Nightchart is a noise meter and decibel (dB) meter that logs neighbor noise all night and checks it against real noise limits (Korea's apartment rules, the UK Noise Act night level, WHO guidelines). Night Watch logs only the moments over the limit while you sleep, a one-tap incident log records time and type, and sessions export as PDF reports. A real sound level meter too: A/C/Z weighting, Fast/Slow, LCpeak, 1/1 and 1/3 octave bands, NIOSH exposure. Built with Flutter. No audio recording by default; measuring is free, Night Watch and PDFs come with a one-time lifetime pass. No subscription, ads or account.