Realistisk formidling af virtuelle lydkilder - 4-to-one

thesis is performed in pfft~ objects with an overlap of 4 windows. The pfft~ objects obtain the HRTFs
by pointing to relevant data in the jit.matrix objects.
Head tracking of the listener’s orientation was implemented in order to compensate for the fact that
headphones, and thereby the whole sound environment, move along when the listener rotates his/her
head. The x-IMU 82 sensor was mounted on top of headphones and special Java externals based on the x-
IMU API 83 were created in order to be able to communicate with the sensor in Max.
Simulation of room acoustics was implemented to achieve a realistic sense of the sound sources being
placed in the room outside the listener’s head, and also to support localization capabilities. Since it is
mostly the room’s early reflections that change with changing listener rotation and position 84 , only these
early reflections were calculated dynamically and real-time. Reflections up to 2 nd order were calculated
for each sound source using the image-source method as described in Modeling Techniques for Virtual
Acoustics 85 . As it is not possible (processor-wise) to perform binaural synthesis on each of the 36 reflec-
tions from each sound source, all reflections were summed per surface in the room before performing
one binaural synthesis for each surface in regard to the surface’s position in relation to the listener’s
position and orientation. This resulted in six syntheses overall for room simulation instead of 36 for
each sound source in a regular box-shaped room. The ‘tail’ of the reverberation was handled by a static
VST convolution reverb.
Two examples of sound content were created with the aim of investigating the system’s (and the tech-
nology’s) potential ability to communicate an experience to the listener. One of these is a kind of sound
narrative, where my grandmother talks about her life – both her present life and experiences from her
youth. Occasionally, the narrative ‘dives into’ specific narrated situations, creating a kind of auditory
flashbacks. An important aspect of this narrative as sound content is Augmented Reality. The listener
will experience the narrative in the same physical room as the basic ‘room of narration’. The idea was
that the listener should have an impression of the physical room being sonically augmented in such a way
that, for example, my grandmother is perceived as sitting in the empty chair that is physically present in
the room.
The other sound content that was created was an example of how music could be mediated in such a
system. More precisely, it consisted of a four-voiced choir (SATB) that was positioned as individual
sound sources in the system/room.
82 http://www.x-io.co.uk/node/9
83 http://www.x-io.co.uk/res/sw/ximu_api_13_1.zip
84 Zotkin, Duraiswami, and Davis.
85 Savioja
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