Unwanted wanted sounds Perception of sounds from water structures in urban soundscapes

Sammanfattning: Water structures, for example, fountains, are common design elements in urban open public spaces. Their popularity is probably explained by their visual attractiveness. Less is known about how the sounds of water struc-tures influence the urban soundscape. This thesis explores the potential ef-fects of water sounds on urban soundscapes based on the character of water sounds. Three psychoacoustic studies were conducted in which listeners rated the perceptual properties of various water sounds. Study I found that water sounds had a limited ability to mask traffic noise, as the frequency composition of the sounds resulted in road-traffic noise masking fountain sounds more than the reverse. A partial loudness model of peripheral audito-ry processes overestimated the observed masking effect of water sound on road-traffic noise, and it was suggested that this was related to central pro-cesses, in particular, target/masker confusion. In Study II, water sounds of different degrees of perceived pleasantness were mixed with road-traffic noise to explore the overall effect on soundscape quality. The overall pleas-antness was increased substantially by adding a highly pleasant water sound; however, less pleasant water sounds had no effect or even reduced overall pleasantness. This result suggests that the perceptual properties of water-generated sounds should be taken into consideration in soundscape design. In Study III, this was explored by analyzing a large set of recordings of sounds of water fountains in urban open spaces. A multidimensional scaling analysis of similarity sortings of sounds revealed distinct groups of percep-tually different fountain sounds. The group of pleasant fountain sounds was characterized by relatively low loudness and high fluctuation strength and tonality, generating purling and rippling sounds. The group of unpleasant fountain sounds was characterized by high loudness and low fluctuation strength and tonality, generating a steady-state like noisy sound.. A joint result of all three studies is that sounds from water structures with a high flow rate (i.e., a large jet and basin in Study I, a waterfall in Study II, and large fountains in Study III) generating a steady-state noisy sound should be avoided in soundscape design. Instead, soundscape design might better focus on more fluctuating water sounds, which were considered more pleasant in both studies II and III. A general conclusion from this thesis is that water-generated sounds may be used to improve the soundscape, but that great care must be taken in selecting the type of water sound to use.