2.89 that's most likely way too low i would suggest taking some classes to bring it up to a least 3.5 before applying; you'll need a even higher to get in the top schools like Vanderbilt. Most students applying to AuD programs have bachelor degrees in Communication Sciences & Disorders although not necessary to get in.
No specific courses are required. However, courses in life science (e.g., zoology, biology); behavioral science (e.g., psychology, sociology); physical science (e.g., physics, chemistry); and mathematics or statistics are required for ASHA certification. Completion of a course in Normal Language Development or Language Acquisition at the undergraduate level will reduce the academic load for students during one semester of the Au.D. program. There are four basic areas that you will want to consider: (1) Biological Sciences (at least one course, for example, Intro to Biology)
(2) Physical Sciences (at least one course, for example, Intro to Physics, Intro to Acoustics)
(3) Mathematics (at least one course, for example, Into to Statistics)
(4) Behavioral Sciences (at least one course in Psychology, for example, Intro to Developmental Psych)