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Humpback whales can generate intricate bubbly regions, called bubble nets, via their blowholes. They appear to exploit these bubble nets for feeding via loud vocalizations. A fully-coupled phase-averaging approach is used to model the flow, bubble dynamics, and corresponding acoustics. A previously hypothesized waveguiding mechanism is assessed for varying acoustic frequencies and net void fractions. Reflections within the bubbly region result in observable waveguiding for only a small range of flow parameters. A configuration of multiple whales surrounding and vocalizing towards an annular bubble net is also analyzed. For a range of flow parameters the bubble net keeps its core region substantially quieter than the exterior. This approach appears more viable, though it relies upon the cooperation of multiple whales. A spiral bubble net configuration that circumvents this requirement is also investigated. The acoustic wave behaviors in the spiral interior vary qualitatively with the vocalization frequency and net void fraction. The competing effects of vocalization guiding and acoustic attenuation are quantified. Low void fraction cases allow low-frequency waves to partially escape the spiral region, with the remaining vocalizations still exciting the net interior. Higher void fraction nets appear preferable, guiding even low-frequency vocalizations while still maintaining a quiet net interior., 11 pages, 9 figures, submitted to J. Acoust. Soc. Am

Comodulation masking release (CMR) was investigated in normal-hearing and cochlear-impaired listeners. The narrow-band masker centered on the tonal signal was flanked by a series of other narrow noise bands, some of which had temporal envelopes that were the same as that of the on-signal band (comodulated bands) and some of which had different temporal envelopes (codeviant bands). Previous research using such stimuli with normal-hearing listeners indicated that CMR was often substantially reduced when two codeviant bands were present at spectral locations close to the signal frequency, but that CMR recovered to some extent when more codeviant bands were added. In the present study, cochlear-impaired listeners showed an abnormally large reduction in CMR when codeviant bands were present, and poorer recovery of CMR with increasing number of codeviant bands. Supplementary experiments suggested that the poor recovery of CMR with increasing number of codeviant bands may have been due to the small range (in dB) over which CMR could occur in cochlear-impaired listeners. It is possible that abnormal reduction in CMR with codeviant bands present was due to poor peripheral analysis in hearing-impaired listeners.

Echolocating big brown bats perceive target range from overall echo delay. Neuronal networks acting as delay‐lines retain the volley of spikes evoked by each broadcast for coincidence‐comparisons with volleys of spikes evoked by echoes. These circuits are similar to delay‐line/coincidence‐detectors proposed for determining periodicity pitch of unresolved frequency components. Bats use resolved frequency components to detect harmonic coherence as the criterion for deciding whether multiple‐harmonic sounds are true echoes. These circuits involve FM1‐FM2 facilitatory neurons in circuits similar to what has been proposed for spectral pattern matching based on detection of coincidences of spikes at harmonic frequencies, another route for extracting periodicity pitch. Additionally, bats perceive small range separations between target glints from the frequencies of spectral notches produced by interference between overlapping reflections at small time offsets. This psychophysical effect is similar to determining...

There is current interest in using Hartmann–Whistle type powered resonance tube actuators for aeroacoustic control. Previous experiments (Raman et al. (2000, 2001) AIAA 2000‐1930; Stanek et al. (2000) AIAA 2000‐1905) have shown that such actuators with no moving parts are very effective in the suppression of flow impingement and cavity noise. However, fixed geometry actuators can only produce effective actuation over a small range of frequencies. Our idea is to use a variable depth powered resonance tube actuator where the depth of the resonance tube and the distance between the supply jet and the resonance tube can be controlled actively during the experiment. The experimental setup consists of a 1/4′′ diameter jet facing the open end of the resonance tube that is closed at the other end. The tube depth is changed by a computer controlled piston fitted inside the tube. Microphone and pressure sensors located at various locations in the vicinity of actuation were used to measure the frequency and amplitude of the fluctuations produced by this device. Due to the high amplitudes of pressure within the resonance tube the linear eigenfrequencies do not predict the measured frequencies. [Work supported by AFOSR.]

Inverse scattering of fluid‐loaded, elastic, thin‐walled cylindrical shells is addressed by multiple‐aspect resonance analysis. A set of aspect‐dependent acoustic phenomena is selected from membrane wave and resonance scattering theories, which are expected to be backscattered by fluid‐filled or empty thin‐walled shells and to give rise to resonance phenomena in the ka range (1,50). The features selected are from spatial axial modes, and Lamb‐type, Scholte–Stoneley, and shear helical waves. The last three wave families are significant only over a small range of target aspects near broadside, with the width of this range depending on shell properties. Approximate equations are formulated relating resonance behavior in the aspect‐frequency domain, to target parameters such as shell outer radius, thickness, length, and material. The inverse methodology is validated on experimental data from a steel cylindrical shell with flat end‐caps, filled with air or water and suspended in the water column. The target wa...

Interaural cross‐correlation coefficient (IACC) and lateral efficiency (LF) as correlates with subjective ratings [see companion paper, L. Beranek, ‘‘Determination of categories of acoustical quality in concert halls’’ (this session)] were analyzed. To make IACC sensitive to quality ratings, a multi‐octave‐band average was developed, based on Blauert et al. [Acustica 59, 292] and on a subjectively derived set of equal ASW contours that showed the 0.5, 1.0, and 2.0 octave bands to be of equal importance. This IACC3 was divided into IACCE3 integrated over first 0.08 s after arrival of the direct sound, and IACCL,3 same, 0.08 to 1 s. Subjective judgments were also made to determine the effects of increased sound levels of symphonic music at frequencies above and below 355 Hz on apparent source width ASW. IACCE3 and GL both appear important for determining ASW. The measured quantity [1−IACCE3] alone was found to separate the 17 concert halls of this study for which IACC data were available into the same three category groups as those determined from the interviews. Lateral fraction (LF) was found to extend over a very small range and there were so many overlaps among halls when separation into three rating groups was attempted that LF was judged not to be suitable for rating acoustical quality.

