Humming

A 'hum' or 'humming' by humans is created by the resonance of air in various parts of passages in the head and throat, in the act of breathing.

Joseph Jordania suggested that humming could have played an important role in the early human (hominid) evolution as contact calls.

[1] Many social animals produce seemingly haphazard and indistinct sounds (like chicken cluck) when they are going about their everyday business (foraging, feeding).

[3] In Pirahã, the only surviving dialect of the Mura language, there is a special register of speech which uses solely humming, with no audible release.

[4] Humming is often used in music of genres, from classical (for example, the famous chorus at the end of Act 2 of Giacomo Puccini's Madama Butterfly) to jazz to R&B.