You just started a summer internship at a manufacturing plant. On your first day, you notice constant high noise levels on the shop floor. You want to apply what you learn in ISEN 630 regarding hearing and noise, so you start asking your co-workers what they think of the constant noise. Mostly you hear complaints from the staff about the noise, and headaches. The room measures 75 ft by 105 ft and the ceiling is unpainted, smooth concrete. Noise level in this room is assessed at 90 dB. A salesman from the Muffleit Manufacturing Co. drops in, and tells you that if you install Muffle-Right acoustic ceiling tiles you will reduce the noise sound pressures (in dynes) by 75%. What would be the predicted noise level in dB if you have the ceiling tiles installed?

The equation used is dB = 20log(p/p₀)

The answer is that the reducttion in dB = 20log(0.25) = -12.04

so, 90 +(- 12.04) = 77.96dB = the new noise level if ceiling tiles installed.

Can someone please explain to me why this is because with the dB = 20log(p/p₀) equation I thought that you must use the reference pressure of p₀ = 0.0002 dyne/cm² . Even if that's not the case and we don't use 0.0002 because we are just finding dB change of a ratio... if the reduction is 0.75 why do we find 0.25 and add it to the current dB? I hope my question is clear, thank you.

Answer rating: 100% (QA)

The Equation has a factor approach P is the current changed noise leve... View the full answer