Limitations of the A-weighting Network in Measuring noise with Substantial Infrasound and Low-frequency Components – A Computational Approach

Aim: This study seeks to investigate the inadequacy of the A-weighting network for measuring noise characterized by substantial infrasound and lower frequency components. Utilizing a computational approach, the research aims to elucidate the limitations of A-weighting, which primarily focuses on frequencies perceptible to the human ear. Methods: The methodologies and equations employed in this analysis adhere to the international standard IEC 61672-1 for the computation of the A, C, and Z frequency-weighting networks. Weighting values for these three different networks were determined across various frequencies within one-third octave bands. Subsequently, utilizing the derived weighting values, sound pressure levels were calculated across 34 distinct one-third octave band frequencies, ranging from 10 to 20,000 Hz, as well as the total sound pressure level for artificial high-content and low-frequency noise. Results: The largest (most negative) weighting factor was at 10-Hz frequency for both the A and C networks. The weighting factor decreases with increasing frequency: for the A-network, from 10 to 500 Hz, and for the C-network, from 10 to 160 Hz. Above those frequencies, the weighting factor becomes smaller (more positive). The C weighting was zero (0 dB), for nine, contiguous one-third octave frequency bands from 200 Hz to 1250 Hz, while for the A-weighting, only the 1000 Hz frequency band has zero (0 dB) weighting. Weighting for the Z-network was zero (0 dB) at all frequencies. For an artificial high-content and low-frequency noise, the A network greatly reduces the value of the total sound pressure level (73.68 dB) when compared to the C network (96.44 dB), and especially when compared to the Z network (104.33 dB). Conclusions: The utilization of the A-weighting network in noise measurement fails to adequately identify locations characterized by high levels of infrasound and low-frequency noise. Consequently, individuals residing in these areas may inadvertently be exposed to noise-induced health effects, yet the lack of recognition regarding this issue may hinder appropriate public health responses and interventions.