Sound Exposure Level corrections for flight altitudes of small aerial vehicles

Recent noise measurements have shown that the sound exposure level duration correction used in the US federal aviation certification requirements for small, conventional, crewed helicopters does not accurately predict noise level differences from altitude changes for small uncrewed aerial system (sUAS) vehicles. This article proposes a modification to the method found in the certification requirements that may allow acousticians to scale the measured noise from sUASs to a common reference altitude with minimal errors. The article presents a mathematical proof of the scaling correction that supports the measured data. The mathematical proof may also have implications for modeling the noise of sUAS vehicles in the publicly available aviation noise computer models.