| 摘要 |
<p>A test apparatus (1) comprises a test signal generator (21) which transmits a test stimulus comprising two signals RR, S. The signal S is transmitted to a customer equipment interface (2), for transmission over the system (5) under test to a complementary remote apparatus (1a). The test apparatus (1) further comprises two inputs which are to be processed by a number of functional elements. The first input is the reference signal RR. The other input is a corresponding test signal R' having been generated at the remote test apparatus (1a) as a test signal R, R' having been generated at the remote test apparatus (1a) as a test signal R, identical with the reference signal RR, and transmitted over the system (5) under tests, to be processed by the customer interface (2). These two versions RR, R' of the same test signal are compared in the test apparatus (1). Firstly, the signals RR, R' are processed by a psycho-acoustic model (22), the output of which is transmitted to a perceptual layer (23), and then to a conversion unit (24) which also receives a further input from a non-optimum loudness rating unit (25). The output from the conversion unit (24) is transmitted to a signal quality determination unit (26), which also receives an input from the customer equipment interface (2). The non-optimum loudness rating unit (25) processes inputs from the customer equipment interface (2) and signal generator (21). During the iterative process to be described, the signal generator (21) receives feedback control from the signal quality determination unit (26). The remote test apparatus (1a) similarly receives a modified version of signal S (viz S') from the network (5) and compares it with a locally-generated reference version SR. In an alternative arrangement (figure 11), the same test apparatus (1) is connected to both test points (4, 4a) of the network (5) and processes both signals S and R, either serially or in parallel.</p> |
