An audio signal detection system based on laser speckle and multi-channel data fusion is presented. A linear CMOS array is used as the detector, which owns a fast line rate and suitable sensing size. The signals from the pixels are selected and fused to enhance the reconstructed signal. The reconstructed audio signals are evaluated with a segmental SNR (SegSNR) algorithm. The experimental results of three categories of audio sources (single voice audio, conversation and music) show that data fusion can improve the SegSNR scores. Especially, direct phase-error based filtering (pbf) fusion gives a nearly 3.0 dB increase and obtains another 1.0 dB increase with the combination of single channel process. The experimental results show that the fusion algorithms are not sensitive to audio types and the performance of multi-channel data fusion is not weakened with the increase of measuring distance. This feature has potential applications in remote sensing. The intelligibility of the fused audio signals is evaluated with normalized subband envelope correlation (NSEC) algorithm and the evaluation results shows that fusion can also enhance the intelligibility of the recovered signal.INDEX TERMS Audio signal detection and enhancement, linear CMOS array, multi-channel data fusion.
Based totally on the intrinsic difference of polarizing emission spectra and birefringence of the a-cut Nd:YAP gain crystal, an orthogonally polarized 1079.5 and 1099 nm dual-wavelength laser is demonstrated. A specially designed dielectric Fabry-Perot filter is exploited as output coupler and gain balancer of the laser cavity. The maximum output power and slope conversion efficiency of the dual-wavelength laser is 976 mW and 7%, respectively. The experimental results show that the intrinsic birefringence of the laser gain material is the principle source for the generation of the orthogonal polarized laser. The competition between the two lasing wavelengths is analyzed and attributed to the stark energy levels involved. The method presented can be used to other biaxial laser gain crystals for the generation of orthogonal polarized dual-wavelength lasers.
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