Why are buses so noisy?

Is there any reason OC Transpo buses are so noisy?

I live in a Centretown apartment. I am on the fourth floor near a bus stop and traffic-lighted intersection. When a bus pulls up, it is so loud that, if I am watching a film, I have to pause it until the bus is gone because I can’t hear the dialogue. On top of that, bus brakes always seem to put out an ear-piercing squeal.

I don’t understand it. Garbage trucks, delivery vehicles and heavy goods lorries go by without worry. But buses are hugely noisy.

From what I understand, a city bus costs somewhere in the range of $500,000 to $750,000. For that kind of money, surely they should be quiet. Mark Hill, Ottawa