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It goes without saying that a recording artist should want to sound their best. While the lo-fi movement of the 90s used tape noise and ambient room sound to its advantage, these days, home recording is something almost everybody does, from Billie Eilish to your next-door neighbor.
Unless you happen to have a functional reel-to-reel tape recorder, most musicians record digitally on ProTools, Logic Pro, or some other kind of DAW (Digital Audio Workstation). When recording digitally, it’s important to know how audio bitrate affects your sound. So, what is bitrate in audio and how does it impact audio mastering?
Audio bitrate explained
“Audio bitrate” refers to the amount of data being transferred into your audio files. Every moment of digital audio contains data or bits. Audio bitrate defines the audio quality of a file: a higher bitrate means better audio quality but also requires higher bandwidth and results in a larger file size.
Two types of bitrate
When exporting your files for MP3 or AAC, you can encode your audio files using Constant Bitrate (CBR) or Variable Bitrate (VBR). CBR is preferred for streaming situations, as the size or complexity of the files being encoded doesn’t matter; it outputs at a constant bitrate. It’s important to set the bitrate relatively high to handle your files with CBR, but not higher than the bitrate of your connection.
VBR, on the other hand, allows the bitrate to increase or decrease based on the quieter or louder parts of a track. This results in smaller files and can be more efficient in the same way an MP3 file audio format is often more efficient than a WAV file format. If it’s quality you’re after, though, CBR is probably the best choice.
Why audio bitrate is important
Audio bitrate is important because the quality of the file depends on it. Listeners will judge your sound quality based on the strength and depth of your low frequencies and the clarity and sharpness of your high frequencies. Particularly with streaming, a balance must be struck between quality and increasing the file size so that it becomes unwieldy for users to stream.
How audio bitrate affects audio quality
In short, the higher the bitrate, the higher quality your audio will be. Bitrate is determined by the sampling rate and the bit depth. Most digital audio is sampled at a rate of 44.1 kHz, which is the standard for audio CDs. Film uses 48 kHz, and these days, hi-res audio will sample up to 192 kHz.
The difference is minimal to all but the most trained ears (human hearing can only go up to about 20 kHz), but a higher sample rate does capture more of the audio signal and leads to larger files.
Bit depth is the number of bits in each sample. CDs are 16 bit, DVD and Blu-Ray Audio are 24 bit. Unless your goal is high-resolution files, 16 bit is probably sufficient for all your needs; audio experts are divided on whether 24 bit even makes any difference. Though when manufacturing physical products, it is important to capture as much of the natural sound waveform as possible. So, in these days where artists are pressing vinyl from digital files, 24 bit is a good safeguard against digital artifacts showing up on your record.
Different audio formats
CD audio format has a bitrate of 1,411 kbps at 16 bits as an industry standard. High quality WAV file format, AIFF, and PCM files are uncompressed, meaning they include all the audio information, have the same audio bitrate as CDs, and are the largest file sizes. FLAC and ALAC files are compressed but lose no information; they are known as lossless audio formats. WMA files can be lossless as well. FLAC is an especially versatile lossless audio format as it reduces file size by up to 70 percent and can recreate files up to 32 bits and a 192 kHz sampling rate.
The low-end file formats are MP3 file format, OGG, and AAC. These files are compressed with a loss of audio information, but because of their small size, they’re the go-to for streaming and file exchange. They are generally what you hear on Spotify and Apple Music, reaching a maximum bitrate of 320 kbps.
Tips for achieving the best sound quality
To achieve great sound quality in your final audio files, you’ll need to start with great microphones and a top-notch microphone preamp, or — if recording direct — a clean signal into your recording interface. You’ll want to record with the highest bit depth and sample rate possible: 44.1 and 16 bits will probably be fine for most purposes, but remember, you can’t ever upsample.
If you record at 192 kHz and 24 bit, you can always make smaller files, but you can’t turn a lower sample rate into a higher bitrate one. You will also need plenty of headroom in the files to leave space for the mastering engineer to add EQ and compression. Having the audio files professionally mixed and mastered is the best choice.
No matter how lo-fi the sound of your recordings, you will want your final audio files to be the highest-quality uncompressed files you can make. From there, you can downsample them into mp3s or whatever format is needed to distribute your music. There is nothing sexy or cool about digital artifacts, they just sound bad and can even become a glitch on a CD.
Finding the best bitrate for your CD or vinyl LP
Hopefully, we’ve answered your initial question, “what is bitrate in audio?” To recap, audio bitrate is the amount of data being transferred into your audio file. The higher the bitrate, the better the audio quality.
So, when making a physical product such as a CD or a vinyl record, you’ll want your files at the highest possible bitrate. The audio information on CDs is transferred at 1,411 kbps, so if your audio files have a lesser bitrate, you will be able to hear the difference and it will not sound good.
Don’t use mp3 for your CD master! This is doubly true for vinyl, where even more of the original sound waveform is captured in the analog transfer process. Putting digital compression on a vinyl record will do nothing but antagonize your fans.
So, if using digital audio files, you’ll want those WAVs at 24 bit and 192 kHz, if possible, a minimum of 16 bit, and 44.1 kHz. If you’re making vinyl and CDs, you will want to make a separate master for each, as the sound requirements are different in each format.
Your mastering engineer can assist in this department. A solid rule of thumb is to always use the best and highest audio bitrate for your master files when making physical products.
Chris Huff has been a professional singer, multi-instrumentalist, songwriter, and producer for over 20 years. He has worked as a sideman with Peter Yarrow (Peter, Paul, and Mary), Echo and the Bunnymen, Chuck Hammer (David Bowie, Lou Reed), and Tom Kitt (Broadway composer of Next To Normal). Chris also wrote liner notes for David Bowie’s Live And Well CD, and has two full-length albums of original music available on iTunes.
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