Sound-second Scale

(all except usa) for usa inc 20907 canceled replaced by scale, plotting: inc 08929, fiig t144, appl key pb. A thin, flat strip of metal or plastic, having one edge graduated in sound-seconds, and/or tenths of a sound-second. It is used to evaluate the linear distance of time intervals recorded by various previously oriented microphones when the sound is received. Each sound-second graduation is equivalent to 337.6 meters under standard atmospheric conditions, at 50 degrees fahrenheit (10 degrees celcius).