bluuebunny/crossref_metadata_2025 huggingface dataset:
Audiometric data base analysis (ADBA): Opening comments
Authors: Royster Larry H. , Royster Julia Doswell
Published: October 2005

The primary goal of audiometric data base analysis (ADBA) procedures is the determination of the effectiveness of an existing hearing conservation program in terms of the program's ability to prevent significant on-the-job noise induced hearing loss. To be able to achieve this goal in the real world, it is necessary that one or more reliable indicators be defined that can be implemented practically within the management and personnel framework of existing industrial hearing conservation programs. The paper present some history-related information regarding past efforts in developing ADBA procedures and the efforts of the S12.12 Working Group (Evaluation of Hearing Conservation Programs), and the objectives for this special session on ADBA procedures. Some considerations for the requirements of an ADBA procedure to be useful in indicating the level of effectiveness of a hearing conservation program will be reviewed, as well as factors that have been shown or are assumed to significantly influence audiometric data and thereby affect the outcome of applying different ADBA procedures.
The need for and benefits of audiometric data base analysis procedures
Authors: Suter Alice H.
Published: October 2005

Some noise-exposed employees are losing their hearing despite the implementation of hearing conservation programs (HCPs). Employers do not know how to evaluate HCP effectiveness, and audiograms arc often filed away after testing. Employers lack guidance from professionals. They also lack regulatory guidance, since OSHA's hearing conservation amendment has no provisions for evaluating HCP effectiveness. Compounding the confusion is OSHA's policy not to issue citations for average noise exposure levels between 90 and 100 dBA when “the results of audiometric testing indicate that any existing controls and hearing protectors are adequately protecting employees.” OSHA gives no guidance, however, as to the assessment of adequate protection. Audiometric data base analysis (ADBA) procedures can yield valuable information on HCP effectiveness. They encourage accountability by management, consultants, employees, and compliance officers. They provide feedback to supervisors, motivating them to promote and enforce good HCPs in their departments. They provide feedback to employees, which can change or reinforce their behavior, as appropriate, toward hearing protector use. ADBA procedures provide the means for identifying and the stimulus for improving poor HCPs, and they provide a source of satisfaction and potential reward for effective ones.
Predicting hearing loss for noise-exposed populations using ISO 1999
Authors: Johnson Daniel L.
Published: October 2005

The International Organization for Standardization (ISO) is publishing a standard, commonly called ISO 1999, entitled “Acoustics—Determination of occupational noise exposure and estimation of noise-induced hearing impairment.” The predictive procedures of this standard will be discussed. Three different nonoccupational noise-exposed data bases will be used to illustrate the relation between noise exposure, aging, and the screening procedures used in selecting the nonoccupational noise-exposed data base. The author will provide background for limiting the resulting hearing threshold level associated with both age and noise (H′) to less than the simple addition of age (H) and noise-induced permanent threshold shift (N) by the equation H′ = H + N - HN/120. Finally, a procedure for using ISO 1999 to predict the effects of changing noise exposures (such as workers exposed to 95 dB for 10 years, then 85 dB for 30 years) will be presented.
Predicting TT'S for a noise-exposed population
Authors: Ward W. Dixon
Published: October 2005

One source of test-retest variability in serial audiometry is the temporary threshold shift (TTS) caused by prior exposure to sound above 75 dB SPL. In industrial audiometry, TTS is always convolved with the effects of other sources of variability, such as earphone placement, headband tension, instrument calibration, internal physiological noise level, listener criterion, “learning,” etc., as well as with the “true” permanent change in hearing threshold level that is generally the only statistic of interest. However, enough is known about TTS that relatively valid prediction can be made of the mean and standard deviation of the TTS to be expected at test frequency A in an ear with a pre-exposure hearing threshold level of B dB, measured C minutes after exposure to a noise having spectral characteristics D, level E, duration F, and temporal pattern G. Two propositions will be examined: (1) that this knowledge can be utilized in order to “correct” group audiometric data for TTS, i.e., that TTS can be deconvoluted from the total variance, and (2) that adequacy of use of hearing protection devices can be assessed by means of TTS.
Third-order effects in the propagation of finite amplitude stress waves
Authors: Shu Kun-tien , Ginsberg Jerry H.
Published: October 2005

The propagation of a finite amplitude stress wave through a homogeneous, isotropic elastic solid is analyzed for cases of one-dimensional dilatation and shear deformation. The strain energy function is expanded in invariant form as a fourth-order polynomial in displacement gradients. The displacement equations of nonlinear dynamic elasticity are solved by perturbation techniques that yield a uniformly valid approximation. The result for a dilatational wave, which matches previous predictions, is essentially like a planar wave in a fluid, aside from redefinition of the coefficient of nonlinearity. The primary nonlinear effect for a dilatational wave is encountered at the second order. In contrast, the shear wave case, which was not fully analyzed in previous investigations, has no analog in inviscid fluids. The first-order shear displacement leads to a second-order dilatational displacement, which then influences the shear displacement at the third order. The overall effect of nonlinearity is to produce amplitude dispersion, as well as a small phase shift in the waveform. [Work supported by the NSF.]
Nonlinear effects in focused sound fields
Authors: Hart Timothy S. , Hamilton Mark F.
Published: October 2005

