Page 52 - Spring2020

Virtual Sounds
field and the comparison of standing singers with moving singers in processions.
Noise Impact on Auditory Attention: Architectural Acoustics Meets Psychoacoustics
The objectives in this example are investigations of methods
for simulating sound insulation of complex architectural structures and application in cognitive science. It includes predictions of direct and flanking transmission sound energy paths in the building structures based on standardized insu- lation metrics and, from this, development of VR-rendering techniques for the interactive auralization of such structures. Calculation procedures and models have been developed for the characterization of the impact of airborne and structure- borne sounds in building acoustics. These models, based on certain assumptions and simplifications, incorporate typical room-to-room situations for predicting insulation metrics and sound transmission across adjacent rooms. The simu- lation was used for auralization in dynamically varying scenarios at interactive rates and was finally presented in
VR with HMDs.
Historically, the study of the effective protection of humans from noise in buildings (e.g., apartments, office, classrooms) used subjective ratings that were combined with direct assessments of the noise (loudness, annoyance scales) in psy- choacoustic experiments or in questionnaires. Such tests, in fact, draw the test subject’s attention and concentration to the sound event, forming an implausible laboratory or field situ- ation. In contrast to these sound-focused procedures applied in the laboratory or in the field, in real life, background noise
from neighbors, building equipment, and traffic is present while people are engaged in their normal activities such as working, learning, resting, and so on. Thus, the important question is the impact of real-life background noise on cog- nitive performance.
In a recent VR application in the game engine Unity, differ- ent background speech conditions, convolved with sound insulation filters of adjacent office rooms, were presented in a virtual office environment where the effects on cognitive per- formances and subjective ratings were measured (Figure 5). This exemplary study promises new options for research on noise effects by the use of virtual built environments that are of high plausibility and unlimited variability (Imran et al., 2019).
The Human Factor: Plausibility, Immersion, and Illusion All Meet Psychological Acoustics
Whatever the virtual scene and the sound will be (music,
speech, noise), the user should feel present in the virtual environment to the point of feeling immersion in the sound (Figure 6). Immersion is defined by Lombard and Ditton (1997) as a partial aspect of “presence” in two levels of percep- tion. The first level mainly depends on stimulating the senses by technology, while the second level refers to the acceptance of the virtual environment by the human. Slater and Wilbur (1997) define immersion as the extent to which simulated environments are capable of conveying an inclusive, extensive, surrounding, and living illusion of reality to the senses of a human. There is, however, no standard definition. Indeed, Witmer and Singer (1998) rejected the exclusive loca- tion of immersion at the level of technology. They refer
Figure 5. Virtual acoustic environments (VAE) in architectural acoustics for research in a selective attention task in cognitive science for the evaluation of work performance under background noise from the adjacent office room. Left: 3-D model of the Institute of Technical Acoustics (ITA) building with a view into the test room. Right: test subject solving the selective attention task (Imran et al., 2019). See video at bit.ly/2O73xvG.
52 | Acoustics Today | Spring 2020