Hertz is a linear scale of sound frequency. Pressure is a linear scale of sound intensity.
The ear does not "hear" sounds in a linear fashion, rather it transforms them into a non-linear scale. How does the physiology of the ear contribute to this non-linear perception of sound frequency (pitch) and intensity (loudness)? What is the benefit of a non-linear scale in terms of the range of sounds that we are able to then perceive?