But what are "tolerable levels?" At a meeting held in November 2003 by the Federal Aviation Administration's Office of Environment and Energy, government and industry groups discussed the latest boom-reducing technologies and designs. Among the offerings was a NASA presentation called "Human Response to Sonic Booms," which highlighted the science and the sociology behind the public's acceptance of noise. To gauge tolerance levels, researchers performed a variety of tests, including having subjects sit inside a sonic boom simulator--a cozy audio-modified "shed." But these physiological measurements are only part of the story. NASA officials say that people's attitudes toward the source of the noise play a big role in how willing they are to put up with it. For example, people are less likely to accept a sonic boom if they are concerned about its impact on wildlife, if they have negative attitudes toward the military, or if they live in a rural area where the noise would be more pronounced. Until low-sonic-boom aircraft move beyond the development stage, making it possible for tests to be conducted in the real world, public tolerance of the boom will remain an open question.