Robotic Voice and Ping Pong Effect

Two well-known special effects, Robotic Voice and Ping Pong Effect, are not explicitly detected by the objective analysis method mentioned above. Both effects have a strong impact on the subjective impression of speech quality. The frequency of occurrence of these effects, which originate in the frame repetition feature of the GSM standard (GSM 06.11), is also a well-suited measure for the quality of the radio link.

The first lost speech frame is substituted with either a repetition or an extrapolation of the previous good speech frame(s). For subsequent lost speech frames, a muting technique is used that will gradually decrease the output level, resulting in silencing of the output after a maximum of 320 ms.

Whilst the cause of the effects is the same, the perception of the effects is quite different: Robot Voice is perceived as an incorrect reproduction of the fundamental frequency of the transmitted speech. (Synthetic, monotonous voice of a robot), Ping Pong, on the other hand, denotes the occurrence of additional disturbing sounds with rapidly-decaying signal power. Ping Pong is found to be the more annoying effect of both. QVoice can also detect these effects.

download all samples in a *.ZIP file  (1.2 MB)

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