KEEN is a sound pressure level (SPL) meter specialized for the 18–20 kHz ultrasonic band. It lets you easily check sounds near the upper limit of the audible range — often outside the scope of ordinary sound level meters — using an iPhone and a measurement microphone. FEATURES - Real-time sound pressure level (dB SPL) display for the 18–20 kHz band - Switchable time weighting (Fast 125 ms / Slow 1000 ms) - Supports USB measurement microphones (such as the Dayton Audio iMM-6C) - Automatically applies per-microphone calibration data - Detects the microphone's serial number on connection and fetches its registered calibration data - Also supports entering the identifier printed on the microphone or scanning its QR code - Calibration files can be imported as well - Manual calibration with a pistonphone (94 dB SPL @ 1 kHz) NOTES - For accurate measurement in the 18–20 kHz band, we recommend using a supported external measurement microphone with its calibration data applied (high-frequency sensitivity is not guaranteed with the built-in microphone). - Microphone access permission is required for measurement.