Memory for the locations of environmental sounds

The accuracy with which a single source of sound can be localized has been examined in many studies, but very few studies have examined the ability of participants to determine the absolute locations of multiple sources of sound. The current study assessed participants' abilities to determine and remember the locations of up to six sources of environmental sound that were positioned at a range of azimuths and elevations in virtual auditory space. In experiment 1, a sequence of one to six sounds was presented one, three, or five times in each trial and the target sound was nominated following presentation of the last sequence. In experiment 2, memory load was held constant by nominating the target sound prior to a single sequence presentation. Localization accuracy was observed to decrease as the number of sounds was increased to three or more under the conditions of experiment 1, but not those of experiment 2. In experiment 1, localization was more accurate when sequences were presented more than once. Pronounced primacy and recency effects were observed for the six sound conditions in experiment 1. An analysis of errors for those conditions indicated that immediate temporal errors, but not immediate spatial errors, were over-represented.     

Individual differences in source identification from synthesized impact sounds

Impact sounds were synthesized according to standard textbook equations given for the motion of freely vibrating membranes, bars, and plates. In a two-interval, forced-choice procedure, highly practiced listeners identified from these sounds predefined target sources based on their material and size, the hardness of the striking mallet, and the presence or absence of light damping applied to the center of the source. Listener decision strategy in each case was determined from a discriminant analysis of trial-by-trial responses resulting in a vector of regression weights given to different acoustic parameters. The analysis revealed significant differences in decision strategy across listeners within identification task, but similarity in decision strategy within listeners across variations in task. Only when the acoustic information for identification was highly constrained (identification of damping) did listeners adopt similar decision strategies approaching that of an ideal observer. Despite the large individual differences in decision strategy, identification accuracy was, in most cases, similar across listeners. Where there were differences in identification accuracy the differences appeared largely related to differences in internal noise and not decision strategy. The results are generally comparable to those obtained for the discrimination of arbitrary tone patterns.     

Perceptual learning of spectrally degraded speech and environmental sounds

Adaptation to the acoustic world following cochlear implantation does not typically include formal training or extensive audiological rehabilitation. Can cochlear implant (CI) users benefit from formal training, and if so, what type of training is best? This study used a pre-/posttest design to evaluate the efficacy of training and generalization of perceptual learning in normal hearing subjects listening to CI simulations (eight-channel sinewave vocoder). Five groups of subjects were trained on words (simple/complex), sentences (meaningful/anomalous), or environmental sounds, and then were tested using an open-set identification task. Subjects were trained on only one set of materials but were tested on all stimuli. All groups showed significant improvement due to training, which successfully generalized to some, but not all stimulus materials. For easier tasks, all types of training generalized equally well. For more difficult tasks, training specificity was observed. Training on speech did not generalize to the recognition of environmental sounds; however, explicit training on environmental sounds successfully generalized to speech. These data demonstrate that the perceptual learning of degraded speech is highly context dependent and the type of training and the specific stimulus materials that a subject experiences during perceptual learning has a substantial impact on generalization to new materials.     

Spectral-temporal investigations of the backscattered radiation from laser plasma

Spectral and time-resolved investigations of the back-scattered light from aluminium laser-produced plasmas at frequencies ω_L and 2ω_L are performed. Good correlation between maxima of the scattered light at ω_L and minima at 2ω_L was discovered. This correlation has been predicted by the theory. These experiments show that the spectrum width and intensity of the second harmonic essentially depend on the velocity of the expanding plasma.     

Listeners' identification and discrimination of digitally manipulated sounds as prolongations

The present study had two main purposes. One was to examine if listeners perceive gradually increasing durations of a voiceless fricative categorically ("fluent" versus "stuttered") or continuously (gradient perception from fluent to stuttered). The second purpose was to investigate whether there are gender differences in how listeners perceive various duration of sounds as "prolongations." Forty-four listeners were instructed to rate the duration of the // in the word "shape" produced by a normally fluent speaker. The target word was embedded in the middle of an experimental phrase and the initial // sound was digitally manipulated to create a range of fluent to stuttered sounds. This was accomplished by creating 20 ms stepwise increments for sounds ranging from 120 to 500 ms in duration. Listeners were instructed to give a rating of 1 for a fluent word and a rating of 100 for a stuttered word. The results showed listeners perceived the range of sounds continuously. Also, there was a significant gender difference in that males rated fluent sounds higher than females but female listeners rated stuttered sounds higher than males. The implications of these results are discussed.     

Personal evaluation structure of environmental sounds: experiments of subjective evaluation using subjects’ own terms

In this study, we conducted an experiment to investigate the evaluation structure that lies at the basis of peoples’ psychological evaluation of environmental sounds. In the experiment, subjects were given cards on each of which a name of one of the environmental sounds in the specified context is written. Then they did the following three tasks: (1) to sort the cards into groups by the similarity of their impressions of the imagined sounds; (2) to name each group with the word that best represented their overall impression of the group; and (3) to evaluate all sounds on the cards using the words obtained in the previous task.These tasks were done twice: once assuming they heard the sounds at ease inside their homes and once while walking outside in a resort theme park. We analysed the similarity of imagined impression between the sounds with a cluster analysis and clusters of sounds were produced, namely, sounds labelled “natural,” “transportation,” and so on. A principal component analysis revealed the three major factors of the evaluation structure for both contexts and they were interpreted as preference, activity and sense of daily life.     

