Measuring Sound Intensity(Decibel)

Created for CVCA PhysicsBy

Dick Heckathorn25 April 2K + 5

2m

Wattsin

Area

Power

AreaTime

EnergyIntensity

Definition

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

212101m

Wx

A sound which will displaceparticles of air by a mere

one-billionth of a centimeter has an intensity of

212101m

Wx

Known as the threshold of hearing

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/m2) Intensity (dB)

1 x 10-12 0

1 x 10-11 10

1 x 10 -10 20

Decibel (dB) Scale Intensity Intensity (W/m2) (dB)

1 x 10-12 0 threshold of hearing1 x 10-11 10 normal breathing1 x 10-10 20 average whisper (2m)1 x 10-9 30 empty theatre1 x 10-8 40 residential area-night1 x 10-7 50 quiet restaurant1 x 10-6 60 2-person conversation1 x 10-5 70 busy street traffic1 x 10-4 80 vacuum cleaner

Decibel (dB) Scale Intensity Intensity (W/m2) (dB)

1 x 10-3 90loud stereo

1 x 10-2 100concert hall 13th row

1 x 10-1 110pneumatic chisel

1 120max level rock

group 10 130

threshold of pain1 x 102 140

military jet taking off1 x 103 150

wind tunnel1 x 104 160

instant braking ear drum

Decibel (dB) ScaleWith each increase in intensity of 10-dB, the intensity of sound

increases in intensityby a factor of ten.

Thus if the intensity of sound is increased by 30 decibels, the

intensity is 1000 times greater.

Decibel (dB) Scale

The earplugs providedstate that they reduce

the sound level by 31 decibels.

Thus the intensity of sound is reduced by a factor of 1259.

Sound in the Workplace

The earplugs providedstate that they reduce

the sound level by 31 decibels.

Thus the intensity of sound is reduced by a factor of 1259.