Rosen Stuart, Zhang Yue, Speers Kathryn
Speech, Hearing and Phonetic Sciences, University College London, Chandler House, 2 Wakefield Street, London WC1N 1PF, United Kingdom
J Acoust Soc Am. 2015 Sep;138(3):EL318-23. doi: 10.1121/1.4929618.
For small numbers of channels, tone vocoders using low envelope cutoff frequencies are less intelligible than noise vocoders, even though the noise carriers introduce random fluctuations into the crucial envelope information. Here it is shown that using tone carriers with a denser spectrum improves performance considerably over typical tone vocoders, at least equaling, and often surpassing, the performance possible with noise vocoders. In short, the spectral sparseness of tone vocoded sounds for low channel numbers, separate from the degradations introduced by using only a small number of channels, is an important limitation on the intelligibility of tone-vocoded speech.
对于少量声道，使用低包络截止频率的音调声码器的可懂度低于噪声声码器，尽管噪声载波会将随机波动引入关键的包络信息中。本文表明，使用频谱更密集的音调载波，相比于典型的音调声码器，性能有显著提升，至少能达到，且常常超过噪声声码器的性能。简而言之，对于低声道数量的音调声码语音，其频谱稀疏性，与仅使用少量声道所引入的退化无关，是对音调声码语音可懂度的一个重要限制。
