Intermittent Static on Boot

[Guest r.bobbington]

I've rooted my Pulse and installed Paul's custom ROM (1.7 U8230 Vanilla) onto it, but whenever I boot up the device static (and a little pop) starts being produced from the speakers as soon as I click on anything on the screen or press any button. After a few seconds of doing nothing the static stops. If I continue to press things the static continues. Does anybody know:

i) why it is doing this?

ii) how to stop it doing this?

I bought my Pulse after they came back into stock on PAYG and it already had the December update installed.