* Sounds that physically *feel* hard? Like the sound of a rock hitting concrete, or a heavy metal song with a lot of distorted bass.
* Sounds that are *difficult* to understand or process? Like a language you don't speak, or a complex piece of music.
* Sounds that are *intense* or *powerful* ? Like a loud explosion, or a soaring operatic aria.
Could you please clarify what you mean by "sounds like hard"?