1.
When used sound channel 4 (noise part) in GBA, the sound is very small volume.
-Drill Dozer / Screw Braker
-etc... (Perhaps, All GBA titles which use this sound channel for.)
Reference: tokyo.cool.ne.jp/kataikamo/sb.7z
rec source: nogba2.6 no$gba 2.6, vba-msvn956 VisualBoyAdvance-M SVN956, gbasp Original Hardware(GBA-SP)

2.
Audio of Direct Sound Channel is a very low tone.
-Magical Vacation
Reference: tokyo.cool.ne.jp/kataikamo/mv.7z
rec source: vba-msvn956 VisualBoyAdvance-M SVN956, gbasp Original Hardware(GBA-SP)

3.
When moved some GBA titles, the noise that does not sound usually sounds in sound left channel.
-Golden Sun 2 / Ougon no Taiyou: Ushinawareshi Toki
-Made in Wario / Wario Ware, inc.
-Guru Logi Champ