Musketeer 23 Pilot reported a NMAC event during landing pattern entry when a regional jet flew 300 feet above and separated away. After landing; the pilot discovered the audio panel volume had been turned down.

Narrative

I entered the traffic pattern for Runway XX on an extended right hand downwind 10 NM southwest of the airport and began making position reports on CTAF at that point. Among multiple calls; I called midfield downwind. I had not I heard any other radio calls which I thought unusual at this airport. So; I verified that I had the correct CTAF frequency set. I called base. I called turning final. Up until now; I had seen no traffic and nothing on my ADS-B display. On rolling out on final; I suddenly saw and heard an ADS-B traffic alert 300 ft. directly overhead. I noted that the altitude separation was increasing. Seconds later; I saw a company regional jet climbing and accelerating away from me in an apparent go-around due to the traffic conflict. After landing and clearing the runway I again checked the radio; then the audio panel and found the audio panel volume turned down. I turned the volume up and immediately began hearing other traffic. I had no problem with communication at my departure airport. So; I assume that I inadvertently changed that knob sometime during cruise due to some moderate turbulence.