Study of factors governing intelligibility in multi-speaker environments from an experiment with a large panel of listeners.

The problem of intelligibility in multi-speaker environments is of great interest in different domains of application: the problem of audio communication in military operations engages the safety of people involved in conflicts; regarding occupational health and safety, the issue of noise disturbance in open-plan offices due to conversations is also of prime importance. Recently, a collaboration between the French-German Research Institute of Saint-Louis (ISL) and the French Institute for Occupational Safety and Health (INRS) has led to a large experimental study consisting in evaluating the capabilities of 42 subjects in repeating French sentences in different listening environments. Many factors were changed during the experiment, such as the number, the location and the gender of the speakers, the mode of sound presentation (diotic, dichotic, virtual 3D on headphone, real 3D on loudspeakers), and the presence or the absence of noise. The statistical analyses performed during this study provide significant results as they involved a large number of listeners. For instance, it was demonstrated that at a constant signal to noise ratio, the influence of noise on intelligibility differs according to the mode of sound presentation and that virtual 3D presentation has many advantages over headphones in preserving intelligibility in audio communications.