It's possible to record yourself, and have students record themselves, in audio-only clips. An obvious advantage here is not having to produce visual content (especially where it isn't necessary) and audio-only podcasts have become popular media. You can add audio clips to your course within D2L, within a Google Sites lesson (as here), or learn how to syndicate a series of episodes as a podcast.
These allow you to record great-sounding audio clips. The resulting audio files can be uploaded to D2L, or other web spaces such as Google Sites lessons.
Audacity is a free but powerful audio content editor, that's a standard for podcasters. It's not difficult to pick up if you wish to include audio clips in your course. But budget several hours before it's necessary, just to learn Audacity's interface, and practice recording and editing.
You or your students can create audio clips as podcasts, or episodes that together form a series. Many podcasts out on the internet are into the hundreds (or more) episodes. But for podcasting within a course, you or your students will naturally produce something more limited.
If you want your or your students' podcasts to be hearable by the rest of the world, you can use dedicated hosting services, such as podbean or soundcloud, and can investigate having those podcasts listed in directories such as Apple Podcasts. Otherwise, you could simply collect .mp3 files from students, and post them in a place within D2L where students can hear them.
The History Department at the University of Rochester has students podcasting in a series called "Hear UR." They call it an "alternative to the traditional history paper."
Podcasts are something you and your students can do, but they also can be resources for you. Someone probably has a weekly or monthly podcast in your discipline, and there are several that focus on teaching in higher education. See for example Teaching in Higher Ed.
Plus, many news sources have turned to podcasting as a low-cost, practical way to extend print or radio journalism.
The Jesuits' America magazine has several podcasts as well.
Listen to these for their content, as well as to understand the possibilities of audio content generally.