Academic literature on the topic 'Precedence effect; Sound location'
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Journal articles on the topic "Precedence effect; Sound location"
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Tollin, Daniel J., and Tom C. T. Yin. "Psychophysical Investigation of an Auditory Spatial Illusion in Cats: The Precedence Effect." Journal of Neurophysiology 90, no. 4 (October 2003): 2149–62. http://dx.doi.org/10.1152/jn.00381.2003.
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The precedence effect (PE) describes several spatial perceptual phenomena that occur when similar sounds are presented from two different locations and separated by a delay. The mechanisms that produce the effect are thought to be responsible for the ability to localize sounds in reverberant environments. Although the physiological bases for the PE have been studied, little is known about how these sounds are localized by species other than humans. Here we used the search coil technique to measure the eye positions of cats trained to saccade to the apparent locations of sounds. To study the PE, brief broadband stimuli were presented from two locations, with a delay between their onsets; the delayed sound meant to simulate a single reflection. Although the cats accurately localized single sources, the apparent locations of the paired sources depended on the delay. First, the cats exhibited summing localization, the perception of a “phantom” sound located between the sources, for delays < ±400 μs for sources positioned in azimuth along the horizontal plane, but not for sources positioned in elevation along the sagittal plane. Second, consistent with localization dominance, for delays from 400 μs to about 10 ms, the cats oriented toward the leading source location only, with little influence of the lagging source, both for horizontally and vertically placed sources. Finally, the echo threshold was reached for delays >10 ms, where the cats first began to orient to the lagging source on some trials. These data reveal that cats experience the PE phenomena similarly to humans.
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Tollin, Daniel J., Luis C. Populin, and Tom C. T. Yin. "Neural Correlates of the Precedence Effect in the Inferior Colliculus of Behaving Cats." Journal of Neurophysiology 92, no. 6 (December 2004): 3286–97. http://dx.doi.org/10.1152/jn.00606.2004.
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Several auditory spatial illusions, collectively called the precedence effect (PE), occur when transient sounds are presented from two different spatial locations but separated in time by an interstimulus delay (ISD). For ISDs in the range of localization dominance (<10 ms), a single fused sound is typically located near the leading source location only, as if the location of the lagging source were suppressed. For longer ISDs, both the leading and lagging sources can be heard and localized, and the shortest ISD where this occurs is called the echo threshold. Previous physiological studies of the extracellular responses of single neurons in the inferior colliculus (IC) of anesthetized cats and unanesthetized rabbits with sounds known to elicit the PE have shown correlates of these phenomena though there were differences in the physiologically measured echo thresholds. Here we recorded in the IC of awake, behaving cats using stimuli that we have shown to evoke behavioral responses that are consistent with the precedence effect. For small ISDs, responses to the lag were reduced or eliminated consistent with psychophysical data showing that sound localization is based on the leading source. At longer ISDs, the responses to the lagging source recovered at ISDs comparable to psychophysically measured echo thresholds. Thus it appears that anesthesia, and not species differences, accounts for the discrepancies in the earlier studies.
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Gai, Yan, Janet L. Ruhland, and Tom C. T. Yin. "Behavior and modeling of two-dimensional precedence effect in head-unrestrained cats." Journal of Neurophysiology 114, no. 2 (August 2015): 1272–85. http://dx.doi.org/10.1152/jn.00214.2015.
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The precedence effect (PE) is an auditory illusion that occurs when listeners localize nearly coincident and similar sounds from different spatial locations, such as a direct sound and its echo. It has mostly been studied in humans and animals with immobile heads in the horizontal plane; speaker pairs were often symmetrically located in the frontal hemifield. The present study examined the PE in head-unrestrained cats for a variety of paired-sound conditions along the horizontal, vertical, and diagonal axes. Cats were trained with operant conditioning to direct their gaze to the perceived sound location. Stereotypical PE-like behaviors were observed for speaker pairs placed in azimuth or diagonally in the frontal hemifield as the interstimulus delay was varied. For speaker pairs in the median sagittal plane, no clear PE-like behavior occurred. Interestingly, when speakers were placed diagonally in front of the cat, certain PE-like behavior emerged along the vertical dimension. However, PE-like behavior was not observed when both speakers were located in the left hemifield. A Hodgkin-Huxley model was used to simulate responses of neurons in the medial superior olive (MSO) to sound pairs in azimuth. The novel simulation incorporated a low-threshold potassium current and frequency mismatches to generate internal delays. The model exhibited distinct PE-like behavior, such as summing localization and localization dominance. The simulation indicated that certain encoding of the PE could have occurred before information reaches the inferior colliculus, and MSO neurons with binaural inputs having mismatched characteristic frequencies may play an important role.
