Hi,
Is it possible to download the Audios from text-to-speech?
Depending on the client application which you use.
This is not related to the text-to-speech service but to the client side. In your application which uses the text-to-speech API you can control the client Audio volume
Parameters which are related to the server side include for example: Language, Voice, Speaking style, and Pitch
For example, using the Microsoft online demo: https://azure.microsoft.com/en-us/services/cognitive-services/text-to-speech/#features