How to whistle loudly

First of all, put the big finger and any finger relative to the ring into the mouth, into the mouth of the part of about a centimeter or so, and then put the tip of the tongue from the bottom of the two fingers in the place of the joint, slowly blowing with the mouth.

When you first start practicing, you may not be able to make a sound, but if you keep at it and keep adjusting the direction and angle of your hand, you will be able to make the sound you want. When you become very skillful, you will be able to play different tones with a small amount of airflow, and you will be able to play a melody when you reach a certain level.