  Virtual acoustic environments enable the creation and simulation of realistic
and ecologically valid daily-life situations with applications in hearing
research and audiology. Hereby, reverberant indoor environments play an
important role. For real-time applications, simplifications in the room
acoustics simulation are required, however, it remains unclear what acoustic
level of detail (ALOD) is necessary to capture all perceptually relevant
effects. This study investigates the effect of varying ALOD in the simulation
of three different real environments, a living room with a coupled kitchen, a
pub, and an underground station. ALOD was varied by generating different
numbers of image sources for early reflections, or by excluding geometrical
room details specific for each environment. The simulations were perceptually
evaluated using headphones in comparison to binaural room impulse responses
measured with a dummy head in the corresponding real environments, and partly
using loudspeakers. The study assessed the perceived overall difference for a
pulse, and a speech token. Furthermore, plausibility and externalization were
evaluated. The results show that a strong reduction in ALOD is possible while
obtaining similar plausibility and externalization as with the dummy head
recordings. The number and accuracy of early reflections appear less relevant,
provided diffuse late reverberation is appropriately accounted for.
