A unit called a phon is used to describe human hearing numerically. When phon curves are displayed on a decibel - frequency graph, the curve is ’U" shaped. The higher the decibel level the more the phon curve flattens out.
At very low volume levels we are more inclined to hear only midrange frequencies and not very low or very high frequencies. As the volume increases our hearing changes and we start perceiving low and high frequencies also.
Hearing | Physics (lumenlearning.com)
At very low volume levels we are more inclined to hear only midrange frequencies and not very low or very high frequencies. As the volume increases our hearing changes and we start perceiving low and high frequencies also.
Hearing | Physics (lumenlearning.com)