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Spitzer, Matthew W., Avinash D. S. Bala, and Terry T. Takahashi. "A Neuronal Correlate of the Precedence Effect Is Associated With Spatial Selectivity in the Barn Owl's Auditory Midbrain." Journal of Neurophysiology 92, no. 4 (October 2004): 2051–70. http://dx.doi.org/10.1152/jn.01235.2003.
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Sound localization in echoic conditions depends on a precedence effect (PE), in which the first arriving sound dominates the perceived location of later reflections. Previous studies have demonstrated neurophysiological correlates of the PE in several species, but the underlying mechanisms remain unknown. The present study documents responses of space-specific neurons in the barn owl's inferior colliculus (IC) to stimuli simulating direct sounds and reflections that overlap in time at the listener's ears. Responses to 100-ms noises with lead-lag delays from 1 to 100 ms were recorded from neurons in the space-mapped subdivisions of IC in anesthetized owls (N2O/isofluorane). Responses to a target located at a unit's best location were usually suppressed by a masker located outside the excitatory portion of the spatial receptive field. The least spatially selective units exhibited temporally symmetric effects, in that the amount of suppression was the same whether the masker led or lagged. Such effects mirror the alteration of localization cues caused by acoustic superposition of leading and lagging sounds. In more spatially selective units, the suppression was often temporally asymmetric, being more pronounced when the masker led. The masker often evoked small changes in spatial tuning that were not related to the magnitude of suppressive effects. The association of temporally asymmetric suppression with spatial selectivity suggests that this property emerges within IC, and not at earlier stages of auditory processing. Asymmetric suppression reduces the ability of highly spatially selective neurons to encode the location of lagging sounds, providing a possible basis for the PE.
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Litovsky, Ruth Y., Brad Rakerd, Tom C. T. Yin, and William M. Hartmann. "Psychophysical and Physiological Evidence for a Precedence Effect in the Median Sagittal Plane." Journal of Neurophysiology 77, no. 4 (April 1, 1997): 2223–26. http://dx.doi.org/10.1152/jn.1997.77.4.2223.
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Litovsky, Ruth Y., Brad Rakerd, Tom C. T. Yin, and William M. Hartmann. Psychophysical and physiological evidence for a precedence effect in the median sagittal plane. J. Neurophysiol. 77: 2223–2226, 1997. A listener in a room is exposed to multiple versions of any acoustical event, coming from many different directions in space. The precedence effect is thought to discount the reflected sounds in the computation of location, so that a listener perceives the source near its true location. According to most auditory theories, the precedence effect is mediated by binaural differences. This report presents evidence that the precedence effect operates in the median sagittal plane, where binaural differences are virtually absent and where spectral cues provide information regarding the location of sounds. Parallel studies were conducted in psychophysics by measuring human listeners' performance, and in neurophysiology by measuring responses of single neurons in the inferior colliculus of cats. In both experiments the precedence effect was found to operate similarly in the azimuthal and sagittal planes. It is concluded that precedence is mediated by binaurally based and spectrally based localization cues in the azimuthal and sagittal planes, respectively. Thus,models that attribute the precedence effect entirely to processes that involve binaural differences are no longer viable.
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Mickey, Brian J., and John C. Middlebrooks. "Sensitivity of Auditory Cortical Neurons to the Locations of Leading and Lagging Sounds." Journal of Neurophysiology 94, no. 2 (August 2005): 979–89. http://dx.doi.org/10.1152/jn.00580.2004.
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We recorded unit activity in the auditory cortex (fields A1, A2, and PAF) of anesthetized cats while presenting paired clicks with variable locations and interstimulus delays (ISDs). In human listeners, such sounds elicit the precedence effect, in which localization of the lagging sound is impaired at ISDs ≲10 ms. In the present study, neurons typically responded to the leading stimulus with a brief burst of spikes, followed by suppression lasting 100–200 ms. At an ISD of 20 ms, at which listeners report a distinct lagging sound, only 12% of units showed discrete lagging responses. Long-lasting suppression was found in all sampled cortical fields, for all leading and lagging locations, and at all sound levels. Recordings from awake cats confirmed this long-lasting suppression in the absence of anesthesia, although recovery from suppression was faster in the awake state. Despite the lack of discrete lagging responses at delays of 1–20 ms, the spike patterns of 40% of units varied systematically with ISD, suggesting that many neurons represent lagging sounds implicitly in their temporal firing patterns rather than explicitly in discrete responses. We estimated the amount of location-related information transmitted by spike patterns at delays of 1–16 ms under conditions in which we varied only the leading location or only the lagging location. Consistent with human psychophysical results, transmission of information about the leading location was high at all ISDs. Unlike listeners, however, transmission of information about the lagging location remained low, even at ISDs of 12–16 ms.
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Moore, Christopher A., Jerry L. Cranford, and Angela E. Rahn. "Tracking of a “Moving” Fused Auditory Image Under Conditions that Elicit the Precedence Effect." Journal of Speech, Language, and Hearing Research 33, no. 1 (March 1990): 141–48. http://dx.doi.org/10.1044/jshr.3301.141.
