Spectrum Analyzer: Audio FFT

See every frequency in real time: a studio-grade spectrum analyzer in your pocket, free. Spectrum Analyzer: Audio FFT turns your phone's microphone into a real-time frequency analyzer. A smooth FFT curve on a logarithmic axis from 20 Hz to 20 kHz, octave and third-octave RTA bars, peak hold, averaging, the dominant frequency with its musical note, snapshots for before/after comparisons and a feedback finder. For sound engineers, musicians, teachers, students of physics and anyone curious about sound. LIVE SPECTRUM • FFT from 1024 to 32768 points, Hann, Blackman-Harris or flat-top window, 50% or 75% overlap. • Logarithmic frequency axis and dBFS grid, with a smooth, interpolated curve. • Real-time analyzer view: octave, third-octave (IEC centre frequencies) and sixth-octave bands. • Up to 60 updates per second; the analysis runs in the background so the display stays fluid. MEASURE • Peak hold that holds or falls slowly or fast. • Averaging: exponential with a time constant, or the mean of the last N spectra. • Dominant peak: frequency interpolated to a fraction of a hertz, nearest note with cents, level. • Touch the plot for a cursor with frequency, level and note under your finger. • Pinch to zoom the frequency and level axes, drag with two fingers, double-tap to reset. • Freeze the display to read it calmly. • A, C or Z weighting and optional fractional-octave smoothing. COMPARE • Snapshot saves the curve on screen and draws it over the live one: before and after an EQ change, two microphone positions, two rooms, two instruments. • The cursor shows the difference in dB from the saved curve. • Copy the curve as CSV (frequencies and levels) to paste into a spreadsheet. FIND FEEDBACK • The feedback finder spots narrow peaks that keep ringing and growing, the howl of a microphone too close to a speaker, and lists their frequencies and notes so you can cut them with a narrow EQ band. HONEST ABOUT THE MICROPHONE • Raw capture where the device allows it: automatic gain and noise suppression off. • Levels in dBFS, not dB SPL: a phone microphone is not a calibrated measurement microphone. The app says so, and shows what your device reports about its audio path. • Clipping indicator when the input saturates. LANDSCAPE • Works in portrait and landscape; turn the phone sideways for the widest plot. FREE AND PRIVATE No ads, no in-app purchases, no subscription, no account. Works offline. The sound is analysed on your device and never recorded or sent; no data collected. Dark and light theme, 71 languages. Made by FELICE MARRA / MUSIC STUDIOS.