Nouns

(n)hearer, listener, auditor, attendersomeone who listens attentively
(n)attendant, attender, tendersomeone who waits on or tends to or attends to the needs of another
(n)attendant, attender, attendee, meetera person who is present and participates in a meeting“he was a regular attender at department meetings”, “the gathering satisfied both organizers and attendees”