorption characteristics of the vertical panels not only influence speech privacy but also affect the general acceptability of the open-plan acoustical environment.
Source strength relations for the Boehm flute
Authors: Benade A. H.
Published: October 2005

The flute is unusual among woodwinds because it radiates sound from the embouchure hole and from its tone holes. Coltman (1969) showed accurately equal source strengths at the blown and unblown mouths of a double-ended organ pipe. On a flute the standing wave flow divides: Part enters the compliance of the headjoint cavity, and part traverses the embouchure hole into the room. Similarly, some flow exists from the first tone hole, and the (attenuated) remainder travels toward the other holes. Calculation shows the source strength ratio Semb/Sfirst hole is roughly constant (+3 dB) below 1 kHz, 0 dB 1.55 kHz and −3 dB at 1.8 kHz. The summed effect of all the tone holes subtracts 6 dB from the figures given. Above the tone hole cutoff frequency (≃2 kHz) the ratio can be anywhere between −2 dB and +5 dB. Experiment confirms all this for a first class silver flute playing mezzoforte G4. The overall S/N ratio is 46 dB at the embouchure hole, and considerably better at the tone hole. The frequency dependence of the noise source ratio is unlike that of the signal: the noise is thus not associated with the standing wave. The free space radiated angular distribution is little affected by Semb/Shole ≠ 1. Even partials show a notch near the equatorial plane; odd partials radiate preferentially in a similar direction. In a room the two sources add incoherently since their spacing exceeds the room's autocorrelation distance. [Work supported by NSF.]
Mathematical studies of air-loaded membrane vibrations with application to the kettledrum
Authors: Tubis Arnold , Christian Richard S.
Published: October 2005

The effect of air loading on the normal modes of a vibrating membrane may be systematically calculated by making use of the relevant Green's functions for the air medium. Formal and numerical results have been obtained for the case of rectangular membranes with and without rectangular-box and split-cylinder air enclosures, and of circular membranes with and without cylindrical and hemispherical air enclosures. Our analysis may be used to assess the relative importance of bowl shape, enclosed-air loading, and outside-air loading on the normal modes of the kettledrum.
Use of aqueous foam to reduce blast noise
Authors: Raspet R.
Published: October 2005

Various laboratories have investigated the use of aqueous foam to reduce blast overpressures. In 1976, the Royal Armament Research and Development Establishment of the United Kingdom measured the reduction in environmental noise produced by filling bomb chambers with high-expansion fire fighting foam. Reductions in the A-weighted peak levels were measured as high as 20 dB. However, these results cannot be applied to other configurations because of the confinement of the explosives and the indirect propagation path from explosives to microphone. This paper describes a study conducted by the US Army Construction Engineering Research Laboratory (CERL) which measured the reduction in (1) C-weighted and flat-weighted sound exposure level and (2) the flat-weighted peak level produced by covering explosive charges with high-expansion foam. CERL used charges ranging in size from 0.135 to 5 lb (0.06 to 2.3 kg): foam depths varied from 6 in. to 4 ft. 9 in. (0.15 to 1.4 m). All of these data, with the exception of the 0.135-lb (0.06-kg) data, display a linear relationship between reduction in levels and cube-root scaled foam depth. The 0.135-lb data are also linear within experimental accuracy, but display less reduction with scaled foam dimensions.
Reduction of centrifugal fan noise by use of resonators
Authors: Koopmann G. , Neise W.
Published: October 2005

The subject of this paper centers around a method by which an acoustic resonator can be used to reduce the aerodynamic noise generated by turbomachinery. In the study reported, the casing of a small, centrifugal blower was modified by replacing the cutoff of the scroll with the mouth of a quarter-wavelength resonator. The mouth of the resonator was constructed from a series of perforated plates with the same curvature as the cutoff to preserve the original geometry of the casing. Tuning of the resonator was achieved by changing the length via a moveable end plug. The noise measurements were made in an anechoically terminated outlet duct at nearly a free delivery operating condition of the blower. With appropriate tuning of the resonator, reductions in the blade passing frequency tones of up to 29 dB were observed with corresponding overall sound pressure levels reductions of up to 7 dBA. Parameters which influenced the bandwidth of the resonator response were the porosity and hole size of the resonator mouth and the flow velocity near the cutoff region. Throughout the tests, the aerodynamic performance of the blower was unaffected by the addition of the resonator to the casing.
Environmental noise emissions from on-site diesel electric generators
Authors: Teplitzky Allan M. , Miller Laymon N.
Published: October 2005

