呯 is less common than 砰 (pēng), which is the standard onomatopoeia for banging sounds. Both are used in the pattern X的一声 to describe a sudden loud noise.
Left mouth radical — universal flag for onomatopoeia. Placing 口 on the left signals 'this character represents a sound, not a meaning,' the trick used in 嗖, 嗡, 哗, 嘎, 啪. Without it, the right side is just a flat 平; with it, the character is reserved for sound effects.
Right 平 supplies the sound — píng → pīng, only the tone shifts. The 'flat' meaning is irrelevant. This is a rare colloquial onomatopoeia, mostly written 砰 (stone radical) in standard usage; 呯 is the mouth-radical variant flagging the noise as a struck-mouth sound like a gong's clang or gunshot's crack.
No stroke data for 呯; the glyph shown is your device font, so component strokes can't be highlighted.
