Here is the full list of all 12 Unheard achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Checked each room in the five maps.
Passed the first test without fast-forwarding and rewinding the audio or using the progress bar.
Passed the second test without fast-forwarding and rewinding the audio or using the progress bar.
Passed the third test without fast-forwarding and rewinding the audio or using the progress bar.
Passed the fourth test without fast-forwarding and rewinding the audio or using the progress bar.
Passed the fifth test without fast-forwarding and rewinding the audio or using the progress bar.
Listened to Emily humming a snatch of a song from end to end.