Defect in iPhone 6s causes distorted sound from the external speaker at higher volumes. Buzzing and crackling of sound can be heard from iOS sounds (i.e. send message "swoosh") and from outside sources (Music, YouTube, voice calls, etc.)
Plug in earbuds, and sound quality is fine. Here is how it is supposed to sound:
https://www.youtube.com/watch?v=bbU31...