# Why does the bubbling of a soda bottle pulsate?

If I take a bottle of carbonated water and open the cap slightly to allow the gas to escape, there will be a sudden rush of bubbles foaming to the top of the liquid for a few seconds, then a partial lull for a few seconds, then another smaller rush of bubbles, then a smaller lull, etc, like a damped oscillation. What causes this pulsation?

It would be interesting to measure the pressure above a saturated CO$_2$ solution as a function of gas flow through the cap. I don't have the kit to do this, but it wouldn't be a difficult experiment.