It's important for instructors to know their students learning preferences and needs early in an online course in order to provide the best possible learning environment. One way to get to know your students is to conduct a survey at the beginning of the course, asking students about their preferences and experience with the subject matter and the online learning environment.
In addition to providing useful information that can help you adapt the course to improve the learning experience, such a survey also can be a great way to find out if you any students who need accommodations under the Americans with Disabilities Act.
However, regardless of ADA requirements, students appreciate options when it comes to learning. For example, one way to offer options would be to provide lectures in multiple formats: text (available as a Word document or PDF), audio/video, and audio only. This is something Andy Stanfield, director of the Center for Teaching and Learning Excellence at Florida Institute of Technology, did this in a recent course so that students could choose the best way for them to take in the information.