Effects of indoor water sounds on intrusive noise perception and speech recognition in rooms

While water sounds have been used for soundscape improvement, little is known about their applicability in indoor environments. In order to investigate the effects of indoor water sounds on noise perception, a simple indoor water fountain system was used to produce water sounds over three different types of indoor intrusive noise (traffic noise, higher frequency dominated noise of a chair scraping the floor above, lower frequency dominated impact noise of a man running on the floor above) and speech in a test laboratory. Intrusive noise perception (annoyance and pleasantness) and speech recognition (KS-MWL-A) were assessed with three water sound levels (40, 50, 60 dBA) at two exposure times (immediate and 50 min) of water sounds by 54 participants. Short-term exposure to indoor water sounds improved the pleasantness of intrusive noise without increasing annoyance except lower frequency dominated impact noise. The increase in exposure time to indoor water sounds did not affect intrusive noise perception and speech recognition. The water to noise ratio significantly affected annoyance and pleasantness of traffic noise only; however, the level of water sounds did not significantly affect intrusive noise perception. Indoor water sounds can be used to improve intrusive noise perception except lower frequency dominated floor impact noise with no adverse effects on speech recognition dependent upon the speech to water sound ratio. Practical application: This simple indoor water fountain can be directly applied to small offices or rooms to improve intrusive noise perception. When the simple fountain produces water sounds in a room, pleasantness of traffic noise throughout window openings or higher frequency dominated noise such as chair scraping noise can be improved without increment of annoyance and decrement of speech recognition. Short-term exposure to indoor water sounds is effective to increase pleasantness of the intrusive noises.