The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.Contrary to studies on speech learning of consonants and vowels, the issue of individual variability is less well understood in the learning of lexical tones. Whereas existing studies have focused on contour-tone learning (Mandarin) by listeners without experience of a tonal language, this study addressed a research gap by investigating the perceptual learning of level-tone contrasts (Cantonese) by learners with experience of a contour-tone system (Mandarin). Critically, we sought to answer the question of how Mandarin listeners' initial perception and learning of Cantonese level-tones are affected by their musical and pitch aptitude. Mandarin-speaking participants completed a pretest, training, and a posttest in the level-tone discrimination and identification (ID) tasks. They were assessed in musical aptitude and speech and nonspeech pitch thresholds before training. Hexa-D-arginine clinical trial The results revealed a significant training effect in the ID task but not in the discrimination task. Importantly, the regression analyses showed an advantage of higher musical and pitch aptitude in perceiving Cantonese level-tone categories. The results explained part of the level-tone learning variability in speakers of a contour-tone system. The finding implies that prior experience of a tonal language does not necessarily override the advantage of listeners' musical and pitch aptitude.While source localization and seabed classification are often approached separately, the convolutional neural networks (CNNs) in this paper simultaneously predict seabed type, source depth and speed, and the closest point of approach. Different CNN architectures are applied to mid-frequency tonal levels from a moving source recorded on a 16-channel vertical line array (VLA). After training each CNN on synthetic data, a statistical representation of predictions on test cases is presented. The performance of a single regression-based CNN is compared to a multitask CNN in which regression is used for the source parameters and classification for the seabed type. The impact of water sound speed profile and seabed variations on the predictions is evaluated using simulated test cases. Environmental mismatch between the training and testing data has a negative impact on source depth estimates, while the remaining labels are estimated tolerably well but with a bias towards shorter ranges. Similar results are found for data measured on two VLAs during Seabed Characterization Experiment 2017. This work shows the superiority of multitask learning and the potential for using a CNN to localize an acoustic source and detect the surficial seabed properties from mid-frequency sounds.The ability to discriminate frequency differences between pure tones declines as the duration of the interstimulus interval (ISI) increases. The conventional explanation for this finding is that pitch representations gradually decay from auditory short-term memory. Gradual decay means that internal noise increases with increasing ISI duration. Another possibility is that pitch representations experience "sudden death," disappearing without a trace from memory. Sudden death means that listeners guess (respond at random) more often when the ISIs are longer. Since internal noise and guessing probabilities influence the shape of psychometric functions in different ways, they can be estimated simultaneously. Eleven amateur musicians performed a two-interval, two-alternative forced-choice frequency-discrimination task. The frequencies of the first tones were roved, and frequency differences and ISI durations were manipulated across trials. Data were analyzed using Bayesian models that simultaneously estimated internal noise and guessing probabilities. On average across listeners, internal noise increased monotonically as a function of increasing ISI duration, suggesting that gradual decay occurred. The guessing rate decreased with an increasing ISI duration between 0.5 and 2 s but then increased with further increases in ISI duration, suggesting that sudden death occurred but perhaps only at longer ISIs. Results are problematic for decay-only models of discrimination and contrast with those from a study on visual short-term memory, which found that over similar durations, visual representations experienced little gradual decay yet substantial sudden death.Distortion of acoustic wave caused by nonlinear propagation transfers acoustic energy into higher harmonics of the transmitted signal. When operating several broadband echosounders with non-overlapping frequency bands to cover a wide frequency range, higher harmonics generated by one band may interfere with the fundamental band of others. This interference (i.e., crosstalk) can adversely affect the measured backscattered amplitude frequency response and in some circumstances, appears as spurious targets above and/or below the main target in pulse-compressed echograms. The nonlinear propagation of frequency-modulated acoustic waves in a directional beam was modeled and used to assess methods to reduce the deleterious effects of harmonic components in the signal, and was also compared to field experiments using the seabed echo and a metallic target sphere, with good agreement. Two methods are shown to materially reduce crosstalk (1) reduction in transmit power, which reduces crosstalk amplitude by a larger amount than the associated reduction in transmit power, and (2) selection of a proper Fourier window length in the processing stage. The effect of crosstalk was small ( less then 0.4 dB or 10%) for area backscattering measurements, but could be several dB for target strength measurements at different frequencies, depending on the transmit signals and processing parameters.Opto-acoustophoretic mobility has been demonstrated recently for fluorescent and colored particles acoustically levitated in a stationary ultrasonic field when illuminated with the appropriate optical wavelength [Dumy, Hoyos, and Aider, J. Acoust. Soc. Am. 146, 4557-4568 (2019); Zhou, Gao, Yang, Li, Shao, Zhang, Li, and Li, Adv. Sci. 5, 1800122 (2018)]. It is a repeatable phenomenon, needing both acoustic trapping and specific optic excitation to occur. However, the physical origin of the phenomenon is still debated. In this study, we provide more insights into the probable origin of this phenomenon by confronting numerical simulations with temperature controlled experiments. The phenomenon properties are well reproduced by our model, relying on a thermofluidic instability, hinting at the potential thermally induced fluid density gradient as a drag source for the observed ejection of particles. Thermostated experiments exhibit a surprising threshold above which the phenomenon is not observed anymore no matter how large the optic or acoustic energies used.