Key research themes
1. How can subspace and spectral subtraction methods improve low-bit-rate speech compression in noisy environments?
This research theme explores advanced preprocessing techniques aimed at enhancing the signal-to-noise ratio (SNR) of speech signals before compression under low-bit-rate conditions, particularly for applications like cellular communication. The focus lies on comparing and combining signal-subspace-based speech enhancement with spectral subtraction algorithms to mitigate additive noise effects and improve quality in bandwidth-constrained speech coding frameworks.
2. What are the benefits and challenges of wavelet transform-based speech compression methods?
Wavelet transform methods, particularly Discrete Wavelet Transform (DWT), have been widely studied for speech compression due to their ability to efficiently represent non-stationary signals by capturing both temporal and spectral properties. This research theme examines how DWT-based methods exploit multi-resolution analysis to achieve high compression ratios while preserving signal quality and how these approaches compare to traditional coding standards and other transforms, including practical implementation aspects and trade-offs.
3. Can integration of speech recognition features into low-bit-rate compression enhance recognition accuracy and system efficiency?
This theme investigates methods to reconcile low-bit-rate speech compression with speech recognition performance by incorporating recognition-relevant features (e.g., MFCC) into the compression pipeline. The aim is to minimize recognition degradation commonly caused by traditional waveform compression, enabling direct recognition from compressed representations and reducing retraining needs, facilitating distributed speech recognition, and improving playback on devices with storage constraints.