A.C frequency is 50Hz.is it audible?

No, the A.C frequency of 50Hz is not audible. The audible frequency range for humans is generally considered to be between 20Hz and 20,000Hz (20kHz). Frequencies below 20Hz are considered infrasonic, while those above 20kHz are considered ultrasonic. Therefore, a 50Hz AC frequency falls below the audible range and is not something that humans can hear.