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Pursuit auditory tracking of a fused auditory image (FAI), based on stimulus conditions known to elicit the precedence effect phenomenon in sound localization, was investigated in 36 normal subjects and in a small group of subjects with known neuropathology. Movement of the FAI was simulated by incrementally varying the delay between two clicks presented, one each, from two loudspeakers placed on opposite sides of the listener. The group of normal listeners tracked the movement of the FAI without difficulty and with great accuracy; the perceived location of the FAI varied linearly with the interspeaker delay. The sensitivity of the task in detecting neural timing or integration deficits was investigated in 5 subjects with neuropathology, including subjects with unilateral temporal lobe lesions, multiple sclerosis, or dyslexia. These disorders, previously shown to disrupt neural timing, yielded characteristic patterns of tracking inaccuracy for this task. These subjects had no difficulty localizing either a moving unitary click source or sounds in daily life. These data support the suggestion that sound localization using stimulus conditions known to elicit the precedence effect places greater demands on neural timing and integration than conventional tests of localization, and may provide a more sensitive index of neural function.
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Cranford, Jerry L., Marci A. Andres, Kristi K. Piatz, and Kay L. Reissig. "Influences of Age and Hearing Loss on the Precedence Effect in Sound Localization." Journal of Speech, Language, and Hearing Research 36, no. 2 (April 1993): 437–41. http://dx.doi.org/10.1044/jshr.3602.437.
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Cranford, Boose, & Moore (1990a) reported that many elderly persons exhibit problems in perceiving the apparent location of fused auditory images in a sound localization task involving the Precedence Effect (PE). In the earlier study, differences in peripheral hearing sensitivity between young and elderly subjects were not controlled. In the present study, four groups of young and elderly subjects, matched with respect to age and the presence or absence of sensorineural hearing loss, were examined to determine the effects of these two factors on performance with the PE task. Although significantly poorer performances on the PE task were found to be associated with both increased age and hearing loss, additional tentative evidence was obtained that the presence of hearing loss may have a relatively greater detrimental effect on the performance of at least some elderly subjects than it does on younger persons.
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Brown, Andrew D., Heath G. Jones, Alan Kan, Tanvi Thakkar, G. Christopher Stecker, Matthew J. Goupell, and Ruth Y. Litovsky. "Evidence for a neural source of the precedence effect in sound localization." Journal of Neurophysiology 114, no. 5 (November 1, 2015): 2991–3001. http://dx.doi.org/10.1152/jn.00243.2015.
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Normal-hearing human listeners and a variety of studied animal species localize sound sources accurately in reverberant environments by responding to the directional cues carried by the first-arriving sound rather than spurious cues carried by later-arriving reflections, which are not perceived discretely. This phenomenon is known as the precedence effect (PE) in sound localization. Despite decades of study, the biological basis of the PE remains unclear. Though the PE was once widely attributed to central processes such as synaptic inhibition in the auditory midbrain, a more recent hypothesis holds that the PE may arise essentially as a by-product of normal cochlear function. Here we evaluated the PE in a unique human patient population with demonstrated sensitivity to binaural information but without functional cochleae. Users of bilateral cochlear implants (CIs) were tested in a psychophysical task that assessed the number and location(s) of auditory images perceived for simulated source-echo (lead-lag) stimuli. A parallel experiment was conducted in a group of normal-hearing (NH) listeners. Key findings were as follows: 1) Subjects in both groups exhibited lead-lag fusion. 2) Fusion was marginally weaker in CI users than in NH listeners but could be augmented by systematically attenuating the amplitude of the lag stimulus to coarsely simulate adaptation observed in acoustically stimulated auditory nerve fibers. 3) Dominance of the lead in localization varied substantially among both NH and CI subjects but was evident in both groups. Taken together, data suggest that aspects of the PE can be elicited in CI users, who lack functional cochleae, thus suggesting that neural mechanisms are sufficient to produce the PE.
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Dent, Micheal L., Daniel J. Tollin, and Tom C. T. Yin. "Influence of Sound Source Location on the Behavior and Physiology of the Precedence Effect in Cats." Journal of Neurophysiology 102, no. 2 (August 2009): 724–34. http://dx.doi.org/10.1152/jn.00129.2009.
