sound, to put in the mouth
唅 centers on producing a sound or holding something in the mouth. The two given meanings are not obviously connected; one relates to vocal sound, the other to containing something orally.
唅 combines 口 (mouth) with 含 (contain, include), which likely contributes both sound and the idea of holding in the mouth. The exact historical development is uncertain.
The mouth radical 口 beside 含 (contain) suggests holding something in the mouth or producing a contained sound.
For カン, imagine a can held in the mouth: can -> カン, and the mouth holds the can while making a muffled sound.