The big cause of listener’s fatigue is the un-natural sound. All audio systems in the world sound un-natural (except Wavetouch audio which is an only natural sounding audio system).
When we hear a natural sound, our ears and brain don’t need to work hard to understand. When we hear un-natural sounds, our ears and brain must adjust and work hard to comprehend the un-natural sound. While we hear un-natural sounds, we can’t understand natural sounds such as dog barking or noise from neighbor. So, our ears and brain must quickly change to a natural sound mode. It is hard to our brain and ears switching very fast between the natural and un-natural sound modes.
The un-natural sound makes a listener dizzy and fall asleep easily because the un-natural sound is very confused sounds. It is warning from our brain to our body to take a break. Once broken (distorted) audio signals can’t be restored and most signals are broken from the source (CD Player or DAC).
The characteristics of un-natural sound is confused, grain, harsh, bright, thin, vague, very forward glare, very far sound-stage (tunnel sound), etc. They hurt/irritate our ears always. And our brain and ears are too tired to make out from very confused and vague un-natural sounds. And it causes the listener’s fatigue. Alex/Wavetouch