After having tried to look for answers as to why the ear hears different pitches for soft and loud 100 Hz tones, here's what I've found :
Pitch of the low frequency tone decreases with the increase in intensity, and pitch of the high frequency tone increases with increase in intensity.
This is applicable to sustained pure tones and not impulses.
There was an article that summarized this behavior as - "due to the resonant characteristics of the inner ear".
I would really love someone to explain as to WHY the ear responds this way. WHY does it perceive this pitch shift with increase in intensity.
https://asa.scitation.org/doi/10.1121/1.1915715 - Article suggests that the change in pitch with intensity is due to the resonant characteristics of the ear.
http://romainbrette.fr/WordPress3/wp-content/uploads/2017/02/Pitch.pdf - Article contains discussion based on experiment carried out to investigate the pitch intensity relationship.