Spatio-Temporal Characterization and Acoustic Mapping of Ambient Noise Levels at Ogbonnaya Onu Polytechnic, Aba, Nigeria: A Multi-Source Compliance Analysis

Abstract

This study investigates the spatio-temporal distribution and acoustic mapping of ambient noise levels at Ogbonnaya Onu Polytechnic, Aba, Nigeria, with emphasis on compliance with international environmental noise standards. Sound pressure levels (SPL) were measured using an Extech 407730 sound level meter at fifteen representative campus locations during morning, afternoon, and evening periods and at distances of 5–25 m from dominant noise sources, yielding 75 pooled observations. The inverse square law of sound propagation was evaluated using a log-distance regression model and nonlinear intensity fitting. The regression produced a slope of −19.63 dB per decade (p < 0.001), closely matching the theoretical −20 dB expected for free-field propagation. Mean SPL decreased from 88.50 dB at 5 m to 74.52 dB at 25 m, yet all values exceeded the WHO-recommended outdoor limit of 55 dB(A) for educational environments. Spatial and temporal analyses revealed the highest noise levels near generator/welding zones, business center areas, and campus gates, highlighting the need for improved campus noise management strategies.