Humming is also known as closed-mouth singing, commonly referred to as humming. People often use this method to hum a melody in daily life. In artistic singing, whether it's solo, duet, or chorus, humming might be used. For example, there is a famous humming chorus in Puccini's opera "Madama Butterfly", which has a soft and pleasant timbre. When humming, there is a vibration sensation between the eyebrows, making it easier to achieve vocal resonance.