Sensing subtle sounds Sensing subtle sounds (January 25, 2006)

Caption with Dave Boyce picture in print edition: This man has his hand raised for a reason: Using a tape recorder and a microphone 1,000 times more sensitive than the human ear, acoustics consultant Timothy Brown is recording equipment noise outside The Sequoias retirement community in Portola Valley for later analysis. Mr. Brown, who works for San Francisco acoustics firm Charles M. Salter Associates, is searching for a subtle low-frequency hum that has disturbed the nights of some Portola Valley residents since August 2005.

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