Something like this might work:
Global snd=Load3DSound("sounds\bla.wav")
Global chn=0
if Not ChannelPlaying(chn)
chn=EmitSound(snd,p\entity)
endif
Global snd=Load3DSound("sounds\bla.wav")
Global chn=0
if Not ChannelPlaying(chn)
chn=EmitSound(snd,p\entity)
endif