" and a measurable clinical effect. In fact, the Council for the Protection of Rural England (CPRE), founded in 1926, devoted itself to these places, promoting a “sustainable future” for the English countryside. A “tranquil zone” was later defined by the CPRE as “anywhere that lies at least 4 km [about 2.5 miles] from a large power station, 3 km from a major motorway, major industrial area or large city, 2 km from other motorways, trunk roads or smaller towns, 1 km from busy local roads carrying more than 10,000 vehicles per day or the busiest main-line railways. It should also lie beyond the interference of civil and military aircraft.” In addition, one of the criteria was the ability to turn 360 degrees and not have any visual interference from power "
― Bernie Krause , Sounds from The Great Animal Orchestra (Enhanced): Earth