Requirements for Drone Operations to Minimise Community Noise Impact

Abstract

The number of applications for drones under R&D have growth significantly during the last few years; however, the wider adoption of these technologies requires ensuring public trust and acceptance. Noise has been identified as one of the key concerns for public acceptance. Although substantial research has been carried out to better understand the sound source generation mechanisms in drones, important questions remain about the requirements for operational procedures and regulatory frameworks. An important issue is that drones operate within different airspace, closer to communities than conventional aircraft, and that the noise produced is highly tonal and contains a greater proportion of high-frequency broadband noise compared with typical aircraft noise. This is likely to cause concern for exposed communities due to impacts on public health and well-being. This paper presents a modelling framework for setting recommendations for drone operations to minimise community noise impact. The modelling framework is based on specific noise targets, e.g., the guidelines at a receiver position defined by WHO for sleep quality inside a residential property. The main assumption is that the estimation of drone noise exposure indoors is highly relevant for informing operational constraints to minimise noise annoyance and sleep disturbance. This paper illustrates the applicability of the modelling framework with a case study, where maximum A-weighted sound pressure levels LAmax and sound exposure levels SEL as received in typical indoor environments are used to define drone-façade minimum distance to meet WHO recommendations. The practical and scalable capabilities of this modelling framework make it a useful tool for inferring and assessing the impact of drone noise through compliance with appropriate guideline noise criteria. It is considered that with further refinement, this modelling framework could prove to be a significant tool in assisting with the development of noise metrics, regulations specific to drone operations and the assessment of future drone operations and associated noise.

Keywords: community noise impact; drone noise; noise annoyance; noise metrics; noise regulation; sleep disturbance.

Figure 1

Framework for drone operating recommendations based on acoustic metrics analysis.

Figure 2

The measurement setup. Adapted with permission from Ref. [18].

Figure 3

Spectrograms and $L{A}_{max}$ values for three drone models: GD28X (left), M200 (middle), and Typhoon (right) during fast (top) and slow (bottom) flyover operations at ~47.5 m altitude above the CLG. Data adapted with permission from Ref. [18].

Figure 4

The modelling framework for the requirements of drone operations based on the guidelines for indoor acoustic objectives.

Figure 5

Sound exposure level $SEL$, maximum noise level $L{A}_{max}$, and effective time $t_e$. The presented data corresponds to a recording during a fast flyover operation of the drone Typhoon.

Figure 6

$L{A}_{max}$ for the drone Typhoon during fast flyover operations (left); adapted with permission from Ref. [18]. Sound reduction index of a 70 mm PVC-U bottom hung inward tilt window 4-16-4 mm (0.94 m²; 26.00 kg/m²). Predicted $R$ by INSUL software (middle) and measured $R^{\prime }$ (right); reprinted with permission from Ref. [32]. Note that “shifted reference curve” is the specific term used in [31] for obtaining a single value from frequency-dependent sound reduction index.

Figure 7

$L{A}_{max}$ by frequency as a function of the drone/façade distance $r$, outdoors (left) and indoors (right) through the assumed partition ($0.05 {\mathrm{m}}^2$ window open area). The measured apparent sound reduction index $R^{\prime }$ of the partition due the glazing open area is included (middle); adapted with permission from Ref. [32].

Figure 8

Drone/façade distance $DFd$ as a parameter to estimate fitting curve model as a function of $L{A}_{max,indoors}$.

Figure 9

Recommended drone/façade distance based on the $L{A}_{max,indoors}$ for drone GD28X at fast and slow flyover operation near a façade with a conventional window–open area 0.05 m².

Figure 10

Recommended drone/façade distance based on the $L{A}_{max,indoors}$ for the tested drones at fast flyover operation near a façade with a conventional window–closed.

Figure 11

Recommended drone/façade distance for the drone Typhoon based on $L{A}_{max,indoors}$(left) and $SE{L}_{indoors}$ (right).