174
M. W˛ asowicz
5 Acoustics
Visual information—even in itself a powerful means of exploring virtual realities—
can be enhanced by auditory information. In some scenarios this will be more effective than in others, such as in situations in which the sense of hearing can be particularly effective, like in virtual walks through urban or architectural interiors. People are
responsive to the temporal, spectral and spatial acoustic stimuli in the built environment. Requiring large amounts of data, this sensitivity hinders realistic simulation of
interior acoustics, and so, to transmit auditory environment in a persuasive way, highquality measures are needed. Acoustic simulation needs to include sounds affecting
surface materials and architectural features, such as room volume and its structural
properties [2]. So detailed resemblance of sounds does not pertain to all aspects of
acoustic simulation, however. Human perception research has revealed that, exposed
to visual and acoustic stimuli at the same time, people react to the former much more
than to the latter [26]. It is thus the accuracy of visual simulation that makes a difference, and acoustic simulation’s less so: if the visuals are accurately conveyed, even
less accurate acoustics should do the job [27]. Thus, dissimilarities between real and
virtual sound turn out to be less apparent when accompanying visual stimuli. This
is not to say, however, that the industry is happy with inaccurate visual sound only
because it is less important than the visual display it accompanies. Soon, all modern
VR systems exploiting acoustic stimuli will do so with accuracy, searching for the
simulation of real environments in all their aspects.
In order to use auditory support, the user has a sound system fixed to her head:
headphones. The system can be independent of the visual display, but modern HMD
go a step farther, joining the two systems into one whole: they have an in-built audio
output device (Fig. 1). This integration is crucial in terms of immersiveness, because
acoustic representation directly relates to motion, is interactive, and is determined
by the participant’s movements [2].
Recent years have brought about the acknowledgment of how important the
synchronization of spatial audio reproduction with visual information is for
increasing VR immersion. Hansung et al. used the state-of-the-art of VR systems to
reproduce a VR environment with acoustic properties based on a real interior scene
captured by two 360° cameras. The participants navigated through the captured scene
represented as a virtual model. The researchers compared the sound recorded in the
actual location with that digitally generated. The participants explained their impressions, which enabled Hansung et al. conclude that digitally generated sound could
be of sufficient quality to sufficiently represent real sound in VR [27].
Vorländer discussed the limitations of architectural acoustics in virtual reality.
[2] (Problematic back in 2015, when Vorländer wrote his article, not all of them are
currently seen as limitations.) Among those he mentioned, two seem particularly
important. To map realistic virtual sounds is much more challenging than to generate
visual images. The real-time integration and processing of data from motion-tracking
equipment, audio hardware, signal processing, and audio replication is difficult and
has constraints, because of latencies resulting from computation time. Therefore,
M. W˛ asowicz
5 Acoustics
Visual information—even in itself a powerful means of exploring virtual realities—
can be enhanced by auditory information. In some scenarios this will be more effective than in others, such as in situations in which the sense of hearing can be particularly effective, like in virtual walks through urban or architectural interiors. People are
responsive to the temporal, spectral and spatial acoustic stimuli in the built environment. Requiring large amounts of data, this sensitivity hinders realistic simulation of
interior acoustics, and so, to transmit auditory environment in a persuasive way, highquality measures are needed. Acoustic simulation needs to include sounds affecting
surface materials and architectural features, such as room volume and its structural
properties [2]. So detailed resemblance of sounds does not pertain to all aspects of
acoustic simulation, however. Human perception research has revealed that, exposed
to visual and acoustic stimuli at the same time, people react to the former much more
than to the latter [26]. It is thus the accuracy of visual simulation that makes a difference, and acoustic simulation’s less so: if the visuals are accurately conveyed, even
less accurate acoustics should do the job [27]. Thus, dissimilarities between real and
virtual sound turn out to be less apparent when accompanying visual stimuli. This
is not to say, however, that the industry is happy with inaccurate visual sound only
because it is less important than the visual display it accompanies. Soon, all modern
VR systems exploiting acoustic stimuli will do so with accuracy, searching for the
simulation of real environments in all their aspects.
In order to use auditory support, the user has a sound system fixed to her head:
headphones. The system can be independent of the visual display, but modern HMD
go a step farther, joining the two systems into one whole: they have an in-built audio
output device (Fig. 1). This integration is crucial in terms of immersiveness, because
acoustic representation directly relates to motion, is interactive, and is determined
by the participant’s movements [2].
Recent years have brought about the acknowledgment of how important the
synchronization of spatial audio reproduction with visual information is for
increasing VR immersion. Hansung et al. used the state-of-the-art of VR systems to
reproduce a VR environment with acoustic properties based on a real interior scene
captured by two 360° cameras. The participants navigated through the captured scene
represented as a virtual model. The researchers compared the sound recorded in the
actual location with that digitally generated. The participants explained their impressions, which enabled Hansung et al. conclude that digitally generated sound could
be of sufficient quality to sufficiently represent real sound in VR [27].
Vorländer discussed the limitations of architectural acoustics in virtual reality.
[2] (Problematic back in 2015, when Vorländer wrote his article, not all of them are
currently seen as limitations.) Among those he mentioned, two seem particularly
important. To map realistic virtual sounds is much more challenging than to generate
visual images. The real-time integration and processing of data from motion-tracking
equipment, audio hardware, signal processing, and audio replication is difficult and
has constraints, because of latencies resulting from computation time. Therefore,