How does one physically measure the decibel level of sound?
In: 3
With a sound meter. It’s a precision microphone with a signal meter.
Sound is changes in air pressure. Pressure is Force applied to area/surface. We can measure how hard air is pushing against surface, and track these changes. After that we can convert this force (N) in pressure units (Pa) and then into units if dBA. This conversation is purely mathematical.
To measure force we use super sensitive scales – a microphone. Air pushes membrane, which moves and this movement is measured. Knowing all the parameters, we know how much force is necessary to move it a given amount.
You measure the changes in air pressure.
dB = 10 log (I/I0) where I is the intensity of the sound you’re trying to measure, and I0 is the
Intensity of sound is I = 2 π^2 f^2 A^2 ρ c
f is the frequency (how often the wave oscillates)
A is the amplitude (how far from ambient pressure the wave oscillates)
ρ is the density of the medium (usually air)
c is the speed of sound in that medium
I0 is simply defined as 10^-12 Watts/m^2 which is the lower threshold of human hearing.
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