Scale-free distribution of silences

Area of Science:

• Acoustic ecology
• Bioacoustics
• Environmental science

Background:

• Soundscape studies are crucial for understanding ecological processes, biodiversity, and human impact.
• Previous research often focused on differences between soundscapes.
• A universal characteristic of soundscapes remains unexplored.

Purpose of the Study:

• To identify common characteristics shared by all soundscapes.
• To propose a universal distribution for quiet-time and sound-time.
• To investigate the fractal nature of background noise and the temporal characteristics of acoustic events.

Main Methods:

• Analysis of one hour of daylight and one hour of night audio recordings.
• Sampling from ten randomly selected days across seven diverse environments: urban, dry forest, savanna, rupestrian field, Atlantic forest, marine, and freshwater.
• Statistical analysis of quiet-time (background noise) and sound-time (acoustic energy bursts) distributions.

Main Results:

• Quiet-time histograms consistently followed a power law across all analyzed soundscapes, indicating fractal or scale-free distributions (exponent 1.6≤α≤2.0).
• Sound-time distributions exhibited a log-normal or timescale dependence in all environments.
• A typical duration for sound events was found to be between 0.06 and 0.12 seconds.

Conclusions:

• A universal distribution of quiet-time and sound-time exists across diverse soundscapes.
• The power-law distribution of background noise suggests scale-free processes influencing sound environments.
• The consistent, short duration of sound events may be linked to animal physiology and sound production mechanisms.