Nightchart is a noise meter and decibel (dB) meter for Android that logs neighbor noise all night — footsteps, music, barking — and checks it against real noise limits (Korea's apartment noise rules, the UK Noise Act night-time level, or WHO guidelines). Night Watch logs only the moments over the limit while you sleep, a one-tap incident log saves the time, type and a note, and sessions and incidents export as PDF reports ready to hand in. It is also a real sound level meter: A/C/Z weighting, Fast/Slow, LCpeak, octave bands and NIOSH hearing exposure. No audio is recorded by default, and it is honest that a phone is not a certified meter. Measuring and the incident log are always free; recording sessions, Night Watch and PDF reports come with a one-time lifetime pass. No subscription, ads or account.