1

Intensity

• Scales• Exponents• Logarithms• dB• dB SPL

2

Scales

• Linear

• Ratio

3

Exponents

• Shorthand method of displaying very large or small numbers

• Numbers greater than 1 involve positive exponents

• Numbers less than 1 involve negative exponents

4

Logarithms

• Base 10 logarithms used in the decibel• Examples

• 1000 = 10 4 = 4• 1 = 10 0 = 0• .001 = 10 -3 = -3

5

Decibel

• Standard measure of intensity• dB = 20 (log Po / Pr)

• Where Po = pressure output• Where Pr = pressure reference

6

dB SPL

• Decibel Sound Pressure Level (dB SPL)• Standard reference level.• dB SPL = 20 (log Po / 20µPa)

• Where Pa = Pascal (measure of force)

• dB SPL = 20 (log Po / .0002 dynes/cm2)• Where dynes are a measure of force

7

Summary