Infrasound is a type of sound that is inaudible to the human ear.

Debuccalization refers to the phenomenon in phonetics where a specific sound is pronounced outside the oral cavity.

Kunminjōon is a book for teaching the correct pronunciation of Hangul.

This ancient proverb, 'know the other side and yourself, and you will not be in danger in a hundred battles', teaches us the importance of understanding ourselves and others.

Understanding the concept of 'Ha-line conversion sounds' is important in learning Japanese.