Helmholtz made the first psychoacoustic observations in hearing

Evidence

Despite the impact that Fechner and Weber have had on the field, neither conducted experiments in hearing. Rather, Hermann von Helmholtz (1821–1894), made some of the first psychoacoustic observations in the auditory modality. His book, Sensations of Tone, published in 1863, served as the foundational text on auditory perception for decades. This book, along with Fechner’s, allowed the evaluation of hearing to be more than scientific observation. Rather, experimentation allowed auditory perception to be quantified under systematic evaluation. We could now connect physical acoustics with the perception of the physical dimensions. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 62