Flight Experience Sydney - What a beauty! This is a 1973 Learjet 25B, with the mandated hush kit for stage 3 noise compliance. Airplanes like this, with turbojet engines, are very loud.
![Engine Hush kit for Super Q MD 80 airliner jet plane at the Farnborough International Airshow 2006. MD-82, fitted with Super 27 aero engine mufflers Stock Photo - Alamy Engine Hush kit for Super Q MD 80 airliner jet plane at the Farnborough International Airshow 2006. MD-82, fitted with Super 27 aero engine mufflers Stock Photo - Alamy](https://c8.alamy.com/comp/2FKEAP4/engine-hush-kit-for-super-q-md-80-airliner-jet-plane-at-the-farnborough-international-airshow-2006-md-82-fitted-with-super-27-aero-engine-mufflers-2FKEAP4.jpg)
Engine Hush kit for Super Q MD 80 airliner jet plane at the Farnborough International Airshow 2006. MD-82, fitted with Super 27 aero engine mufflers Stock Photo - Alamy
![aviation history - What noise reduction measures were taken in the time between hush kits and chevrons? - Aviation Stack Exchange aviation history - What noise reduction measures were taken in the time between hush kits and chevrons? - Aviation Stack Exchange](https://i.stack.imgur.com/KtHiK.jpg)