Ohm proposed it and Helmholtz elaborated it in a book he published about "sound sensations", which I suppose would be called "psychoacoustics" in modern parlanc

Ohm proposed it and Helmholtz elaborated it in a book he published about "sound sensations", which I suppose would be called "psychoacoustics" in modern parlance. I found it online [1] and let Google translate it [2]. [1] https://psychologie.lw.uni-leipzig.de/wundt/opera/helmhltz/toene/TonEmpIn.htm https://psychologie.lw.uni-leipzig.de/wundt/opera/helmhltz/t... [2] https://psychologie-lw-uni--leipzig-de.translate.goog/wundt/opera/helmhltz/toene/TonEmpIn.htm?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp https://psychologie-lw-uni--leipzig-de.translate.goog/wundt/...