I dont think there is a set number.
My friends exam, who took it on the same day as me in the same center, had 2-3 audio questions in each block! So total of around 15-20... I on the other hand had 3 audio questions total only...
Also, there can be a varied type of audio/media questions. Heart sounds, gaits, reflexes and respiratory sounds can be present. I had two heart and 1 respiratory if i can remember clearly... Some random person in the test center had a video of intention tremor lol i noticed it as i walked out to take a break.