Dayton EMM-6 measurement microphone, calibrated by Cross-Spectrum Labs
SONARWORKS SoundID Reference Speaker and Headphone 12-41467 B&H
Portable Microphone Calibration Kits
Amazon.com: Digital Sound Level Meter Calibrator 94dB & 114dB for 1/2" and 1" inch Microphone, Professional Noise Decibel Calibration Tool Measurement Accuracy Check : Industrial & Scientific
Microphone Calibration using Free FFT Analyzer - YouTube
Review - Reference 3 Studio Calibration Software & Measurement Microphone by Sonarworks - YouTube