A method and apparatus are provided for determining the quality of a
speech transmission, including temporal clipping, delay and jitter, using
a carefully constructed test signal (300) and digital signal processing
techniques. The test signal that is to be transmitted through a speech
transmission system (100) is created (700). Then the test signal is
transmitted through the speech transmission system such that the speech
transmission system creates an output signal that corresponds to the
input signal, as modified by the speech transmission system (702). The
test signal includes multiple segments (500) of speech signals
interleaved with periods of silence. The periods of silence vary in
duration according to a predefined pattern. Each segment of speech
signals includes multiple predefined speech samples or symbols (400, 402,
404, 406, 408, 410, 412, 414) interleaved with a plurality of silence
gaps. The speech samples have a common period of duration, but the
silence gaps do not. The output signal from the speech transmission
system is preferably recorded (704) and analyzed to determine its
quality, including temporal clipping (706). This analysis preferably
includes comparing the output signal with a reference signal derived from
the test signal using a cross correlation function. A processor (114)
coupled to memory (116) records and analyzes the output signal.