Individual differences in reaction time (RT) to subjectively comfortable, loud, and soft tones were assessed for ten young adult subjects with longstanding, less‐than‐profound sensorineural hearing losses and ten normal hearing controls. To support estimation of the sensory, central, and motor components of RT, subjects were also tested using an equivalent protocol with bright and dim visual stimuli. Subjects with normal hearing listened to 500‐Hz tones at fixed intensities that pilot testing established as corresponding to comfortable, loud, and soft levels. Prior to RT testing, subjects with hearing losses individually adjusted tone intensity to ‘‘most comfortable,’’ ‘‘very loud but not painful,’’ and ‘‘very soft but definitely audible’’ levels. Results show larger modality‐dependent and level‐dependent individual differences in RT than have been previously noted in the literature, pointing up a need for individual subject baselines in cognitive experiments that use RT as a dependent variable. Results also indicate that the typically small range between threshold and pain in listeners with hearing losses is, with respect to RT, functionally equivalent to larger ranges in normal hearing listeners in some individuals but not in others. [Work supported by NIH‐NIDCD.]

In most previous experiments on the ability to identify sound intensity, the stimulus set has been chosen such that the range of intensities is many times larger than the value of the “just‐noticeable difference” in intensity that has been derived from the results of intensity discrimination experiments. In such cases, the resolution obtained in the identification experiment is much worse than would be expected merely on the basis of the pairwise discriminability of the stimuli. In this paper, we report the results of a study designed to explore the prediction [Durlach and Braida, J. Acoust. Soc. Amer. 46, 372–382 (1969)] that this discrepancy between identification and discrimination does not occur if the range of intensities employed in the identification experiment is sufficiently small. Generally speaking, the results of this study support the prediction.

One problem of the investigation of musical instruments concerns the statement of physical characteristics of the tone quality. By musical experts' collaboration, old Italian violins and modern ones have been classified according to their tonal quality and physically examined by obtaining their response curves. The best old Italian master violins show physical particularities of tone quality which modern violins do not generally have. They affect the sound‐color, transient phenomena, and “carrying power”—very important properties. Within a comparatively small range, conditioned by different musical taste, we can state an optimum response curve of violins. Curves of good and bad violas and violincellos have been taken, but are not sufficient for stating optimum curves. Furthermore, we must try to find fit measures of violin making, by means of which the optimal physical characteristics of tone quality can be attained. Methods must be found for building these optimum qualities into new violins. Such factors as shape, thickness of material, and varnish, seem quite important, while the bass bar, sound post, bridge, and strings are of less importance. Comparisons are given between a violin made on the basis of these researches and a Stradivarius instrument.

Electropalatographic and acoustical data on VCV coarticulation for the alveopalatals [ʎ], [ɲ] versus consonants of different place have been collected, mainly for one Catalan speaker. For alveopalatals, EPG data show almost no effect of vocalic context over time or on the point of palatal maximum constriction; consistently, corresponding acoustical measurements indicate small or no transconsonantal effects and a small range of variation for F2 frequency values at the closure period for different vocalic environments. On the other hand, palatographic and acoustical data on other consonants, e.g., alveolars, show large transconsonantal coarticulatory effects. These results allow for two different articulatory preprogramming strategies largely dependent on constraints imposed by the articulators, one appropriate to a highly invariant vocal tract configuration shaped by a tongue dorsum raising gesture towards the alveopalatal area and another one appropriate to a more variable configuration subject to coarticulation with the surrounding vocalic environment.

The effect of the number of stimulus‐response alternatives on the human observer's probability of making a correct response was predicted by three models: a simple threshold model; the constant‐ratio rule with simplifying assumptions; and the theory of signal detectability with simplifying assumptions. Four types of signal ensembles were used in these experiments: (a) speech signals; (b) a sinusoidal signal occurring in one of n intervals in time; (c) sinusoidal signals of varying amplitude; and (d) sinusoidal signals of varying frequency. In all of these experiments the listeners had complete knowledge of the set of stimuli under test and limited their responses accordingly. The simple threshold model failed to account for any of the data. The simplified version of the constant‐ratio rule and the simplified version of the theory of signal detectability were both compatible with the data obtained in the speech experiments. Also, over the small range tested, both handled data obtained when a sinusoidal signal occurred in one of n intervals. No model tested was sufficiently complex to account for data when the sinusoidal signals varied only in amplitude or only in frequency. (Work under sponsorship of Operational Applications Laboratory, Air Force Cambridge Research Center, and U. S. Army, Signal Corps Engineering Laboratories, Fort Monmouth.)

A viola with electronically synthesized normal body modes provides a flexible means for getting correlation between the subjective observations of tone quality and the known physical characteristics responsible for producing the tone. The Q and the amplitudes of all the normal modes are easily adjustable. It is desirable to have the frequency of a few of the modes variable over a small range. The viola used is somewhat similar to the violins described by Max Mathews and is a development from the instrument demonstrated in 1972. Both laboratory studies and the subjective results of extensive playing in chamber music groups will be described. The instrument will be demonstrated with settings to produce tone qualities typical of several different types of violas.