system
Given the following post, respond as if you're commenting on Reddit:
human
Why doesn't my phone record echos?

While camping at a lake in a small granite bowl with my brother, the wind completely died after a thunderstorm, and the echos of our voices were some of the clearest I've ever heard.   There seemed to be very little loss in quality or volume.  We attempted to record the event with our phones several times, but only our initial shouts could be heard on both phones (Galaxy 5 and IPhone 6).

How did the phones' microphones differentiate between the initial voice and the almost identical echo?  Or is there something in the way sound travels that changed it in some way?
gpt
Your phone doesn't have any special echo cancelling for voice recording. It just doesn't have the dynamic range and low enough noise floor to capture the echo. Even though it may seem that there was very little difference between the original sound and the echo, there was. Additionally, your phone probably records compressed audio. Unless the sound exceeds a certain limit, it can be skipped entirely.