Lavalier microphone with cardioid pickup pattern. High gain before feedback. Sensitivity according to 121 TR 9-5, MKE 40-ew: 42 mV/Pa +- 2.5dB, MKE 40-4: 42 mV/Pa +- 2.5dB. (audio) frequency response 40 - 20,000 Hz. Maximum sound pressure level, MKE 40-ew: 118 dB (k=1%).