In-Depth Explanation
Peak is the maximum instantaneous amplitude an audio signal reaches during playback or recording. It is measured in decibels relative to full scale (dBFS), where 0 dBFS is the loudest signal a digital system can represent. Any signal that exceeds 0 dBFS clips, meaning the waveform is cut off and produces audible distortion. Peak levels differ from RMS level, which measures average loudness over time. A track can have a moderate RMS level but still hit dangerous peaks on transient sounds like snare hits.
How Peak Works
In digital audio, every sample has a value between negative infinity and 0 dBFS. The peak value is simply the highest (or lowest, in negative direction) sample value in a given time window. Your DAW's meter shows peak levels as the fastest-moving bars on the display. Most meters also show a "peak hold" indicator that marks the highest level reached and holds it for a few seconds so you can read it.
There are two types of peak measurement. Sample peak is the highest single sample value. True peak is an interpolated measurement that estimates the level between samples, which is what analog converters and intersample peaks actually produce. True peak is measured in dBTP (decibels true peak). A signal can show a sample peak of -0.1 dBFS but a true peak of +0.3 dBTP, which means it will clip on playback even though the sample meter says it is safe.
Streaming platforms have specific true peak limits. Spotify requires -1 dBTP. Apple Music requires -1 dBTP. YouTube requires -1 dBTP. If your master exceeds these limits, the platform will turn it down or apply its own limiting, which can degrade the sound.
Real-World Example
A producer masters a track and sets the ceiling on their limiter to -0.1 dBFS. The sample peak meter never exceeds -0.1 dBFS, so they assume the master is clean. When they upload to Spotify, the track sounds quieter than other songs and slightly distorted.
The problem is intersample peaks. The limiter's sample peak ceiling of -0.1 dBFS does not account for the true peak, which reaches +0.4 dBTP on a snare hit. Spotify's playback pipeline clips the signal at its internal ceiling, causing distortion, and then applies its loudness normalization, which turns the track down by 2 dB to meet its -14 LUFS target.
The producer remasters with a true peak limiter set to -1.0 dBTP. The track now passes Spotify's requirements without clipping. It plays back cleanly and at the correct normalized loudness.
Why It Matters for Independent Artists
If you ignore peak levels, your masters will clip on streaming platforms, sound harsh on consumer speakers, and fail loudness normalization. The fix is simple. Always use a true peak limiter on your master bus. Set the ceiling to -1.0 dBTP for streaming releases. This gives you a safety margin for intersample peaks and platform encoding artifacts.
Do not confuse peak level with loudness. Peak only tells you the maximum instantaneous level. Loudness is measured in LUFS and accounts for how the human ear perceives sustained volume over time. A track mastered at -8 LUFS with peaks at -1 dBTP will sound louder than a track mastered at -14 LUFS with peaks at -0.1 dBFS, even though the second track has higher peaks. For more on this distinction, read our guide on mastering for streaming platforms and our comparison of mixing vs mastering.
Use our Decibel Meter Tool to measure peak and RMS levels in real time while mixing.
Related Terms
For the ITU standard on true peak measurement, see ITU-R BS.1770.
