iSTI Signal Generator is an application that generates the STIPA test signal for measuring the speech transmission index according to IEC 60268-16 4th edition. The speech transmission index predicts speech intelligibility. NOTE: in order to measure the speech transmission index, software or hardware is needed to analyze the STIPA test signal, such as the iSTI Professional app. This app is only a signal generator; it is a handy tool to use a a separate source of the STIPA test signal for those who already have a 4th edition-compliant STIPA measuring solution.