The installation of on-site diesel generators as an alternative to purchasing electric power from a central source may be accompanied by an adverse environmental noise impact. Noise vibration emissions from on-site diesel engine generators need not become a source of community annoyance if regulatory agencies require and review noise impact analyses for new installations, and if adequate noise abatement devices are installed and maintained. A noisy installation may become a chronic source of community annoyance, since retrofitting noise controls to an existing installation, when feasible, can be extremely costly and may therefore not be implemented. This paper reports on a study which developed procedures for (1) calculating environmental noise and vibration emissions from on-site diesel generators which consider variables such as proximity to nearest neighbor, local ambient sound levels, location of the facility, method of cooling and type, size and quality of equipment to be installed, and (2) estimating noise abatement costs for on-site diesel generators. In urban areas where there are insufficient open spaces to provide for adequate noise abatement buffer zones, the installation of noise abatement devices such as vibration isolators, mufflers, and enclosures are an absolute necessity, and the cost to abate diesel engine-generator noise may be as high as $42 000 per engine. [The Consolidated Edison Company of New York Inc., sponsored the study, “Diesel-Engine Generator Noise and Vibration Abatement,” prepared by Bolt Beranek & Newman Inc., Report No. 4187, November 1979.]
Effects of the A-weighting tolerance limits on rms measurements
Authors: Wong G. S. K.
Published: October 2005

The effects of type 1 A-weighted tolerance limits on rms measurements have been investigated theoretically and verified experimentally. Three A-weighted circuits, each of which satisfied type 1 tolerances, were tested with pulse trains with various crest factors; and depending on the frequency-band limits of the measuring system, erroneous rms readings could be obtained. For example, at a constant repetition rate of 10 kHz and a crest factor of 3, the measured rms readings obtained with the A-weighted circuits spanned a range of 4 dBA when the frequency-band limit was increased from 30 to 100 kHz.
Coding of interaural time differences in the microsecond range by auditory units of echolocating bats
Authors: Harnischfeger G.
Published: October 2005

The coding of interaural time differences (Δt) by single auditory units was investigated by extracellular recordings from the brainstem in the echolocating bat, Molossus ater. Phase-locked constant frequency tone bursts (2 ms duration, 0.5 ms rise/decay-time) delivered through earphones could be time delayed with an accuracy of <1 μs by using two “bucket-brigade-devices.” Nine percent of the 79 binaural units studied showed dependence on Δt-variations in the animals' relevant time range (±50 μs 17 mm interaural distance). From the steepest Δt-impulse count functions measured for a fixed interaural intensity difference, a minimum detectable time difference of less than 4 μs could be calculated. These small time differences were coded from the envelope of signals with comparatively long rise times. The use of phase differences can be excluded. Due to the high best frequencies of the units (18–61 kHz) the half periods of the sine waves were always shorter than the working ranges of the Δt-impulse count functions measured. Furthermore, the Δt-functions were never periodic. [Work supported by DFG: Br 593/2, Ne 146/10, and SFB 45.]
Neuronal critical bands (NCBs)—Determined for single units of the inferior colliculus of the CF-FM bat Rhinolophus ferrumequinum
Authors: Engelstätter R.
Published: October 2005

NCBs, were estimated by determining the thresholds for noise of variable bandwidth centered around the best frequency (BF) of the neuron and by masking a pure tone at the BF with the same noise. In most cases the values can be fitted by two straight lines whose intersection defines the size of the NCB. Single units with a BF in the frequency range of the CF-orientation call (about 83 kHz) are characterized by extremely small NCBs (0.2–0.4 kHz). For neurons with a BF around 81.5 kHz the sensitivity for noise is lower as expected from the psychophysical critical ratio (CR) curve of Rhinolophus [Long, G. R., J. Comp. Physiol. 116, 247–255 (1977)]. Presumably the high signal-to-noise ratios (SNRs) in this frequency range are responsible for this discrepancy. No correlation was found between the size of the neuronal CRs estimated from the SNR measured with wide-band noise and the size of the NCB. [Work supported by DFG Br 593/2.]
Predicting the results of forward masking experiments for tonal probes and maskers
Authors: Kidd Gerald , Wilcox Kim A. , Feth Lawrence L.
Published: October 2005

A simple computational model was devised to predict the results of forward masking experiments which use tonal probes and maskers. Using straight-line approximations for the hypothetical underlying excitation patterns and a fixed “detection” criterion, the model predicts “masked threshold” for a given combination of masker and probe parameters. Discussion will center upon the validity of the simplifying assumptions and the comparisons between predicted and observed values. [Work supported by a David Ross Fellowship from Purdue University and grants from N.I.H.]
Effects of MRF stimulation on the auditory-evoked potential
Authors: Cassady J. Michael , Lewis Richard , Kitzes Leonard M.
Published: October 2005