Focused finite amplitude sound fields are investigated with numerical solutions of the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation. The numerical solution is based on the algorithm developed by Aanonsen et al. [J. Acoust. Soc. Am. 75, 749–768 (1984)], who used a Fourier series expansion of the sound pressure to reduce the KZK equation to a set of coupled parabolic equations. The basic algorithm has been modified by introducing a coordinate system that follows the convergent geometry of focused sound fields. In this way, more efficient numerical evaluation of the detailed field structure within the focal region is achieved. Arbitrary axisymmetric sources can be modeled. Here, circular sources having linear focusing gains of order 50 will be considered. The calculated time waveforms, propagation curves, and beam patterns illustrate clearly the combined effects of nonlinearity, diffraction, and absorption on finite amplitude sound that passes through a focal region. Among the new results are power curves that show the exchange of energy between harmonies and beam patterns that show the location of nonlinearly generated sidelobes in the focal plane. [Work supported by ONR.]
Ultrasonic absorption in the critical mixture of methanol and cyclohexane
Authors: Fast Steven I. , Yun S. S. , Stumpf F. B.
Published: October 2005

The ultrasonic data for the critical mixture of methanol and cyclohexane are analyzed using the dynamic scaling theory. The experimental value of the slope of α/f2 at the critical temperature versus f−1.06 is compared to the theoretical value. The plot of α/f2 at the critical temperature versus f−1.06 yields a straight line as predicted by theory. The experimental values of α/αc for methanol and cyclohexane are compared to the scaling function F(ω*) and to the values of α/αc of 3He and Xe.
The dependence of binaural detection and interaural discrimination on interaural time and intensity in normal and impaired listeners
Authors: Koehnke J. , Colburn H. S.
Published: October 2005

Measurements of binaural performance by normal and hearing-impaired listeners are reported for large reference values of interaural time delay (ITD) and interaural intensity difference (IID). NoSπ detection thresholds and just-noticeable differences (jnds) in ITD and IID were measured with 1/3-oct noise bursts at 500 and 4000 Hz, using reference ITDs and IIDs up to 600 μs and 34 dB. As expected, jnds and thresholds for normal and impaired subjects increase as the reference IID increases. In contrast, increasing the reference ITD shows relatively small effects for most subjects. The present data are consistent with those described previously [C. Passaro, J. Koehnke, and H. S. Colburn, J. Acoust. Soc. Am. Suppl. 1 79, S21–S22 (1986)] but are more pronounced with larger reference ITDs and IIDs. For example, performance is generally poorer for the impaired listeners than the normal listeners. Also, for both groups, measurements of IID jnds consistently result in smaller jnds for the canceling combinations of reference ITD and IID than reinforcing combinations. [Work supported by NIH.]
A comparison of the effects of time and intensity during the auditory brain-stem response to lateralized clicks
Authors: Stephenson Mark , Melnick William
Published: October 2005

A group of 12 otologically normal subjects were presented with binaural clicks at 70 dB nHL. During one condition, subjects delayed the onset of the click to the left ear until a single image was percieved either midway between the center of the head and the right ear (referred to as the “midway” location), or until the image was perceived just at the right ear. In a second condition, subjects attenuated the click to the left ear until the acoustic image was lateralized either midway towards the right ear, or just at the right ear. These same stimuli conditions were then used to evoke auditory brain-stem responses (ABRs). When clicks were lateralized midway, ABR latencies from delayed versus attenuated clicks were not significantly different. However, when clicks were lateralized just at the right ear, there were statistically significant differences between latencies from delayed versus attenuated clicks. There was also a consistent ordinal relationship noted: In nearly every case, delayed clicks yielded longer latencies than attenuated clicks. The clear perceptual equivalence observed psychoacoustically was not fully reflected in the corresponding auditory brain-stem responses. [Work supported by AFOSR.]
Sound localization in the budgerigar and the interaural pathways
Authors: Park Thomas , Okanoya Kazuo , Dooling Robert
Published: October 2005

