A relationship that it's easy of understanding when it comes to numbers. For instance, in a low pitch piano key, the first A key, it's a frequency of 27.5 hertz but the highest A in a concert piano, named A7 goes to 3520 hertz!
From A6 to A7 it's a difference of 1760 hertz, from A5 to A6 that quantity divided by two until A0 to A1 then with a mere difference of 27.5 hertz.
A good reason why the human ear system finds more difficulties handling low frequencies than higher ones. Thus the differences from semitones in a low pitch scenario must be more subtle because music also has a mathematical representation. In paper all is clear.
You need to divide an entire octave with its semitones in 27.5 Hz, so approximately 27, 29, 30, 32, 34 and so on, but nonetheless the ear system is capable of doing it accurately. Sometimes with a bit of training, or simply who can difference those notes naturally.