The effects of mesencephalic reticular formation (MRF) stimulation on cortical-evoked potentials was studied in nine cats. The interval between MRF stimulation and delivery of tonal stimuli (i.e., delay) was varied as was the intensity of electrical stimuli at 52 sites in MRF. The effects of MRF stimulation on auditory-evoked potentials were, as in the visual system, time dependent: with a 30 ms delay, the N1 wave (latency 10–15 ms) was usually augmented; with a 25 ms delay, the P2 wave (latency 20–25 ms) was consistently suppressed; with a 5 ms delay, the N2 wave (latency 35–50 ms) was consistently augmented. The most effective stimulation sites were sharply localized within MRF. Stimulation alone at these sites elicited large field potentials in auditory cortex with a peak latency of 30–50 ms and a duration of 80 ms. Stimulation of neighboring sites evoked only marginal changes even with increased current. Pupillary behavior, used as an experimental control, was affected by broader areas within the MRF. [Work supported by NIH.]
Behavioral threshold for tones in 6- and 10-month-old infants
Authors: Berg Kathleen M. , Smith Melanie C.
Published: October 2005

Behavioral thresholds for 500, 2000, and 8000 Hz tone bursts were determined for 6- and 10-month-old human infants using a transformed up-down tracking procedure in a conditioned head turn paradigm. In experiment 1, stimuli were presented in free field and tracking was initiated at an intensity well above threshold. For 10-month-old infants, threshold estimates were approximately 15 dB above adult values at all three frequencies. Six-month-old thresholds were slightly higher and relatively flat across frequencies. In experiment 2, stimuli were presented via earphone, tracking was initiated below threshold, and supra threshold probe trials were introduced to assess the infants' motivation to respond. With these changes in procedure, 6-month-olds showed the adult U-shaped sensitivity function. [Work supported by NINCDS.]
Large-scale check on the consistency of coupler threshold standards
Authors: Corliss Edith L. R.
Published: October 2005

The Health and Nutrition Examination Survey (HANES), conducted by the US Public Health Service in 1971-75, provided hearing data on a population sample of approximately 3000 individuals on whom both pure-tone and speech audiometric measurements were made. All audiometers were equipped with TDH-49 earphones with supra-aural MX41/AR cushions. The speech test was used at the National Bureau of Standards to select normal individuals from HANES, and was a criterion essentially independent of the pure-tone thresholds. For each individual earphone. The pure-tone threshold data were referred to standard coupler pressures, taking into account the audiometer output pressures as calibrated weekly. Over this large group of earphones the thresholds obtained are uniform; this study thus verifies the logic of maintaining standard data for audiometric thresholds in terms of sound pressures produced in the calibrating coupler for each type of earphone. However, this extensive group of normal individuals yields threshold data differing significantly and systematically from the ANSI-1969 Standard for Normal Threshold of Hearing. The situation warrants further study.
Flat-plate coupler calibration of circumaural audiometric and hi-fi earphones
Authors: Kruger B. , Solomon B. , Cohen R.
Published: October 2005

Circumaural earphones have been shown to provide improved coupling when compared with the standard supra-aural audiometric earphone (TDH-39,49; calibrated with a standard NBS 9A coupler) [E. Villchur, J. Acoust. Soc. Am. 48, 1387–1396 (1970); N. P. Erber, J. Acoust. Sec. Am. 44, 555–562 (1968)]. A standard coupler is needed for circumaural carphone calibration. A flat-plate coupler has been designed for calibration of a circumaural earphone (Telephonics model 556) for hearing testing [P. L. Michael and G. R. Bienvenue, J. Acoust. Soc. Am. 66, 944–950 (1976)] and proposed as a standard coupler for circumaural calibration [J. Prout, ANSI S3.37, Working Group Draft (1979)]. The use of this flat-plate coupler for calibration of circumaural earphones for audiometry (Telephonics model 556, Beltone Auraldome and Audicup, and Phonic Ear) and for hi-fi listening (Sennheiser HD430, Koss VFR and HV1LC, and AKG 240) was studied systematically. Repeated intra and intertester comparisons, and control of earphone position suggested guidelines for reducing variations. The utility of this flat-plate coupler as a means of checking stability of earphone frequency response is supported. Differences in earphone responses, effects of leakage, and resonances will be demonstrated and discussed. [Work partially supported by AOS.]
Cricothyroid activity during speech
Authors: Dixit R. Prakash
Published: October 2005

