Question

Arrange in the correct order of noise produced by engine type.

(a) Turbojet > turbofan > reciprocating engine

(b) Turbojet < turbofan < reciprocating engine

(c) Turbojet > turbofan = reciprocating engine

(d) Turbojet > turbofan < reciprocating engine

The question was posed to me in an international level competition.

The above asked question is from Configuration Layout Considerations topic in portion Configuration Layout Considerations of Aircraft Design

Answer 1

The correct answer is (a) Turbojet > turbofan > reciprocating engine

For explanation I would say: Engine exhaust aural signatures will be affected by type of engine used. A large diameter propeller with limited tip speed will generate less noise as compare to high speed turbojets. Turbofan aural signature is less than that of the turbojet but greater than the reciprocating engine. Hence, the correct order will be Turbojet > turbofan > reciprocating engine.