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Psychophysical experiments on the precedence effect (PE) in cats have shown that they localize pairs of auditory stimuli presented from different locations in space based on the spatial position of the stimuli and the interstimulus delay (ISD) between the stimuli in a manner similar to humans. Cats exhibit localization dominance for pairs of transient stimuli with |ISDs| from ∼0.4 to 10 ms, summing localization for |ISDs| < 0.4 ms and breakdown of fusion for |ISDs| > 10 ms, which is the approximate echo threshold. The neural correlates to the PE have been described in both anesthetized and unanesthetized animals at many levels from auditory nerve to cortex. Single-unit recordings from the inferior colliculus (IC) and auditory cortex of cats demonstrate that neurons respond to both lead and lag sounds at ISDs above behavioral echo thresholds, but the response to the lag is reduced at shorter ISDs, consistent with localization dominance. Here the influence of the relative locations of the leading and lagging sources on the PE was measured behaviorally in a psychophysical task and physiologically in the IC of awake behaving cats. At all configurations of lead-lag stimulus locations, the cats behaviorally exhibited summing localization, localization dominance, and breakdown of fusion. Recordings from the IC of awake behaving cats show neural responses paralleling behavioral measurements. Both behavioral and physiological results suggest systematically shorter echo thresholds when stimuli are further apart in space.
Dissertations / Theses on the topic "Precedence effect; Sound location"
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Tollin, Daniel Joshua. "Some aspects of the lateralization of echoed sound in man." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363729.
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Shub, Daniel E. (Daniel Eric) 1974. "The role of the precedence effect in sound source lateralization." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/86768.
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Paterson, Miles Andrew McLean. "Sound localization in reverberant environments : physiological bases of the precedence effect." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1445900/.
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Localization dominance, a phenomenon of the precedence effect, refers to the dominance of directional cues conveyed by sound arriving directly from the source over cues conveyed by reflected copies on the perception of sound source location. One theory of localization dominance is that leading sounds suppress neural responses to lagging sounds (Yin, 1994 Litovsky & Yin, 1998 a, b). Neurons in auditory nuclei respond best to a leading sound and have a reduced response to a lagging sound, supporting this hypothesis. It has been proposed that GABA-ergic or glycinergic inhibition suppresses neural responses to lagging sounds (Yin, 1994 Fitzpatrick et al. 1995 Pollack & Burger, 2002). An alternative hypothesis states that cochlear processing in low-frequency hearing animals alters directional cues conveyed by the leading and lagging sound, emphasising those present in the leading sound (Tollin, 1998 Hartung & Trahiotis 2001). Responses of single neurons in the inferior colliculus (IC) of anaesthetised guinea pigs were recorded to binaural click pair stimuli. Responses of some neurons were recorded before, during, and after iontophoresis of either the GABAa receptor antagonist gabazine, or the glycine receptor antagonist strychnine. Blocking glycine did not decrease neural suppression of the lagging click in 8/10 neurons. Blocking GAB A did not decrease neural suppression of the lagging click in 11/16 neurons. The neural representation of directional cues in the output of low-frequency neurons to the leading click of a binaural click pair differed from those actually conveyed by the stimulus in 20/20 neurons. Examination of the responses of several such neurons indicated responses to the leading click represented a direction between that conveyed by the leading and lagging click. The results supported the hypothesis that cochlear processing of binaural click pairs alters directional cues conveyed by the stimulus. Limited support was also found for the hypothesis that GABA-ergic and glycinergic suppress lagging click responses in some neurons.
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Yao, Norikazu. "Auditory localisation : contributions of sound location and semantic spatial cues." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16504/.
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In open skill sports and other tasks, decision-making can be as important as physical performance. Whereas many studies have investigated visual perception there is little research on auditory perception as one aspect of decision making. Auditory localisation studies have almost exclusively focussed on underlying processes, such as interaural time difference and interaural level difference. It is not known, however, whether semantic spatial information contained in the sound is actually used, and whether it assists pure auditory localisation. The aim of this study was to investigate the effect on auditory localisation of spatial semantic information. In Experiment One, this was explored by measuring whole body orientation to the words "Left", "Right", "Back", "Front" and "Yes", as well as a tone, each presented from left right, front and back locations. Experiment Two explored the effect of the four spatial semantic words presented either from their matching locations, or from a position rotated 20 degrees anticlockwise. In both experiments there were two conditions, with subjects required to face the position indicated by the sound location, or the meaning of the word. Movements of the head were recorded in three dimensions with a Polhemus Fastrak system, and were analysed with a custom program. Ten young adult volunteers participated in each experiment. Reaction time, movement time, initial rotation direction, rotation direction at peak velocity, and the accuracy of the final position were the dependent measures. The results confirmed previous reports of confusions between front and back locations, that is, errors about the interaural axis. Unlike previous studies, many more back-to-front than front-toback errors was made. The experiments provided some evidence for a spatial Stroop interference effect, that is, an effect on performance of conflicting information provided by the irrelevant dimension of the stimulus, but only for reaction time and initial movement direction, and only in the Word condition. The results are interpreted using a model of the processes needed to respond to the stimulus and produce an orienting movement. They suggest that there is an asymmetric interference effect in which auditory localisation can interfere with localisation based on semantic content of words, but not the reverse. In addition, final accuracy was unaffected by any interference, suggesting that these effects are restricted to the initial stages of response selection.