Simultaneous recordings of voice and cricothyroid activity during speech production by one speaker of Hindi were made. The subject produced utterances containing stops, affricates, and fricatives. All utterances were embedded in carrier sentences. The results show markedly higher levels of cricothyroid activity for the voiceless stops, affricates, and fricatives than for their voiced cognates. This suggests that the cricothyroid may play some role in maintaining voiced versus voiceless contrast in consonant segments. It does so at least in this subject.
Determination of vocal tract shape during phonation from input/output measurements of throat-wall vibration near the glottis and microphone pressure at the lips
Authors: Vemula N. R. , Engebretson A. M. , Elliott D. L.
Published: October 2005

A reflectionless terminator tube at the lips was used to measure the inside surface response of the throat wall when the wall was mechanically excited with a vibrator. The “acoustic” transfer function characteristic of the wall (relating the supraglottal sound pressure and the “acoustic” component of the wall vibration) revealed by these measurements can be well approximated when the wall, consisting of cartilages, muscles, and soft tissue, is modeled as a lumped-parameter mechanical system. Earlier attempts to obtain the vocal tract shape during phonation have used the speech signal alone and made some simple assumptions about the glottal source. In the present study simultaneous measurements of the inside surface pressure with the terminator tube and of throat-wall external vibration during phonation are made to determine (total) transfer function characteristic of the wall. A pole-zero model for this (total) transfer function characteristic is then used to specify the source signal for a model of the vocal tract. More consistent tract shapes are found using the input/output approach compared to those derived from linear predictor procedures based on the speech signal alone.
Simultaneous cineradiographic-electromyographic-acoustic analysis of vowel production
Authors: Baer Thomas , Alfonso Peter J.
Published: October 2005

In an x-ray study of vowel production, three types of measurements, namely articulator movement, EMG, and acoustic, were simultaneously made as a single subject produced various vowels in a ∂pVp environment. Movement measurements were obtained from the lips, tongue, jaw, and velum. EMG signals were collected from a single lip muscle, the Orbicularis Oris, and from two tongue muscles, the Genioglossus and Superior Longitudinal. Formant frequencies and amplitude measures were extracted from the audio signals. The subject's vowel space was plotted for each of these three types of measures. For the tongue, jaw, and lip, amplitude and timing relationships among movement, EMG, and acoustic signals were analyzed. Movement measurements indicated minimal jaw movement. The tense-lax vowel distinction was characterized by differences in articulator position, EMG amplitude, formant frequency, acoustic amplitude, and vowel duration. Relative timing of vowel (tongue) and prevocalic consonant (lip) activities was also analyzed for each of the three types of measures. The onsets of vertical tongue dorsum activity were closely associated with the timing of the lip gesture. However, horizontal tongue dorsum activity for back vowels began much earlier than the lip gesture. [Work supported by NINCDS and BRSG grants.]
Correlation of mandible position and vowel durations
Authors: Condax I. D.
Published: October 2005

It has been shown that in Fijian, relatively well-defined targets exist for the position of the jaw at greatest opening during vowels or greatest closing during consonants [1. D. Condax, J. Acoust. Soc. Am. Suppl. 65, S25(A) (1979)]. It has also been shown that a model can be constructed to account for most of the variance in vowel durations in connected speech [I. D. Condax, J. Acoust. Soc. Am. Suppl. 66, S50(A) (1979)]. It is here proposed that the duration and jaw position for vowels are correlated in a model of speech production that describes vowel duration as independent (determined by phonological and phonetic factors such as length, stress, and height), and where jaw position can be predicted from duration, although it is also dependent on position during adjacent consonants, and, to an unexpectedly small extent, on vowel height. [Work supported by NEH and the University of Hawaii Foundation.]
Motor equivalence for vertical lip separation
Authors: Hasegawa Akira , McCutcheon Martin J. , Fletcher Samuel G.
Published: October 2005

The objective of this study was to document important kinematic characteristics of lip and jaw coordination. A new experimental paradigm was developed, which involved matching computer-controlled, video-displayed articulatory targets to articulations with or without visual feedback. The study was conducted with three male adult subjects to examine motor equivalence for vertical lip separations of 10, 20, 30, and 40 mm. A series of “target dots” were displayed one at a time on a TV monitor in front of the subject. The target dot indicated the vertical distance between the upper and lower lips. The subject was first trained with the aid of another dot on the screen which indicated vertical lip separation between his lips as determined by lateral gnathometry. The subject was instructed to follow the target as accurately as possible. Data collection in lateral gnathometry was carried out first with visual feedback and then without visual feedback. The results indicated that target lip separations were achieved by systematically different combinations of lip and mandible displacement. [Work supported by NIH grant NS11852-04.]
Speaking backwards: A case study
Authors: Cowan N. , Leavitt L. A. , Massaro D. W. , Kent R. D.
Published: October 2005

