Ottorino Respighi
(1879
- 1936)
| E = Energy | |
| t = Time | |
| P = Power | |
| P = E/t | |
| =Joule/s = Watt = W |
| Gasoline | |
| Solar Energy | |
| P = Power | |
| S = Surface Area | |
| I = Intensity | |
| I = P/S (W/m2) |
| Example: over a 5 minute period 3 x 105 Joules of energy from the sun hit a surface. What is the power? |
| I2/I1 = (r1/r2)2 | |
| or | |
| I ~ 1/r2 |
| Audio demo Track 11 | |
| If the Intensity at 25 cm was 8 x 10-6 W/m2, what are the intensities at 50 cm, 1 m, and 2 m? |
| Sound Source Intensity (W/m2) | |
| Saturn rocket at 50 m 108 | |
| Jet engine at 10 m 103 | |
| Jet engine at 50 m 10 | |
| SST takeoff at 500 m; Pneumatic drill 100 = 1 | |
| Amplified Rock Music 10-1 | |
| Machine shop 10-2 | |
| Jackhammer at 1 m; Subway train 10-3 | |
| Factory 10-4 |
| Sound Source Intensity (W/m2) | |
| City traffic 10-5 | |
| Normal conversation at 1 m 10-6 | |
| Office; Classroom; Quiet auto interior 10-7 | |
| Library 10-8 | |
| Empty auditorium; City street, no traffic 10-9 | |
| Whisper at 1 m 10-10 | |
| Rustle of leaves; Falling pin 10-11 | |
| Limit of audibility 10-12 |
| If I2/I1 = 10, then, | |
| by definition | |
| SIL2 - SIL1 = 10 dB |
| SIL2 - SIL1 = 10 log(I2/I1) | |
| thus if | |
| SIL2 - SIL1 = 20 then I2/I1=100 | |
| SIL2 - SIL1 = 30 then I2/I1=1000 | |
| SIL2 - SIL1 = 40 then I2/I1=10,000 |
| Sound Source Intensity/SIL | |
| Saturn rocket at 50 m 108 = 200 dB | |
| Jet engine at 10 m 103 = 150 dB | |
| Jet engine at 50 m 10 = 130 dB | |
| SST takeoff at 500 m; Pneumatic drill 100 = 120 dB | |
| Amplified Rock Music 10-1 = 110 dB | |
| Machine shop 10-2 = 100 dB | |
| Jackhammer at 1 m; Subway train 10-3 = 90 dB | |
| Factory 10-4 = 80 dB |
| Sound Source Intensity/SIL | |
| City traffic 10-5 = 70 dB | |
| Normal conversation at 1 m 10-6 = 60 dB | |
| Office; Classroom; Quiet auto interior 10-7 = 50 dB | |
| Library 10-8 = 40 dB | |
| Empty auditorium; City street, no traffic 10-9 = 30 dB | |
| Whisper at 1 m 10-10 = 20 dB | |
| Rustle of leaves; Falling pin 10-11 = 10 dB | |
| Limit of audibility 10-12 = 0 dB |
| Two sounds have a ratio of intensities of 4,700. Find the difference in SIL for the two sounds. | |
| If the difference in SIL for two sounds is 8 dB, what is the ratio of the intensities? |
| Audio demo Tracks 8-10 |
| SIL (dB) Occupational Occasional | |
| 80 No limit 4 hours | |
| 85 No limit 2 hours | |
| 90 8 hours 1 hour | |
| 95 4 hours 30 minutes | |
| 100 2 hours 15 minutes | |
| 105 1 hour 8 minutes | |
| 110 30 minutes 4 minutes | |
| 115 15 minutes 2 minutes |
| In traditional music, the sound intensity level is usually in the range of 45 to 95 dB. | |
| dB meter |
| What happens if we add a 60 dB sound to a 70 dB sound? | |
| 60 dB + 70 dB \ 120 dB!!! | |
| Instead, Intensities Add. | |
| Ic = I1 + I2 |
| What happens if we add a total of n sources of sound having the same SIL? |