PSNR = 20 log(Max Pixel/sqrt(MSE))

= 20 log(Max Pixel) - 10 log(MSE)

If the reconstructed audio signal is exactly same as original signal then MSE =0. And if Max pixel value is 255 (8-bit representation), then the value of PSNR = 20*log(255) = 48dB. This is the maximum value of PSNR when signal is represented in 8-bits.

Dear,

There is no specific range for SNR or PSNR. SNR and PSNR denote the comparison of signal power against noise power. Hence, the higher value indicates the bigger signal power than noise power.

PSNR may go up to infinity, in the formula below

PSNR = 20 log(Max Pixel) - 10 log(MSE)

for 0 < MSE < 1, log is negative making overall term additive and hence increasing the PSNR beyond 48 (PSNR when MSE is 0 in above equation).