Using the interaural time difference and cross-correlation to localise short-term complex noises

The mammalian binaural cue of interaural time difference (ITD) and cross-correlation have long been used to determine the point of origin of a sound source. The ITD can be defined as the different points in time at which a sound from a single location arrives at each individual ear [1]. From this time difference, the brain can calculate the angle of the sound source in relation to the head [2]. Cross-correlation compares the similarity of each channel of a binaural waveform producing the time lag or offset required for both channels to be in phase with one another. This offset corresponds to the maximum value produced by the cross-correlation function and can be used to determine the ITD and thus the azimuthal angle θ of the original sound source. However, in indoor environments, cross-correlation has been known to have problems with both sound reflections and reverberations. Additionally, cross-correlation has difficulties with localising short-term complex noises when they occur during a longer duration waveform, i.e. in the presence of background noise. The crosscorrelation algorithm processes the entire waveform and the short-term complex noise can be ignored. This paper presents a technique using thresholding which enables higher-localisation abilities for short-term complex sounds in the midst of background noise. To determine the success of this thresholding technique, twenty-five sounds were recorded in a dynamic and echoic environment. The twenty-five sounds consist of hand-claps, finger-clicks and speech. The proposed technique was compared to the regular cross-correlation function for the same waveforms, and an average of the azimuthal angles determined for each individual sample. The sound localisation ability for all twenty-five sound samples is as follows: average of the sampled angles using cross-correlation: 44%; cross-correlation technique with thresholding: 84%. From these results, it is clear that this proposed technique is very successful for the localisation of short-term complex sounds in the midst of background noise and in a dynamic and echoic indoor environment.

The Undersea World of the Sound Department: the Construction of Sonic Conventions in Sub-aqua Screen Environments

The availability of new underwater cameras and sub-aqua diving gear in the immediate post-war era opened up exciting possibilities for both narrative and documentary filmmakers. While the visual elements of this new world could now be more easily captured on film, the sound elements of the sub-aqua environment remained more elusive. What did, or should, this undersea world sound like? This article examines the use of sound in the sub-aqua scenes of both fictional and documentary films in the 1950s and asks questions about the methods used in the sonification of these worlds. Comparing the operation of underwater sound and human hearing with the production and post-production strategies used by filmmakers, I seek to identify the emergence of a sound convention and its implications for issues of cinematic realism. Central to this convention is the manipulation of sonic frequencies. The sound strategies adopted also raise questions about the malleability of viewer perspective and sound-image relationship in terms of a realist mode of address. Linked to this is the use of sound to enhance audience experience on an affective level. As well as underpinning cinematic realism, these new sound environments offered fresh experiences to audiences seeking new reasons to visit the cinema in an era of widening forms of entertainment.

Monsters Take to the Streets! Monstrous Street-Art as Pedagogy of Resistance to Post-Olympic Regeneration in Hackney Wick?

This chapter explores geographies of gentrification and resistance in relation to the monstrous through the lens of street-art in post-Olympic London. It takes as a geographic case study Hackney Wick, which has for a long time been a bastion of alternative and creative living due to cheap rents in large, ex-industrial warehouse spaces. The artistic sociality of the area is imbued within its landscape, as prolific street artists have adorned ex-industrial warehouses and canal-side walls with graffiti and murals. Since the announcement of the 2012 Olympic Games, the area has been a site of intense political and aesthetic contestation. The post-Olympic legacy means that the area has been earmarked for redevelopment, with current residents facing the possibility of joining thousands already displaced by the games. The anxiety of dispossession is reflected by monstrous characters and sinister disembodied teeth, eyes and fingers embedded within the landscape, painted by local artists. Using geographically sensitive mobile and visual methodology to document the landscape and artwork, the chapter analyses and interprets the monstrous themes using a range of theorists including Mikhail Bakhtin, Georges Bataille and Nick Land. I argue that monstrous street-art lays visible claim to public territory for aesthetic purposes at odds with the visions of redevelopers and the needs of capital. Whilst street-art and graffiti do not fit easily within frameworks of organized political resistance or collective social movements, they operate as a kind of epistemological transgression that triggers transformative affects in the viewer. This creates conditions for pedagogies of resistance to gentrification by expressing and mobilizing political affects such as anger and anxiety, raising awareness of geographical politics, and encouraging the viewer to question the status quo of the built environment.