CTSE-Net: Resource-efficient convolutional and TF-transformer network for speech enhancement

Deep Neural Networks (DNNs) are powerful tools in real-time speech enhancement (SE) since they automatically learn high-level feature representations from raw audio, resulting in significant advancements. Therefore, demand for resource-efficient DNNs for speech enhancement is increasing, mainly using embedded systems. Still, a lightweight and resource-efficient DNN with optimal speech enhancement performance is a challenging task. Dual-path attention-driven architectures have shown notable performance in SE, primarily because of their ability to capture time and frequency dependencies. This paper proposes a resource-efficient SE using a codec-based dual-path time–frequency transformer (CTSE-Net) to improve noisy speech and apply it to speech recognition tasks. The proposed SE employs a codec (coder–decoder) architecture with feature calibration in skip connections to obtain fine-grained frequency components. The codec is interconnected using a dual-path time–frequency transformer incorporating time and frequency attentions. The encoder encodes a time–frequency (T–F) representation derived from the distorted compressed speech spectrum, whereas the decoder estimates the compressed magnitude spectrum of enhanced speech. Further, dedicated speech activity detection (SAD) is employed to identify speech segments in the input signals. By distinguishing speech from background noise or silence, the SAD block provides important information to the decoder for target speech enhancement. The proposed resource-efficient approach ensures attention across time–frequency and distinguishes speech from background noise, leading to more effective denoising and enhancement. Experiments indicate that CTSE-Net shows robust noise reduction and contributes to accurate speech recognition. On the benchmark VCTK+DEMAND dataset, the proposed CTSE-Net demonstrates better SE performance, achieving notable improvements in ESTOI (33.69%), PESQ (1.05), and SDR (11.36 dB) over the noisy mixture.