General synonyms:
* Orally
* Verbally
* Out loud
* Audibly
* Loudly (implies a higher volume)
More specific synonyms:
* Articulately (implies clear and precise speaking)
* Distinctly (implies clear and easily understood)
* Plainly (implies simple and straightforward)
* Clearly (implies easily understood)
The best synonym will depend on the specific meaning you want to convey.