A 31-year-old male philosophy professor (Prof. B) who can speak backwards fluently, at a normal rate, was studied. To define Prof. B's ability, recordings, spectrograms, and phonetic transcriptions were obtained. In an impromptu backwards monologue and in passages, sentences, and isolated words translated into backwards speech from written and spoken input sources in real time, Prof. B maintained the original word order but reversed the order of phonemes within each word. These reversals were not always phonetically complete, e.g., diphthongs were not reversed. Forward intonation was preserved. Although reversals were primarily phonologically based (e.g., silent consonants were rarely pronounced), there was a partial reliance on orthography even with spoken input (e.g., “xerox” was reversed as [ksɔriks], not [skariz]). Additional experiments investigated the processes contributing to Prof. B's special ability. In contrast to control subjects, Prof. B generally accomplished speech reversals “automatically.” However, reversal greatly increased Prof. B's recitation times when a processing load was introduced (e.g., in Z-to-A alphabetic recital). Finally, Prof. B possessed a much greater ability to identify words spoken backwards than did trained volunteers.
Effects of nasal coupling on the vowels
Authors: Nguyen D. T. , Guérin B.
Published: October 2005

The appearance of new formants in the vowel spectrum when the nasal tract is connected with the oral tract, has been studied. With a numerical harmonic simulation of the transmission-line analogy taking into account all losses (radiation, heat, viscosity, wall vibration), the variation of the input impedances with frequency looking into the three tubes from the coupling point of nasal tract (called Xn and Xbp) have been calculated. With these data, we can explain graphically the formation of the peaks and dips on the spectrum. From circuit analogy, the nasal formant Fn is the frequency where the reactance looking into the nasal tract from the coupling point is infinite, and the nasal zero An is where this reactance is zero. The intersections of a branch of −Xn and two branches of Xbp are considered as the two “formants” newly created by splitting of the original formant by the zero An. These peaks can be defined as: (1) The shifted frequency of the original formant (termed “the primary formant”); (2) the newly created formant accompanying (termed “the secondary formant”). This formant was generally referred as “nasal formant.” Taking into account all kinds of losses leads, sometimes, to the decrease of the number of intersections (of −Xn and Xbp) when comparing with results obtained without losses. The zeros found in the spectrum of a nasalized vowel at the nasal antiformant frequencies are greatly diminished by high losses in this tract.
Mechanisms of wind-induced low-frequency ambient sea noise in the deep ocean
Authors: Yen N. , Perrone A. J.
Published: October 2005

Theories of wave interaction and turbulence have been extended to the study of noise-generating mechanisms for the interpretation of the reported experimental low-frequency ambient noise data in the frequency range of 1 to 10 Hz. The problem is formulated by assuming a stationary disturbed ocean surface which also serves as the interface of wind turbulence and wave turbulence. The noise spectrum level at deep depths in the ocean is hypothesized as the result of the convolution of surface wave, wind turbulence, and wave turbulence actions which satisfy the radiation condition. Due to the scaling difference between acoustic waves and flow disturbance, the physical arguments have been applied to obtain a simplified mathematical derivation. With incorporation of propagation conditions and the ocean bottom, the noise level received by a sensor in the water column is predicted from the assumed noise-generating mechanisms and appears to agree in order of magnitude with the experimental data. The theoretical approach to ambient noise problems from this study suggests some important parameters for noise modeling and also provides a reference for planning experiment and data comparison. [Work supported by ONR.]
Gravity-wave-induced pressure fluctuations in the deep ocean
Authors: Kadota T. T. , Labianca F. M.
Published: October 2005

We establish a mathematically consistent theory of the pseudosound pressure fluctuation (below 1 Hz) in the deep ocean induced by nonlinearly interacting random plane waves on the surface. In the process, a new set of second-order perturbation equations is derived. A phenomenological model is adopted for wind pressure which serves to excite a two-component surface-wave field, namely wind-driven sea and swell. By solving the perturbation equations through second order with this wind pressure as the excitation, we obtain an expression for the deep water pressure fluctuation and its power spectral density in the gravity-wave regime. Contrary to the previous theory not all of the surface waves contribute to the generation of the pressure fluctuation. Only the swell component does. Moreover, the customary Gaussian-distribution assumption of the surface waves leads to an incorrect power spectrum of the pressure. A more general probability distribution is required for obtaining a meaningful power spectrum formula. [This research has been supported by the Office of Naval Research, Code 480.]
Predicting the density of spectral lines in ocean ambient noise
Authors: Short Robert D. , Toomey J. P.
Published: October 2005

