1. Measuring Sound Intensity (Decibel) Created for CVCA Physics By Dick Heckathorn 25 April 2K + 5

2. Definition The faintest sound which the typical human ear can detect has an intensity of

3. A sound which will displace particles of air by a mere one-billionth of a centimeter has an intensity of Known as the threshold of hearing

4. Decibel (dB) Scale This scale is a logarithmic scale used for measuring the intensity of sound. The threshold of hearing is assigned a sound level of zero decibels. Intensity (W/m 2 )Intensity (dB) 1 x 10 -12 0 1 x 10 -11 10 1 x 10 -10 20

5. Decibel (dB) Scale Intensity Intensity (W/m 2 ) (dB) 1 x 10 -12 0threshold of hearing 1 x 10 -11 10normal breathing 1 x 10 -10 20average whisper (2m) 1 x 10 -9 30empty theatre 1 x 10 -8 40residential area-night 1 x 10 -7 50quiet restaurant 1 x 10 -6 602-person conversation 1 x 10 -5 70busy street traffic 1 x 10 -4 80vacuum cleaner

6. Decibel (dB) Scale Intensity Intensity (W/m 2 ) (dB) 1 x 10 -3 90loud stereo 1 x 10 -2 100concert hall 13 th row 1 x 10 -1 110pneumatic chisel 1120max level rock group 10130threshold of pain 1 x 10 2 140military jet taking off 1 x 10 3 150wind tunnel 1 x 10 4 160instant braking ear drum

7. Decibel (dB) Scale With each increase in intensity of 10-dB, the intensity of sound increases in intensity by a factor of ten. Thus if the intensity of sound is increased by 30 decibels, the intensity is 1000 times greater.

8. Decibel (dB) Scale The earplugs provided state that they reduce the sound level by 31 decibels. Thus the intensity of sound is reduced by a factor of 1259.

9. Sound in the Workplace The earplugs provided state that they reduce the sound level by 31 decibels. Thus the intensity of sound is reduced by a factor of 1259.