The recognition systems improve the more people use them, but they are closed systems so no one other than Apple, Amazon, or Google.
The project named Project Common Voice website includes an option to donate your voice.
If you opt to do so, a number of sentences will be popped up in your web browser for you to say. Once recorded, you can play them back to check they are acceptable before submitting them to help the voice recognition engine learn.
You need to read a sentence to help our machine learn how real people speak.
The area of interest for this project come with demographic data. You can try this project on the official website.