Limitations and future directions
In this study, we used ground-truth F0 information for periodicity enhancement. The F0 values were estimated from clean speech utterances using the auto-correlation algorithm in PRAAT, and then verified manually. In Milczynski et al (2012), F0 information was also extracted from clean speech for investigating Mandarin tone perception in noise. Although both studies demonstrated the benefits of periodicity enhancement, a valid question to be asked is whether reliable F0 estimation can be done for noise-corrupted speech. Indeed, robust F0 estimation is a challenge for all existing periodicity enhancement algorithms (Vandali & van Hoesel, 2011; Milczynski et al, 2012). Recently, a number of robust techniques have been proposed to deal with low-SNR conditions (Gonzalez & Brookes, 2011; Jin & Wang, 2011; Chu & Alwan, 2012).