Outdoor Noise Barrier Calculator

Barrier Height has the largest measured effect on Insertion Loss at this calculator's defaults, ahead of Frequency, Source to Barrier distance, and Barrier to Receiver distance -- taller barriers force sound to diffract around a longer path, which the Maekawa formula (Z. Maekawa's 1968 published diffraction relationship, IL = 10 x log10(3+20N) for Fresnel number N) converts directly into more attenuation. That relationship is not open-ended, though: the Maekawa method's underlying Fresnel-number formula would keep predicting ever- increasing loss for an ever-taller barrier, but this calculator caps the displayed Insertion Loss at 24 dB, the practical maximum recognized for a single barrier. At the calculator's default source and receiver geometry, that cap is reached once Barrier Height climbs to roughly 8.5-9 m -- well within the input's 20 m maximum -- so raising barrier height past that point no longer changes the result at all, even though the underlying diffraction physics is still technically improving.

Don't assume a barrier is working proportionally better just because it's taller once you're already reading the maximum; check whether Insertion Loss has plateaued at 24 dB before spending more on barrier height. Frequency matters because higher frequencies (shorter wavelengths) produce a larger Fresnel number for the same physical path difference, which is why the calculator's helpText correctly notes that higher frequencies are blocked more effectively -- the same barrier geometry blocks high-pitched noise better than low-pitched noise. Every one of this calculator's six inputs feeds into the geometry that determines path difference, so none of them are structurally inert on Insertion Loss the way some coded selections are in other calculators here.