Speech intelligibility improvement in car noise environment by voice transformation

The typical application targeted by this work is the intelligibility improvement of speech messages when rendered in car noise environment (radio, message alerts,…). The main idea of this work is to transform the original speech to “Lombard” speech or more precisely to simulate some of the strategies followed by humans to render their speech clearer when they are surrounded by noise. Three main effects are considered in this work, namely non uniform-time scale modification, formant shifting and a combination of these modifications along with energy redistribution between speech regions. All effects are studied with specific transformations for voiced and unvoiced segments. The proposed modifications are then evaluated by means of subjective and objective tests. The results of these tests conducted with normal hearing and impaired listeners demonstrate the potential of the selected transformations for voice intelligibility improvement.