Improved structural similarity measurement for vocal signals

In recent years, the SSIM was proposed for image and vocal signal assessments to match human perception. The existing SSIMs for vocal signals are similar to those for images. However, the human perceptions for voices and images are different. If two vocal signals differ only by phase, delay, or logistic frequency shift, they are heard similarly. In this paper, we propose the non-uniform sampling frequency mean SSIM (NUS-FMSSIM) to highly match the human perception for voices. Simulations show that it is more robust to phase change, time shift, and logistic frequency shift than the existing SSIMs for vocal signals.