uas-sound-event

Simulates simple atmospheric acoustic propagation effects for rendering multichannel auralisations of unmanned aerial systems (UAS - drones), or other airborne sources, in motion.

The model assumes that input source signals have been recorded at a fixed distance and with a fixed rotational speed. Auralisations are created assuming free-field propagation and account for the following: * Doppler effect * Distance-dependent atmospheric absorption of high frequencies * Ground reflection (including path length difference and angle-dependent high-frequency absorption) * Distance-based amplitude panning (DBAP) to spatialise source in 3D loudspeaker array (direct sound and ground reflection spatialised separately).

Author: Marc C. Green (m.c.green@salford.ac.uk)

Affiliation: University of Salford (Acoustics Research Centre)

Copyright statement: This file and code is part of work undertaken within the REFMAP project (www.refmap.eu), and is subject to license.

Based on method detailed in: Heutschi, K., Ott, B., Nussbaumer, T., and Wellig, P., "Synthesis of real world drone signals based on lab recordings," Acta Acustica, Vol. 4, No. 6, 2020, p. 24.

Usage

The main object implementing the propagation model is UASEventRenderer. This object is initialised using CSV files defining flightpaths in segments. Each segment requires the definition of start and end points in cartesian co-ordinates, along with starting and ending speeds in meters per second. The following is an example flightpath configuration file with four segments. Further examples can be found in the flights/ directory.

segment, startxyz, endxyz, speeds constant-speed flyby, 10 -200 30, 10 180 30, 30 30 decelerate, 10 180 30, 10 200 30, 30 0 accelerate, 10 200 30, 10 180 30, 0 30 flyby back, 10 180 30, 10 -200 30, 30 30

Using these CSV flightpath definitions, UASEventRenderer calculates the position of the source at every sample time. These positions are used to calculate the delays, distances, and angles required to render the propagation effects based on a listener located at the origin of the co-ordinate system.

The listener height is set to 1.5 m by default. This affects the calculation of the ground reflection signal in particular. Additional parameters include the ground material, which can be selected from 'grass', 'soil', or 'asphalt', and the loudspeaker layout to target with the DBAP panning (currently only 'Octagon + Cube' is implemented).

The object's render() method can then be used to generate a time-series signal at the receiver point. The input source used should be sufficient in length to cover the time taken to cover the entire defined flightpath.

The following is a basic script for rendering an event:

``` import soundfile as sf from uasevent.environment import UASEventRenderer from uasevent.utils import load_params

x, fs = sf.read('examplesource.wav') renderer = UASEventRenderer( loadparams('flightpath.csv'), receiver_height=1.5, fs=fs)

output = renderer.render(x) ```