Duostories uses different services for text to speech generation. Depending on which voice name you select a different engine will be uses.
The voices have the format en-GB-SoniaNeural.
You can get a list of voices: here.
The voices have the format tr-TR-Wavenet-A or tr-TR-Standard-A.
The voices with "Wavenet" use an AI method for voice generation and produce typically a better output.Duostories
You can get a list of voices: here
These voices have a format Justin.
You can ge a list of voices: here