Cepstrum

That hum in your bedroom at night. The bass leaking through the wall. The "quiet" air purifier that isn't. Cepstrum shows you exactly what you're hearing — a live picture of sound, measured with nothing but your iPhone.

SEE THE NOISE, NOT JUST HEAR IT
A real-time spectrum from deep bass to the top of your hearing, with a sharpened spectrogram that turns tones into crisp lines. Point it at a mystery sound and get its fingerprint: the fridge hum at 50/60 Hz, the fan bearing whining at 4 kHz, the feedback frequency before it screams at your venue.

KNOW HOW LOUD IT REALLY IS
A proper sound level meter with A/C/Z weighting and Fast, Slow and Impulse response. Is the gym actually too loud? The restaurant? Your kid's headphones? Set the offset against a meter you trust and read real dB SPL — not a guess.

PROVE THE DIFFERENCE
Capture a measurement, overlay another, and read the change in decibels. Did the new windows cut the street noise? Is the replacement fan quieter than the old one? Before and after, one seat against another — the answer on screen, not in your head.