That’s because no matter whether your headphones are in-ear or head-mounted, their sound isolation ability cannot actually be said to be able to completely isolate external noise. There are always gaps. But if you cover it with your hands, When listening to the ears, the gap is undoubtedly blocked. Naturally, the volume of music is enhanced, and there is less external interference, so the three-dimensional sense is stronger. If you imagine, all the sounds are just lingering in your ear cavity, even the worst HIFI headphones will be enhanced