ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS INTRODUCTION
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS LOGARITHMIC SCALES
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS SOUND INTENSITY LEVEL
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
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
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
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 (0.48 + 8) = 10 (8.48) = 84.8 DECIBELS STEP 4
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS STEP 5: CHECK YOUR ANSWER. 83 – 80 = 3 83 + 2 = 85 dB STEP 5
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) = 82.03 DB INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS MULTIPLE SOURCES
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS INVERSE SQUARE LAW
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS INVERSE SQUARE LAW
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
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS SAMPLE PROBLEM
ACOUSTICAL CALCULATIONS INTRODUCTION LOGARITHMIC SCALES SOUND INTENSITY LEVEL ADDING DECIBELS INVERSE SQUARE LAW SAMPLE PROBLEMS SAMPLE PROBLEM
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’ -6 + -6 + -6 = -18 90 – 18 = 72 DB CHECKING YOUR ANSWER