Sound localization presents a problem for animals with small heads (closely spaced ears) and poor high-frequency hearing. In recent tests of spatial resolving power, several small songbirds (i.e., great tit, canary, and zebra finch) show rather large minimum audible angles (MAA) on the order of 15–20 deg. These results are expected if conventional binaural time and intensity differences are used. Budgerigars (17-mm interaural distance), on the other hand, demonstrate an MAA of about 5 deg, which approaches the excellent ability of the barn owl with a much larger head (50-mm interaural distance). Recent work has suggested that interaural pathways connecting the two ears of birds could be involved in sound localization. Using latex injection medium, we have demonstrated interaural pathways in the budgerigar, canary, and zebra finch. Taken together, the results of these behavioral and anatomical studies indicate that the budgerigar may use the interaural pathway in sound localization.
Auditory word recognition is not more sensitive to word-initial than to word-final stimulus information
Authors: van der Vlugt M. J. , Nooteboom S. G.
Published: October 2005

Several accounts of the human recognition of spoken words assign special importance to stimulus-word onsets. The experiment described here was designed to find out whether such a word-beginning superiority effect is due to a special sensitivity of the word recognition process to word-initial stimulus information, or rather to the special importance of word onsets for the proper alignment of stimuli with word candidates. Twenty-eight polysyllabic monomorphematic test words were selected, all having the special characteristic that their left-to-right and right-to-left recognition points coincided in the same phoneme. These words were synthesized from diphones, and, of each word, four versions were prepared: (a) without noise; (b) with noise masking segment perception in the word-initial fragment; (c) with noise masking segment perception in the word-final fragment; and (d) with noise masking the whole word. These stimuli were, appropriately blocked, distributed over four stimulus tapes, and presented to four groups of 12 subjects for word recognition. Percentages correctly recognized real words were, for the four conditions: (a) 89%, (b) 54%, (c) 59%, and (d) 13%. The difference between (b) and (c) was not significant. This is interpreted as evidence that (1) auditory word recognition is not more sensitive to word-initial than to word-final stimulus information, and (2) stimulus information from all parts of a spoken word can be used efficiently, as long as its proper time alignment with word candidates in the mind of the listener is ensured.
Effects of talker uncertainty I: Auditory word recognition
Authors: Mullennix John W. , Pisoni David B. , Martin Christopher S.
Published: October 2005

The production and resulting acoustic composition of spoken words vary as functions of individual talker characteristics. However, the effects of talker differences on auditory word recognition processes have been largely ignored by researchers working in speech perception. In the present study, the effects of talker differences on perception of spoken words were examined by manipulating two factors: talker uncertainty (i.e., words produced from a single talker or from 15 talkers) and lexical structure (i.e., high- or low-density lexical items). In the first experiment, identification performance for words presented in noise was worse when the items were produced by different talkers, than by a single talker. In the second experiment, latencies and accuracy in a naming task were also worse under multiple-talker condition. In both experiments, lexical density alone did not have a significant effect on performance. The relationship of these results to the underlying processing operations involved in auditory word recognition will be discussed. [Work supported by NIH.]
Determination of the direction, time, and intensity of arrival of acoustic signals
Authors: Becker Farrel M.
Published: October 2005

There is currently much interest in lateral reflections in concert halls. Attempts to quantify lateral reflections have, up to now, been limited. Lateral energy ratios have been measured using a bidirectional microphone. This technique lacks the resolution necessary to investigate direction other than side to side versus front to back. A new technique, known as the polar energy time curve, will be presented. Utilizing special software for equipment already in common use, this technique extracts accurate directional information from four energy time curve (or impulse response) measurements made with an ordinary cardioid microphone. The direction of arrival versus time or intensity is displayed in polar form. The time, intensity, and exact angle of arrival may be determined in any plane of interest. Three-dimensional displays of energy arrival are also possible. Conventional lateral energy fractions, as well as other quantities, may be computed.
The effects of decorrelation on the discriminability of noise samples
Authors: Fallon Susan M. , Robinson Donald E.
Published: October 2005

In a previous study, it was demonstrated, using a same-different paradigm, that the discriminability of samples of reproducible noise is a function of the correlation between members of a pair of samples to be discriminated [S. M. Fallon and D. E. Robinson, J. Acoust. Soc. Am. Suppl. 1 78, S46 (1985)]. On “different” trials, the second sample of a pair was generated by repeating a temporal segment of the sample presented in the first interval, and combining it with a new segment of noise. The data from that experiment indicate that discriminability at “threshold” is independent of the total duration of the sample, but is highly dependent on the interpair correlation (proportion of common elements). Discriminability was also affected by the temporal position of the new segment of noise. In the work reported here, the correlation (proportion of common variance) between a pair of identical samples was varied by adding a new, independent sample of noise to the sample presented during the first observation interval. The duration and position of the added sample were also varied. The similarities and differences between the two methods used to decorrelate the pairs of samples will be discussed. [Work supported by AFOSR and NMRDC.]
Multiple observations and internal noise
Authors: Berg B. G. , Robinson D. E.
Published: October 2005

