H. W. Gierlich
HEAD Acoust. GmbH, Kaiserstr. 100, 5120 Herzogenrath 3, Germany
New telephone and teleconference systems show increasingly nonlinear time variant behavior. Measurement results of such systems are highly correlated to the measurement procedure used especially for conformance tests and measurements according to several standards. It is highly desirable to achieve comparable measurement results in different labs. These results should correlate well to the subjective impression the user has when telephoning with the measured device. To achieve the desired performance, a suitable test signal must have voice signal properties. On the other hand, measurements have to be carried out in a very short period of time in order to guarantee quasistationary behavior during the time of measurement. To achieve this, a ``composite source signal'' was developed. The signal consists of a voiced sound on 50 ms at the initial phase. This voiced sound is followed by a measurement signal, a pseudorandom noise sequence. To get a modulation typical for speech, the signal is followed by 100-ms pause. Variations of the signal are described for different measurement applications. Measurement results derived from different systems, including various signal processing techniques, are presented.