I have some more information for you;To be honest, the problem with standards is that everyone has their own standards.
AFAIK, Brüel & Kjær spec their capsules at 3% THD, and peak SPL at 10% THD.
Here's what I've gathered so far study on microphone capsules / phantom powered microphones:
In no particular order...
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Brand Model Noise Floor Maximum SPL based on THD (%) dB Not listed 10% 3% 2% 1% 0.5% 0.3% 0.1% 0.03% Sonarworks SoundID Reference(2024)* 124 Merry Electronics MMA209-003* 133 130 128 120 110 94 Sonarworks Xref20/SoundID 24 128 miniDSP Umik-1 133 miniDSP Umik-2 20 125 Line Audio Omni1 18 133 iSEMcon EMX-7150 30 144 136 130 CPX-1212 155 micW M215 18 135 Earthworks(2022) M23 20 Earthworks M23R 140 Earthworks M30 20 140 Earthworks M50 20 140 Audix TM1/Plus 28 140 130 ACO Pacific 7502PH 18 150 PCB Piezotronics 376A31 40 165 156 376A33 22 150 376A32 15 137 Dayton AudioEMM-6 24 127 Behringer ECM8000 NL NTI Audio M2010 24 142 M2215 25 153
https://www.pcb.com/contentstore/MktgContent/LinkedDocuments/Reports/3P03218condensedreport.pdf