Fiona! How annoying! lol Charlotte is like that sometimes too - night time is usually fine, but day sleeps suck!
I have found something really interesting though. Generally, babies will sleep if they will sleep - noise or not. For example, if the vacuum cleaner is going when they fall asleep, they will sleep through that noise, or if the builders were working when she FELL asleep, she will be more likely to sleep through it. So if she is going to sleep in a silent or super quiet environment, the the noises (that will seem 'sudden' to her) will more likely wake her. Where as if she goes to sleep while you are unloading the diswasher or someone is walking around the house loudly, she will be more tolerant of noise during her sleeps. (Quote; LimeSlice)

Same here for DS; keep making 'continuous' noise while he is going to sleep and he sleeps through everything. Otherwise I can't go to the bathroom because the noise will wake him.