In call notification beep

[Gunslingre]

How do you turn off the in call notification beep for incoming messages? If you have the volume turned up for the voice call it's piercing when a message alert goes off.

[_alexdon_]

There doesn't seem to be a way:

/t5/Xperia-Z3-Compact/disable-in-call-notifications/m-p/922248#M5855