What is a spectrum analyzer?

A spectrum analyzer shows how much energy sits in different frequencies at a moment in time. On a phone it is usually an FFT or octave display of whatever the microphone hears — useful, but not a certified room RTA.

FFT bars

A Fast Fourier Transform splits a short slice of audio into frequency bins. Tall bars mean more energy in that region. Resolution trades against how quickly the display updates.

Octave bands

Octave (or third-octave) displays group energy into wider bands that match how people often talk about bass, mids and treble. They are still shaped by the mic and the room.

Practical uses

Finding a hum near mains frequency, comparing two speaker placements on the same phone, or watching a whistle slide are fair uses. Certifying a studio or proving a noise complaint is not.

In DecibelDock

Spectrum lives on the main console so you can switch among Meter, Frequency and Spectrum without killing a running measurement. Freeze helps you compare a stored trace with the live one. Layout stays stable so labels do not jump.

Freeze and compare

Freezing a trace lets you change something in the room and see whether peaks moved. Keep the phone position fixed. Changing weighting or input route mid-compare muddies the lesson.

Not a spectrogram lecture

A spectrogram plots frequency against time as an image. Some apps include one; DecibelDock's console Spectrum focuses on live bars, freeze and octave grouping. Either way, phone displays describe the captured signal, not a certified room curve.

Reading peaks without overclaiming

A tall peak means relatively more energy in that band on this phone right now. It does not name the brand of appliance or prove a code violation. Combine Spectrum with Frequency Finder when you need a Hz number for a stable tone, and with the level meter when you care about overall loudness.

Keep sessions short enough that battery and thermal throttling do not change phone behavior mid-test.

Putting it to work in DecibelDock

Open Spectrum after you read this guide so the ideas attach to real controls. Use the same phone, the same weighting or instrument preset, and the same physical position whenever you compare two scenes. Prefer a blank reading, a held value, or a written rejection over a number that looks definitive but came from silence, clipping or chaos.

DecibelDock is built for exploration and relative checks on Android. It is not a calibrated or certified sound level meter, not a medical device, and not a substitute for professional instruments when safety, health or compliance are on the line. Direction, Doppler and Distance stay approximate and depend on your phone. The learn section exists to make those limits understandable — and to help the feature pages show up for the questions people already type into a search box.

When you are done experimenting, skim a related article below and the matching feature page. Internal links are intentional: each guide should send you somewhere useful next, not leave you on a dead-end paragraph.

If something in the app disagrees with this guide after a future update, trust the in-app How to use notes for that build, and treat marketing copy as secondary to what the screen actually shows.

Key takeaways

• Use the same phone and setup when you compare scenes.
• Prefer a blank or rejected result over a confident wrong number.
• Phone tools are for exploration and relative checks, not certification.
• Read the matching feature page for what the app actually shows on screen.