To investigate the audio-vocal feedback responses of (F0) to hearing amplification in severe-to-profound prelingual hearing loss (SPHL) using power spectral analysis of F0 contour of sustained vowels. Sustained phonations of vowel/a/of seventeen participants with SPHL were acquired with and without hearing-aid amplifications. The vocal intensity was visually fed back to the participants to help controlling the vocal intensity at 65-75dBA and 85-95dBA. The F0 contour of the phonations was extracted and submitted to spectral analysis to measure the extent of F0 fluctuations at different frequency ranges. The results showed that both high vocal intensity and hearing-aid amplification significantly improved voice F0 control by reducing the low-frequency fluctuations (low-frequency power, LFP, 0.2-3Hz) in F0 spectrum. However, the enhanced feedback from higher vocal intensity and/or hearing amplification was not adequate to reduce the LFP to the level of a normal hearing person. Moreover, we found significant and negative correlations between LFP and supra-threshold feedback intensity (phonation intensity - hearing threshold level) for the frequencies of 500-2000Hz. Increased vocal intensity, as well as hearing-aid amplification, improved voice F0 control by reducing the LFP of F0 spectrum, and the subtle changes in voices could be well explored using spectral analysis of F0.