High-Resolution Measurement of Infrasound and Low Frequency Noise in a Subway-Driver Compartment

Background: Quantification of acoustic energy within the Infrasound (≤20 Hz) and Low Frequency Noise (≤100 Hz) (ILFN) range is infrequently achieved. Subway-driver compartments are occupational environments where ILFN can impact worker safety and performance. The goal here is to quantify ILFN levels within these compartments. Methods: Using high-resolution data acquisition (SAM Scribe system), continuous acoustical recordings were captured within the compartment for a total of 16 h (Day 1, weekday) and 13 h (Day 2, Sunday). Quantification of ILFN (≥0.5 Hz) used a spectral resolution of 1/36th octave and 1-s temporal resolution rendering unweighted sound pressure level (SPL). Results: For each of the 173, 10-min recordings, sonograms and frequency-distribution plots were constructed. A total of 69 harmonic series with distinct fundamental frequencies were repeatedly identified, the most common being 45.97 Hz (N = 21). Within the infrasonic range alone, a total of 35 harmonic series were repeatedly identified, the most common fundamental frequency being 16.0 Hz. SPL at 8 Hz and at 16 Hz were particularly elevated (85–91 dB). Conclusion: High-resolution ILFN measurements might provide more appropriate measures with which to establish dose-response relationships, which are still lacking among the scientific and medical communities.