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"Investigating Compensatory Mechanisms for Sound Localization: Visual Cue Integration and the Precedence Effect." Master's thesis, 2015. http://hdl.handle.net/2286/R.I.34880.
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abstract: Sound localization can be difficult in a reverberant environment. Fortunately listeners can utilize various perceptual compensatory mechanisms to increase the reliability of sound localization when provided with ambiguous physical evidence. For example, the directional information of echoes can be perceptually suppressed by the direct sound to achieve a single, fused auditory event in a process called the precedence effect (Litovsky et al., 1999). Visual cues also influence sound localization through a phenomenon known as the ventriloquist effect. It is classically demonstrated by a puppeteer who speaks without visible lip movements while moving the mouth of a puppet synchronously with his/her speech (Gelder and Bertelson, 2003). If the ventriloquist is successful, sound will be “captured” by vision and be perceived to be originating at the location of the puppet. This thesis investigates the influence of vision on the spatial localization of audio-visual stimuli. Participants seated in a sound-attenuated room indicated their perceived locations of either ISI or level-difference stimuli in free field conditions. Two types of stereophonic phantom sound sources, created by modulating the inter-stimulus time interval (ISI) or level difference between two loudspeakers, were used as auditory stimuli. The results showed that the light cues influenced auditory spatial perception to a greater extent for the ISI stimuli than the level difference stimuli. A binaural signal analysis further revealed that the greater visual bias for the ISI phantom sound sources was correlated with the increasingly ambiguous binaural cues of the ISI signals. This finding suggests that when sound localization cues are unreliable, perceptual decisions become increasingly biased towards vision for finding a sound source. These results support the cue saliency theory underlying cross-modal bias and extend this theory to include stereophonic phantom sound sources.Dissertation/Thesis
Masters Thesis Bioengineering 2015
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Ziemer, Tim. "Perceptual sound field synthesis concept for music presentation." 2017. https://slub.qucosa.de/id/qucosa%3A70632.
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A perceptual sound field synthesis approach for music is presented. Its signal processing implements critical bands, the precedence effect and integration times of the auditory system by technical means, as well as the radiation characteristics of musical instruments. Furthermore, interaural coherence, masking and auditory scene analysis principles are considered. As a result, the conceptualized sound field synthesis system creates a natural, spatial sound impression for listeners in extended listening area, even with a low number of loudspeakers. A novel technique, the “precedence fade”, as well as the interaural cues provided by the sound field synthesis approach, allow for a precise and robust localization.Simulations and a listening test provide a proof of concept. The method is particularly robust for signals with impulsive attacks and long quasi-stationary phases, as in the case of many instrumental sounds. It is compatible with many loudspeaker setups, such as 5.1 to 22.2, ambisonics systems and loudspeaker arrays for wave front synthesis. The perceptual sound field synthesis approach is an alternative to physically centered wave field synthesis concepts and conventional, perceptually motivated stereophonic sound and benefits from both paradigms.
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Li, Na 1980 Oct 2. "Binaural mechanism revealed with in vivo whole cell patch clamp recordings in the inferior colliculus." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2065.
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Many cells in the inferior colliculus (IC) are excited by contralateral and inhibited by ipsilateral stimulation and are thought to be important for sound localization. These excitatory-inhibitory (EI) cells comprise a diverse group, even though they exhibit a common binaural response property. Previous extracellular studies proposed specific excitatory and/or inhibitory events that should be evoked by each ear and thereby generate each of the EI discharge properties. The proposals were inferences based on the well established response features of neurons in lower nuclei, the projections of those nuclei, their excitatory or inhibitory neurochemistry, and the changes in response features that occurred when inhibition was blocked.
Here we recorded the inputs, the postsynaptic potentials, discharges evoked by monaural and binaural signals in EI cells with in vivo whole cell recordings from the inferior colliculus (IC) of awake bats. We also computed the excitatory and inhibitory synaptic conductances from the recorded sound evoked responses. First, we showed that a minority of EI cells either inherited their binaural property from a lower binaural nucleus or the EI property was created in the IC via inhibitory projections from the ipsilateral ear, features consistent with those observed in extracellular studies. Second, we showed that in a majority of EI cells ipsilateral signals evoked subthreshold EPSPs that behaved paradoxically in that EPSP amplitudes increased with intensity, even though binaural signals with the same ipsilateral intensities generated progressively greater spike suppressions. These ipsilateral EPSPs were unexpected since they could not have been detected with extracellular recordings. These additional responses suggested that the circuitry underlying EI cells was more complex than previously suggested. We also proposed the functional significance of ipsilaterally evoked EPSPs in responding to moving sound sources or multiple sounds. Third, by computing synaptic conductances, we showed the circuitry of the EI cells was even more complicated than those suggested by PSPs, and we also evaluated how the binaural property was produced by the contralateral and ipsilateral synaptic events.text
Book chapters on the topic "Precedence effect; Sound location"
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An, Sung Jun, Rhee Man Kil, and Byoung-Gi Lee. "Zero-Crossings with the Precedence Effect for Sound Source Localization in Reverberant Conditions." In Neural Information Processing, 301–8. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-42051-1_38.
