Degradation of Front-Back Spectral Cues Induced by Tactical Communication and Protective Systems
Invited paper
ISL - APC
Wednesday 3 june, 2015, 09:20 - 09:40
0.4 Brussels (189)
Abstract:
In many military or civilian situations, it is important to be able to
communicate, perceive and interpret the acoustic environment while still
being protected against damaging continuous and impulsive noises. Tactical
communication and protective systems (TCAPS) correctly protect the
listener’s ears from hazardous sounds and preserve intelligibility, thus
allowing low-level speech communication. Our actual problematic deals with
the conservation of the sound localization capability when wearing TCAPS. A
previous subjective experiment, in which listeners were asked to localize
sound sources in the horizontal plane with and without acoustically
transparent earmuffs, highlighted that wearing the protection significantly
degraded the listeners’ localization capability. This degradation was mainly
caused by front-back confusions. It has therefore been concluded that the
protector altered the spectral cues used in open ear condition for the
resolution of front-back ambiguities.
In order to characterize the TCAPS-induced degradation of the spectral cues,
directional transfer functions (DTFs) have been measured in the horizontal
plane on an artificial head with and without TCAPS: passive and active
earplugs and acoustically transparent earmuffs. DTFs are first averaged in
each quadrant and the number of measurement positions which are needed in
each quadrant is discussed. Front-back spectral cues are then defined,
separately for ipsilateral and contralateral side, as the difference between
front and back mean DTF. Results confirm that ipsilateral cues are
preponderant for the resolution of front-back ambiguities in open ear
condition, and show that wearing TCAPS affects not only ipsilateral but
contralateral spectral cues. An index characterizing the alteration of the
spectral cues allows the ranking of the different TCAPS according to how
they induce degradation of the sound localization capability.