Frequency-adaptive post-filtering for intelligibility enhancement of narrowband telephone speech

Post-filtering methods are used in mobile communications to improve the quality and intelligibility of speech. This paper introduces a frequency-adaptive post-filtering algorithm that selects from a predefined set of filters the one that reallocates the largest amount of speech energy from low to high frequencies. The proposed method and another post-filtering technique were compared to unprocessed speech in subjective listening tests in terms of intelligibility. The results indicate that the proposed method outperforms the reference method in difficult noise conditions.