Core noise source diagnostics on a turbofan engine using correlation and coherence techniques

Noise-Source Separation Using Internal and Far-Field Sensors for a Full-Scale Turbofan Engine

Full-Scale Turbofan Engine Noise-Source Separation Using a Four-Signal Method

Contributions from the combustor to the overall propulsion noise of civilian transport aircraft are starting to become important due to turbofan design trends and expected advances in mitigation of other noise sources. During on-ground, static-engine acoustic tests, combustor noise is generally sub-dominant to other engine noise sources because of the absence of in-flight effects. Consequently,...

The Effects of Using Noise Reduction Turbofan Engine Nozzle Designs on a Turbojet Engine

Aircraft noise is a complex topic which is projected to increase with the increasing number of aircraft and size of the engines. Turbine-powered aircraft produce sounds that are considered pollutants at certain decibel levels. Turbofan engines are inherently quieter than turbojet engines for a given level of thrust. The purpose of this research is to determine if current turbofan noise reductio...

Separating Turbofan Engine Noise Sources Using Auto- and Cross Spectra from Four Microphones

The study of core noise from turbofan engines has becomemore important as noise from other sources such as the fan and jet were reduced. A multiple-microphone and acoustic-source modeling method to separate correlated and uncorrelated sources is discussed. The autoand cross spectra in the frequency range below 1000Hz are fitted with a noise propagation model based on a source couplet consisting...

Estimation of signal coherence threshold and concealed spectral lines applied to detection of turbofan engine combustion noise.

Combustion noise from turbofan engines has become important, as the noise from sources like the fan and jet are reduced. An aligned and un-aligned coherence technique has been developed to determine a threshold level for the coherence and thereby help to separate the coherent combustion noise source from other noise sources measured with far-field microphones. This method is compared with a sta...