EDUCATION
Spectrum analyzer, see frequencies live
Every sound has a shape across the frequency spectrum, not just a volume. Watch it move in real time and start connecting what you hear to what you see.
This is a free online spectrum analyzer. Pick a source, press play, and the frequency content is drawn live from 20 Hz to 20 kHz, with the peak frequency, its note name, the peak level and the spectral centroid read out underneath. FFT size decides the trade you make between frequency detail and speed, peak hold keeps the highest points on screen, and freeze stops the picture so you can actually look at it.
Try it
- Play a bass-heavy sound and note where most of the energy sits on the display.
- Play a bright, treble-heavy sound and compare the shape.
- Boost a frequency with an EQ (open the EQ tool in another tab) and watch the spectrum respond.
What to listen for
Bass-heavy sounds pile energy on the left of the display, treble-heavy sounds spread it to the right. Once you can see this shape, EQ decisions stop being guesswork.
Questions
What is FFT size and which one should I use?
It is how many samples the analysis looks at each time. Large values such as 4096 give you fine detail in the low end but react slowly; small values react fast but smear the bass. Use large for judging a kick's fundamental, small for watching transients.
What does the centroid number mean?
The spectral centroid is where the energy of the sound balances, and it lines up well with what we call brightness. Two sounds at the same volume with very different centroids will not sit in the same place in a mix.
Why does the low end look so much bigger than it sounds?
Because your ears are less sensitive down there, and the display is not. A spectrum shows physics, not loudness as you perceive it. Use it to find problems, not to decide balance.
What is peak hold for?
It marks the highest level reached at each frequency and leaves it there, which is how you catch a resonance that only appears for a fraction of a second.
This tool is one part of the picture. Electronic Music Production for Beginners covers the rest.