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. Author manuscript; available in PMC: 2016 Sep 1.
Published in final edited form as: IEEE Trans Biomed Eng. 2015 Apr 13;62(9):2279–2288. doi: 10.1109/TBME.2015.2422698

Fig. 1.

Fig. 1

Spectrogram representation of four lung sound excerpts. Top panel: internal microphone; middle panel: external microphone recording; bottom panel: signal as outputted by spectral subtraction algorithm B. The quasi-periodic energy patterns, more pronounced in (a) and (b), correspond to the breathing and heart cycles and are well preserved in the enhanced signal. (a) Electronic interference contaminations and (b) soft background cry have successfully been removed. Panels (c) and (d) show cases heavily contaminated by room noise and loud background crying which have substantially been suppressed using the proposed algorithm. Notice how concurring adventitious events were kept intact in (c) at 1.5–3 s and in (d) at 0.6–0.8 s . The period at the beginning of (d) corresponded to an interval of no contact with the child’s body and was silenced after the postprocessing algorithm.