No Acoustic Feedback for DTMF

Hey there, 

I don't get any acoustic feedback, while using the build in DTMF touchpad. 
But despite this, the numbers are being sent. I checked this!

Is this lack of feedback by design? Or can I somehow activate it?

Best greetings from Germany!

PS: I am very glad to back on the good old rich and luxurious Twinkle! :-)