A multiple observation task was used to evaluate models of “internal noise.” On each trial, n tones (n = 1,2,3,4,6,8,10, or 12 within a block) were independently sampled from one of two probability density functions on frequency; each was normal in form with a standard deviation of 100 Hz. The two distributions had means of 1000 and 1100 Hz, respectively. The sample was presented through headphones as n, 50-ms tone bursts separated by 50 ms. The subjects' task was to decide from which of the two distributions the tones were sampled. A model partitioning internal variance into peripheral variance, added to each observation prior to formulating a decision statistic, and central variance, added to the decision statistic, provided a good description of the data of all four subjects. A subsequent study counterbalanced two levels of the difference between distribution means (Δμ = 100 or 150 Hz) with two levels of the standard deviation (σ = 100 or 150 Hz). Increasing Δμ did not affect estimates of internal variance. However, increasing σ resulted in increased estimates of internal variance for both levels of Δμ. One interpretation of this result is that external and internal variance are not independent. [Work supported by AFOSR and NMRDC.]
Temporal resolution in preschool children
Authors: Wightman F. L. , Dolan T. R. , Allen P. , Jamieson D.
Published: October 2005

An adaptive three-alternative forced-choice paradigm, in the form of a video game, was used to test auditory temporal processing skills in young children. Thirty children between the ages of three and seven were asked to detect a temporal gap in a burst of octave band noise, centered at 400 or 2000 Hz. The minimum detectable gap (gap threshold) was estimated by taking the median of the threshold estimates from at least three 20-trial adaptive runs. While the variability in the median threshold estimates was substantial, the data suggest that low-frequency gap thresholds were higher for the children than for adults, with the younger children producing higher thresholds. High-frequency gap thresholds were comparable to adult values for all children. All the individual adaptive runs were “adult-like,” suggesting that the subjects were concentrating on the task. However, run-to-run variability, as well as subject-to-subject variability, was high. It seemed that the children had “good days” and “bad days,” and that the younger children were more influenced by these variations than their older colleagues. [Work supported by NICHD Grant 5 P30 HD03352.]
Second formant transition discrimination
Authors: Besing Joan , Cullen John K. , Porter Robert J. , Rampp Randal , Collins M. Jane
Published: October 2005

The ability of listeners to process information conveyed by second formant transitions may be expected to be limited by their ability to detect differences in the rate of frequency change for the transition. To examine this question, difference limens (DLs) for initial transitions of isolated second formants were established using a four interval “same-different” procedure. These single formant signals were 300 ms in duration (60-ms transitions and 240-ms steady-state portions). The DLs for starting frequency, and thus rate of frequency change, were established for three standards which varied in rate and direction of transition; all had steady states at 1800 Hz. One standard had no transition and two had transitions of 2.5 Hz/ms that either fell from 1950 Hz or rose from 1650 Hz. The DLs were established for transitions with starting frequencies above and below each standard condition. The DLs for three of four experienced listeners were smaller for transitions in the frequency range above the steady state than for transitions in the frequency range below the steady state. Mean discriminable differences in starting frequency were 67 and 87.5 Hz in the frequency ranges above and below the steady state, respectively. [Supported by NINCDS and the Louisiana Lions Foundation.]
From acoustic tube to acoustic cues
Authors: Kuhn G. M.
Published: October 2005

The relation between sound propagation in the acoustic tube and formant-based acoustic cues for the phonetic dimension of place of articulation is illustrated. The model for sound propagation comes from Chiba and Kajiyama [The Vowel (Phonetic Society of Japan, Tokyo, 1941)]. The evidence for the acoustic cues comes from the experimental literature published after 1941. The following are emphasized: (1) constriction of tubes and changes in formant frequencies; (2) constriction of tubes and invariants in the changes in formant frequencies; and (3) complexities of the changes in formant frequencies and simplifying rules derived from perceptual tests. A tape of modeled speech sounds will be played.
Difference in second-formant transitions between aspirated and unaspirated stop consonants preceding [ɑ]
Authors: Lin Hwei-Bing , Repp Bruno H.
Published: October 2005

Perceptual experiments with synthetic speech have shown that the category boundary on an acoustic [pɑ-tɑ] continuum (obtained by varying the onset frequencies of the second and third formants) is closer to the labial endpoint than the boundary on a [pbɑ-tbɑ] continuum. Of several possible explanations, the most plausible seems to be that natural unaspirated and aspirated stops have different formant transitions. To supplement limited data in the literature, an acoustic analysis of CV syllables produced by ten male speakers of American English was conducted. The results show very clearly that the second formants of [pbɑ] and [tbɑ] start 100–200 Hz higher than those of [pɑ] and [tɑ], and reach comparable frequency values only at voicing onset. This difference, which is probably an acoustic consequence of subglottal coupling during aspiration, seems to be part of a listener's tacit knowledge of phonetic regularities and thus explains the perceptual boundary shift. It also needs to be taken into account in realistic speech synthesis. [Work supported by NICHD.]
Motor-motor adaptation
Authors: Shuster Linda I.
Published: October 2005

