When listening to the Hebrew speakers, learners need a "speak slowly" button. The female voice, in particular, speaks much too fast to be understood.
I think it would depend on the phone. Mine is an Android Motorola-something. So, when I am in the Duolingo app, and the onscreen keyboard is in the Hebrew layout, there is a microphone icon in the top left corner of the keyboard (if in English, it is in the top right corner). This icon activates the speech-to-text function.
But again, this is in my phone, and yours could be different. Hope it works out for you!