Fig. 1. Sensor head structure. (a) Main view; (b) left view

Fig. 2. Schematic of F-P microcavity sensing

Fig. 3. Fabricated GO diaphragm

Fig. 4. Packaged sensor head. (a) Spectrometer display at the maximum interference contrast; (b) encapsulated F-P sensor head

Fig. 5. Optical fiber acoustic sensor syQstem based on F-P microcavity structure

Fig. 6. Speech signals collected by the system

Fig. 7. Wavelet packet decomposition tree

Fig. 8. Multiple-frame comparison method

Fig. 9. Trend term eliminated by least square method. (a) Speech signals collected by the system; (b) speech signals after elimination trend terms

Fig. 10. Signal before and after Wiener denoising. （a） Speech signal;（b） speech signal after Wiener denoising

Fig. 11. Speech spectra before and after Wiener denoising. （a） Speech spectrum； （b） speech spectrum after Wiener denoising

Fig. 12. Reconstructed graphs of one-dimensional wavelet packet coefficient

Fig. 13. One-dimensional wavelet packet coefficient after Wiener denoising

Fig. 14. Speech signal graph and speech spectrum graph obtained by Wiener denoising method based on wavelet packet transform. (a) Speech signal graph; (b) speech spectrum graph