Richter Scales define the magnitude of an earthquakes:
SOUND INTENSITY LEVEL:
Threshold of hearing is the minimum intensity detectable by the human ear. Loudness of sound at the threshold of hearing is equal to zero dB. Threshold of pain is about 120 dB.
pH = - log [H+]
pH: Acidity or alkalinity of liquid, pH level, rangers form 0 to to 14
[H+]: Hydrogen ion concentration, number of moles of hydrogen ions per litre (mol/L)
pH = 7 for distilled water
1 mol = 6.02 x 1023 molecules (Avogadro number)