Perceptuomotor adaptation experiments have demonstrated that a purely perceptual task can have a significant effect upon a subsequent production task. Cooper has argued that these perceptual effects upon production reflect a link between the cognitive systems underlying perception and production. This argument might be stronger if it could be demonstrated that the effect that a repetitive perceptual task (such as selective adaptation) has on production is the same as that obtained using a repetitive production task. An experimental technique was developed called motor-motor adaptation. In this task, subjects produced a monosyllabic CV repeatedly (the adaptor}. After 20–40 repetitions, the subject produced a second CV syllable once (the test syllable). There were two adaptors ([bi] and [phi[) and two test syllables ([di] and [thi]). Each test syllable was produced in each adaptor condition. Subjects produced only a single adaptor and a single test syllable within each of the four blocked conditions. Analysis of the obtained voice onset times indicated that for the voiceless test syllable, VOT was significantly shorter after adaptation to [phi] than to [bi]. However, for the voiced test syllable, there was no significant difference obtained between the two adaptor conditions. These findings are similar to those Cooper obtained using perceptuomotor adaptation and will be discussed with regard to possible links between speech perception and speech production.
Release burst masking effects for temporal order identification
Authors: Pastore Richard E. , Layer Jody K. , Logan Robert J. , Morris Crystle B.
Published: October 2005

Nearly three decades ago, Hirsh [J. Acoust. Soc. Am. 31, 759–761 (1959)] found that the threshold for identification of temporal order of onset is significantly longer than the threshold for detection of onset asynchrony, and proposed that the order identification threshold might serve as a basis for the contrast between voiced and unvoiced aspirated stop consonants in initial position. In the last decade, a number of researchers have argued that temporal order identification threshold does not play a significant role in voicing contrast. One basis for this argument against a phonetic perception role is that the 15- to 20-ms range of typical order identification thresholds for simple stimuli are significantly shorter than VOT boundaries typical for synthetic stop consonants which include an initial release burst. The current research investigated the possible contribution of an initial noise burst analog as a masking stimulus. The initial noise burst shifts temporal order identification thresholds to significantly longer onset asynchronies which are equivalent in magnitude to VOT voicing contrast boundaries.
Effects of preceding context on perception of voice onset time
Authors: Repp Bruno H.
Published: October 2005

When discriminating pairs of stimuli from an acoustic voice-onset-time (VOT) continuum, English-speaking listeners typically show a performance peak in the region of the phonetic category boundary. An ongoing series of experiments demonstrates that the location and height of this peak are affected by preceding phonetic context. While any preceding context appears to lower discrimination performance, perhaps by interfering with auditory memory, a preceding [s] also shifts the peak towards the short-VOT end of the continuum and, correspondingly, increases “voiceless” responses in a labeling task. This latter effect (trivial within a syllable because of English spelling conventions) occurs even when a word boundary intervenes and does not seem to be mediated by the duration of the silent closure interval following the [s]. A hypothesis currently being pursued is that phonological voicing decisions for word-initial stop consonants are sensitive to the voicing status of preceding phonetic segments. [Work supported by NICHD.]
Instrument calibration: A legal perspective in the context of enforcement
Authors: Lopez Manuel R.
Published: October 2005

There is widespread use of noise dosimeters, sound level meters, and acoustical calibrators in statutory enforcement schemes. As a general rule, there are three prerequisites to be met in order for evidence obtained through the use of these instruments to be sufficient and admissible. First, in the performance of the intended function, the scientific reliability of the instrument must be established. This is often accomplished by showing that the instrument is permitted by law or acknowledged as reliable by the court. Second, it must be established that the instrument has been properly operated. This is done by showing that the operator is properly trained, followed applicable instructions, and is familiar with the instrument. Third, the accurate calibration of a particular instrument that is used in a given case must be shown; statutory calibration procedures, where they exist, must be strictly adhered to; acoustical calibrators where used to calibrate other instruments must also be calibrated; and, should the accuracy of the instrument to be calibrated contain a variance, enforcement allowances should be made.
Comparison of backscattered and forward scattered fields for objects immersed in a shallow water waveguide
Authors: Werby M. F. , Norton Guy
Published: October 2005

A noise source will form a guided wave in a suitable environment at sufficiently high frequencies. When the guided wave encounters a submerged object, the field scattered from the object will itself form a guided wave when suitably far from the object. The object scatters the field in a fairly complicated manner and depends on the relative direction of measurement from that of the incident field as well as the orientation of the object relative to the guided wave. A recent numerical development at NORDA enables calculations to be simulated for such physical situations. The objective of this study is to assess the relative importance of forward scattered to backscattered fields. Calculations are performed and compared for several frequencies for the two configurations and will be presented. Results indicate that, above a frequency limit, forward scatter is stronger, while, below that frequency, backscatter is favored.
Acoustic scattering in an ocean environment: III. Scattering in an inhomogeneous layered waveguide
Authors: Hackman Roger H. , Sammelmann Gary S.
Published: October 2005

