If a child is doing something to get attention, and it's then ignored he will ALWAYS try harder before he gives up. This is called an extinction burst. If you reward the behaviour during the extinction burst (i.e. giving him the attention when he gets REALLY LOUD) you teach him that persistance pays, and he will probably start at the louder level next time! (For example, if you tried to open a door but it wouldn't open, you would push harder. If it opened when you pushed harder, next time you needed to get through you would probably give it a big shove, as that's what worked last time!)
When you decide on a behaviour plan (and ingoring it really is the best you can do)you have to follow through for it to work - it WILL get worse before it gets better but it WILL decrease eventually if you don't give the attention. And make sure EVERYONE is doing the same thing, helpers, Granny etc, teachers too if they'll agree (although it's hard to get other children at school not to react!)
As well as this approach, you must teach your child a more appropriate way to get you attention - i.e. 'mummy will you play with me' or 'mummy, look what I'm doing/ I've got' etc. When your child is calm, teach him this language, maybe do a funny role play with puppets or the two of you acting it out. While your child is learning these new requests for attention, you must always reward them and make a big fuss of how well he's doing.
You can also make a 'nice words' reward chart. For example, draw a square and stick it to the wall. Set a timer (whatever you think is achievable- can be five minutes at first then increase the time) if your child swears during the time, you go and put a cross on the square (without giving the child attention - also best to keep it out of his reach). When the timer goes off, immediately you go together to 'check' the square, if it's not crossed out make a big fuss 'well done, you kept your square' and he gets a prize (e.g. watches a short thomas clip on youtube). If it is crossed out, say 'oh no Mummy's very sad that you won't get your prize, the square is crossed because you used bad words.' This will teach him to regulate his own behaviour in a more positive way than punishment, and you can increase the 'timer' eventually it'll be if he does a whole week without swearing that he gets a prize.
Please contact me if you'd like any more advice, I'm an applied behaviour analyst.
and tell him that we wouldn't like to hear these words from him and ask him to apologise. he needed a bit of coaxing but he did get into the habit of saying "sorry" whenever he blurted it out by mistake or in anger. he doesn't swear anymore...for now!