Define what you mean by "diverse voices." Are you including racial, gendered, able-bodied, cultural, geographical, open vs paid, etc. diversity? What makes the most sense for the context of your course?
Inventory and diversify course readings to include diverse voices. There are a few ways that you might do this:
Are the authors of readings from diverse backgrounds and cultures?
Incorporate readings on the topic that include elements of IDEA (e.g Inclusion & diversity within the U.S. housing market; a discussion of a reading about whether straight actors should play gay characters/should actors with disabilities only portray characters with disabilities).
Select readings that are open access (e.g. In open projects like those hosted in Wordpress, encourage students to link out to the preprint or openly available copy of an article or at the very least to the article in Google Scholar for articles or Worldcat.org for books rather than just a citation without any hyperlink or that only refers readers to a database behind a paywall);
When we cannot find diverse readings, openly acknowledge to students the dearth and the failings within the academy that perpetuate marginalization.
Intentionally include IDEA elements in assignment prompts - assignments that allow students to reflect on issues of diversity, inclusion & equity and requires them to look for diverse voices when researching and writing on a topic (e.g. Have them reflect on questions like: How diverse is my works cited list for this research project? Has my bias overlooked a diverse voice/perspective/experience/meaning/way of knowing? if there are none, why is there a lack in the sources I’ve found?).
Model IDEA (Inclusion, Diversity, Equity & Access)
Model inclusive language, ask for and use accurate names/pronouns, acknowledge your bias/privilege, provide context when using idioms, metaphors or pop culture references. Encourage students to use inclusive language, to share their/ask for & use of accurate names/pronouns.
Dismantle colonial and historical oppression by acknowledging different holidays & the privileges of holidays celebrated, offering flexibility around other religious holidays.
Utilize indigenous pedagogy, androgogy, and ethno-knowledge into learning activities to further help de-colonize the course (e.g. using Talk Story/Story Circles as the framework for a community discussion on tenant/Landloard equity issues).
Address and acknowledge the bias and racism in seemingly unbiased sources, such as data, publishing, and library cataloging systems.
Make content more representative of a diverse population