From the Forums area, you can create audio-enabled discussion boards that will allow you to post text as well as record messages. Forums allow you and your students to communicate asynchronously. See the online user guides:
Educator Guide
https://support.vhlcentral.com/hc/en-us/articles/214575857-Communication-Forums-for-Educators
Student Guide
https://support.vhlcentral.com/hc/en-us/articles/214878597-Communication-Forums-for-Students