Heinrich Wilhelm Dove discovered binaural beats in 1839. While research about them continued after that, the subject basically remained a scientific curiosity until 134 years later, with the publishing of Gerald Oster's article "Auditory Beats in the Brain" (Scientific American, 1973). Oster's paper was landmark not so much for its own new laboratory findings, but rather that in the way in which it identified and tied together the isolated islands of relevant research done since Dove, in a way that gave the subject fresh insight and relevance to scientific research.
In particular, Oster saw binaural beats as a powerful tool for cognitive and neurological research, addressing questions such as how animals locate sounds in their three-dimensional environment, and also the remarkable ability of animals to pick-out and focus-on specific sounds in a sea of noise (what is known as the "cocktail party effect").
Oster also considered binaural beats to be a potentially useful medical diagnostic tool, not merely for finding and assessing auditory impairments, but also (because they involved different neurological pathways than ordinary auditory processing) for more general neurological conditions. For example, Oster found that a number of the subjects he worked with that were incapable of perceiving binaural beats suffered from Parkinson's disease. In one case, Oster was able to follow one such subject through a week-long treatment of Parkinson's disease; at the outset the patient couldn't perceive binaural beats, but by the end of the week of treatment, the patient could hear them again.
Oster also reported (in corroborating an earlier study) that there were gender differences in the perception of beats. Specifically, women seemed to experience two separate peaks in their ability to perceive binaural beats that seemed to correlate with specific points in the menstrual cycle (one at the onset of menstruation, one around 15 days later), which led Oster to wonder if binaural beats could be used as a tool for measuring relative levels of estrogen.