Abstract

Historically there have been two methods used to measure the noise level reduction (NLR) of structures exposed to aircraft noise. The first employs aircraft as the exterior noise source; the second uses a fixed loudspeaker or a tripod as an artificial noise source placed outside the building on the ground. The purpose of this study was to investigate the feasibility of using an unmanned aircraft system (UAS), or drone, as the carrier of a loudspeaker in space, which would simulate the effects of realistic flight operations and the associated shielding effects from building structures.

Several UAS and loudspeaker models were evaluated for testing criteria, and the final assembly of the UAS-mounted loudspeaker consisted of a JBL 108BT loudspeaker (17.6 lb), with an inverter (5.3 lb), mounted on and powered by a Hylio AG110 battery-powered UAS. The system was capable of generating an overall aircraft spectrum sound level of 87 A-weighted sound pressure level (dBA) at a distance of 11 m (36 ft).

The UAS-mounted loudspeaker system provides a flexible method for positioning the loudspeaker for hover and flyover measurements. The flight path and trajectory of the UAS can be preprogrammed or input manually, to provide an array of simulated aircraft flight paths. Applications of the system include:

• Measuring NLR of complex structures with limited access.
• Validating corrections for roof contribution.
• Investigating the difference between aircraft and loudspeaker NLR measurements.
• Measuring NLR in multi-story buildings where other methods are not possible.