This tool was mentioned by US Army Band trumpet player Kevin Gebo on a recent episode of The Brass Junkies podcast. For context, you can listen to the episode here… link text
The tool is free, online and so accessible from your phone, pc, whatever. You simply start the app which plays random pairs of notes separated by random, different intervals. Just listen and play. Guaranteed to improve your playing by ear.
I’ve found that after using this tool for 5-10 minutes a day over the past few weeks, that I’m gradually getting better at picking the first note - almost always within a semitone. I don’t have “perfect pitch”. Am now managing to nail the intervals pretty consistently.
Playing along with random tunes has improved too.
Enjoy. https://www.iwasdoingallright.com/tools/ear_training/online/