| Sound pressure is a physical size and can therefore be measured. The intensity at which a person perceives sound pressure is a physiological size that depends on the sense of hearing.
The level of loudness is an empirically determined size. The perception of loudness has been tested in series of experiments with different people and an average value formed. The level of loudness is given in Phon.
At 1000 Hz the sound intensity level matches the unassessed sound pressure level. The sound intensity level can not be measured with technical instruments. This is why comparative measurements are very difficult, if not impossible. |