# Advanced Aero-Acoustic Research Facilities at NASA Glenn

Exploring specialized ground-based testing rigs designed to mitigate aircraft noise and improve propulsion efficiency.

- **Source:** [NASA](https://www.nasa.gov)
- **Published:** 2026-10-19
- **Topic:** [Business](https://brifing.si/c/business)
- **Original article:** <https://www.nasa.gov/centers-and-facilities/glenn/acoustics-experimental-facilities/>
- **On Brifing:** https://brifing.si/s/42cc6e2b-ac62-4d5b-acc4-945c21e3eab1

## Facility Overview and Purpose

NASA Glenn Research Center operates specialized facilities including the 9x15 Low-Speed Wind Tunnel and the Aero-Acoustic Propulsion Laboratory. These sites provide controlled environments for studying aircraft engine aerodynamics and acoustics. By simulating takeoff and landing conditions, researchers gather critical data to reduce noise pollution in communities located near major commercial airports.

## Wind Tunnel Infrastructure Upgrades

The 9x15 Low-Speed Wind Tunnel underwent major modifications in 2019 to enhance airflow quality and minimize background noise. A new five-sensor traversing microphone rake was integrated to measure sound from experimental propulsors. These improvements allow for more precise analysis of engine performance during critical flight phases, directly supporting quieter aircraft design.

## Aero-Acoustic Propulsion Laboratory Design

Constructed in 1993, the AAPL is a 65-foot radius geodesic dome designed to prevent sound reflections. It utilizes 17,000 custom-made, two-foot thick fiberglass wedges on its walls and floor. This configuration creates an anechoic environment, making it the first free-standing dome of its kind to effectively isolate and absorb internal sound transmissions.

## Small Hot Jet Acoustic Rig

The SHJAR is a key tool for testing single-stream nozzles up to 5 cm in diameter at Mach 2.0. Researchers use this rig to connect nozzle geometry with jet flow and noise production. Advanced diagnostic techniques like Rayleigh Scattering and Particle Image Velocimetry are deployed here to map turbulence and validate computational models.

## Breakthroughs in Jet Noise Research

In 2006, SHJAR researchers achieved the first time-resolved particle image velocimetry to measure turbulent velocities in hot jets. More recently, Raman-based optical methods enabled high-frequency thermodynamic temperature measurements. These statistics are essential for refining turbulence models, which help engineers predict noise levels more accurately for future aircraft engine designs and configurations.

## Nozzle Acoustic Test Rig Capabilities

The NATR is a free-jet wind tunnel used to evaluate nozzle noise reduction concepts before full-scale testing. It simulates flight conditions up to Mach 0.35, allowing engineers to test military and commercial scale models. This facility was instrumental in the 1997 discovery of chevron nozzles, which are now standard on modern aircraft.

## Supersonic and Future Engine Testing

NATR supports testing for supersonic airliners to ensure they meet environmental standards for airport operations. By testing dual-fan systems and other low-noise concepts, NASA reduces the risk associated with unconventional engine designs. The ability to measure far-field noise while simulating flight velocity remains a unique and critical capability of this specific facility.

## DART Turbofan Research Integration

The DGEN 380 Aero-propulsion Research Turbofan, or DART, serves as a flexible testbed for multidisciplinary research. Tests completed in August 2019 focused on propulsion-noise sources using circumferential infinite-tube-probe arrays. This data helps refine noise-prediction methods and mitigation techniques, providing a comprehensive understanding of how engine controls and installation effects influence overall acoustic output.

## Acoustical Testing Laboratory Versatility

The ATL supports both human space exploration and aeronautics missions through its configurable anechoic chamber. With walls lined by 34-inch deep fiberglass wedges, it absorbs 99% of sound above 100 Hz. Recent projects include quantifying noise from International Space Station experiments, calibrating microphones, and evaluating engine inlet models for future supersonic flight applications.

## Sources covering this story

- https://www.nasa.gov/centers-and-facilities/glenn/acoustics-experimental-facilities/ — 

---

_Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._