ustd doesnt saying Allahs speech is audible and is in words claiming knowing kayfiyah of His attribute, as we believe that mountains speak(tasbih) and our hands and limbs will speak on last day but kayfiyah is unknown and they dont have mouth, lips etc. yet im not sure if that speech is audible too?

No, that is not claiming to know the kayfiyyah. Affirming that Allah Subhanahu wa Taʿala (Glorified and Exalted is He) speaks with letter and voice, and that His speech is heard, is affirming only what the texts themselves affirm, while the kayfiyyah, meaning how it is, is the part we do not know and do not ask about. Keep in mind that it has a kayfiyyah, we just don't know it.