Personalized Voice Recognition and your privacy
Google takes your privacy seriously. Information that you provide to Google often helps improve product performance. However, some people value greater privacy over performance. Therefore, personalized speech recognition is an opt-in service that you can choose not to use if you prefer.
To opt in, go to Settings > Language & input > Voice Search, then check the box next to Personalized Recognition.
What is the benefit of personalized voice recognition?
Knowing what you said in the past allows Google to build specialized models that match your voice and your words. Over time, this allows Google to improve the speech recognition accuracy for you. To do that, Google keeps samples of what you said in the past.
Why does Google link you to your voice recordings?
Normally, all saved speech samples remain anonymous. In other words, Google stores millions of voice recordings with no way of telling who was speaking. When you sign up for personalized speech recognition, Google creates an electronic key that links your speech samples with your Google Account. Google uses this key to access voice samples and improve recognition of your speaking voice.
How is your data protected?
The electronic keys that link your samples to your account are designed to be accessed by machines, not people. Very few people within Google can access these keys, and only after strict vetting. Your customized voice recognition models are binary files also designed for use by machines.
What if you change your mind?
To opt out of personalized voice recognition on your Android device, go to Settings > Language & input > Voice Search, then uncheck the box next to Personalized Recognition.