There have been nearly a dozen papers published in the last 5 years which compare community response to noise from several different sources such as road and rail traffic. This paper draws on those and other studies to address three questions. First, is the variation in results simply due to random sources or measurement error, such that use of an "average" dose-response curve is appropriate, or is there some identifiable systematic variation? Second, what characteristics of the noise or community might lead to systematic variation, if there is any? Third, under what conditions is it reasonable to use an average function, even if there are systematic variations? Both of the first two questions receive only tentative answers on the basis of available studies. Although the evidence shows different functions for different sources (e.g., rail and road noise), for different types of one source (e.g., air carrier airports and general aviation airports), and even for different studies at the same location (e.g., Heathrow), the evidence is not sufficiently strong to totally reject the idea that all of this is just random variation about an "average" response. As yet, there is no clear identification of what acoustical or community factors explain the differences in response, so it is sensible simply to use the type of source (i.e., road, rail, or air traffic noise) to categorize the differences. The answer to the third question, then, is that an "average" dose-response curve is useful in the face of limited information--that is, when we cannot specify precisely the conditions calling for different functions.