Intermittency ratio: A metric reflecting short-term temporal variations of transportation noise exposure

Wunderli, Jean Marc; Pieren, Reto; Habermacher, Manuel; Vienneau, Danielle; Cajochen, Christian; Nicole Probst‐Hensch; Röösli, Martin; Brink, Mark · 2015 · OpenAlex-citations

DOI: 10.1038/jes.2015.56

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This paper addresses the limitations of standard acoustic exposure metrics, such as the equivalent continuous sound pressure level ($L_{eq}$), in predicting health effects like annoyance and sleep disturbances. While $L_{eq}$ measures average energetic dose over time, it fails to capture short-term temporal variations and the emergence of individual noise events from background noise. The authors hypothesize that intermittent noise sources (e.g., railways, aircraft) may have different health impacts than continuous sources (e.g., busy highways) even at equal average levels. To address this, the study introduces the "intermittency ratio" (IR), a new metric designed to quantify the proportion of total acoustic energy contributed by distinct noise events exceeding a specific threshold. The IR is defined as the ratio of event-based sound energy to total sound energy, expressed as a percentage. The calculation method involves estimating the distribution of maximum pass-by levels using traffic flow data, vehicle speeds, geometry, and single-event levels. A threshold is set relative to the long-term average noise level plus a 3 dB offset to distinguish events from background noise. The authors implemented this calculation method in the Swiss noise mapping database (sonBASE) and applied it to approximately 54.3 million facade points across Switzerland. This allowed for the generation of noise maps visualizing both $L_{eq}$ and IR simultaneously for road, rail, and aircraft traffic. The results demonstrate that IR effectively distinguishes between intermittent and continuous noise scenarios. For instance, railway noise exhibited high IR values (e.g., 87%) due to distinct events emerging from quiet backgrounds, while dense highway traffic showed low IR (e.g., 19%) due to near-constant noise levels. Crucially, the study found low correlations between IR and standard $L_{eq}$ metrics (Pearson coefficients ranging from 0.10 to 0.46), confirming that IR provides independent information not captured by average levels. Maps revealed that IR varies significantly based on source type and receiver position; for example, aircraft noise had high IR only in areas with low background road noise, whereas road traffic IR was higher near smaller roads with sparse traffic than near highways. The significance of this work lies in providing a practical, calculable metric that complements traditional exposure assessments. By quantifying the "eventfulness" of noise, IR offers a tool to better explain variance in epidemiological studies regarding cardiovascular effects and annoyance. The authors conclude that incorporating IR alongside $L_{eq}$ can improve the prediction of noise-induced health outcomes, particularly for sleep disturbances and cardiovascular arousals triggered by intermittent events. The study validates the metric's applicability in large-scale environmental health research, such as the SiRENE study, and encourages further validation through subjective resident ratings.

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• exposure measurement