Echolocation is using lagging sounds as cues to localize the objects reflecting them. The precedence effect (PE) occurs when echoic signals are suppressed in favour of leading signals. In this study, the ability of nine listeners to overcome the PE when detecting and lateralizing echoic signals through headphones was measured and compared. Threshold estimates of the lead-lag ratio (dB) for lead-lag click-pairs at eight different inter-click intervals (ICIs) between 6-200ms were obtained. Further, two listeners trained each task at two ICIs (12 and 200ms) for seven days to investigate training, and transfer of training, effect between tasks. The results revealed that the PE is still present in lateralization tasks when ICI is at least 48ms. A threshold level difference between echo detection and lateralization was observed, indicating a possibility of different processing mechanisms between tasks. No training effects were found although longer training periods could provide more answers to what lies behind the ability to overcome the PE and echolocate efficiently in everyday life.

Despite the importance of auditory selective attention in everyday communication, the cortical mechanisms underlying the amazing ability of human brain to focus on a sound stimulus and suppress others are not well understood. Recent studies have led to the hypothesis that alpha band oscillation (8-14Hz) is a neural signature of multimodal spatial attention. Research in multiple sensory domains has shown that alpha synchronizes in the hemisphere contralateral to unattended stimuli and desynchronizes on the hemisphere contralateral to attended stimuli, suggesting it is a marker of an inhibition process for filtering out unattended stimuli. However, further research is needed to understand the possible functional role of these alpha oscillations as well as their correlation with other cortical activity. Moreover, it is not clear whether different forms of auditory attention employ different cortical mechanisms, mediated through different brain networks. This study aims to combine brain stimulation methods (transcranial Direct/Alternative Current Stimulation) with electrophysiological measurements of electroencephalography (EEG) to measure and interpret the underlying cortical activity during different forms of auditory selective attention. More specifically, there are four studies, each of which employs behavioral tasks to test specific hypotheses. First, we studied alpha oscillatory activity during auditory spatial attention. Second, we compared and contrast cortical activity during auditory spatial and non-spatial attention. Third, we used brain stimulation to see if we can show a causal relationship between alpha oscillation and selective auditory attention performance. Lastly, we applied the existing results on alpha power to use it as a quantitative biomarker to indicate the level of spatial attention network engagement. Our results contributed to the growing body of knowledge about how the brain employs auditory selective attention for effective communication. / 2021-06-04T00:00:00Z

No description available.

No description available.

Hospital noise has been an area of concern for medical professionals and researchers for the last century. Researchers have attempted to characterize the soundscape of hospital wards and have made some preliminary links between noise and human outcomes. In the past, most of the research has used traditional acoustic metrics. These traditional metrics, such as average sound level, are readily measured using sound level meters and have been the primary results reported in previous studies. However, it has been shown that these traditional metrics may be insufficient in fully characterizing the wards. The two studies presented here use traditional metrics and nontraditional metrics to define the soundscape of hospital wards. The uncovered links, between both sound level metrics and psychoacoustic metrics and patient physiological measurements, are discussed. Correlations and risk ratios demonstrate the presence and the strength of these relationships. These results demonstrate the relationships between hospital acoustics and patient physiological arousal. Additionally, the effects of adding absorption in a hospital ward are presented. Sound level, sound power, reverberation time and other acoustic metrics are directly affected. The speech intelligibility in these wards is evaluated in order to highlight the temporal nature of speech intelligibility. With both studies combined, both traditional and nontraditional acoustic measures are shown to have statistically significant relationships to both patient and staff outcomes.

