Lost Sound on iMac running Mojave

I am running Mojave 10.14.6 on a late 2013 iMac. I lost the sound, voice, music, etc. Was advised to Reset the Pram which I did and after several tries, the sound was restored. Shortly thereafter it went out again and resetting the Pram does not restore it. I have tried 6 times and still no luck. Is there something else I might try short of taking it to the Apple store?