“The frequencies of the notes in a scale—do, re, mi, fa, sol, la, ti, do—sound to us like they’re rising in equal steps. But objectively their vibrational frequencies are rising by equal multiples. We perceive pitch logarithmically.”
Source : Steven Strogatz (2012). “The Joy of x: A Guided Tour of Math, from One to Infinity”, p.65, Houghton Mifflin Harcourt