Effects of simulated helicopter cabin noise on intelligibility and annoyance

Abstract

Helicopter cabin noise was simulated by combining a broadband signal (pink noise, or PN) with a triad of pure tones (PT) at 650,1900, and 5000 Hz. Each component was presented at four loudness levels (0,60,70, and 80 dB[A]), with all 16 combinations arranged in two unsystematic orders. Intelligibility was measured by means of sentences to be judged as true or false. A male speaker presented 10 sentences at each noise condition. One group of subjects heard the sentences at 50 dB(A) and another group at 55 dB(A). The annoyance of each noise combination was rated by the same subjects on a 5-point scale. Both sources and their interaction were significantly related to reduced intelligibility and increased annoyance at both speech levels. In general, the PN component was more responsible for loss of intelligibility, and the PT component more responsible for annoyance.