why you should leave headroom for both online broadcasting and production..

Normalized Audio and 0dBFS+ Exposure
Updated 2012-03-26

Because an analog-to-digital converter or sample rate converter sample clock generally has an arbitrary time relationship to a given piece of program material applied to its input, the same audio can be represented in an infinite number of ways if correctly dithered before the quantizer. Many CDs produced today are normalized to 0dBFS in the digital domain by digital signal processing that is not oversampled and is thus unaware of the peak values of the waveform following playback device D/A converters. Following reconstruction into the analog domain, the peak level of the audio waveform can exceed 0dBFS, a phenomenon commonly known as “0dBFS+,” “intersample peak clipping,” or “true peak clipping.” If the digital-to-analog converter in a consumer playback device does not have 3dB of headroom (3dB being the maximum possible increase in peak level if the reconstruction filter is phase-linear), the converter can produce massive clipping and aliasing distortion components on top of any distortion components introduced by the digital signal processing. Add these to the artifacts produced by the MP3/AAC encode/decode process and it is no wonder that much of today’s aggressively mastered music sounds so unpleasantly distorted.

What is particularly pernicious is that if mastering engineers monitor their work through converters having the required 3dB of headroom and do not use meters that show intersample peaks, these engineers will be completely unaware of the additional distortion that many consumer playback devices will produce. Mastering engineers who do not use intersample peak meters are therefore likely to process more aggressively than would if they were able to hear the additional distortion introduced by poorly designed playback components.

Over-processed audio simply creates bad sound. Bad sound in, more bad sound out. It is really no wonder at all why it is so difficult to make radio stations and netcasts sound good with modern material, because it is all grossly pre-distorted! We are pleased to note that in the last year or so, the mastering community has finally started to become more aware of the intersample peak problem, but we are still seeing many major-label CDs that produce intersample peaks above 0 dBFS.

Normalized Audio and 0dBFS+ Exposure