Melvin L.Kreithen, ahli burung yang meneliti indra pendengaran burung, mengamati bahwa beberapa jenis burung dapat mendengar bunyi yang berfrekuensi sangat rendah, yang tersebar jauh dalam atmosfer.
Melvin L.Kreithen, an ornithologist who made research into birds? sense of hearing, observed that some birds can hear sounds of extremely small frequencies, which diffuse to great distances in the atmosphere.