It goes without saying that tranquility is the state which calmly gives you some sort of silent mood. It is silent to some extent. However, you listen to some sounds in its silent mood.
"The concept of no sound" is different from "the concept of tranquility." No sound is the state of the following, "there is absolutely no sound." You don't listen to any of sounds at all.
You are again guided to listen to Toshiyuki Namai's English every day every night. I'd like you to have time of the state of no sound as musch as you can.
You will listen to some English words or some part of lectures given to you in the inner part of your heart or brain in experiencing the state of no sound. When those come to you, those shall be yours by inches.