Blind  people use echoes to detect  objects  and  to  find their  way, the  ability  being known as human echolocation.   Previous  research  have found some of the  favorable  conditions  for the  detection  of the object,  with  many  factors  yet  to  be analyzed  and  quantified.    Studies  have  also shown  that blind people are more efficient than  the  sighted  in echolocating,  with  the  performance  varying  among  the individuals.   This  motivated the  research  in human  echolocation  to move in a new direction  to get a fuller understanding for the high detection  of the blind.  The psychoacoustic  experiments solely cannot determine  how the superior echo detection  of the blind listeners should be attributed to perceptual or physiological causes.  Along with the perceptual results it is vital to know how the sounds are processed in the  auditory system.   Hearing  research  has led to the  development of several auditory  models by combining  the  physiological  and  psychological  results  with  signal  analysis  methods.    These  models try  to describe how the auditory system  processes the signals.  Hence, to analyze how the sounds are processed for the high detection  of the blind, auditory  models available  in the literature were used in this thesis.  The results  suggest  that repetition pitch  is useful at  shorter  distances  and is determined from the peaks in the temporal  profile of the autocorrelation function computed  on the neural activity pattern. Loudness attribute also plays a role in providing information  for the listeners to echolocate at shorter  distances.  At longer distances  timbre  aspects such as sharpness  information  might be used by the listeners  to detect  the objects.  It was also found that the repetition pitch,  loudness and sharpness attributes in turn  depend on the room acoustics  and type of the stimuli  used.  These results  show the fruitfulness  of combining  results  from different  disciplines  through  a mathematical framework  given by signal analysis.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaves 90-92. / by Eric Michael Hildebrant. / B.S.

Abstract not available

Psychological research on cross-modal auditory-visual perception has focused predominantly on the manipulation of sensory information by visual information. There are relatively few studies of the way auditory stimuli may affect other sensory information. The Sound-induced Illusory Flash is one illusory paradigm that involves the auditory system biasing visual information. However, little is known about this cross-modal illusion. More research is needed into the structure of the illusion that investigates the different conditions under which the Sound induced Illusory Flash manifests and is enhanced or reduced. The research conducted for this thesis investigates the effect of new auditory stimulus variables on the Sound-induced Illusory Flash. The variables to be discussed concern the formation of a contrast in the auditory stimuli, with the contrast creating a rhythm that emphasises the discontinuous nature of the auditory stimuli, and therefore emphasises the illusory percept. The auditory stimulus contrasts include pitch separation with the octave interval, using the frequencies of 261.5 and 523Hz; and spatial separation in the auditory stimuli, presenting the monophonic auditory stimuli binaurally so that individual tones alternate between the left and right channels. I furthered this concept of auditory stimuli separation biasing an illusory percept, by investigating pitch and spatial presentation and localisation of the visual stimuli presentation, when multiple dots were presented. I also conducted analyses to determine if factors other than the auditory stimuli biased the illusory percept. These included the use of non-illusory trials and determining if their inclusion biased the illusory trial percept; and the impact of physical factors such as handedness, eye dominance, corrected vision, and musical experience on the illusory percept. My ultimate aim is to develop the illusory effect as a basis for new intermedia techniques to create the perceptual synchronisation of sound with images. These would be perceived as visually spliced according to the rhythm of the music on the micro time scale. / Master of Arts (Honours)

In the past decade, the availability of digitally encoded, downloadable music has increased dramatically, pushed mainly by the release of the now famous MP3 compression format (Fraunhofer-Gesellschaft, 1994). Online sales of music in the US doubled in 2005, according to a recent news article (*), while the number of files exchanged on P2P platforms is much higher, but hard to estimate. The existing and coming informational flood in digital music prompts the need for sophisticated content-based information retrieval. Query-by-Humming is a prototypical technique aimed at locating pieces of music by melody; automatic annotation algorithms seek to enable finer search criteria, such as instruments, genre, or meter. Score transcription systems strive for an abstract, compressed form of a piece of music understandable by composers and musicians. Much research still has to be performed to achieve these goals. This thesis connects essential knowledge about music and human auditory perception with signal processing algorithms to solve the specific problem of pitch estimation. The designed algorithm obtains an estimate of the magnitude spectrum via STFT and models the harmonic structure of each pitch contained in the magnitude spectrum with Gaussian density mixtures, whose parameters are subsequently estimated via an Expectation-Maximization (EM) algorithm. Heuristics for EM initialization are formulated mathematically. The system is implemented in MATLAB, featuring a GUI that provides for visual (spectrogram) and numerical (console) verification of results. The algorithm is tested using an array of data ranging from single to triple superposed instrument recordings. Its advantages and limitations are discussed, and a brief outlook over potential future research is given. (*) "Online and Wireless Music Sales Tripled in 2005"; Associated Press; January 19, 2006