Effect of background noise on dialogue in telephony

Recent developments of mobile telephones include new sorts of impairments against speech. Conventional evaluation method for impairments by a talker and a few listeners cannot apply to these new ones, because they are brought by long signal delay. The effect of it cannot discriminate by ‘‘one‐sided’’ test. This research relates to a speech quality evaluation by conversation between two persons. Variation of conversation stream is observed by addition of pink noise of various levels to a dialogue by microphones and earphones. Length of sentences and frequency of repeats are quantified and their meanings are discussed