How to analyze an audio file's spectrum
- Drop an audio file into the box. The stats appear right away, and the loudness value fills in a moment later.
- Wait for the spectrogram to render; it shows frequency over time on a log scale from 20 Hz.
- Press play to watch the live spectrum bars move with the audio.
- Click anywhere on the spectrogram to jump playback to that moment.
What you can do with Audio Info & Spectrum
- Full-file spectrogram
- A color spectrogram with a logarithmic frequency axis from 20 Hz to the file's upper limit, labeled from 50 Hz to 20 kHz.
- Live spectrum analyzer
- Frequency bars on a log scale update in real time as the file plays in the built-in player.
- Loudness in LUFS
- Estimates integrated loudness with ITU-R BS.1770 K-weighting and gating, alongside peak and RMS in dBFS and the crest factor.
- File details
- Duration, format, sample rate, channels, bit depth for WAV and FLAC, file size and average bitrate, read from the header where possible.
- Click to seek
- Jump to any moment by clicking the spectrogram, and follow along with a moving playhead.
- Nothing uploaded
- Analysis runs in your browser, so you can inspect unreleased mixes and client masters privately.
Reading a spectrogram and understanding LUFS
A spectrogram is the quickest way to check whether a file is as good as it claims. Lossy encoders remove high frequencies first: a 128 kbps MP3 usually cuts off around 16 to 17 kHz, 192 kbps around 19 kHz, and 320 kbps reaches 20 kHz or more. If a supposedly lossless FLAC or 320 kbps MP3 shows a hard shelf at 16 kHz, it was almost certainly made from a low-bitrate source. The spectrogram also reveals hum (a bright line at 50 or 60 Hz), clicks and stretches of digital silence.
LUFS (loudness units relative to full scale) measures how loud a track sounds rather than its highest peak. Streaming services normalize playback: Spotify and YouTube target around -14 LUFS and Apple Music around -16, so mastering much louder mostly adds distortion that gets turned down anyway. Podcasts commonly aim for -16 LUFS. Crest factor, the gap between peak and RMS, hints at how compressed a track is: under about 8 dB is heavily compressed, while 12 dB or more keeps natural dynamics. The LUFS value here is a close estimate, not a certified reading.
Frequently asked questions
How can I tell if an MP3 is really 320 kbps?
Open it here and look at the top of the spectrogram. A genuine 320 kbps MP3 usually has content up to about 20 kHz. A sharp cutoff near 16 kHz suggests it was transcoded from a 128 kbps file, even if the file's bitrate says 320.
Is my audio file uploaded for analysis?
No. The file is decoded, measured and drawn in your browser, and nothing is sent to a server. That makes the analyzer safe to use with unreleased songs, client masters and private recordings.
Why does the sample rate show an asterisk?
The tool reads the original sample rate from WAV, FLAC and MP3 headers. For other formats, such as M4A or OGG, it shows the rate your browser decoded the audio at, marked with an asterisk, which may differ from the file's native rate.
How accurate is the LUFS reading?
It follows the BS.1770 method, with K-weighting filters and the standard absolute and relative gating, so it lands close to a dedicated meter for integrated loudness. Small differences are normal; for broadcast compliance, confirm with certified metering software.
Which audio formats can I analyze?
Any format your browser can decode, including MP3, WAV, FLAC, M4A/AAC, OGG, Opus and WebM. Bit depth is shown for WAV and FLAC files, which store it in the header; lossy formats don't have a fixed bit depth.