New technologies are providing innovative ways to reduce sound levels in many areas. Aircraft engineers are finding ways to reduce the noise produced by jet engines, while road builders are using rubber-enhanced pavement to quiet highway noise. Indoor acoustics are benefiting from materials that transform sound waves to heat, and so-called active noise control reduces harmful sounds through pro...

An open-jet wind tunnel operating within an anechoic chamber was developed for the purpose of the study of V/STOL noise mechanisms. An existing low-speed conventional hardwalled wind tunnel was modified to operate as an open-jet tunnel; an anechoic chamber was then constructed around the test section. The resulting aerodynamic and acoustic characteristics of the tunnel are discussed. This work ...

Infrasound (low-frequency acoustic waves) has proven useful to detect and characterize subaerial volcanic activity, but understanding the infrasonic source during sustained eruptions is still an area of active research. Preliminary comparison between eruption spectra jet noise similarity suggests that volcanoes can produce form from turbulence. The spectra, empirically derived audible laborator...

The search for an equivalent acoustic source model for high-speed jet noise has recently focused on wavepacket representations. A wavepacket is defined as a spatially extended source with an axial amplitude distribution that grows, saturates and decays, an axial phase relationship that produces directional noise, and correlation lengths longer than the integral length scales of the turbulent st...