Hybrid millidecade spectra: A practical format for exchange of long-term ambient sound data.

S Bruce Martin,David A Mann,Peter J Dugan,Dimitri W Ponirakis,Jennifer L Miksis-Olds,Briand J Gaudet,Holger Klinck,David K Mellinger,Olaf Boebel,Colleen C Wilson,Hilary Moors-Murphy

doi:10.1121/10.0003324

Abstract

This Letter proposes a frequency scaling for processing, storing, and sharing high-bandwidth, passive acoustic spectral data that optimizes data volume while maintaining reasonable data resolution. The format is a hybrid that uses 1 Hz resolution up to 455 Hz and millidecade frequency bands above 455 Hz. This hybrid is appropriate for many types of soundscape analysis, including detecting different types of soundscapes and regulatory applications like computing weighted sound exposure levels. Hybrid millidecade files are compressed compared to the 1 Hz equivalent such that one research center could feasibly store data from hundreds of projects for sharing among researchers globally.

Highlights

In the acoustic realm, the effects of anthropogenic sound on marine and terrestrial life have become a growing concern
The format is a hybrid that uses 1 Hz resolution up to 455 Hz and millidecade frequency bands above 455 Hz. This hybrid is appropriate for many types of soundscape analysis, including detecting different types of soundscapes and regulatory applications like computing weighted sound exposure levels
An excellent example of this type of work is analyzing the change in sound levels due to changes in human activity during the COVID-19 pandemic (Lecocq et al, 2020; Thomson and Barclay, 2020)

Summary

Introduction

The effects of anthropogenic sound on marine and terrestrial life have become a growing concern. Deci-decade resolution, in which a factor of 10 in frequency (e.g., from 1–10 kHz) has 10 frequency bins, and is suitable for many applications, such as quantifying weighted sound levels of human activities, or comparing sound levels to the hearing capabilities of marine and terrestrial life. It is inadequate for quantifying abiotic information, such as wind speed and rainfall, because the spectral slope is not preserved at the decidecade resolution (Vagle et al, 1990; Ma et al, 2005). The millidecade frequency resolution proposed here is a hybrid of the recommended and optimal guidelines that (1) increases data resolution over the decidecade recommendation, and (2) provides information in a format that allows users to calculate decidecade or user-specified band levels, while (3) maintaining a manageable data package size for transfer and comparison

Definition of millidecades

Example results

Discussion

Summary