You are developing an application that analyzes voicemail recordings by using Azure Content Understanding in...

Voicemail recordings are audio content . Azure Content Understanding analyzers define what type of content to process, including documents, images, audio, or video , and what elements to extract, including transcripts and structured fields.

Microsoft’s custom analyzer documentation also shows an audio example based on prebuilt-audio for processing customer support call recordings, which is the same content type as voicemail recordings.

Therefore, to extract a transcript and structured information from voicemail recordings, you should use an audio analyzer .