I witnessed a blind man use their phone with playback speeds that were incredibly fast and completely inaudible to my ears. To my best guess, it would have been about 4-5x speed. (I base this off estimating by going to youtube in chrome, pressing cmd + option + j to bring up developer console, and entering
document.getElementsByTagName("video").playbackRate = 4 to increase the playback speed to 4).
Provided that the content is not anything that requires any deep thought (suppose it's a story or instructions you are already familiar with), can the brain adapt to listening to such audio at very high speeds?