Crackling sound on iPhone 6S

[sza]

Has anyone has the same issue when slide the volume slider? When I receive a Message, the alert sounds crackling however, the 2nd message alert sounds normal. I am on the latest iOS 11.2.5 on iPhone 6s.

 

[sza]

Can anyone reproduce it?

 

[simonsi]

I <very> occasionally have heard a weird version of an alert when two messages come in really close together, when the lock screen is displayed. It doesn't happen often enough or cause enough of an issue for me to investigate further...

 

[TC_GoldRush]

Video sounds the same, I dodn't hear any crackling.