What is the simplest way to describe to someone the benefits of adding more and more bits to a PCM digital audio system? What if you were challenged to prepare an informational guide for newbies to high-resolution audio? How would you try to get a group of up to speed on the potential benefits of high-resolution audio/music? There are lots of websites, articles, and posts that have attempted this trick but most of them seem to mess up the theory while attempting to explain the central point. One of my favorites is the “pixel” mistake.
You may have already heard this one. It goes something like this. Imagine a photograph taken with a camera that has about 65,000 pixels because the camera that took the image has “16-bits of resolution”. If you switch to a camera that has 24-bit resolution, then the number of pixels will dramatically increase to almost 17,000,000 pixels. The realism and detail of the new “higher resolution” image will be much better than the previous one, right? In the world of digital photography…yes, it will, if all you’re doing is using 16 or 24 to generate a number of pixels. But the analogy fails miserably when it comes to audio resolution.
Talking about pixel count is different than “bit depth”, which is where increasing the number of bits really matters. So the issue isn’t really the number of pixels that are present, the more important aspect is the number of colors that can be individually associated with each pixel. Think of it this way. If I have a field of pixels and each one has a bit depth of 1-bit, then each pixel can only display two different colors or shades of black and white. The original Macs had 600 x 400 pixels with a bit depth of 1-bit…each pixel could be either black or white.
When the number of bits is increased from 1-bit to 8-bits, the number of discrete values (think colors or shades of a grayscale) increases to 256 (2 to the 8th power). Every subsequent increase in bit depth allows each pixel to display a wider array of colors. Confusing pixel count with bit depth doesn’t help understand how increased word length helps audio quality. It might be simple to grasp but it’s just plain wrong. Apples and oranges.
Moving from 16 to 24-bits in audio allows the system to identify more unique amplitude levels. And each one that you add provides an additional 6 dB of potential dynamic range and as a result potentially a lower noise floor. For a recording engineer, the increased number of bits gives your recording system more “headroom”, which means that you can capture a much wider range of volumes. In the old days, we had to be careful not to overmodulate the recording system. If you inadvertently pushed too hard into the “red”, distortion would result. Whoops.
To the uninitiated audio enthusiast, it’s enough to say that moving from 16-bits to 24-bits makes it possible to capture wider dynamic ranges. The added dynamic range is great for classical music and jazz but few, if any, pop, rock, or country music ever exceeds the dynamic range of a compact disc. And let’s be honest with these newbies, they aren’t going to hear the potential improvement because there’s no content that exhibits the increased dynamic range AND their systems can’t reproduce it even if there was.
Forget about pixels when it comes to audio discussions.