On FreeBSD 7 you dont need to change such sysctl variables.
Code:
hw.snd.maxautovchans: 16
dev.pcm.0.play.vchans: 1
dev.pcm.0.play.vchanrate: 48000
dev.pcm.0.play.vchanformat: s16le
dev.pcm.0.rec.vchans: 1
dev.pcm.0.rec.vchanrate: 48000
dev.pcm.0.rec.vchanformat: s16le