Audio File Formats Explained
In the audio world, we work with a lot of different file types. From high-res FLAC files to compressed MP3s, it can be tricky to keep them all straight. But, using the right file format can have a big impact on your overall sound. That's why it's important to make sure you're always using the best format for the job.
In this blog, we'll break down the differences between the most common audio file formats to help you determine which is best, including FLAC, WAV, MP3 and more.
What Is an Audio File Format?
Before we get too far along, let's talk about what an audio file format actually is. When we record audio in an analog format, like on a vinyl record or a roll of tape, the original audio waveform is stored directly on the medium.
When we record audio in a digital format, like an MP3 or an audio file on a CD, the original signal is sampled, digitized and stored as binary code (1's and 0's). When a computer scans the code, it recreates the original audio signal. Some formats use data compression to reduce the size of the file—more on that later.
Now that you know the basics of digital audio formats, let's talk about audio resolution, and how it affects the quality of your recordings.
Audio resolution is determined by the sample rate and bit depth of the digital audio recording.
Sample rate is the number of samples of audio taken per second and controls the frequency response of a recording.
When capturing digital audio, your interface takes thousands of snapshots of each waveform and plays them back in order to sound like one cohesive recording. Kind of like how a video appears to be moving, even though it's just a series of still images, like a flipbook.
Think of sample rate as the individual drawings in your audio flipbook. Each sample represents one small frame of the big picture. Using a higher sample rate will result in more samples.
The Nyquist–Shannon sampling theorem states that the maximum frequency response of a digital recording is exactly half of the sample rate used.
The lowest sample rate you should use for professionally released music is 44,100 kHz/sec, often shortened to simple 44.1K. At this sample rate, your track will have a maximum frequency response of 22050Hz - extending just beyond the human hearing range and ensuring you can hear every detail in the recording.
Many professional engineers don’t bother using a sample rate of 48kHz and above because there is no perceivable improvement in quality and the files take up more hard-drive space.
Bit depth is a measurement of how much data can be stored in each sample, and controls the dynamic range of the recording.
The lowest bit depth you should use for professional recordings is 16-bit, unless you're specifically going for a retro 8-bit Chiptune kind of sound.
Many DAWs and digital audio recorders offer settings up to 24 or even 32-bit floating, which offer a lower noise floor and higher dynamic range.
If sample rate is the number of still frames or images in your flipbook, then think of bit depth as the size of the notebook you're drawing in. It dictates how much space you have to capture the recording.
Now that you understand how sample rate and bit depth affect audio quality, let's talk about data compression.
What Is Data Compression?
Not to be confused with dynamic range compression, which occurs when you use a compressor plug-in to create a more consistent performance, data compression occurs when bouncing the final file, and controls how accurately the original recording is recreated.
Each digital audio file takes up hard drive space. In order to reduce the size of digital audio files, some formats use data compression. However, this causes some quality loss, as you're not capturing the full "image" of the original waveform.
Think of it like a teleporter from Star Trek. When you step into the teleporter, all of the DNA in your body is broken down into data and sent to a new location, where it's reassembled. However, with compressed audio files, the data doesn't always come out exactly the same on the other end...
Imagine walking through a teleporter and emerging from the other side a few inches shorter. That's what data compression does to your track.
There are three types of digital audio files:
Uncompressed files do not use data compression. They offer the highest audio quality, but are also the largest files. Using pulse code modulation, uncompressed files offer a 100% accurate recreation of the original recording. Uncompressed files are typically used for physical releases, such as CDs and DVDs.
Lossy files use data compression to greatly reduce the size of audio files. Lossy encoding using algorithms to detect and remove inaudible portions of the recording in order to save space. Like, a lot of space. Lossy files can be as small as 1/10th the size of the original file. However, this can have a negative effect on the quality of your music, and there is no way to retrieve the lost data after compressing the file.
Lossless files offer the best of both worlds. They use a special type of data compression called lossless encoding that reduces the size of the file without affecting audio quality. Similar to a ZIP file, the data is compressed when storing and transferring files, but upon playback, the file is decoded and played back at the original quality.
