Every time we meet a new audio device with a USB interface, we test it for compatibility with the iPad. Once we checked this tiny USB microphone: Shure... | By Open Sound
RTA by Andrew Smith
Mobile measuring rig : r/livesound
Dayton Audio iMM-6 Calibrated Measurement Microphone for Tablets iPhone iPad and Android
Itestmic – Studio Six Digital
iPad RTA Analyser with external mic - YouTube
DBX Driverack VENU 360 Loudspeaker Management System+ RTA-M Omni-Directional MIC
AudioControl New SA-4140i Hi-SPL Measurement Microphone Now Shipping | audioXpress