Can I check voice recording using iPhone emulator or do I need an actual device?
Yes. If you have a microphone on your Mac, the emulator will receive audio from the microphone. iMacs and MacBook have one built-in - for other models you may need to connect an external microphone.
Please note that this can be useful for a rough test, but the volume can differ significantly from your computer, so you really want to test at least once on the actual device before sending.