This link provides a comprehensive list of easy to use audio tools, which can be used as an alternative to written blogs. Ideally, students should be making attempts to write blogs, however teachers can use their professional judgement and make decisions as to whether students would benefit more from an audio blog or written blog. Students using an audio blog will need additional instruction in how to use the audio software.
Students using the audio blogs will still have a student blog on the classroom blog page. They will upload their audio file (with teacher/aide assistance) to their student blog, where they can comment and receive comments on other student blogs.
Alternatively, teachers can source audio programs that translate speech to written text. This does provide opportunities for mistranslation or misinterpretation and is less optimal than an audio blog.
I personally recommend SoundCloud, as the program is easy to use and can be uploaded to media sites (blogs) and embedded into webpages in the same way students would copy and paste a link from a website.