An examination of some thirty available works on physical diagnosis and diseases of the heart reveals that none of them call attention to the fact that there is a physiological difference in the quality of the heart-sounds underneath and in the neighborhood of the sternum, as compared with the sounds over the rest of the heart.
The quality of the sounds in this situation has undoubtedly been observed frequently, but the articles bearing on the subject all assume that the peculiarity is pathological. Laennec undoubtedly heard the sound and described it in his treatise on diseases of the heart. He mistook it at first for pericardial friction, but subsequently decided that this was not the case and considered it an association of cardiac hypertrophy.
F. J. Brown described the sound in 1856 as a "chisel" sound. He also considered it a pathologic manifestation and associated it with dyspepsia.
BLUMER G. A NOTE ON THE NORMAL PECULIARITIES OF THE HEART-SOUNDS IN THE REGION OF THE STERNUM. Arch Intern Med (Chic). 1914;XIV(4):605-607. doi:10.1001/archinte.1914.00070160155011