Why do diesel cars make more noise than petrol cars?

I am doing a project on petrol price fluctuations and how it affects sales of petrol and diesel cars.Pls help?

• I am doing a project on petrol price fluctuations and how it affects sales of petrol and diesel cars.Pls help me to find details related to this topic. Like : petrol ,history and development,petrol price fluctuations,its reasons,car sales during last year.etc...Can anyone help me pls?

• Answer:

  history : one of the magazine wrote " the 10 dollar/barrel is really horrible pricing for crude oil, it will not be long lasting price, it will come down to 5 dollar asap forever. " but the fact ,then that came down to 15 dollar only once in history, while opec decided to increase the asian quota in 90's .now it stands on $120/barrel. indian people were not much interested on international price of crude oil ,while gov had been deciding the price. 3 years before ,gov gave the right to fix the rate of petrol (fact is :only 7% of the indian population use petrol ) to companies (says its bcz of pressure from private companies like essar and reliance and Manmohansingh's liberal market policy ) . indian people always look on running cost of the the vehicle (even in luxury class like bmw ,audi etc). while the petrol price get a hike and the difference between diesel and petrol has a 25 rupee , people try to prefer diesel vehicle . but most of the indian car makers ( world wide passenger car is just petrol ) has been producing petrol car more than diesel . so it effect on availability and sales .