Relationship of above- and below-water sound.

<p>Patterns and correlation of overall sound (average power in dB) between above-water and hydrophone data by frequencies corresponding to anthrophony (•, mean: 1–3 kHz) and biophony (Ο, mean: 3–8 kHz). Regression on individual frequency intervals resulted in a significant correlation for only the 0–1 kHz band (<i>R²</i> = 0.71, <i>p</i> = 0.02, all others <i>R²</i><0.03, <i>p</i>>0.69).</p

Dominant frequencies and acoustic variation by urban category in multivariate space.

<p>Principal component analysis summarizing patterns of relative power in eight frequency intervals across the study lakes. Each data point represents one of four time periods at an individual lake. Urban categories are delineated with ordination hulls (90% confidence interval) according to High (solid), Medium (dotted), and Low (dashed) surrounding urbanization. Inset displays the component loadings (eigenvectors) for each frequency interval.</p

Temporal trends in anthropogenic sound by urban category.

<p>Average power (1–2 kHz) at lakes characterized as Low (<30%, <i>n</i> = 3), Medium (30–50%, <i>n</i> = 3), and High (>50%, <i>n</i> = 4) urbanization. The threshold established by the U.S. Environmental Protection Agency (in dBA) for “outdoor annoyance and disruption” <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0055661#pone.0055661-Environmental1" target="_blank">[7]</a> is shown as a reference; dBA is highly comparable in this frequency range, with a weighting value of +0–1.2 dB between 1–2 kHz; we have considered these equivalent for purposes of illustration.</p

Study area, apparatus, and sampling locations.

<p>A) King County in Washington State, U.S.A., B) floating platform with microphone, and C) location of lakes across an urbanization gradient (green = forested; red = urbanized). The city of Seattle is located on the left (west) of the map.</p

Regression models for fixed effects of spatial and temporal factors on relative power of anthrophony and biophony.

<p>Regression was on mean power by time period for each lake (<i>n</i> = 40); significant fixed effects (<i>p</i><0.05) are highlighted in bold. Tests for interactions of fixed effects resulted in no significant relationships so interaction terms were removed.</p

Changes in importance of frequency intervals by time period for a single lake.

<p>Principal component analysis summarizing patterns of relative power in eight frequency intervals using all 24 time selections for Morton Lake (urbanization = 40%). Labels delineate the multivariate centroid for individual data points for each time period: Night (N), Morning (M), Day (D), and Evening (E). Inset displays the component loadings (eigenvectors) for each frequency interval.</p