This project will provide new insights into the presence and intensity of underwater noise in urban freshwater ecosystems and its effects on wildlife – an area that has been understudied to date. For the first time in Macedonia, passive acoustic monitoring will be applied for ecological assessment of aquatic habitats, combined with biological experiments. The expected scientific contribution includes identifying noise thresholds harmful to local species, documenting the “sound signature” of the Vardar River and surrounding waters, as well as demonstrating the positive role of natural sounds. The results will fill a gap in the literature on aquaacoustics and will serve as a basis for future research and conservation measures, contributing to global efforts to reduce noise pollution.
Comparative Eco-Acoustic Analysis: Anthropogenic Noise vs. Natural Aquatic Environments
Empirical data and hydrophone measurements collected by students in Skopje, North Macedonia, in accordance with the EU Mission "Restore our Ocean and Waters by 2030".
Project: WAVES Initiative — STE(A)M Educational Framework
Research Location: Skopje, North Macedonia
Relevance: Aligned with the EU Mission "Restore our Ocean and Waters by 2030"
1. Introduction and Environmental Context
Within the framework of the WAVES initiative, students conducted underwater eco-acoustic measurements to quantify the impact of urban development on river ecosystems.
From a physics perspective, water is an exceptionally dense medium. The speed of sound in freshwater is approximately v ≈ 1500 m/s, which is nearly 4.5 times faster than in air. Consequently, underwater sound waves experience very little resistance — they travel significantly greater distances, carry higher pressure, and exert direct mechanical and physiological impacts on aquatic biodiversity.
2. Comparative Waveform Analysis
Based on the visual waveforms captured by the students using a hydrophone, two diametrically opposed acoustic profiles were recorded:
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Profile A (Treska River):
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Waveform Description: The graph displays extended periods of acoustic calm and low baseline amplitude, interspersed with sporadic, isolated amplitude spikes.
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Scientific Interpretation: This baseline reflects a healthy natural river balance. Background noise pollution is minimal, and the occasional peaks represent biophonic or geophonic events (hydraulic flow around natural obstacles, movement of riverbed pebbles, or native aquatic fauna communication). This represents a pristine and stable habitat.
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Profile B (Location Vardar River):
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Waveform Description: A chronologically dense, continuous waveform with persistently high amplitude levels fluctuating between 0.5 and 1.0 on the relative volume scale. No periods of silence or pauses are present.
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Scientific Interpretation: This provides direct empirical proof of severe anthropogenic acoustic pollution. Constant vehicle traffic, tire friction, and engine operations on the busy bridge generate low-frequency structural vibrations. These vibrations travel through the bridge pillars directly into the water column, creating a permanent underwater "acoustic smog."