Don't ever give up your efforts to find the noise. If it is not identified, there can be no assurace that the aircraft is airworthy.
I made many reports of slight vibration in an A320 over a 6 month period. After 2 inflight diversions back to base, the company finally got the message. Grounded the aircraft for investigation by an airbus engineer who found extremely serious damage where the horizontal stabiliser attaches to the aircraft. Of 4 essential bolts, 1 was broken and 2 loose. One bolt separated the crew and pax from eternity.