The contribution of sound source characteristics in the assessment of urban soundscapes

The aim of this research is to characterize the appraisal of urban soundscapes where sound sources are explicitly recognized. A series of three experiments is conducted in a laboratory where subjects listen to twenty 15-s sound samples representing a sound environment along a classical street in Paris. In these samples, listeners can recognize cars, mopeds, motorbikes, buses, birds and human voices. The first experiment collects ratings of the subjective descriptors "prominence, presence and proximity" of sound sources, the second and third respectively obtain assessments of the overall hedonic judgment and of the loudness of the sound samples. Physical parameters of the different sound sources are extracted from the coded L Aeq curves. Multiple regressions provide a good of the relationship between appraisal and subjective descriptors or objective parameters. They show that, by adding the information about sound source characteristics to the perceived loudness or to the Zwicker's Loudness, the percentage of explained variance increases. To investigate the appraisal of other typical urban soundscapes such as market and park, an on-site experiment using the same procedure is carried out during an urban walk divided into sixteen 90-s sequences. Again the percentage of the explained variance of the hedonic judgement is increased by taking into account the sound source characteristics. The prediction of the scale unpleasantness can even be effective based only on objective characteristics of sound sources such as the number of sources or their time ratio of presence. These results are discussed in terms of sound "events" compared to ambient sound.