What is the absolute power of a sound with the following….doc

What is the absolute power of a sound with the following intensity levels? 60 dB IL 60 = 10 log (implies) 6 = log 106 = (Therefore) = 10-6 10-12 = 10-6 w/m2 70 dB IL 10-5 w/m2 80 dB IL 10-4 w/m2 110 dB IL 10-1 w/m2 What is the absolute pressure of a sound with the following sound pressure levels? 60 dB SPL 2 104 μPa or 20 103 μPa 70 dB SPL 2 104.5 μPa or 20 103.5 μPa 80 dB SPL 2 105 μPa or 20 104 μPa 110 dB SPL 2 106.5 μPa or 20 105.5 μPa Combining EQUAL intensities from different sources Two sounds A and B have the same intensity of 60 dB IL. When these two sounds are presented together, what is the resulting overall intensity? ** HINT: You cannot add decibel values directly since they are relative values. Hence, the answer to this question is NOT 120 dB IL. You will first need to convert dB to absolute power units, and then work through the problem. Solution In this case, each sound has the same intensity of 60 dB IL. 60 dB IL corresponds to an absolute power of 10-6 w/m2. Combining absolute powers for both sounds, the total absolute power is 2 10-6 w/m2. Converting this back into dB IL, the total intensity is 63 dB IL. Steps: 10 log = 10 log = 10 (log 2 + log 106) = 10 (0.3 + 6) = 6.3 10 = 63 dB IL What would be overall resulting intensity of these two sounds when expressed in dB SPL? **** HINT: Remember the relation p2 ∞ I . Therefore when power is doubled/increased by a factor of 2, pressure only increases by a factor of = 1.414. Solution The absolute pressure corresponding to 60 dB SPL is 2 104 μPa. So the new (combined power) is 1.414 2 104 μPa. Using this in the formula, New SPL = 20 log = 20 log (1.414 103) = 20 (log 1.414 + log103) = 20 (0.15 + 3) = 63 dB SPL If the absolute power is doubled, what is the resulting increase in dB IL? 3 dB If the absolute pressure is doubled, what is the resulting increase in dB SPL? 6 dB Combining UNEQUAL intensities from different sources Two sounds A and