The relationship between speech intelligibility and the assessment of noise annoyance

When thinking about noise annoyance, the tendency is to imagine a person’s rest being disturbed by noise. Although this idea is not formulated explicitly, the majority of traditional experiments implicitly assume that absence of activity during rest represents the typical situation in which noise annoyance should be studied. We propose that research should be extended to different kinds of activities. This study focuses on one kind of activity: verbal communication. Our hypothesis is that the assessment of difficulty with speech comprehension can be replaced by a speech intelligibility measure, which could assess annoyance experienced during communicative activities. Finally, we would like to find out how noise annoyance disturbs communicative activity, and to compare this with annoyance experienced during rest. To test our hypothesis, two psychoacoustic experiments were performed. In Experiment I, speech intelligibility was measured for eight environmental noises at seven signal-to-noise ratios (SNRs). For these SNR values, the participants assessed their difficulty with speech comprehension. This established the relationships between the intelligibility functions and the difficultly in speech comprehension for all the investigated noises. The results of Experiment I show that the potential noise annoyance rating could be predicted on the basis of the speech intelligibility scores, as they give much smaller inter-individual differences between participants than an annoyance assessment test. In Experiment II, the standard “resting” method of noise annoyance assessment was applied to the same eight noises. A comparison of the results indicated a correlation between the annoyance ratings obtained in both the experiments. Some limitations of this approach are also discussed in the paper.