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1. Novel anthropogenic noise has received considerable attention in behavioural ecology, but the natural acoustic environment has largely been ignored as a niche axis. 2. Using arrays of speakers, we experimentally broadcasted whitewater river noise continuously for three summers, and monitored spider abundance and behaviour across 15 sites, to test our hypothesis that river noise is an important structuring force as a niche axis. 3. We find substantial evidence that orb-weaving spiders (Araneidae and Tetragnathidae) are more abundant in high sound level environments, but are not affected by background noise spectrum. 4. We explore multiple possible mechanisms underlying these patterns, such as loss of vertebrate predators and increased prey capture, and assess spider web-building behaviour and body condition in noise. Continued research on the natural and anthropogenic acoustic environment will likely reveal a web of connections hidden within this neglected ecological niche axis.