AnkiMobile 2.0.56+ supports using TTS tags in card templates. Please see the computer manual for more information.
To get the best quality sound, please go to the iOS Settings app, then:
Tap on Accessibility
Tap on VoiceOver
Tap on Speech
Tap on Voice
Tap on the voice you want to use
If there is an (Enhanced) version available, download it.
Please note that Apple limit Siri to their own apps, so you will need to pick a voice other than Siri.
The Voice section will only show options for your current language. To add voices for other languages, tap on "Rotor Languages", and after selecting another language, you will have a chance to download voices.
Like regular audio, text to speech will not play automatically when your device’s mute/vibrate switch is enabled.