Audio Spectrum Viewer

How to read the spectrum

The horizontal axis shows frequency; the vertical axis shows level in dB. A sharp high-frequency cutoff can be a clue that the file came from a lossy source, but it can also reflect the recording or mastering process.

What is max-hold spectrum?

The tool analyzes the file in overlapping windows and keeps the highest amplitude found at each frequency bin. This gives a stable "peak" view rather than a live scrolling display.

Common use cases

Check FLAC files for high-frequency rolloff

Drop a FLAC file and look for a sudden drop in high-frequency energy. If the spectrum cuts off sharply at 16–20 kHz, the file may have been transcoded from a lossy source.

Compare MP3 quality settings

Drop two MP3 files encoded at different bitrates and compare where the high-frequency content ends. Higher bitrate MP3 files retain energy up to higher frequencies.

Inspect audio before archiving

Look for unusual frequency cutoffs before archiving a file. Use the graph alongside other information about the source.

Frequently asked questions

What does the spectrum tell me?

It shows where the file has frequency energy. A cutoff may suggest prior lossy encoding, but the graph cannot prove whether a file is lossless or how good it sounds.

What is the Nyquist limit?

The Nyquist limit is half the sample rate. For a 44.1 kHz file, it is 22.05 kHz. A recording does not need to contain energy all the way to that limit to be lossless.

Is my audio uploaded?

No. All analysis happens locally in your browser using the Web Audio API.

Why is analysis slow for long files?

The tool samples up to 64 evenly spaced windows from the file regardless of duration, so analysis time is roughly the same for short and long files.