A technique for predicting the expected number of shipping-produced lines in an observed underwater acoustic ambient noise spectrum is described. The method is based on a mathematical model which includes the sonar equation, available information on the acoustic signatures of individual ships, and data concerning the oceanic distribution of shipping. The average number of apparent spectral lines in a given frequency band (line density) is shown to depend on the location of the sensor, sea state, and frequency. The line density also depends on the parameters of the sensor system. Conclusions drawn from the model show, for example, that the spectra observed with more directive receivers will contain more spectral lines. The results and methods described have application to passive sonar systems engineering.
Musical spectrum and transfer function measurements: Techniques, pitfalls, interpretation
Authors: Benade A. H.
Published: October 2005

Sound spectrum measurements are difficult. The priorities follow: Instrument and player mutually comfortable. Player's task familiar and specified in the terms of his profession. Adequate averaging by microphone and source motion (net displacement ≫ λmax, distance from walls and floor > λmax). Care that microphone is truly in the reverberant field despite source directionalities. Signals from several microphortes summed or averaged only after analysis (otherwise results fluctuate as do 1-mike data). Angular distribution and frequency response measurements differ widely in very-nearfield (kR <<< 1), nearfield 1 < kR, ka < 6, and farfield R/a ≪ 1, kR ≪ 1. Here a = instrument size and R = microphone distance. Choice of transfer impedance, admittance, or simple ratio is governed by musical function. Excitation source impedance must be measured via response of known inertance, elastance, or transmission line. Similar (small) perturbers at driving point aid verification that Zs does not alter significant modes of the driven system. Parallel criteria exist for detectors. Care is required to prevent mechanical, acoustical, or electrical leakage from exciter to detector. [Work supported by NSF.]
The difference between difference tones and rapid beats
Authors: Hall Donald E.
Published: October 2005

Simultaneous production of two pure tones with frequencies f1 and f2 is associated both with auditory beats (rapid fluctuations in loudness) and with audible difference tones. Since the same frequency f1−f2 is encountered in both cases, students tend to think a difference tone is nothing more than a beat phenomenon whose frequency is high enough to be in the audible range. But, in fact, these are two entirely distinct effects. I will discuss how to convincingly present this difference at three levels: (1) Simple theory of added and multiplied waveforms, (2) visual demonstration with oscilloscope plug-in Fourier analyzer, and (3) audible demonstration. These show that our ears can literally hear and distinguish two separate phenomena.
Graphic representations of complex tones
Authors: Lawson Dewey T.
Published: October 2005

An alternative to standard spectral plots has been developed for graphic representation of complex tones to students of musical acoustics. Based on intervals rather than component tones, this representation offers pedagogical and analytical advantages, particularly when musical transposition is considered. Examples will be given of its use in representing complex intervals and chords, discussing perceptual data, and carrying out various types of consonance analysis.
The laryngograph in singing. I. General methods
Authors: Brown Oren , Fraterrigo Noël , Gates Linda , Potter Charles , Reed William , Reynolds Evelyn , Teaney Dale
Published: October 2005

The Fourcin laryngograph handily provides a voltage output, lx, proportional to the area of the glottal opening. We have investigated the uses of the lx signal in the voice studio as a feedback modality in parallel with the usual kinesthetic, aural, and interpersonal cues by which a singer manages his voice. The lx signal is returned in four ways: (1) The lx waveform, normalized in amplitude and frequency, is displayed on an oscilloscope. The mechanics of phonation are immediately evident in this display. A kinesthetic connection with the visual pattern develops easily as the singer explores the variation of his waveform with pitch or loudness. (2) The power spectrum |Lx′| of the time derivative of lx, is displayed in real time above a keyboard mnemonic. A singer tends to “feel” the waveform lx, including its evident phase relationships, while he “hears” the power spectrum | Lx′|, which is identical to that of the glottal acoustic source. (3) Laryngeal behavior over an extended time is notated as a real time soundscore. Techniques 2 and 3 are applied to the voiced sound as well [see J. Acoust. Soc. Am. Suppl. 1 66, S42 (Fall 1979)]. Feedback modality 4, the laryngeal envelope, surrounds the singer with the amplified sound of his own lx′, which, above a critical loudness level, obliterates normal auditory cues, placing the singer in a new and pedagogically useful relationship with his own voice.
Influence of preceding liquids on stop-consonant perception
Authors: Mann Virginia A.
Published: October 2005

When a syllable-final liquid precedes a syllable-initial stop, it may influence the perceived place of stop-consonant production. To demonstrate this phenomenon, the CV portions of natural tokens of /al da/, /al ga/, /at da/, and /at ga/ were excised and replaced with closely matched synthetic stimuli forming a /da/-/ga/ continuum. The resulting hybrid disyllables were then presented to listeners who labeled both liquids and stops. More “g” responses were given to stops which replaced /ga/ than to those which replaced /da/, indicating that the preceding VC portion (/al/ or /ar/) contained cues to the following stop consonant. In addition, many more “g” responses were given to stops which followed /al/ than to those which followed /ar/. Spectrograms of the original utterances suggest, in accordance with this perceptual finding, that stops following /l/ are produced with a relatively more forward place of articulation than those following /r/. More detailed acoustic measurements are now in progress. Here, it seems, is another instance where coarticulation accounts for a perceptual context effect. [Work supported by NICHD and BRS.]
Psychophysical tuning curves in forward masks
Authors: Small Arnold M. , Busse Catherine
Published: October 2005

