Loudness
Part of speech: noun
Definition: the perceptual strength or amplitude of sound pressure, measured in sones or phons the physical strength of the sound pressure level, measured in decibels
Intensity
Part of speech: noun
Definition: the quality of being intensethe degree of strengthtime-averaged energy flux (the ratio of average power to the area through which the power "flows"); irradiancecan mean any of radiant intensity, luminous intensity or irradiancesyn. radianceThe severity of an earthquake in terms of its effects on the earth's surface, and buildings. The value depends on the distance from the epicentre, and is not to be confused with the magnitude.
Example sentence: In our nature, however, there is a provision, alike marvelous and merciful, that the sufferer should never know the intensity of what he endures by its present torture, but chiefly by the pang that rankles after it.