  Underground stations are a common communication situation in towns: we talk
with friends or colleagues, listen to announcements or shop for titbits while
background noise and reverberation are challenging communication. Here, we
perform an acoustical analysis of two communication scenes in an underground
station in Munich and test speech intelligibility. The acoustical conditions
were measured in the station and are compared to simulations in the real-time
Simulated Open Field Environment (rtSOFE). We compare binaural room impulse
responses measured with an artificial head in the station to modeled impulse
responses for free-field auralization via 60 loudspeakers in the rtSOFE. We
used the image source method to model early reflections and a set of
multi-microphone recordings to model late reverberation. The first
communication scene consists of 12 equidistant (1.6 m) horizontally spaced
source positions around a listener, simulating different direction-dependent
spatial unmasking conditions. The second scene mimics an approaching speaker
across six radially spaced source positions (from 1 m to 10 m) with varying
direct sound level and thus direct-to-reverberant energy. The acoustic
parameters of the underground station show a moderate amount of reverberation
(T30 in octave bands was between 2.3 s and 0.6 s and early-decay times between
1.46 s and 0.46 s). The binaural and energetic parameters of the auralization
were in a close match to the measurement. Measured speech reception thresholds
were within the error of the speech test, letting us to conclude that the
auralized simulation reproduces acoustic and perceptually relevant parameters
for speech intelligibility with high accuracy.
