Static tests of aircraft engines can exhibit greater than 10‐dB random unsteadiness of tone noise levels because flow disturbances that prevail near test site facilities are ingested. Presumably such changes are related to installation and test site features. This paper presents some properties of unsteady noise observed at a NASA—Lewis facility during tests of a Lycoming YF‐102 turbofan engine. Time and spacial variations in tone noise obtained from closely spaced farfield and inlet duct microphones are displayed. Long (0.5‐sec) to extremely short (0.001‐sec) intermittent tone bursts are observed. Unsteadiness of the tone, its harmonies, and the broadband noise show little similarity. In the farfield, identity of tone bursts is retained over a directivity angle of less than 10°. In the inlet duct, tone bursts appear to propagate axially but exhibit little circumferential similarity. They show only slight relationship to tone bursts observed in the farfield. The results imply an intermittent generation of random mixtures of propagating duct modes.