Noise suppression ENGINE NOISE

Fig. 19-4 Comparative noise sources of low and high by-pass engines.

6. Compressor and turbine noise results from the interaction of pressure fields and turbulent wakes from rotating blades and stationary vanes, and can be defined as two distinct types of noise; discrete tone (single frequency) and broadband (a wide range of frequencies). Discrete tones are produced by the regular passage of blade wakes over the stages downstream causing a series of tones and harmonics from each stage. The wake intensity is largely dependent upon the distance between the rows of blades and vanes. If the distance is short then there is an intense pressure field interaction which results in a strong tone being generated. With the high bypass engine, the low pressure

Rolls-Royce RM60 | Rolls-Royce Conway

Rolls-Royce Conway

Rolls-Royce RM60

Produced in response to an Admiralty contract for a coastal-craft engine with good cruising economy, the RM60, although based on aeroengine philosophy, was designed from the first as a marine gas turbine. Two RM60s went to sea in 1953 in the former steam gunboat HMS Grey Goose, the world's first warship to be powered solely by gas turbines.

Noise suppression Introduction

Noise suppression

Introduction 
Engine noise 
Methods of suppressing noise
Construction and materials 

INTRODUCTION
1. Airport regulations and aircraft noise certification requirements, all of which govern the maximum  noise level aircraft are permitted to produce, have made jet engine noise suppression one of the most important fields of research.

Fig. 19-1 Comparative noise levels of various engine types.

2. The unit that is commonly used to express noise annoyance is the Effective Perceived Noise deciBel (EPNdB). It takes into account the pitch as well as the sound pressure (deciBel) and makes allowance for the duration of an aircraft flyover. Fig. 19-1 compares the noise levels of various jet engine types.
3. Airframe self-generated noise is a factor in an aircraft's overall noise signature, but the principal noise source is the engine.

Introduction Noise suppression, Noise suppression Engine noise, Noise suppression Methods of suppressing noise, Noise suppression Construction and materials, Comparative noise levels of various engine types,