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Automatic heart sound analysis offers a low-cost and highly promising diagnostic method, but its effectiveness is often compromised by noise during recording. Nowadays, most advanced blind source separation methods typically employ deep learning techniques based on a U-Net architecture with a short-time Fourier transform (STFT) for time-frequency representation of audio signals. However, alternative time-frequency representations have not been thoroughly explored. In this paper, we enhance phonocardiogram signal denoising by utilizing four distinct time-frequency representations: STFT, continuous wavelet transform (CWT), wavelet synchrosqueezed transform, and the S-transform, processed through a U-Net. We evaluated our denoising algorithm by contaminating heart sound signals with four different types of noise, including non-stationary real-world nuisance signals, at -5 dB and 0 dB signal-to-noise ratios (SNRs). Our results showed that the CWT achieved the best denoising performance, with gains of over 18 dB for heart sounds contaminated with speech at -5 dB SNR. We found that the CWT significantly improves by 2 to 8 dB over STFT while requiring less than double the computational resources. The method\u2019s effectiveness is demonstrated in the time domain, time-frequency, and power spectral density spaces, resulting in a denoising model that surpasses current state-of-the-art techniques.<\/jats:p>","DOI":"10.1007\/s11760-026-05421-3","type":"journal-article","created":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T19:51:30Z","timestamp":1780948290000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Enhancing heart sound signal denoising: unveiling the impact of time-frequency transformation in U-Net performance"],"prefix":"10.1007","volume":"20","author":[{"given":"Crist\u00f3bal","family":"Gonz\u00e1lez\u2013Rodr\u00edguez","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elo\u00edsa","family":"Garc\u00eda\u2013Canseco","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Miguel A.","family":"Alonso\u2013Ar\u00e9valo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Everardo","family":"Inzunza-Gonzalez","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"E. 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