A laboratory investigation into the effect of quiet-time interval between aircraft noise events on overall noisiness.

In order to investigate the effect of the quiet-time interval between aircraft noise events on the overall negative impression of aircraft noise, psychological experiments were conducted in which the quiet-time interval was varied and the number of events and duration of each stimulus were taken into account. For equal A-weighted equivalent continuous sound pressure level (LAeq) among the stimuli, it was found that overall noisiness decreased as the quiet-time interval ratio of the stimulus was increased. It was also found that the correlation between overall noisiness and LAeq was improved by adjusting for the quiet-time interval ratio or the number of events included in the stimuli, especially when participants paid attention to changes in the instantaneous noise level. This study reveals that LAeq is a good basis for evaluating the negative impressions of aircraft noise, but that correcting for the quiet-time interval and/or number of flights improves the correlation between LAeq and the negative impression in such aircraft noise situations.

Overall judgment of loudness of time-varying sounds.

Listeners can judge the overall loudness of time-varying sounds quite easily, i.e., assign a single value that represents the loudness of the entire sound. This holds even if the duration is long and the judgment includes memory effects. Different metrics for calculating overall loudness have been developed. They agree that overall loudness is higher than the mean of loudness over time. Percentiles like the N5, the loudness being exceeded 5% of the time, are adopted by ISO 532-1. In the present study the concept of an energy mean known from level measurements (ISO 1996-1) was applied to the loudness domain. This equivalent continuous loudness level, LLP, was compared to the N5 using a set of real-world sounds that was orthogonal between the two metrics over a wide dynamic range of 30 phon. Cross-modality matching with line length was used in three experiments with a focus on either the overall judgment of loudness, continuous judgment while a sound was played, or both. The LLP showed considerably higher correlations with overall judgments than N5. Comparing continuous instantaneous judgment with calculated instantaneous loudness suggests that the participants might have focused on the sounds' prominent portions.