I trust my ears, but only to a point. We all must trust our own ears, yet it is far too easy to lose objectivitywe need external validation from other disinterested ears, and from empirical measurements.
Well said. Although, I find that disinterested ears don't notice things easily. For example, we were getting out of the car and heading to the wedding reception for a friend. I said to the wife, "how nice they have hired musicians to play at the reception". Since we were in the street, there was no visual way to know that there was live music versus recorded music from inside the recpetion. My wife could not tell from listening and she was curious how I could be sure of myself. I think you can learn these things just as sound engineers are trained - but disinterested ears are very likely to be untrained as these folks just don't bother to listen critically.