# Big-Delay Estimation for Speech Separation in Assisted Living Environments
## 7 Conclusions  
A source demixing technique originally designed to separate music sources mixed using the pan-pot model was reformulated to operate in anechoic scenario characterized by relative attenuations and large delays. The primary objective was to isolate a target speaker of interest using multiple microphones from a mixture of concurrently active voices in a competing acoustic environment, and to transmit the isolated speech to a hearing-aid worn by a patient with hearing impairment in an AL environment. A significant challenge in real-world scenarios is the phase wraparound issue, which arises when the distance between a pair of microphones exceeds the smallest allowable wavelength of the acoustic wave. This causes severe corruption of higher frequencies, rendering traditional separation algorithms ineffective. Demixing algorithms function as filtering techniques involving both analysis and synthesis processes, which may introduce distortions and artifacts into the synthesized utterance. Building on the work in [4; 5; 9], this paper proposed a speech IS scheme utilizing a remote microphone that constituted a near-field microphone setup. The RM-aided ISscheme was designed to enhance the intelligibility of a distant target speaker. Specifically, this paper investigated the feasibility of extending two classical source demixing algorithms, DUET and AdRess, by combining a large delay estimation technique known as the Elevatogram [5]. Generally, the challenge of phase wraparound hinders accurate localization of a source in space. The Elevatogram technique in [5] overcomes this challenge. Both Elevato-DUET and Elevato-AdRess are spatio-spectral masking techniques in which the IID cue depends on the accurate estimation of the IPD cue, making the two cues interrelated. These enhanced versions, named Elevato-AdRess and Elevato-DUET, are designed to operate effectively in scenarios with substantial relative delays of up to 200 samples. This advancement holds significant potential for applications in hearing-assisted living scenarios. Through the derived masks of these algorithms, we demonstrated their capability to perform robustly in large relative delay conditions. In conclusion, the Elevato-AdRess demonstrated superior performance compared to Elevato-DUET in terms of speech separation quality, exhibiting fewer distortions, reduced interference, and enhanced intelligibility for human listeners. It was observed that the Elevato-AdRess technique, by discarding overlapping frequencies, introduced significant artifact noise into the recovered utterance, resulting in a reduced SNR for the extracted source. Finally, the correlation between the BSS_Eval and PEASS separation quality metrics was demonstrated. Specifically, the SDR exhibited a strong correlation with the OPS, which evaluates the quality of the separated utterance. Similarly, the SIR showed a significant correlation with the interference-related IPS metric. The poor quality of separation demonstrated lower scores in both types of objective measures. The SAR of BSS_Eval demonstrated little correlation with the APS of PEASS. The Elevato-AdRess demonstrated better interference reduction in the recovered signal than Elevato-DUET. It remained stable with increases in the number of constituent sources in the mixture. An accurate estimation of the relative delay was crucial for the operation of the Elevato-AdRess because erroneous estimates rendered the application of the mask unsuccessful. The MAE, \(|\delta_{j}-\delta_{j}|\), was also crucial. An estimation error of more than 1 sample rendered the Elevato-AdRess ineffective. From the perspective of human auditory perception, Elevato-AdRess demonstrated better performance in terms of the PESQ MOS intelligibility score compared to Elevato-DUET. S.B. : Conceptualization; Methodology; Software; Validation; Investigation; Resources; Data curation; Writing--original draft preparation; Visualization.