NPS photo

Muir Woods soundscape monitoring volunteers recording ambient noises

Some areas of the park provide visitors with natural quiet. This is the condition attained when a person with normal hearing can hear nothing but the sounds produced by natural components of the park. It may include “silence” — the apparent absence of any sound; or the rush of air over the wings of a soaring bird; the gentle swish of the wind in the trees; or the overwhelming crash and roar of the ocean on a stormy day. Most often, it is thought of as a mixture of mostly low-decibel background sounds, punctuated by the calls and clatter of wildlife. While much of the park is no longer “naturally quiet,” it may be critical to the wildlife to minimize anthropogenic sound. Aircraft, watercraft and road traffic outside the park all contribute to noise levels within the park. Noise generated inside the park includes not only visitor noise (such as vehicles, dogs, and voices), but noise generated by park staff (vehicles, power equipment, and voices). Studies to quantify ambient noise within the park, and the value of natural quiet need to be incorporated into park planning, operations and interpretation.