Spectrum Analyzer+ Audio FFT

Spectrum Analyzer+ Audio FFT shows the live frequency spectrum of any sound your iPhone microphone hears, then lets you capture a 5-second average and read the result: the strongest frequency in Hz, the top components and where the energy sits.

▶ See the spectrum live
• 32 bands from 20 Hz to 20 kHz, computed with a 2048-point FFT
• Four views: Bars with peak hold, Line, Waterfall and Spectrogram
• Peak frequency and peak level update as you listen
• Min / Max traces in the Bars view, tap a bar for a cursor readout, freeze the display to study it
• Adjustable dB range from 30 to 120 dB

▶ Capture 5 seconds, get an answer
Tap Capture 5 s under the graph and hold the sound steady. The app power-averages the spectrum over five seconds and shows a result card:
• Strongest component in Hz, with the musical note and cents in Voice mode
• Up to three top components with their levels
• Share of the detected energy in the low, mid and high part of the selected range
• Strongest band level and the FFT resolution of the measurement
If the sound is too quiet in that range, the card says so instead of inventing a peak.

▶ Compare before and after
Save a capture as a reference (up to 10). Make a change — move a speaker, add treatment, adjust a machine — capture again in the same mode and the card shows the average band-level difference in dB. References can also be overlaid on the live spectrum.

▶ Pick the job
• Voice: 80–4000 Hz, shows the note of the strongest pitch
• Machine: 20–2000 Hz, looks for 50/60 Hz mains hum and its harmonics
• Room: 20–500 Hz, the low end where room modes build up

▶ Export and share
• Export a CSV of the live spectrum or of a 5-second capture
• Share a short text summary of a capture

▶ Extras
• Calibration offset from −20 to +20 dB in 0.5 dB steps to line up with a reference meter
• Pink noise generator, unlocked for 24 hours by watching a short ad
• Interface in 30 languages

▶ Good to know
Levels are relative to the microphone's full scale (dBFS). A phone microphone is not a certified sound level meter, so use the numbers to find frequencies and compare changes, not for compliance measurements. Audio is analysed in memory while you listen and is not saved as a recording.

For musicians checking a tone, home studio and hi-fi owners chasing a boomy note, and anyone tracking down a hum from a fridge, fan or transformer.