Speech intelligibility and speech quality of modified loudspeaker announcements examined in a simulated aircraft cabin

Abstract

Acoustic modifications of loudspeaker announcements were investigated in a simulated aircraft cabin to improve passengers’ speech intelligibility and quality of communication in this specific setting. Four experiments with 278 participants in total were conducted in an acoustic laboratory using a standardised speech test and subjective rating scales. In experiments 1 and 2 the sound pressure level (SPL) of the announcements was varied (ranging from 70 to 85 dB(A)). Experiments 3 and 4 focused on frequency modification (octave bands) of the announcements. All studies used a background noise with the same SPL (74 dB(A)), but recorded at different seat positions in the aircraft cabin (front, rear). The results quantify speech intelligibility improvements with increasing signal-to-noise ratio and amplification of particular octave bands, especially the 2 kHz and the 4 kHz band. Thus, loudspeaker power in an aircraft cabin can be reduced by using appropriate filter settings in the loudspeaker system.

Abstract

Practitioner Summary: Acoustic modifications of loudspeaker announcements were examined in a simulated aircraft cabin via psychological methods with the aim of improving speech intelligibility and subjective speech quality. The findings led to recommendations for improvements of announcement systems concerning sound pressure level and frequencies according to the noise in different cabin sections.

Keywords::

• speech intelligibility
• sound design
• loudspeaker announcements
• aircraft cabin

Acknowledgements

This work was supported by LuFo IV (4th Aviation Research Program) of the German Ministry of Economics and Technology. We thank our colleagues at the Institute of Aerospace Medicine and the Institute of Aerodynamics and Flow Technology at the German Aerospace Center for their assistance in the experiments.