Spectral-temporal dynamics of ultrashort Raman solitons and their role in third-harmonic generation in photonic crystal fibers

We use cross-correlation frequency-resolved optical gating to obtain spectral-temporal portraits of ultrashort Raman solitons in photonic crystal fibers at telecommunication wavelengths. Power-dependent Raman frequency shifts of 200 nm in 63 mm of fiber are observed accompanied by spectral broadening and 2.5-times soliton compression. Complete time-frequency dynamics at the fundamental wavelength thus visualized enables us to explain the details of the intermodally phase-matched third harmonic generation by the propagating solitons.This revised version was published online in August 2005 with a corrected cover date.     

从物理看乐音的和谐--物理与音乐专题之一

"总想对你表白,我的心情是多么豪迈.……"(走进新时代) "五十六个民族,五十六枝花.……"(振兴中华) "五星红旗迎风飘扬,胜利歌声多么响亮!……"(歌唱祖国) "春天来了,大地在欢笑!……"(蓝色的多瑙河)     

Overlapping of sounds in piano passages

It is well known that, in piano passages, specifically, in those played legato, sounds may overlap in time. Our experiments show that this overlapping is much greater than one would expect proceeding from the undistorted pitch perception in a given phrase. Moreover, the sounds produced by piano and perceived by a listener as clearly distinguished in pitch, when subjected to an objective analysis, may prove to be a mixture of equally intense components of the preceding and next sounds. This phenomenon is related to the problem of piano quality, including the still unclarified role of the damper system, as well as to the mysterious manifestation of pianist’s personality that is called the art of touch.     

Classification and identification of recorded and synthesized impact sounds by practiced listeners, musicians, and nonmusicians

Three experiments were conducted to test the viability of a low-parameter modal model for synthesizing impact sounds to be used in commercial and psychoacoustic research. The model was constrained to have four physically based parameters dictating the amplitude, frequency, and decay of modes. The values of these parameters were selected by ear to roughly match the recordings of ten different resonant objects suspended by hand and struck with different mallets. In experiment 1, neither 35 professional musicians nor 187 college undergraduates could identify which of the two matched sounds was the real recording with better than chance accuracy, though significantly better than chance performance was obtained when modal parameters were selected without the previously imposed physical constraints. In experiment 2, the undergraduates identified the source corresponding to the recorded and synthesized sounds with the same level of accuracy and largely the same pattern of errors. Finally, experiment 3 showed highly practiced listeners to be largely insensitive to changes in the acoustic waveform resulting from an increase in the number of free parameters used in the modal model beyond 3. The results suggest that low-parameter, modal models might be exploited meaningfully in many commercial and research applications involving human perception of impact sounds.     

Temporal weights in the level discrimination of time-varying sounds

To determine how listeners weight different portions of the signal when integrating level information, they were presented with 1-s noise samples the levels of which randomly changed every 100 ms by repeatedly, and independently, drawing from a normal distribution. A given stimulus could be derived from one of two such distributions, a decibel apart, and listeners had to classify each sound as belonging to the "soft" or "loud" group. Subsequently, logistic regression analyses were used to determine to what extent each of the ten temporal segments contributed to the overall judgment. In Experiment 1, a nonoptimal weighting strategy was found that emphasized the beginning, and, to a lesser extent, the ending of the sounds. When listeners received trial-by-trial feedback, however, they approached equal weighting of all stimulus components. In Experiment 2, a spectral change was introduced in the middle of the stimulus sequence, changing from low-pass to high-pass noise, and vice versa. The temporal location of the stimulus change was strongly weighted, much as a new onset. These findings are not accounted for by current models of loudness or intensity discrimination, but are consistent with the idea that temporal weighting in loudness judgments is driven by salient events.     

Theory of heart sounds

A phenomenological theory of heart sounds is proposed. The left ventricular wall is modelled as an incompressible spherical shell and the heart valves as two-dimensional membranes. The solutions of the appropriate elasticity equations are matched with those of the hydrodynamical equations describing the propagation of the radiated sound through the soft body tissue. The predicted time plots and frequency spectra show significant resemblance with recorded ones, like equidistant peaks, directional dependence, relationship of sound amplitude and rate of pressure change inside the left ventricle, etc. Sets of parameters are singled out which influence the measured sound. The latter is the integral part of a diagnostic procedure.     

A model concerning the environmental factors that modify the nanocrystallization of current-annealed samples

A new mathematical model to explain the temperature distribution along the width of current-annealed samples is proposed. The model shows that the heat exchange conditions (radiation and free or forced convection) during annealing can dramatically change the crystallization of the sample. To demonstrate the theoretical results, three Vitroperm® samples were annealed and analyzed magnetically and crystallographically by means of transmission electron microscopy.