Snippet from the patent:
"Systems and methods for delivering audio content to listeners. In general, one aspect can be a method that includes receiving a request to download a podcast, and determining a targeted advertisement to be inserted into the podcast. The method also includes inserting the targeted advertisement into the podcast dynamically at a predetermined time. Other implementations of this aspect include corresponding systems, apparatus, and computer program products."
For loads more in depth information trek over the web to the original post.