New Scientist: Humans can be acutely sensitive to certain odors, particularly those perceived to be unpleasant. Now a pair of researchers has developed a mathematical model to rate smells on a numerical scale based on their physical and chemical properties. Canceling out a particular smell requires a compound of equal and opposite rating, such that the two combined yield a zero score overall. Thus, rather than try to mask an existing smell with one that is more powerful, they propose creating the olfactory equivalent of white noise. According to their simulations, eliminating the notoriously pungent odor of an onion, for example, would require a blend of 38 different compounds. Next they plan to work on a device that would put the theory to the test.