1. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
INTRODUCTION

2. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
LOGARITHMIC SCALES

3. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
SOUND INTENSITY LEVEL

4. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
DETERMINE THE COMBINED SOUND INTENSITY AND INTENSITY LEVEL FOR AN 80 DECIBEL AND AN 83 DECIBEL SOUND SOURCE.
SIL = 10 LOG I1/Io
80 = 10 LOG I1/10-16
8.O = LOG I1/10-16
108 = I1/10-16
I1 = (10-16) 108
I1 = 10-8 WATT/CM2
STEP 1

5. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
STEP 2: CONVERT THE 83 DECIBELS FROM A SOUND INTENSITY LEVEL INTO A SOUND INTENSITY.
SIL = 10 LOG I2/Io
83 = 10 LOG I2/10-16
8.3 = LOG I2/10-16
2 X 108 = I2/10-16
I2 = (10-16) 2 X 108
I2 = 2 X 10-8 WATT/CM2
STEP 2

6. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
STEP 3: ADD THE TWO SOUND INTENSITIES TOGETHER.
ITOTAL = I1 + I2
= (1 X 10-8) + (2 X 10-8)
= 3 X 10-8 WATTS/CM2
STEP 3

7. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
STEP 4: CONVERT THE COMBINED SOUND INTENSITY INTO DECIBELS
SIL = 10 LOG ITOTAL/I0
= 10 LOG 3 X 10-8/10-16
= 10 ( LOG 3 + LOG 108)
= 10 ( )
= 10 (8.48)
= 84.8 DECIBELS
STEP 4

8. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS

9. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS

10. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
STEP 5: CHECK YOUR ANSWER.
83 – 80 = 3
= 85 dB
STEP 5

11. ACOUSTICAL CALCULATIONS
FOR THE ADDITION OF SEVERAL SOURCES OF IDENTICAL VALUE, USE THE FORMULA:
SIL (TOTAL) = SIL (SOURCE) + 10 LOG (NUMBER OF SOURCES)
EXAMPLE:
WHAT WOULD THE SOUND INTENSITY LEVEL BE IN A ROOM OF EIGHT PRINTERS, EACH PRODUCING 73 DECIBELS?
SIL (TOTAL) =73 DB + 10 LOG 8
= 73 DB + (10 x 0.903)
= DB
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
MULTIPLE SOURCES

12. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
INVERSE SQUARE LAW

13. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
INVERSE SQUARE LAW

14. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
IF THE SOUND INTENSITY LEVEL OF A CAR HORN IS 90 DB AT 10 FEET AWAY, WHAT WILL BE THE SOUND INTENSITY LEVEL AT 80 FEET AWAY?
SAMPLE PROBLEM

15. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
SAMPLE PROBLEM

16. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
SAMPLE PROBLEM

17. ACOUSTICAL CALCULATIONS
INTRODUCTION
LOGARITHMIC SCALES
SOUND INTENSITY LEVEL
ADDING DECIBELS
INVERSE SQUARE LAW
SAMPLE PROBLEMS
A RULE OF THUMB FOR CHECKING SOUND PROPAGATION CALCULATION IS THAT EVERY TIME THE DISTANCE FROM THE SOURCE DOUBLES THE SOUND INTENSITY LEVEL DECREASES BY SIX DECIBELS.
THEREFORE:
10’ TO 20’; 20’ TO 40’; 40’ TO 80’
= -18
90 – 18 = 72 DB
CHECKING YOUR ANSWER