Whose voice carries the farthest naturally?

Silbo Gomero is a whistled register of Spanish used by inhabitants of La Gomera in the Canary Islands that can be understood at distances of up to 5 km across the island's deep ravines and valleys. Whistles carry farther than spoken voice because they produce a narrower frequency band (between 1,000 and 4,000 Hz) that cuts through ambient noise more efficiently. The language encodes Spanish phonemes into 2 vowel and 4 consonant whistles, allowing speakers to have full conversations. Developed by the island's original Guanche inhabitants (pre-Hispanic), it was adopted for Spanish after colonization. UNESCO recognized Silbo Gomero as an Intangible Cultural Heritage of Humanity in 2009. It is a mandatory subject in La Gomera's schools to ensure preservation.