Bloomin' noisy children

During half term last week I took one and only son to the Imperial War Museum for a day out.  Naturally it was packed out - it was half term so I had expected the place to be heaving with people.  But what I couldn't get over was the amount of children who were allowed, and I carefully use the word 'allowed', to go completely unchecked by parents when the racket levels went way too high.
Obviously I expect the occasional parent not to give a monkey's when their child is annoying somebody, and there will sometimes be a case when a child has special needs, but I take these exceptions into account.
But in that museum there were quite a lot of  instances when an unconcerned parent let their child make an absolute annoyance out of themselves and failed to step in. 
One mum stood passively by while her little girl pressed a button which produced the noise of a ship's bell.  She hit the button 15 times at least - I know this because after the first five I had started counting.  There was a din each time the button was pressed - I know some of the exhibits are deliberately made to attract children to use them and learn about history (and I'm all for it) - but I couldn't understand how the mum couldn't realise that the repetition wasn't doing the girl much good, not to mention my poor old ears.  Why didn't she step in and coax her along to see something else?  Is it me who is overly sensitive?  I don't think I was overly sensitive, and, more interestingly, I noticed other children were put out by the behaviour and turning their heads in exasperation.  Of course, nobody said anything, because we daren't criticise anybody else's children for fear of a mouthful in return.
Another parent had two boys, who would be around 10 and 12, and his voice boomed out as he gave a running commentary.   Fair play to him for trying to get them interested, but they pushed past everyone, made flippant remarks about the information on the boards, and did all this very loudly.  They must have got absolutely nothing out of that visit. Could I suggest that if you know your children are inclined this way, then don't take them.   These types of behaviour were multiplied by other youngsters as we spent a few hours at the museum - they weren't isolated incidents.
I have a theory.  Some families have developed loud voices because they have to make themselves heard over the top of the telly blaring out or those games consoles.  I am  in no 'holier than thou' situation because one and only son does have a games console thingy, but I would definitely step in if his actions were annoying to other people.  If you don't teach them to be aware of other people, you aren't doing them any favours as they approach adulthood.   I'm sure we all know an adult who is totally unaware of everyone else's perception of them.  
This lack of correction or failure to ensure a child behaves well seems to be getting worse.  Or is it me? Are my advancing years making me too intolerant?