Hi @Tempo57, sorry to hear about this.
Is it only during calls on loudspeaker that the loudspeaker sounds distorted or does it sound distorted in general, for example while playing media through the loudspeaker? Also, have you been able to carry out a quick test of the speakers in the phone to see if the hardware works as intended? To do this, find and tap Settings > Support > Xperia Tests > Speakers & microphone.
Another thing that you can try is to reboot your phone in safe mode to see if the loudspeaker works better there. Safe mode is a troubleshooting mode where all apps downloaded from Play Store is temporarily deactivated, that way you can see whether this behaviour is caused by a downloaded app or not. For more information on safe mode and how to use it, click here.
Try this to begin with and feel free to keep me posted with the results!
