Reduced-parameter model of head-related transfer functions for synthesized spatial audio

Digital systems can generate left and right audio channels that create the effect of virtual sound source placement (spatialization) by processing an audio signal through pairs of Head-Related Transfer Functions (HRTFs) or, equivalently, Head-Related Impulse Responses (HRIRs). The spatialization effect is better when individually-measured HRTFs or HRIRs are used than when generic ones (e.g., from a mannequin) are used. However, the measurement process is not available to the majority of users. There is ongoing interest to find mechanisms to customize HRTFs or HRIRs to a specific user, in order to achieve an improved spatialization effect for that subject. Unfortunately, the current models used for HRTFs and HRIRs contain over a hundred parameters and none of those parameters can be easily related to the characteristics of the subject. This dissertation proposes an alternative model for the representation of HRTFs, which contains at most 30 parameters, all of which have a defined functional significance. It also presents methods to obtain the value of parameters in the model to make it approximately equivalent to an individually-measured HRTF. This conversion is achieved by the systematic deconstruction of HRIR sequences through an augmented version of the Hankel Total Least Squares (HTLS) decomposition approach. An average 95% match (fit) was observed between the original HRIRs and those re-constructed from the Damped and Delayed Sinusoids (DDSs) found by the decomposition process, for ipsilateral source locations. The dissertation also introduces and evaluates an HRIR customization procedure, based on a multilinear model implemented through a 3-mode tensor, for mapping of anatomical data from the subjects to the HRIR sequences at different sound source locations. This model uses the Higher-Order Singular Value Decomposition (HOSVD) method to represent the HRIRs and is capable of generating customized HRIRs from easily attainable anatomical measurements of a new intended user of the system. Listening tests were performed to compare the spatialization performance of customized, generic and individually-measured HRIRs when they are used for synthesized spatial audio. Statistical analysis of the results confirms that the type of HRIRs used for spatialization is a significant factor in the spatialization success, with the customized HRIRs yielding better results than generic HRIRs.

Documentary practice in a participatory culture

Debates concerning the veracity, ethics and politics of the documentary form circle endlessly around the function of those who participate in it, and the meaning attributed to their participation. Great significance is attached to the way that documentary filmmakers do or do not participate in the world they seek to represent, just as great significance is attached to those subjects whose participation extends beyond playing the part of eyewitness or expert, such that they become part of the very filmmaking process itself. This Ph.D. explores the interface between documentary practice and participatory culture by looking at how their practices, discursive fields and histories intersect, but also by looking at how participating in one might mean participating in the other. In short, the research is an examination of participatory culture through the lens of documentary practice and documentary criticism. In the process, however, this examination of participatory culture will in turn shed light on documentary thinking, especially the meaning and function of ‘the participant’ in contemporary documentary practice. A number of ways of conceiving of participation in documentary practice are discussed in this research, but one of the ideas that gives purpose to that investigation is the notion that the participant in contemporary documentary practice is someone who belongs to a participatory culture in particular. Not only does this mean that those subjects who play a part in a documentary are already informed by their engagement with a range of everyday media practices before the documentary apparatus arrives, the audience for such films are similarly informed and engaged. This audience have their own expectations about how they should be addressed by media producers in general, a fact that feeds back into their expectations about participatory approaches to documentary practice too. It is the ambition of this research to get closer to understanding the relationship between participants in the audience, in documentary and ancillary media texts, as well as behind the camera, and to think about how these relationships constitute a context for the production and reception of documentary films, but also how this context might provide a model for thinking about participatory culture itself. One way that documentary practice and participatory culture converge in this research is in the kind of participatory documentary that I call the ‘Camera Movie’, a narrow mode of documentary filmmaking that appeals directly to contemporary audiences’ desires for innovation and participation, something that is achieved in this case by giving documentary subjects control of the camera. If there is a certain inevitability about this research having to contend with the notion of the ‘participatory documentary’, the ‘participatory camera’ also emerges strongly in this context, especially as a conduit between producer and consumer. Making up the creative component of this research are two documentaries about the reality television event Band In A Bubble, and participatory media practices more broadly. The single-screen film, Hubbub , gives form to the collective intelligence and polyphonous voice of contemporary audiences who must be addressed and solicited in increasingly innovative ways. One More Like That is a split-screen, DVD-Video with alternate audio channels selected by a user who thereby chooses who listens and who speaks in the ongoing conversation between media producers and media consumers. It should be clear from the description above that my own practice does not extend to highly interactive, multi-authored or web-enabled practices, nor the distributed practices one might associate with social media and online collaboration. Mine is fundamentally a single authored, documentary video practice that seeks to analyse and represent participatory culture on screen, and for this reason the Ph.D. refrains from a sustained discussion of the kinds of collaborative practices listed above. This is not to say that such practices don’t also represent an important intersection of documentary practice and participatory culture, they simply represent a different point of intersection. Being practice-led, this research takes its procedural cues from the nature of the practice itself, and sketches parameters that are most enabling of the idea that the practice sets the terms of its own investigation.

A snoring classifier based on heart rate variability analysis

The effect of snoring on the cardiovascular system is not well-known. In this study we analyzed the Heart Rate Variability (HRV) differences between light and heavy snorers. The experiments are done on the full-whole-night polysomnography (PSG) with ECG and audio channels from patient group (heavy snorer) and control group (light snorer), which are gender- and age-paired, totally 30 subjects. A feature Snoring Density (SND) of audio signal as classification criterion and HRV features are computed. Mann-Whitney statistical test and Support Vector Machine (SVM) classification are done to see the correlation. The result of this study shows that snoring has close impact on the HRV features. This result can provide a deeper insight into the physiological understand of snoring. © 2011 CCAL.

La cronémimca de reuniones multipartitas en videoconferencia : Observaciones en torno al silencio de la fase de preparación

En este estudio se examinan los silencios que aparecen durante la fase de preparación de dieciocho reuniones multipartitas por videoconferencia. Partiendo de la metodología del Análisis Conversacional, el análisis del material muestra que la duración de los silencios entre turnos se reduce considerablemente en dos momentos cruciales de la interacción en línea. Esto a su vez confirma la existencia de tres etapas diferenciadas en la preparación: etapa inicial, etapa de transición y etapa audiovisual, en cada una de las cuales los silencios presentan unas características concretas. Se muestra que en el chat escrito también se producen intervalos y lapsos y que el nivel de tolerancia de los participantes hacia el silencio varía en cada una de las etapas, lo cual puede relacionarse con su nivel de atención y disponibilidad. Se sugiere un estándar máximo aproximado para los intervalos que ocurren en la etapa de transición y se demuestra que, en el canal audio-oral, el límite de tolerancia se sitúa por encima de los tres segundos de duración. Por último, este estudio pone de manifiesto la aparición de diferentes ritmos cronémicos a lo largo de la preparación en videoconferencia, donde elementos como la apertura de la cámara web parecen poseer una gran relevancia interaccional.