Document zQejVg6BvV6mwVbb7ELkwk54g

DISTANCE l 2X 3X INTENSITY'= 10,000,000,000 2,800,000,000 "(APPROXIMATE FIGURES) 1,100,000,000 NOISE CONTROL 8Y DISTANCE Fic 40-1 --As the distance from the noise source increases, the pressure (or in tensity) of the noise decreases faster than its sound level The "intensity" shown here has absolutely no relationship with the sound pressure figures shown below TABLE 40-A SOUND PRESSURE AND DECIBEL VALUES FOR SOME TYPICAL SOUNDS Sound Pressure (mtcrobars) Overall Sound Pressure Level (dB re 0 0002 nucrobar) Example 0 0002 0 Threshold of hearing 000063 10 0 002 0 0063 0 02 20 Studio for sound pictures 30 Soft whisper (5 feet) 40 Quiet office Audiometric testing booth 0 063 50 Average residence Large office 02 60 Conversational speech (3 feet) 063 70 Freight tram (100 feet) 1 0 74 Average automobile (30 feet) 20 80 Very noisy restaurant Average factory 63 90 Subway Printing press plant 20 100 Looms in textile mill Electric furnace area 63 110 Woodworking Casting shakeout area 200 120 Hydraulic press 50 hp siren (100 feet) 2000 140 Jet plane 200,000 180 Rocket launching pad Note that doubling any sound pressure corresponds to an increase of 6 dB in the sound pressure level A change of sound pressure by a factor of 10 corresponds to a change in sound pressure level of 20 dB 1243