The aim of the present research was to build a simple model for tool wear monitoring during the machining process. In addition, by this model a prediction of tool wear for a variety of different cutting speeds and feed rates should be possible. Therefore, the sound pressure at 0.5 m from the cutting zone during the turning was measured by a condenser microphone and analysed in frequency domain from 0 to 22 kHz. The measurement arrangement as well as the possibilities for on-line sensing of the tool wear are presented. The workpiece material was carbon steel Ck15 (DIN) and the cutting insert was made of cermet without coating. The depth of cut was the constant, whereas the cutting speed, feed rate and flank wear of the tool were variables. The results showed that an increase in tool wear correlates with an increase in the amplitude of the recorded sound between 6 and 20 kHz. Similarly, an increase in feed rate resulted in an increase of sound intensity between 2 and 19 kHz. In contrast with these findings, the cutting speed influenced the recorded signals considerably less. It can be concluded that under the given circumstances the monitoring of tool wear by the sound emitted is a possible and relatively simple method.