The MP3 lossy audio data compression algorithm takes advantage of a perceptual limitation of human hearing called auditory masking. In 1894, the American physicist Alfred M. Mayer reported that a tone could be rendered inaudible by another tone of lower frequency. In 1959, Richard Ehmer described a complete set of auditory curves regarding this phenomenon. Ernst Terhardt et al. created an algorithm describing auditory masking with high accuracy. This work added to a variety of reports from authors dating back to Fletcher, and to the work that initially determined critical ratios and critical bandwidths.
Who was the physicist to report that a tone could be rendered inaudible.
Alfred M. Mayer
The context mentions that Alfred M. Mayer reported in 1894, a tone could be rendered inaudible by another tone of lower frequency. The mentioned work is further elaborated upon and described as accurate through the description of auditory masking curves etcetera.

Therefore, based on this information we can conclude that: "Alfred M. Mayer was the physicist to report that a.