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Friday, December 15, 2017
Article written by Allen McKnight

Best Bit Depth For Your Home Recordings

Recording in your home studio is wrought with decisions, like what software to use and which microphones to buy. One of the most important decisions you’ll make is the number of bits to use for your recordings. Depending on your hardware, you likely have a choice between 16-bits, 24-bits, and 32-bits. Which is best?

The maximum difference possible between the softest and loudest sounds in a recording is known as the recording’s “dynamic range.” In recordings made on computers or hard-disk systems, dynamic range is determined by the number of bits used to capture the audio. The math is a little complicated, but in simple terms: 16 bits allows 96dB of dynamic range, and 24 bits allows 144dB. In other words, the loudest sound in a 16-bit recording can be 96dB louder than the quietest sound. To put this in context, a pin drop registers around 15dB, where a typical car horn is 100dB when you’re right beside it.

The background noise in a good home studio is near 30dB. If you bring the quietest sound in your mix just above 30dB in order to hear it, then the loudest sound you can achieve with a 16-bit recording, and its 96dB range, is 126dB. This is approximately the volume of a drum hit at the moment of impact. So, depending on how much detail there is in your mix, it’s entirely possible that you’ll need the full dynamic range provided by 16-bit recordings.

24-bits, then, would seem like a wise minimum choice for bit rate. Even though the extra bits require more storage space, so your recordings will be 50% larger, the extra dynamic range could be required in some situations. And if some is good, then more is better, right? Why not go all the way to 32 bits, or higher?

The dynamic range of a 24 bit recording, 144dB, is outside the realm of "hearing" differences, and into "feeling" them. If the quietest sound you capture is a pin drop, then the loudest sound you can capture using 24 bits is 8 times louder than a jet engine. This isn’t really sound so much as a shockwave, capable of damaging buildings!!

Most condenser microphones fall apart above 120dB. Dynamic mics can go higher, but begin to distort with inputs above 140dB. And while you could probably put the venerable SM57 inside a rocket engine at takeoff, here's the real kicker: There are no consumer speakers capable of emitting volumes beyond 135dB. In other words, there's not a listening system on the planet that can reproduce the full dynamic range of a 24-bit recording.

Recording in 32-bits, then, is simply a waste of space.

One further note on bits: The marketing material accompanying your recording system likely raves about its internal 32-bit or 64-bit signal processing. Internal processing happens after the signal has been captured, so the number of bits used here is unrelated to the dynamic range discussion above. Digital signal processing involves math, and the more bits a computer uses to store numbers, the more accurate the math is. (Remember learning how to multiply fractions with a calculator?) So there is a good case for using more bits to work with sound once you've captured it. And if you were limited to a single bit depth throughout the entire process, from recording to mixing to mastering, then you could strongly argue that starting with the highest bit depth possible is a good idea.

But that's not how it works. Regardless of the number of bits used to capture the input, your software will still do its math using 32- or 64-bit floating point numbers. In short, then, if your recordings have limited dynamic range, you can probably record in 16-bits and no one will be the wiser. But even if you want the extra headroom, there's no reason to ever capture sound using more than 24-bits.
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