This paper investigates the reverberation time estimation methods which employ backward integration of adaptively identified room impulse responses (RIRs). Two kinds of conditions are considered; the first is the “ideal condition” where the anechoic and reverberant signals are both known a priori so that the RIRs can be identified using system identification methods. The second is that only the reverberant speech signal is available, and blind identification of the RIRs via dereverberation is employed for reverberation time estimation. Results show that under the “ideal condition,” the average relative errors in 7 octave bands are less than 2% for white noise and 15% for speech, respectively, when both the anechoic and reverberant signals are available. In contrast, under the second condition, the average relative errors of the blindly identified RIR-based reverberation time estimation are around 20%−30% except the 63 Hz octave band. The fluctuation of reverberation times estimated under the second condition is more severe than that under the ideal condition and the relative error for low frequency octave bands is larger than that for high octave bands under both conditions.

A reverberation time (RT) estimation method is presented which consists of three steps, the anechoic speech is first recovered by maximizing the skewness of the linear prediction residual of the reverberant speech, then room impulse response (RIR) is identified using the recovered anechoic and reverberant speech, finally RIR is truncated to compensate the estimation errors and RT is estimated using the Schroeder's method. Simulations show that the proposed method successfully estimates RT less than 1.4 s and is insensitive to the speech content such as the number of long pauses and sharp offsets.

Structure colors play a key role in display devices, imaging security certification, optical data storage, and so on. However, relatively little work has been done on controlling color brightness, and the reported structures are unable to maintain high saturation at the same time. We demonstrate a symmetry-breaking-driven titanium dioxide (TiO₂) dimer metasurface. By precisely inducing quasi-BIC (q-BIC), this structure achieves a spectral response in the visible light band with a reflectance approaching 1 and a full width at half maximum (FWHM) of less than 7.2 nm. Utilizing global size scaling enables support for an ultra-wide color gamut display covering approximately 149.9% of the sRGB color space. By perturbing the structure on one side, we have achieved independent control over the brightness of structural color whilst maintaining high saturation. Furthermore, it is found that this metasurface structure exhibits good robustness against geometric distortions. The structure proposed in this paper opens the way for a wide range of 3D nanoprinting and modern advanced displays in both scientific fields and practical applications.

Highly saturated structural colors are crucial for the micro-nanophotonic displays. However, achieving Schrödinger’s red pixels remains a challenge due to the difficulty in suppressing higher-order resonances in the blue-green wavelength band. In this paper, we utilize the TuRBO algorithm for global physical parameter optimization of periodic ${\mathrm{Sb}}_2{\mathrm{S}}_3$ nanopillar metasurface structures to realize the high-saturation red. Based on the intrinsic dispersion characteristics of ${\mathrm{Sb}}_2{\mathrm{S}}_3$ characterized by high extinction coefficients in the blue-green wavelength band, the high-saturation Schrödinger’s red that surpasses the Adobe RGB boundary has been produced successfully. The calculated results show that after 45 iterations, the structure achieves gradient refractive index matching, aligning the intrinsic dispersion of ${\mathrm{Sb}}_2{\mathrm{S}}_3$ with the ideal reflection spectrum of Schrödinger’s red pixels, thereby effectively suppressing higher-order resonances in the blue-green wavelength band. Ultimately, an ultra-high saturation red is achieved with CIE coordinates of (0.6507, 0.3043) in the CIE chromaticity space.