The Structure of the Soundhole
The sound hole design will also affect the frequency and SPL (but the chamber design still must be a priority step). There are several points for designing a sound hole: The larger sound hole will raise the frequency, and the smaller one will lower it. When the sound hole is not in the middle of the buzzer, the frequency will shift lower. SPL will get lower if the sound hole is designed to be different shapes rather than a circle type.