1,720,969 research outputs found
Choice of inverse filter design parameters in virtual acoustic imaging systems
No full textReproducing a pair of binaural signals over loudspeakers requires crosstalk cancellation filters that create sound at the two ears corresponding to a transparent delivery of the intended source material. Such filtering is effectively inverting the actual response of the loudspeakers to the two ears. The authors explore the consequences of inversion, especially when the response lasts longer than that of a strictly anechoic environment. The choice of inverse design parameters proves more difficult than expected. The authors conclude that the required knowledge of the actual environment is equivalent to making in situ measurements.<br/
Modelling of the echo generation process in bat echolocation (A)
No full textVery few studies exist that attempt to model the detailed shape of the echoes generated by real targets in bat echolocation. The modelling becomes even more complicated when one attempts to take into account the specific acoustic characteristics of the bat as a source and receiver. Hence, the exact physical acoustics basis that underpins the target detection and classification capabilities demonstrated by bats remains a largely open research question. We use previously published work on real target echo measurement (Simmons and Chen, JASA 1989) as a starting point but modify their experimental method in a way that allows the incorporation of the bat's source and receiver characteristics in the modelling. Furthermore, we compare our measurements with analytically predicted results and show good agreement. We discuss how our experimental method can be used for the prediction of the binaural signals that constitute the actual input to the bat's auditory system during echolocation
Use of binaural and monaural cues to identify the lateral position of a virtual object using echoes
No full textUnder certain conditions, sighted and blind humans can use echoes to discern characteristics of otherwise silent objects. Previous research concluded that robust horizontal-plane object localisation ability, without using head movement, depends on information above 2 kHz. While a strong interaural level difference (ILD) cue is available, it was not clear if listeners were using that or the monaural level cue that necessarily accompanies ILD. In this experiment, 13 sighted and normal-hearing listeners were asked to identify the right-vs.-left position of an object in virtual auditory space. Sounds were manipulated to remove binaural cues (binaural vs. diotic presentation) and prevent the use of monaural level cues (using level roving). With low- (<2 kHz) and high- (>2 kHz) frequency bands of noise, performance with binaural presentation and level rove exceeded that expected from use of monaural level cues and that with diotic presentation. It is argued that a high-frequency binaural cue (most likely ILD), and not a monaural level cue, is crucial for robust object localisation without head movement
Identification of auditory cues utilized in human echolocation - objective measurement results
No full textWe present objective measurements of source-to-ear responses obtained in a previously established experimental paradigm of human echolocation. We identify and analyze the binaural localization cues encoded in those responses and we discuss their significance with respect to the previously reported performance in this specific experimental paradigm. The cues encoded in both the echo (lagging) and the direct transmission and echo (leading and lagging) parts of the responses are examined and their significance in view of the “precedence effect” is discussed. The variation and salience of the binaural cues pertaining to extensions of the previous experimental paradigm are examined and interpreted. This work allows us to formulate more detailed hypotheses and to design more informative subjective listening tests in order to further investigate the viability of using the acquired sensory modality of human echolocation in real-world application
Preliminary reflector-localisation studies using stimuli related to an echolocation task
No full textIdentification of the lateral position of a virtual object based on echoes by humans
No full textis known about the factors influencing object localisation using a ‘searching’ strategy. In this paper, we describe a series of experiments using sighted and blind human listeners and a ‘virtual auditory space’ technique to investigate the effects of the distance and orientation of a reflective object and the effect of stimulus bandwidth on ability to identify the right-versus-left position of the object, with bands of noise and durations from 10–400 ms. We found that performance reduced with increasing object distance. This was more rapid for object orientations where mirror-like reflection paths do not exist to both ears (i.e. most possible orientations); performance with these orientations was indistinguishable from chance at 1.8 m for even the best performing listeners in other conditions. Above-chance performance extended to larger distances when the echo was artificially presented in isolation, as might be achieved in practice by an assistive device. We also found that performance was primarily based on information above 2 kHz. Further research should extend these investigations to include other factors that are relevant to real-life echolocation.<br/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
