Virtual Moving Sound Source Localization through Headphones

Abstract

Humans are able to detect, identify and localize the sound source around them, to roughly estimate the direction and distance of the sound source, the static or moving sounds and the presence of an obstacle or a wall [Fay and Popper, 2005]. Sound source localization and the importance of acoustical cues, has been studied during many years [Brungart et al., 1999]. Lord Rayleigh in his “duplex theory” presented the foundations of the modern research on sound localization [Stutt, 1907], introducing the basic mechanisms of localization. Blauert defined the localization as “the law or rule by which the location of an auditory event (e.g., its direction and distance) is related to a specific attribute or attributes of a sound event” [Blauert, 1997]. A great contribution on sound localization plays the acoustical cues, Interaural Time Difference ITD and Interaural Level Diference ILD, torso and pinnae (Brungart et al., 1999), [Bruce, 1959]. [Kim et al., 2001] confirm that the Head Related Transfer Functions (HRTFs) which represent the transfer characteristics of the sound source in a free field to the listener external ear [Blauert, 1997]), are crucial for sound source localization. An important role in the human life plays the moving sound localization [Al’tman et al., 2005]. In the case of a moving source, changes in the sound properties appear due to the influence of the sound source speed or due to the speed of the used program for sound emission. Several research have been done on static sound localization using headphones [Wenzel et al., 1993], [Blauert, 1997] but few for moving sound source localization. It is well known that on localization via headphones, the sounds are localized inside the head [Junius et al., 2007], known as “lateralization”. Previous studies [Hartmann and Wittenberg, 1996] in their research on sound localization, showed that sound externalization via headphones can be achieved using individual HRTFs, which help listeners to localize the sound out in space [Kulkani et al., 1998], [Versenyi, 2007]. Great results have been achieved with the individual HRTFs, which are artificially generated and measured on a dummy head or taken from another listener. Due to those HRTFs, the convolved sounds are localized as real sounds [Kistler et al., 1996], [Wenzel, 1992]. This chapter presents several experiments on sound source localization. Two experiments are developed using monaural clicks in order to verify the influence of the Inter-click interval on sound localization accuracy. In the first of these experiments [Dunai et al., 2009] the localization of the position of a single sound and a train of sounds was carried out for different inter-click intervals (ICIs). The