At home we normally have a fan running to drown out the little creaks and stuff. When traveling it isn't practical to bring a fan so we run a white noise app to do a similar function.
The app we use is actually called "White Noise" for this, it is available for both
Android and
iOS. I have the full version, which is only $1 in the US, to get more options and get rid of the ads but unless they have changed it the lite version was a decent starting point.