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Effect of listener head orientation on speech reception threshold in an automotive environment

2022; Elsevier BV; Volume: 193; Linguagem: Inglês

10.1016/j.apacoust.2022.108782

1872-910X

Linda Liang, Guangzheng Yu, Huali Zhou, Qinglin Meng,

Vehicle Noise and Vibration Control

The head orientation of the listener significantly affects speech intelligibility (SI) in automobiles due to the effect of binaural listening and special acoustic conditions such as early reflections and seat-back occlusions. However, this issue has not been studied with subjective tests yet. This study investigates SI with various head orientations of a listener in automobiles with an subjective experiment. The sentence speech reception thresholds (SRT) in Mandarin Chinese are measured via headphones virtually in an automobile environment, and compared with results in a weak-reflective listening room. A virtual speaker is located in the front-passenger seat, the right-back seat and the left-back seat in sequence, by convolving the target speech with corresponding binaural room impulse responses measured on a dummy head in the driver's seat with five head orientations. Result shows that the SRT variations caused by head orientations are up to 5 dB in automobile, lower than that of 9 dB in listening room. Under various head orientations, the SRT in automobile decreases as the virtual speaker moves closer to the front lateral direction, which is similar to the change rule in listening room that is mainly determined by the effect of binaural listening. Overall, a lower SRT in automobile can be obtained when the listener in the driver seat turns their head inward, i.e., towards the right. In comparison with the result in listening room, early reflections improve SI in automobile by an SRT decrease of up to 3.5 dB, while seat-back occlusions reduce SI by an SRT increase of up to 5.3 dB. The early reflections play a more significant role when the listener is in an adverse position, e.g., for the head orientations and speaker locations making direct sounds difficult to reach the listener's ears. Comparison between the SRTs based on speech transmission index (STI) and STI-SI models and the SRTs measured by subjective experiment indicates that the STI-based objective method only partially expresses the variation in SI obtained from subjective experiment, and the difference between the subjective results and the objective results is mainly caused by the inapplicability of the STI-SI models derived from the traditional room in the automotive environment. The present work is relevant to understanding the combined effect of various factors on SI under such a special acoustic condition in automobile.