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Toole, Floyd E. "Reflections, Images, and the Precedence Effect." In Sound Reproduction, 73–93. Elsevier, 2007. http://dx.doi.org/10.1016/b978-0-240-52009-4.50010-1.
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"Refl ections, Images, and the Precedence Effect." In Sound Reproduction, 93–114. Routledge, 2009. http://dx.doi.org/10.4324/9780080888019-13.
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Tierno, Michael. "It’s all for effect." In Location and Postproduction Sound for Low-Budget Filmmakers, 180–88. Routledge, 2020. http://dx.doi.org/10.4324/9780429331305-19.
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Mann, J. I., and A. S. Truswell. "Diseases of affluent societies and the need for dietary change." In Oxford Textbook of Medicine, edited by Katherine Younger, 1891–902. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198746690.003.0222.
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Nutritional problems of a country depend more upon the stage of technical and economic development than geographical location. People in affluent societies have ready access to food all year round. The diet is typically energy-dense, high in fat and often also in sugar. There are multiple sources of nutritional advice, not all based on sound science. Obesity is the most obvious and important nutritional disease in affluent societies, with comorbidities including type 2 diabetes, coronary heart disease, hypertension, some cancers, gallstones, osteoarthritis, and obstructive sleep apnoea. Obese people may also be disadvantaged by social, economic, and psychological effects. Particular dietary constituents promote or protect against coronary heart disease by their effect on cardiovascular risk factors, and some promote or protect against various cancers.
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Douglas, Raymond S., and Robert A. Goldberg. "Evaluation and Spectrum of Orbital Diseases." In Surgery of the Eyelid, Lacrimal System, and Orbit. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780195340211.003.0024.
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Although orbital disorders are not frequently encountered in the comprehensive ophthalmologist’s practice, it is essential to be able to diagnose patients with orbital disease and manage them accordingly. Various disease processes can affect the orbit. This chapter endeavors to provide a thoughtful, stepwise, and logical approach to the evaluation of orbital disease. The discussion begins with differential diagnosis, adds an intelligent history-taking and physical examination, and then focuses on efficient use of diagnostic tests to finally arrive at the correct diagnosis. The staging and management of two common orbital disorders, orbital inflammation and thyroid-associated ophthalmopathy, will also be discussed. The differential diagnosis of orbital disease is extensive, and most listings of orbital disease divide the causes between histopathologic and mechanistic categories. This type of grouping is intellectually sound and scientifically useful but does not provide a framework that the clinical practitioner can easily grasp and directly use in sorting through the differential diagnosis of any given patient. In broad terms, orbital disease can be considered in terms of location, extent, and biologic activity. The classification used in this chapter is broken down along clinical lines and takes advantage of the fact that the orbit has a somewhat limited repertoire of ways that it can respond to pathologic conditions. Orbital disease can be categorized into five basic clinical patterns: inflammatory, mass effect, structural, vascular, and functional. Although many cases cross over into several categories, the vast majority of clinical presentations fit predominantly into one of these patterns. As the clinician walks through each step of the evaluation process—history, physical examination, laboratory testing, orbital imaging—a conscious effort should be made to categorize the presentation within this framework. If the practitioner approaches orbital disease with this framework of discrete patterns of clinical presentation, then at every step of the diagnostic pathway (history, physical examination, orbital imaging studies, and special tests), he or she can draw from a defined set of differential diagnoses that characterize each pattern of orbital disease and use that information to efficiently and confidently orchestrate diagnosis and management.
Conference papers on the topic "Precedence effect; Sound location"
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Owens, Steffan, and Stuart Cunningham. "Auditory Masking and the Precedence Effect in Studies of Musical Timekeeping." In AM'18: Sound in Immersion and Emotion. New York, NY, USA: ACM, 2018. http://dx.doi.org/10.1145/3243274.3243312.
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Zhao, Wei, Qifei He, Zhuoran Yang, and Zihan Chen. "Promotion Effect of Sound Image Location by Unity Audio-Visual Interaction." In 2018 Ninth International Conference on Intelligent Control and Information Processing (ICICIP). IEEE, 2018. http://dx.doi.org/10.1109/icicip.2018.8606697.
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Finnegan, Shane Leslie, Craig Meskell, and Samir Ziada. "The Effect of Sound Pressure on the Aeroacoustic Sources Around Two Ducted Tandem Cylinders." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30271.
