Fit the inner lip of the lid (the male part) with the outer lip of the Teapot opening (the female part), and then lift the lid in one smooth motion. During this process:

If the sound is sharp and high-pitched, it indicates that the teapot has been over-fired, resulting in reduced breathability.

If the sound is dull and muffled, it suggests that the teapot has been under-fired, leading to excessive breathability. If the sound is clear and balanced, crisp yet not shrill, with lingering reverberations, it indicates that the teapot has been fired to perfection, achieving an appropriate level of breathability.

It's important to note that different types of clay produce sounds of entirely different qualities. When fired correctly: red clay produces a sharp sound, conglomerate clay a harmonious sound, and purple clay a deep and steady sound. It is not appropriate to compare the sounds produced by different types of clay.

While using sound to judge the quality of a teapot isn't a scientific method, it can reveal certain issues.

The clarity or dullness of the sound is primarily related to the degree of vitrification (firing completeness): a higher degree of vitrification results in a clearer sound, lower water absorption, and a lustrous appearance; a lower degree of vitrification produces a muffled sound, higher water absorption, and a dull appearance lacking luster.