Voice recognition on a uC, especially an Arduino, sounds like a pointless attempt. The thing can barely handle audio at all, so trying to process it would be daring at best. You could theoretically write a Neural Network to figure out the code you need to put on the Arduino, but that sounds like
- a lot of work
- it wouldn’t actually ever function
- more of a hassle than it’s worth, since if you can do that, you could just use the Pi
So using the Arduino alone - no.
If you just want to build the gauntlet, voice recognition will probably not be worth it (if it is at all). Just use a hidden button.
If you absolutely want to complicate things and use Bluetooth, you can either use an ESP8266-based BT-module hooked to the Arduino or just buy an ESP8266/32 or similar which comes with BT onboard. Both ways, with the correct library, you will be able to communicate quite easily (our electronics class worked with this, only took most of them 5 years to figure it out ).
If you really don’t know what you want to do with your time or you are going for a full costume with multiple voice-controlled features, just install a RasPi in the helmet/chestpiece/whatever. Let it do the voice recognition (you will probably still need a button if you don’t wanna call your suit ‘OK, Google’) and send commands via UART/BT.
Hope that helped. Happy Making!