Psychophysical tuning curves [A. Small, J. Acoust. Soc. Am. 31, 1619–1625 (1959)] were determined in a forward masking situation for a variety of signal frequencies, fs; signal levels, Ls; and recovery intervals, Δt. A 4ITFC stimulus paradigm was used in conjunction with an up—down transformed response adaptive procedure. For short ΔTs, typically shaped tuning curves were obtained with the tip positioned at fs, a gradual low frequency slope, and a steep high frequency slope. As Δt was increased the curves were displaced upward reflecting an increase in the level of the masker required to drive the signal to inaudibility, but more importantly the shape of the curves changed. The tip was progressively shifted to frequencies less than fs and the tuning was dramatically broadened. That is, at long Δts the “tip” was absent with the curves very shallow and centered at lower frequencies. Generally tuning was sharper at high values of fs and low values of Ls. These latter results are in accord with those of other investigators, but the broadening of tuning with increasing Δt is at odds with the only other report [M. Rodenburg, J. Verschure, and M. Brocaar, in Psychophysics and Physiology of Hearing, edited by E. Evans and J. Wilson (Academic, New York, 1977)]. The results are discussed in terms of the decay in masker excitation at the frequency region of the signal.
Acoustic transients from force excited planar vibrators with nonuniform velocity distributions
Authors: Stepanishen Peter R.
Published: October 2005

A general approach is presented to evaluate the acoustic transients which result from the forced excitation of planar vibrators. This approach is based on the use of a combined eigenfunction and Green's function technique. The time-dependent velocity of the vibrator is first expressed as an eigenfunction expansion in which the coefficients are related to the force excitation via simple convolution integral relationships. The acoustic pressure at any point in the field is then expressed as a sum of convolution integrals which involve the time dependent velocity coefficients with corresponding mode-dependent impulse responses that are space- and time-dependent. General characteristics of these impulse responses are discussed and related to earlier work on uniform velocity vibrators [P. Stepanishen, J. Acoust. Soc. Am. 49, 1628–1639 (1971)]. As a special case of interest, transient acoustic radiation from the class of circular vibrators, e.g., membranes and plates, is addressed. Series expansions are developed for the generalized impulse responses corresponding to the classical modes of vibration with various boundary conditions. Finally, numerical results are presented to illustrate the characteristics of the transient acoustic field which is generated by a force-excited plate.
Measurement of TTS using two psychophysical procedures
Authors: Plattsmier H. S. , McFadden Dennis
Published: October 2005

Large inter- and intra-subject variability is commonly reported in studies of temporary threshold shift (TTS). In an attempt to determine whether some of the intra-subject variability can be attributed to fluctuations in the subjects' criterion for response, an adaptive two-interval-forced choice (2IFC) procedure was used alternatively with a method of adjustment procedure to follow post-exposure recovery of sensitivity. To our knowledge, forced-choice procedures have not previously been used in TTS experiments. The exposure stimuli were 2500-Hz tones and TTS was monitored at the exposure and one-half octave frequencies. Each adaptive run consisted of 50 trials and took approximately 2 min to complete; each adjustment look approximately 20 s. The design allows comparison of the two methods both within and across the 12 exposure sessions. Advantages and disadvantages of the two procedures in post-exposure studies will be discussed. [Work supported by NINCDS.]
The relationship between noise and cardiovascular function in monkeys
Authors: Peterson Ernest A. , Haselton Carole L.
Published: October 2005

Recently, we reported that nine months' exposure to moderately high, but realistic, noise levels, produced sustained elevations in blood pressure of from 23% to 28% in Rhesus monkeys. The elevations were not reduced after the noise was turned off and they were not accompanied by changes in auditory sensitivity [E. A. Peterson et al., Science 211, 1450–1452 (1981)]. The present study is a replication and an expansion of the above experiment. Four monkeys (M. fascicularis) were studied concurrently. Two were used as controls, and two as experimentals. After three months of low noise conditions during which the average energy level was about 48 dB(A), the two experimental monkeys were exposed to a realistic noise sequence, 24-h per day, for about six months. Compared to the control animals who remained under low noise conditions throughout the experiment, the noise-exposed animals exhibited a substantial increase in blood pressure. Orderly changes were also noted in the diurnal rhythm of heart-rate, heart-rate distribution, cardiac arrhythmias and movement. These results generally substantiate our previous findings but they are not in keeping with the results from earlier epidemiologic studies.
The effects of frequency response smoothness and stimulustype on the loudness discomfort level
Authors: Randolph Kenneth J. , Bornstein Steven P. , Giolas Thomas , Maxon Antonia
Published: October 2005

