Bit Depth

Occasionally there’s a bit of confusion about bit depth, and about what the best bit depth to use in different situations is. In the digital world, there are three bit depths that we might have to deal with – 16 bit, 24 bit and 32 bit.

16 bit
Digital audio at 16 bit is most commonly found in CDs. 16 bit audio allows the audio to have a dynamic range of roughly 96dB – that’s the difference between the loudest possible sound and the quietest possible sound. This is fine for a final delivery medium – the vast majority of music has a dynamic range well within this limit.
On the other hand, 16 bit is not so good as a recording format. Often when recording audio, the nominal level has to be quite low so that accidental peaks don’t distort (the distance between the nominal level and 0dBFS in a digital system is the amount of headroom). Because of this, low level signals (such as the decay of notes, or subtle details in the sound) may be recorded at a very low level below 0dBFS. When recording at 16 bit, any audio below 48dB (such as the decay of notes or subtle detail in the sound) is actually captured with less than 8 bits. This can give those low level signals a crunchy or distorted sound. This may be exacerbated in the mix by further processing such as compression and EQ. 
24 bit
Professional analog-to-digital converters can capture low level details at higher resolution. This means that the low level
32 bit

Bit depth determines the accuracy of low-level details in the audio. This includes the subtle details in the sound and the decay of notes or reverb tails. 

16 bit

Digital audio at 16 bit is most commonly found in CDs. 16 bit audio allows the audio to have a dynamic range of roughly 96dB – that’s the difference between the loudest possible sound and the quietest possible sound. This is fine for a final delivery medium – the vast majority of music has a dynamic range well within this limit.

On the other hand, 16 bit is not so good as a recording format. Often when recording audio, the nominal level has to be quite low so that accidental peaks don’t distort (the distance between the nominal level and 0dBfs in a digital system is the amount of headroom). Because of this, low level signals (such as the decay of notes, or subtle details in the sound) may be recorded at a very low level below 0dBfs. When recording at 16 bit, any audio below 48dB (such as the decay of notes or subtle detail in the sound) is actually captured with less than 8 bits. This can give those low level signals a crunchy or distorted sound. This may be exacerbated in the mix by further processing such as compression and EQ.

24 bit

Professional analog-to-digital converters can capture low level details at higher resolution. This means that the low level signals can be captured accurately without having to record with less headroom. Recording at 24 bit allows the finest details to be saved. 24 bit recording provides a theoretical dynamic range of 144dB (compared to 96dB at 16 bit), but no analog-to-digital converter records with this much range (figures of around 110dB are typical). However, capturing at 24 bit is appropriate because computers are more efficient at handling data in 8 bit “chunks”.

The problem with 24 bit audio is that it can be limiting when mixing. Mixing often involves summing a large number of tracks, each with several stages of processing. In this scenario, small errors can accumulate.

32 bit

Many software mixers convert audio to 32 bit internally during processing. This goes some way to reduce the effect of low level errors accumulating, and also has the added bonus of being able to have audio that excedes 0dBfs without clipping  – as long as it happens internally to the software (that is, before it leaves the mix bus).

It is also sometimes worthwhile rendering audio at 32 bit. This would be a good idea if you intend to further process the audio. An example of this is if you render a mix to a stereo file, intending to import the stereo file into a mastering project. This means no resolution is lost between mixing and mastering. 32 bit audio is not suitable for recording or distribution.

 

It might be a good idea to start with an approach of recording at 24 bit, mixing at 32 bit and mastering to 16 bit for distribution.

-Kim.

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  1. I’m not a geek about audio/sound thingy.. though I like it. :) Keep it up!

  2. Im checking your site daily for new blogs! :) lots of useful information… these days your the only person that seems to be able to teach me anything new!

    thanks again!

    • mattconnolly
    • September 8th, 2009

    Processing at 32 bit is convenient for 32 bit processors. If you’re referring to 32 bit floats, they have essentially the same dynamic range as 24 bit ints.

    Considering 24-bit has more dynamic range than the human ear can respond to, why use 33% more disk space to record 32-bit to disk.

    • Jeff Duncan
    • December 5th, 2011

    Software mixers use 32 bit as a standard, most of my equipment internally use 48 bit and its true the reasons is not to loose any information between mixing and then the mastering of your audio. I still master out on 24 bits then down sample with dither to 16 bit, 44,100hz for people who still use CD’s to listen to audio.

    I use my blueray player for audio and video, and output all my masters at 96,000hz 24bit stereo which I record onto a DVD, Yes an Audio DVD, the sound is way way way better compared to the old CD’s of yesterday. The sounds you here are more life like, it feels like your sitting next to the band members as they play.

    Nothing beats recording in 24bit stereo, even analog still has faults like digital in many ways with the noise floor, its more work reducing this in analog, digital 24bit recording is the best for audio reprodution in the 21st century. Thats my opinion and you decided on your own what work for you.

  3. @Jeff Duncan
    Sounds like you’ve worked out a sensible approach, Jeff.

    -Kim.

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