[Openal] Sound crackling

[Søren Christiansen]

Hi all,
I'm encountering crackles and pops if I change the source.volume  
frequently like this (pseudo code):

// called 100 pr sec
void Update()
{
	read out [volume]
	alSourcef(id, AL_GAIN, [volume] + 0.01);		
}

Is this expected and/or can I do something to prevent it?
Im on a intel macbook pro.

cheers,

Søren C.