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.