Previously, the formal solution to the scattering from an elastic target in a waveguide with an arbitrary number of homogeneous layers was presented [R. H. Hackman and G. S. Sammelmann, J. Acoust. Soc. Am. Suppl. 1 78, S76 (1985)]. The solution is valid to all orders of multiple scattering among the target and waveguide boundaries. Here, this scattering formalism is extended to an inhomogeneous layered waveguide with an arbitrary number of layers. As a first application of this formalism, the long-range, low-frequency scattering from an elastic spherical shell in a range-independent waveguide with a sound-speed profile of the kind leading to caustic formation is considered. The focus of this study is the extent to which the elastic information in the scattered wave is modified by the propagation of both the incident and scattered signals through a convergence zone. [Work supported by the Office of Naval Research.]
Bragg imaging of high-intensity ultrasonic waves
Authors: Breazeale M. A. , Na Jeong Kwan , Leroy Oswald
Published: October 2005

Light incident on ultrasonic waves at the Bragg angle produces a diffraction pattern described by nλ = 2λ * sin θ8. Korpel [Optical Imaging of Ultrasonic Fields by Acoustic Bragg Diffraction (Rotterdam, 1962)] studied, in detail, the condition n = 1 and the image produced in the first diffraction order. Martin [J. Appl. Phys. 43, 1480 (1972)] observed Bragg diffraction with high-intensity ultrasonic waves and noted that for n>2 one observes multiple images in the diffraction orders. A somewhat successful modification of the mapping theory of Korpel was developed, although it had distinct limitations. The present discussion is focused on n>2 and the optical conditions leading to multiple images in the higher diffraction orders. The existence of two images is conveniently explained on the basis of the theory of Blomme and Leroy [Acustica 59, 1821 (1986)]. [Research supported by the U.S. Office of Naval Research and by the UT-ORNL Science Alliance.]
A computer-based noise measurement system
Authors: Luquet Patrick
Published: October 2005

This paper describes a computer-based measurement system that enables the operator to identify different noise sources and to measure their separate acoustical contribution to noise buildup. The principle is based upon the storage of 131 072 short-term Leq's (through a sound level meter with built-in memory) that are processed by personal computer. The method is illustrated by case studies ranging from urban noise surveys to industrial noise exposure monitoring, and includes environmental noise mapping. It is shown that both the method and the instrument have made it possible to reduce study costs while increasing the number and duration of sampling measurements, improving reliability factor of analyzed results, and allowing for the identification and quantification of multiple noise sources. The data-processing software presented in this paper provides the means to speed up report production while guaranteeing minimum-error data interpretation.
Effect of noise in ICU on heart rate and annoyance in adult postoperative patients
Authors: Baker Carol F.
Published: October 2005

The relationships of environmental noise in a surgical ICU, measured as sound pressure levels in dBA, to changes in heart rate and perceived annoyance were determined in 28 postoperative adult patients. Levels were recorded for a continuous 6-h period on calibrated graph paper. Heart rate was recorded simultaneously by converting ECG signals from the bedside monitor. Data were sampled every 12 s and a mean obtained within each noise episode. The graph patterns were classified into four types of noise: talking inside the room, talking outside, nontalking, and ambient. The means within each type were averaged. Annoyance to ICU noise, which included disturbance from sound, disturbance to activities and to sleep, was measured by a questionnaire. Intervening variables of noise sensitivity and hearing acuity were also determined for each subject. Results showed noise levels in patients' rooms ranged from 60–64 dBA. A high ambient level was created by the use of oxygen which masked outside sounds. Sixty-eight percent of subjects showed a significant (p = 0.10) increase in heart rate with an increase in decibel from a previous noise level. Mean heart rate was greatest during talking inside the room. Heart rate was second highest during nontalking noise. Heart rate during ambient conditions was highly variable within subjects. The majority of subjects reported little annoyance to ICU noise, except when it interfered with sleep. Noise sensitivity and mild hearing loss were not significant factors in annoyance to ICU noise.
Laboratory measurements of geo-acoustic properties of the New Jersey Shelf sediments
Authors: Badiey Mohsen , Yamamoto Tokuo , Turgut Altan
Published: October 2005

Laboratory measurements of selected geo-acoustic properties of sediment samples collected at the New Jersey Shelf are presented. A high precision torsional resonant column apparatus was used to determine both the shear modulus and the attenuation at different confining stress conditions. Porosity and permeability of these sediments were also measured. These measurements are compared to both the existing geological data in this region and the remote measurements of the shear modulus using the Bottom Shear Modulus Profiler (BSMP). Finally, the quality factor and the attenuation are calculated using measured properties as input to a numerical model for acoustic wave propagation in shallow water. [Work supported by ONR.]
Effects of message redundancy on the calculations of speech intelligibility
Authors: Pavlovic Chaslav V.
Published: October 2005

