Frequency Counter: Hz Meter

Frequency Counter is an audio frequency meter, Hz counter, and instrument tuner for Android. Measure the dominant sound frequency in real time with your phone's microphone — no extra hardware needed. Turn your Android phone into a four-in-one frequency lab: read any tone in hertz, tune instruments, count RPM, and verify 50/60 Hz mains hum. ▶ MAIN FEATURES • Frequency meter — dominant frequency in Hz, live from the microphone • Instrument tuner — tune guitar, piano, violin and more with cents precision • RPM counter — measure rotation speed from sound or vibration • 50/60 Hz mains mode — check power-line and electrical hum frequency • Real-time FFT with high-resolution peak detection (20 Hz–20 kHz) • Adjustable averaging, smoothing and sensitivity • Hold mode to freeze the reading • Dark mode, works fully offline, no account needed ▶ HOW TO USE 1. Open Frequency Counter and allow microphone access 2. Pick a mode: frequency, tuner, RPM or 50/60 Hz mains 3. Point the phone at the sound source 4. Read the live frequency in hertz, the musical note, or the RPM ▶ WHO USES FREQUENCY COUNTER • Musicians and instrument makers tuning by exact frequency • Audio and AV engineers checking tones and signal pitch • Electricians and technicians verifying 50/60 Hz mains • Mechanics and makers measuring motor and fan RPM • Piano tuners needing cents-accurate pitch • Students learning acoustics, sound and signal processing • DIY hobbyists testing speakers, buzzers and alarms Microphone permission required. External USB microphones supported.