The effects of frequency response smoothness and stimulus-type on the loudness discomfort level were examined. Two major questions were asked: (1) Does a smooth frequency response elicit a judgment of loudness discomfort at a higher sound pressure level than an irregular response? (2) Does a speech-spectrum shaped noise elicit a judgment of loudness discomfort at a higher sound pressure level than a multitalker bubble? The irregular response consisted of five peaks, one-third octave wide and 10 dB in amplitude. Both stimulus-types were processed through a master hearing aid with the electroacoustic parameters set to either the smooth frequency response or the irregular frequency response, and then presented to 20 normal hearing subjects listening in the sound field at zero degrees azimuth. The stimulus intensity was manipulated according to a simple updown adaptive procedure [H. Levitt, J. Acoust. Soc. Am. 49, 467–477 (1971)]. The smooth frequency response elicited loudness discomfort level judgments at significantly higher sound pressure levels. There was no significant difference in the measured loudness discomfort levels as a function of stimulus-type. The dependence of results on the calibration procedure for both frequency response and stimulus-type conditions will be discussed.
Recovery from induced loudness adaptation
Authors: Scharf Bertram , Botte Marie-Claire , Canévet Georges
Published: October 2005

An intermittent sound to one ear often causes a large decrease in the loudness of a steady sound to the other ear, a decrease that does not disappear upon termination of the intermittent sound. To study this phenomenon, we measured the loudness of a 1000-Hz tone to the right ear before, while, and after it was accompanied by an intermittent (500 ms on, 500 ms off) 1000-Hz tone to the left ear. Both tones were 60 dB SPL. Ten listeners assigned a number every 20 s to represent the loudness of the steady tone which lasted 5 min. During the 160 s that the intermittent tone was on, the loudness of the steady tone declined by 60% (equivalent to 13 dB). After cessation of the intermittent tone, loudness increased slowly over 100 s but only to about 35% of its preadaptation value. To return loudness to its full value, the steady tone had to be interrupted for at least 20 s after cessation of the intermittent tone. Apparently, an intermittent tone unleashes a long-lasting suppression of the loudness of a steady tone in the contralateral ear. [Work supported by NIH.]
Appropriate models for acoustic response of bilaminar plates
Authors: Unver E. , Kalnins A. , Gaunaurd G. C.
Published: October 2005

The objective is to determine the effect of a bilaminar plate to its surrounding acoustic medium, when the plate is subjected to an incident plane wave, coming from the medium. The medium can be on one or both sides of the plate. In the first case, it is bonded to a rigid foundation and only reflection of acoustic waves into the medium occurs. In the second case, both reflection and transmission can occur. The question is: what are the simplest plate models that can be used without sacrificing any of the important features of the process? This question applies not only to the prediction of the reflected and transmitted waves in the medium, but also to the motion of the plate itself, because, if the plate material is viscoelastic, then the dissipation through internal damping is very much dependent on the various strain amplitudes of the plate material. This is especially important if the stiffness of one of the lamina is small (soft plate) and that of the other is large (hard plate). It is concluded in this investigation that each of the two lamina must be able to model not only the bending and lowest antisymmetric thickness-shear modes, but also the lowest symmetric thickness-stretch and shear modes. An appropriate model is one that is a combination of Timoshenko-Mindlin and Mindlin-Medick models. With such a model for each of the lamina, the composite, bilaminar plate is constructed by matching tractions and displacements at the interface. This model can predict total reflection and total transmission and it accounts for the major motions of the Plates. A significant feature of this model is that the thickness-stretch mode has a dispersive wave speed which depends on the Poisson's ratio, ν. When ν is larger than 13, the frequency of this mode is higher than the frequency of the lowest symmetric thickness-shear mode, which is independent of ν. This characteristic plays an important role for a bilaminar plate which is composed of materials with Poisson's ratios on the opposite sides of ν = 13. Also, it is noted that for such bilaminar plates, the flexural modes of a hard plate (with ν < 13), and the extensional modes of a soft plate interact considerably at low frequencies, and the inclusion of the latter modes becomes crucial. Numerical results are presented to illustrate the interaction of the different plate modes, and the effects of the angle of incidence, plate thicknesses and the Poisson's ratios on the transmission and reflection characteristics of bilaminar plates in water.