The articulation index methods used today assume that the distribution over frequency of the usable information content of speech does not depend on various sequential or contextual constraints existing in the message. This assumption has repeatedly been shown to be inaccurate, but the suggested alternative approaches reduce the generality of the theory. They require a separate frequency importance function for each degree of redundancy. In this study, the frequency importance function for the material of average everyday redundancy is derived. The function is flat on the Bark scale. This suggests that the speech code is optimally matched to the receiver (auditory system). The optimization refers to maximizing the reception rate of information.
History and development of hearing protection devices
Authors: Acton W. Ian
Published: October 2005

Military need has spurred the invention of hearing protector since the times of Greek mythology. Earplugs were patented in 1864 and canal caps attached to an adjustable headband in 1884 as protection for soldiers and sailors. Attempts to limit gunfire noise by mechanical devices commenced in 1905, leading to Mallock-Armstrong plugs for use in the First World War. Disposable earplugs were patented in 1914 also. Systematic development of earplugs for forces during the Second World War culminated in the V-51R. Leather flaps over the ears were supposed to protect the crews of military aircraft. The increased noise of jet engines led to the production of recognizable earmuffs, although the stiffness of the cushions required a strong headband to ensure a seal against the head. This caused a vicelike grip. The problem was overcome with the development of fluid-filled cushions by Shaw in 1954. Progress has continued towards comfort and acceptability, with glass-down appearing in the late 1950's, conformable foam plugs in the 1970's, and nonlinear electronic systems incorporated into muffs in the 1980's.
Exact reconstruction of ocean bottom velocity profiles from monochromatic scattering data
Authors: Merab Andre A. , Frisk George V.
Published: October 2005

A technique for exactly reconstructing ocean bottom velocity profiles from monochromatic scattering data is presented. The method involves an adaptation of the Gelfand-Levitan inversion procedure, originally developed in the context of quantum mechanical potential scattering, to the problem of determining the acoustic properties of the bottom. In this approach, if the bottom plane-wave reflection coefficient at a fixed frequency is known for all angles of incidence, then the sound velocity versus depth can be uniquely recovered. If the reflection coefficient at all angles is known at two frequencies, then both the density and velocity profiles can be uniquely reconstructed. The inversion scheme consists of Fourier transforming the reflection coefficient and solving the Gelfand-Levitan integral equation. This procedure is implemented numerically and applied successfully to synthetic data for several typical profiles. The stability of the method in the presence of noise is also demonstrated. [Work supported by ONR.]
Determination of modal attenuation coefficients and the attenuation profile of the bottom in shallow water
Authors: Rajah Subramaniam D. , Lynch James F. , Frisk George V.
Published: October 2005

Techniques for determining modal attenuation coefficients and the compressional wave attenuation profile of the bottom in shallow water are presented. The required input data consist of measurements of the pressure field versus range due to a monochromatic point source. Several methods are described for obtaining modal attenuation coefficients from the pressure field or its Hankel transform (the depth-dependent Green's function versus horizontal wavenumber). These modal attenuation coefficients can be related to the bottom attenuation profile through an integral equation that can be solved using linear inverse theory. The method is demonstrated using synthetic noise-free and noisy data. The results of inverting experimental data from Nantucket Sound at 140 and 220 Hz are also described. Resolution and variance estimates for the bottom attenuation profile are presented. [Work supported by ONR.]
Psychometric functions for multicomponent maskers with spectral uncertainty
Authors: Neff Donna L. , Callaghan Brian P.
Published: October 2005

Previous experiments used a two-alternative, forced-choice, adaptive procedure to measure thresholds for a 1000-Hz signal in the presence of maskers composed of multiple sinusoids. These sinusoids were drawn at random from a 300- to 3000-Hz range, excluding the signal frequency and frequencies within a critical band around the signal. This experiment examined psychometric functions for 50 of the original 200 maskers with 10 components, using signal levels from 10–80 dB SPL. The psychometric functions were well fitted in d′ by signal level coordinates, but individual functions typically spanned a 30- to 40-dB range. Corresponding adaptive thresholds did not differ from thresholds based on 200 maskers and were in agreement with the average of the predicted thresholds across the 50 maskers. Although individual maskers could differ in effectiveness by 10–15 dB, the majority produced similar masking. Overall, the adaptive procedure adequately characterizes performance in these conditions. [Work supported by NIH.]
Spectral shaping options for persons with low- or high-frequency sensorineural hearing loss
Authors: Schum Donald J. , Collins M. Jane
Published: October 2005

