One of the great thing about water is the sound of it. When people explain why they find New York's Paley Park so quiet and restful, one thing they always mention is the water wall. In fact, the water wall is quite loud: the noise level is about 75 decibels close by, measurably higher than the level out on the street. Further more, the sound - taken by itself - is not especially pleasant. They have played tapes to people and asked them what they thought it was. Usually they grimace and say a subway train, trucks on a freeway, or something just as bad. In the park, however, the sound is perceived as quite pleasant. It is white sound and masks the intermittent honks and bangs that are the most annoying aspects of street noise. It also masks conversations. Even though there are many others nearby, you can talk quite loudly to a companion - sometimes you almost have to - and enjoy a feeling of privacy. On the occasions when the water wall is turned off, a spell is broken, and the place seems nowhere as congenial. Or, as quiet.