The anechoic chamber in this building is rated to minus 9.4 decibels, A-weighted, 69,000 times lower in intensity than the quiet of the conference room and eight times lower than zero decibels. Orfield reminds me that zero decibels is not an absolute measurement but simply the point below which a person with unimpaired hearing no longer perceives sound.

George Michelsen Foy, Zero Decibels, loc. 473