When hearing loss is limited to one particular frequency region, amplification is traditionally provided in the region of the poorest audiometric thresholds. To the extent that audiometric data correlate with auditory system damage, the usefulness of information provided to these regions of greatest damage is questionable. Optionally, gain may be provided to frequency regions where thresholds are improving towards normal. To that end, continuous discourse intelligibility ratings and consonant discrimination scores were obtained from individuals with either low-frequency or precipitously sloping high-frequency sensorineural hearing loss. During testing, spectral emphasis was variously placed in regions of hearing impairment and/or improving thresholds. For the low-frequency impaired subjects, consistently inferior subjective ratings and discrimination scores were obtained when spectral emphasis was placed solely in the region of hearing loss. For the high-frequency impaired subjects, no single spectral weighting scheme emerged as superior or inferior. The current results are consistent with previous findings which have suggested that pure-tone thresholds may underestimate the degree of apical region damage in low-frequency sensorineural hearing loss. [Work supported by DRF.]
Auditory/phonetic categories in a patient using a multichannel cochlear implant
Authors: Dorman M. F. , McCandless Geary
Published: October 2005

Identification functions in response to stimuli from several acoustic continua from a patient using a Symbion multichannel cochlear implant have been obtained. Auditory/phonetic categories of normal configuration were obtained for stimuli which varied in event duration (“slit”-“split” and “chop”-“shop”), in steady-state frequency composition (/I/-/E/ and /s/-/∫/, and in event duration and low-frequency composition (/ga/-/ka/). For the /ga/-/ka/ contrast, F1 onset frequency and VOT “trade” to determine categorization. Abnormal categories were obtained for stimuli which varied in F2/F3 onset frequency (/ba/-/da/) and for stimuli which varied in signal amplitude (/s/-/θ/). These data indicate that, in at least some instances, the implant can provide auditory information with sufficient resolution to afford normal phonetic categorization.
Performance on SPIN as a function of subject age
Authors: Matthies Melanie L. , Bilger Robert C.
Published: October 2005

The effect of aging on word-recognition ability typically has been confounded with the effect of hearing loss in studies involving the analysis of age-group means. A correlational approach allows for an efficient analysis of the increasing heterogeneity with age in word-recognition performance and the effects of hearing impairment. Correlational analyses of performance on SPIN and subject age are described for four experiments. The data sets include subjects from the SPIN standardization study (19–69 years), a hearing-aid fitting experiment (29–74 years), a study of older listeners (60–81 years), and subjects from a study of word recognition in noise (18–70 years). All subjects were tested at a single presentation level calculation + 50 dB re: babble threshold but at a variety of signal-to-babble ratios (+ 8 to −2 dB S/B). Correlations between SPIN scores and age were only occasionally significantly different from zero and were found to increase slightly with the signal-to-babble ratio used and to decrease with the severity of hearing impairment. [Work supported by NINCDS.]
Effects of contextual prosodic patterns on the auditory comprehension of normally stressed targets
Authors: Kimelman Mikael D. Z. , McNeil Malcolm R.
Published: October 2005

Reports indicate that neurologically normal subjects produce faster reaction times to phoneme targets when the context preceding the targets is produced with a stressed versus normally stressed prosodic pattern. The effects of contextual prosodic patterns on the auditory comprehension of normally stressed targets by aphasic listeners were investigated. Target words were computer edited out of paragraph-length stimuli that had been produced with emphatic stress and with normal stress. The target words were then replaced with normally stressed cognates. Analysis revealed that aphasic auditory comprehension was better when the context surrounding the target words had been produced with an emphatically stressed rather than a normally stressed prosodic pattern. Acoustic analyses of the emphatically stressed and normally stressed stimuli revealed differences in duration but not peak fundamental frequency of words preceding target words. [Work supported by NICHD Core Grant ♯ 5 P30 HD03352 to Waisman Center, University of Wisconsin–Madison.]
Anticipatory coarticulation in aphasia: Acoustic and perceptual evidence
Authors: Katz William F.
Published: October 2005

Acoustic analyses of anticipatory coarticulation were conducted for the initial consonants of CV [si su ti tu ki ku] and CCV [sti stu ski sku] productions by six normal and ten aphasic (five anterior, five posterior) subjects. For normal subjects' productions, reliable coarticulatory shift was found for almost all measurements, indicating that acoustic correlates for anticipatory coarticulation obtain for [s], [t], and [k] in a prevocalic environment as well as when [s] is the initial consonant of a CCV syllable. The data for the aphasic subjects were statistically indistinguishable from those of the normal group, with no differences noted as a function of aphasia type. In the perceptual experiment, a subset of the consonantal stimuli produced by the normal and aphasic subjects was presented to a group of ten naive listeners for a vowel identification task. Listeners were able to identify the productions of all subjects at a level well above chance. In addition, small but statistically significant group differences were observed, with the [sV], [skV], and [tV] productions by anterior aphasics showing significantly lower perceptual scores than those of normal subjects. The results suggest a model of speech programming in which coarticulatory processes are largely preserved in aphasia. [Work supported in part by grant NS-22282 to Brown University Department of Linguistics.]