[History of instrumental measuring of hearing acuity: the first acumeter]

The necessity of measuring the acuity of hearing in a reproducible way arose for the first time when the invention of Volta's pile in 1800 seemed to present the opportunity of curing deafness. For this purpose Chr. H. Wolke in Jever, Northern Germany, in 1802 devised two instruments which he called "acumeter". Details of these instruments were hardly known, and Wolke's publication was believed to be lost. The author has now succeeded in tracing Wolke's publication and another associated paper by J. J. A. Sprenger. Hence, the circumstances of Wolke's and Sprenger's work and details of these first acumeters are now being published together with original figures and the correct dimensions of the instruments. The acumeters had a pendulum-like hammer that would strike against a plate swinging down from varying heights that could be read in degrees of angle from a scale. One of the instruments was made of wood. It was 1.50 m high, with the pendulum raised to the maximal position 2.70 m. The other instrument of similar construction was made of metal and about half the size of the first one, with a height of 0.70 m or 1.30 m respectively. For comparison Itard's acumeter is presented which was published in 1821. It worked on the same principle, and it is likely that Itard had been inspired by Wolke's paper. The development of mechanical acumeters after Wolke's and Itard's instruments is outlined briefly.