There is a noise underneath the engine of my Mazda rx8what could it be?

A noise coming from underneath the engine of your Mazda RX-8 could be caused by several issues, such as a loose or damaged exhaust component, a failing belt or pulley, or low oil levels leading to engine noise. It might also indicate a problem with the rotor or apex seals, which are critical in rotary engines. It's best to have a qualified mechanic inspect the vehicle to diagnose the issue accurately and prevent further damage.