Student Pilot on a solo cross-country flight reported an NMAC with another aircraft seen on ADS-B. The reporter was receiving flight following from ATC but had inadvertently turned down the volume of the radio and missed the traffic advisory for the aircraft.

Narrative

I was a student pilot on a solo cross-country flight. I picked up VFR flight following at my home airport and was handed off to an Approach Controller and then to a second Approach Controller. I began having difficulty hearing this second Approach Controller due to ambient flight noise. Despite turning up the volume on my headset and the comm panel I had to focus intently to understand the controller's voice. A few minutes after checking in with this controller I am given a traffic advisory for traffic which I see displayed on my ADS-B In display as going in a similar direction to me. I do not make visual contact with this traffic. I also see on ADS-B In that there is traffic a few miles further away converging with me. I see the converging traffic on the ADS-B display and begin to focus on listening for ATC communications as well as visually scanning out the window to try and get visual on the converging traffic. After about a minute of not hearing any ATC communication directed at me as well as not getting visual on the traffic; I initiated a climb to get altitude over the incoming traffic. About thirty seconds after I began my climb; I get visual on the converging traffic. Said traffic then passed under me and slightly behind me 20 seconds after that. As the aircraft passed below me ATC gave me a traffic advisory for the traffic and said he called me earlier. I did not hear this call despite listening out for it. Communication issues persisted until I terminated flight following and landed at my home airport. After landing I realized I was turning the volume up on the wrong comm panel as I was turning the comm1 volume up even though I had ATC active in comm2. This is why despite me thinking I turned the volume all the way up I had trouble hearing ATC communications. I believe that a couple things caused the problem. The first item that contributed to the problem was my mistake of turning up the wrong volume knob on the comm panel. The second thing that contributed was that the controller was speaking faster than I was used to and was not using phraseology I was used to at times; which made it difficult to understand as a student pilot coupled with the low volume. The final contributing factor was me not communicating that I was having difficulty hearing the controller. This could have allowed for the controller to slow his speech or enunciate clearer to assist me with hearing him. Going forward I will be more aware of what radio I have comms active on. Also; going forward; I will communicate better with ATC and make the controller aware of any comms issues. Going forward I intend to check in with each controller as my callsign plus student pilot solo so they know to speak slower with more standard phraseology. Finally; I wish to acknowledge the help that having ADS-B In equipped on my plane gave me. ADS-B In gave me situational awareness to look out for incoming traffic and gain visual contact for separation despite not hearing ATC communications. It allowed for me to take preemptive action to get separation so that rapid evasive maneuvers were not required.