Hi flogger83, the sound in the tutorial missions has always been a little ropey. Sometimes I've experienced prolonged pauses between speech, but don't believe I've ever encountered what you are experiencing.
Also, as you mention that your game seems to increase in speed, I can only think that it might be a CPU-related speed issue. I've heard of the game being 'too fast' in its entirety before, but never just 'sometimes'.
What glide wrapper are you using? If it has the option, make sure to enable 'VSync' as that will reduce and hopefully even-out your framerates. If it's dgVoodoo you're using, see the settings in the shots posted above by gaskin.
Also, you could try a CPU slowdown program, such as Turbo
. There was a topic that someone created a while ago about the slowdown percentages in Turbo, but can't find it right now. Play around with the speed setting in Turbo and see if you can find one that works for you.