title: Signal-to-noise ratio adaptive post-filtering method for intelligibility enhancement of telephone speech.
abstract: Post-filtering can be utilized to improve the quality and intelligibility of telephone speech. Previous studies have shown that energy reallocation with a high-pass type filter works effectively in improving the intelligibility of speech in difficult noise conditions. The present study introduces a signal-to-noise ratio adaptive post-filtering method that utilizes energy reallocation to transfer energy from the first formant to higher frequencies. The proposed method adapts to the level of the background noise so that, in favorable noise conditions, the post-filter has a flat frequency response and the effect of the post-filtering is increased as the level of the ambient noise increases. The performance of the proposed method is compared with a similar post-filtering algorithm and unprocessed speech in subjective listening tests which evaluate both intelligibility and listener preference. The results indicate that both of the post-filtering methods maintain the quality of speech in negligible noise conditions and are able to provide intelligibility improvement over unprocessed speech in adverse noise conditions. Furthermore, the proposed post-filtering algorithm performs better than the other post-filtering method under evaluation in moderate to difficult noise conditions, where intelligibility improvement is mostly required.
authors.affiliation: Department of Signal Processing and Acoustics, Aalto University, P.O. Box 13000, Fi-00076 Aalto, Finland. emma.jokinen@aalto.fi
authors.forename: Emma
authors.initials: E
authors.lastname: Jokinen
authors.forename: Santeri
authors.initials: S
authors.lastname: Yrttiaho
authors.forename: Hannu
authors.initials: H
authors.lastname: Pulakka
authors.forename: Martti
authors.initials: M
authors.lastname: Vainio
authors.forename: Paavo
authors.initials: P
authors.lastname: Alku
mesh_terms: D000161:Acoustic Stimulation; D000162:Acoustics; D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D040421:Cell Phone; D005260:Female; D006801:Humans; D008297:Male; D009622:Noise / Q000009:adverse effects; D010470:Perceptual Masking; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D013061:Speech Acoustics; D013065:Speech Intelligibility; D013069:Speech Reception Threshold Test; D014833:Voice Quality; D055815:Young Adult