Computers have difficulty doing what the brain does easily: concentrating on one voice while ignoring other sounds. University of Toronto electrical-engineering professor Parham Aarabi created an algorithm that calculates the difference between the times at which a sound reaches two closely spaced microphones. Based on the delay, the software can determine the direction of speakers and amplify the speech of any one of them; all other conversation is reprocessed into a slight hum. Aarabis invention, which is 30 percent more accurate than other multimicrophone systems, could filter out extraneous voices in cell-phone conversations or enhance voice control in cars.