Pitch or frequency is measured in Hertz and Kilohertz (kHz), while the loudness or amplitude of sound is measured in Decibels. As amplitude increases, intensity also increases. Intensity is the amount of energy a sound has over an area. The more energy a sound wave has, the higher its amplitude or loudness.
A sound you hear in a large area is more intense if you hear it in a smaller area. In other words, the same sound has greater intensity or is louder in a smaller area or in the area where the sound immediately emanates from. This is because the energy of a particular sound distributed throughout a smaller area means more sound waves per unit of space, compared to the same sound distributed throughout a much bigger area. In other words, in layman’s terms, the further away you are from a sound, the less likely you can hear it.
A whisper is about 10 decibels while thunder is 100 decibels. Normal conversation is around 60 decibels, and an operating lawn mower, 100 decibels loud. The weakest sound that can be heard is measured at 0 decibel. There are such things as “decibel meters” which allow one to measure how loud a sound is.