You are checking the sound level of a noisy \"Cooch\" roll in a pulp and paper p

Question

You are checking the sound level of a noisy "Cooch" roll in a pulp and paper plant. This sound, which is one of the most dangerous in such a plant, is an ear-splitting pure tone, like that of a nearby siren. For this particular Cooch roll the frequency is 1455 Hz. Using a calibrated microphone in a place where a worker might happen to be you observe a signal on your oscilloscope that shows the pressure oscillation at the microphone to have an amplitude of 5.000 Pa. What is the sound level in decibels? (Use 28.0 microPascals as the pressure amplitude at zero decibels.)

Explanation / Answer

Sound intensity I = 10^-3 W/cm² = 1 mW/cm² = 10 W/m². Nowadays the unit of sound intensity is watts per square meter (W/m²). Greetings to your old teacher.Reference sound intensity Io = 10^-12 W/m² (Threshold of hearing) Reference sound intensity level LIo = 0 dB-SIL (Threshold of hearing level) Get sound intensity level LI in dB when entering sound intensity I = 10 W/m² Sound intensity level LI = 10×log (I / Io) dB = 10×log (10 / 10^-12) dB = 130 dB.

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