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An empirical investigation of the spatial distribution of aeroacoustic sources around two tandem cylinders subject to ducted flow and forced transverse acoustic resonance is described. The work builds on a previous investigation by the authors and utilises Howe’s theory of aerodynamic sound. The influence of the sound pressure level in the duct on the strength and location of the aeroacoustic sources in the flow was the main focus of the investigation and experiments to resolve the aeroacoustic source distribution were concentrated at a low main-stream flow velocity (before acoustic-Strouhal coincidence), at a medium mainstream flow velocity (just after acoustic-Strouhal coincidence) and at a high mainstream flow velocity (substantially higher than acoustic-Strouhal coincidence). The sound pressure level was found to have a considerable effect on the “lock-in”’ range of the cylinders which widened as the sound pressure level increased. A proposed normalisation of the net acoustic energy transfer per spanwise location appears to show good metric for the distribution of the aeroacoustic sources in the flow field. Using this, it was found that the amplitude of the sound pressure had a negligible influence on the aeroacoustic sources in the wake and the gap region for all the tested cases apart from the lowest flow velocity. This particular case showed indications that the aeroacoustic source strength and location could be altered for certain changes in sound pressure level.
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Gu¨lac¸ti, B., S. Aubrun, A. Seraudie, and D. Arnal. "The Effect of the Source Location on the Acoustic Excitation on Laminar-Turbulent Transition on Swept Wing Boundary Layer." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31397.
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The effect of the source location and the direction of the propagation on the laminar-turbulent transition on swept-wing three-dimensional boundary layers are investigated experimentally. Also the crossflow case is handled in detail. The source for the acoustic excitation is placed in four different locations: in front of the wing, on top of the test section, behind the wing and in front of the wind tunnel. Three different experimental cases (streamwise, crossflow and mixed cases) are examined for each location with two different excitation bands. For the most efficient frequency ranges and the highest sound pressure levels an upstream shift of transition motion between 20%–35% of chord length for streamwise case and between 5%–10% for the crossflow case are observed. While in front of the wing and behind the wing are the most efficient loudspeaker positions in the streamwise case, in the crossflow case the most efficient locations are observed to be in front of the wing and on top of the test section. It is concluded that acoustic sound level plays a more important role in the upstream shift of the transition than the source location and placing the loudspeaker in front of the wind tunnel is not an efficient position. For the crossflow instabilities dominated transition the stationary vortices are clearly seen from the velocity contours obtained by the hot-wire. Secondary instabilities couldn’t be observed in the hot-wire spectra. The surface roughness of the wing that is reduced to 0.25µm does not change the transition location in the crossflow case.
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Herman, Cila. "Quantitative Visualization of the Thermoacoustic Effect." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-23286.
Full textAbstract:
Thermoacoustic energy conversion was introduced into engineering systems during the past three decades as a new, alternative, environmentally safe energy conversion technology. It uses noble gases and mixtures of noble gases as working fluids rather than hazardous refrigerants required for the vapor compression cycle. A thermoacoustic system can operate both as a prime mover/engine (a temperature gradient and heat flow imposed across the stack lead to the generation of acoustic work/sound in the resonator) and, when reversing the thermodynamic cycle, as a refrigerator (acoustic work is used to pump heat from the low temperature reservoir and release it into a higher temperature ambient). Energy transport in thermoacoustic systems is based on the thermoacoustic effect. Using an acoustic driver, the working fluid in the resonance tube is excited to generate an acoustic standing wave. When introducing a stack of parallel plates of length Δx into the acoustic field at a suitable location, a temperature difference ΔT develops along the stack plates. This temperature difference is caused by the thermoacoustic effect. In this paper the thermoacoustic effect is visualized using real-time holographic interferometry combined with high-speed cinematography. In holographic interferometry both temperature and pressure variations impact the refractive index and both of these variations are present in our thermoacoustic system. In our analysis temperature variations are uncoupled from pressure variations to quantitatively visualize the oscillating temperature fields around the stack plate.
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Golubev, Vladimir, Cody Sewell, Lap Nguyen, and Reda Mankbadi. "Effect of Synthetic-Jet Actuation on Airfoil Acoustic Radiation." In ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fedsm2012-72462.
Full textAbstract:
Synthetic jet actuators (SJAs) have been primarily investigated as means of unsteady flow control on aircraft wing. The current work for the first time explores the effectiveness of SJAs for control of a low-speed airfoil acoustic radiation both with the uniform upstream flow conditions (with noise dominated by the trailing-edge sources) and in the presence of an upstream flow disturbance (with noise dominated by the leading-edge sources or stall-related phenomena depending on the disturbance character and amplitude). In the high-fidelity numerical study, the effect of the selected SJA location and other parameters characterizing SJA performance are determined. In the adopted numerical procedure, the actuator is modeled without its resonator cavity through imposing a simple fluctuating-velocity boundary condition at the bottom of the actuator’s orifice. The orifice cavity with the properly defined boundary condition is then embedded into the airfoil surface for conducting high-accuracy viscous analysis of SJA-based active noise control. The effects of the actuation on sound radiated by the airfoil both in presence and absence of the upstream flow disturbance are examined for a benchmark problem of time-harmonic gust interaction with a symmetric Joukowski airfoil.
