I have tub/shower that makes a very slight creek/noise when using. It happens only once or twice when moving towards the drain - then stops.

I have looked at things, tighted the drain cover (the screw wasn't tighted all the way down) and the noise has decreased but is still there - again slightly.

It is a very small "tap" noise and again only happens when I first use the shower. By the end of my shower I can't replicate the noise.

There doesn't appear to be any leaks - but it doesn't mean there isn't. This is a 2nd floor bath - concerned about creating a 1st floor one.

Are there any methods to determine what is going on? This is an original bath (10 years).

Thanks for any input.