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Elnajjar, Emad, Mohamed Y. E. Selim, and Farag Omar. "Effect of Dual Fuel Engine Parameters and Fuel Type on Engine Noise Emissions." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24253.
Full textAbstract:
Investigating experimentally the effects of different fuel types and engine parameters on the overall generated engine noise levels. Engine parameters such as: Engine speed, Injection timing angle, engine loading, different pilot fuel to gases fuel ratio and engine compression ratio. Engine noises due to combustion, turbulent flow and motoring were reported in this study by direct sound pressure level SPL (dB) measurements and compared to the maximum cylinder pressure rise rate with respect to the engine crank angle (dP/dθ)max. Experimental procedures conducted using a Ricardo diesel version variable compression research engine. The study was conducted for three different fuels: single diesel fuel, and dual fuel engine that uses LPG or natural gas. The study for each fuel type covered the following operating parameters range, engine speed from 20–28 rev/sec, injection timing form 20 to 45° BTDC, compression ratio from 16 to 22, load range 2 to 14 N.m, and ratio of pilot to gaseous fuel from 0 to 10%. The study reported the location (crank angle) corresponding to maximum cylinder pressure and max pressure rise rate. Results from testing dual fuel engine with varying design and operating parameters are presented and discussed. The present work reported higher SPL (dB) generated from burning a dual fuel compared to burning diesel fuel only.
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Vázquez, Raúl, Diego Torre, and Adolfo Serrano. "The Effect of Airfoil Clocking on Efficiency and Noise of Low Pressure Turbines." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94243.
Full textAbstract:
The effect of airfoil clocking (stator-stator interaction) on efficiency and noise of low pressure turbines (LPT) was investigated experimentally in a multistage turbine high-speed rig. The rig consisted of three stages of a state-of-the-art LPT. The stages were characterized by a very high wall-slope angle, reverse cut-off design, very high lift and very high aspect ratio airfoils. The rig had identical blade count for the second and third stators. The circumferential position of the second stator was individually adjusted with respect to the third stator. Eight different circumferential clocking locations over one pitch were back-to-back tested. The rig was heavily instrumented with miniature five hole probes, hot wires, hot films, total pressure and temperature rakes, pressure tappings on the airfoil surface, two array of Kulites in a rotatory module, etc. Every clocking location was tested with the same instrumentation and at the same operating conditions with the intention of determining the impact of the clocking on the overall efficiency and noise. Due to the large amount of data, the results of this test will be reported in several papers. The present paper contains the impact on the overall efficiency, radial traverses, static pressure fields on the airfoils and averaged sound pressure levels in the duct. The comparison of the results suggests that the efficiency is weakly affected by clocking; however the effect on noise is noticeable for some acoustic tones at certain operating conditions.
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Patching, Richard G. "Pipe Supports and Skid Platforms: An Overlooked Noise Problem." In 2000 3rd International Pipeline Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/ipc2000-269.
Full textAbstract:
When an energy industry facility must meet environmental noise regulations, the primary noise sources are the drivers (such as engines and motors), driven tools (such as compressors and pumps), air moving devices, and turbulent flow in valves and piping. The primary sound transmission path is the airborne radiation of noise, which is controlled by enclosures, lagging and silencers. The opportunity for sound energy to be transmitted through structural vibration and reradiated at another location is largely overlooked in typical acoustic impact analyses. Pipe support and skid structures often have large flat panels which are very efficient radiators of noise energy, where the sound energy generated by compressors can be emitted into the environment at some distance from the actual energy source. How a pipe is mounted on its supports, and the design of those supports, can have a significant effect on the noise emissions from its support structures.
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Ozer, Mehmet Bulent, and Thomas J. Royston. "Applications of the Sherman-Morrison Matrix Inversion Formula in Linear and Non-Linear Vibrations, Controls and Acoustics." In ASME 2003 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/detc2003/vib-48554.
Full textAbstract:
Applications of the Sherman-Morrison matrix inversion formula are reviewed and demonstrated for several problems in sound and vibration control. The inversion formula enables one to easily separate the effect of a perturbation or subcomponent on the dynamic behavior of the overall system. Applications of this technique that are demonstrated here include: identifying optimal PZT electrical shunt parameter values to minimize sound radiation from a PZT-plate structure, identifying the optimal location and parameter values of a tuned dynamic vibration absorber attached to a multi-degree of freedom, damped system, and identifying and quantifying an isolated non-linearity in an otherwise linear system. Extensions to active control system design are also discussed.