OK, now that we've covered the basics of digital audio and data compression, let's take a look at the different types of digital audio formats, and how they compare. Here's a quick breakdown of what we'll cover:
WAV stands for Waveform Audio. This uncompressed file type was originally developed by IBM and Microsoft in 1991, and is the still default file type on Windows machines. It supports sample rates up to 192kHz, bit depth up to 32-bit.
WAV files are very common, and are compatible with all hardware and software players that support digital files. However, WAV files tend to be very large, and can take a long time to download or buffer while streaming.
AIFF stands for Audio Interchange File Format. Developed by Apple in 1988, this uncompressed audio file is essentially the Apple version of a WAV file. It also supports sample rates up to 192kHz, bit depth up to 32-bit.
AIFF files support metadata tags, which WAV files do not. While AIFF was originally developed exclusively for Apple machines, it can now be used on almost any device.
FLAC stands for Free Lossless Audio Codec and is an open-source lossless digital audio format. FLAC files can be streamed and decoded with lightning-speed, making them a popular choice for HD streaming.
Additionally, FLAC offers nine different levels of data compression, based on the encoding speed (decoding speeds are relatively consistent). Despite being one of the most popular lossless formats, there is still no FLAC support on Apple Music or iTunes.
ALAC stands for Apple Lossless Audio Codec, and is Apple's take on a lossless audio codec. Unlike most other file types, ALAC files use an extension other than their name. You may be more familiar seeing ALAC files with ".m4a" extensions.
When compressed, ALAC files are about 60% the size of the original file. Just like FLAC, they are uncompressed when played back and sound identical to the original recording. While ALAC is supported by Mac and PC, hardware support is limited to mostly iOS devices. ALAC files can be uploaded to digital streaming sites, but they are converted to MP3 for playback.
Arguably the most popular lossy digital audio format, MPEG-1 Audio Layer 3, or MP3 was introduced in 1993. At the time, bandwidth was limited, and MP3's compact size made it easy to share and distribute online. However, this comes at the cost to audio quality.
When encoding an MP3, the bitrate, or speed of conversion, dictates the size and quality of the audio file. The highest bitrate is 320kbps, which takes the longest to encode but delivers the highest quality results. The lowest suggested bitrate is 128kbps. Even those who have no ear training can typically tell that something sounds "off" with 128kbps MP3s, so if you do decide to use this format, it's best to stick to 320kbps.
AAC stands for Advanced Audio Coding, and was originally developed by a team of tech companies in 1997, including Bell, Fraunhofer, Dolby, Sony, Nokia, LG Electronics, NEC, NTT Docomo, and Panasonic. AAC delivers better audio quality than MP3s, although they still don't sound as good as lossless files.
However, it does offer sample rates up to 96 kHz, unlike MP3's cap of 48 kHz. Because of this, AAC files are able to capture a wider frequency range. Thanks to its compact size and improved audio quality, AAC quickly became the go-to file type for mobile services and streaming software such as, iTunes, YouTube and Tidal.
WMA stands for Windows Media Audio. As you may have guessed by the name, this is Microsoft's version of the MP3. Similar to AAC, WMA files offer improved audio quality over MP3s at the same bitrate. However, the WMA file type never caught on quite like AAC and MP3, and is still not supported by Android devices.
Of course, these are not the only file types available—just the most popular and widely used formats.
OGG Vorbis is another new file type designed to improve upon the MP3 format. OOG is an open-source format, meaning it is free for commercial and non-commercial use, making it a popular choice for those who don't want to pay for high-end encoder software. Spotify actually uses OOG files as the default audio format, as it is the smallest audio file format. However, most hardware devices still aren't compatible with OOG, making it difficult to use with some devices.
What Is the Best Audio File Format?
At this point, you may be wondering which file type is best. Well, that really depends on what you're doing with the files.
For recording, mixing and mastering, you should always use uncompressed audio files, like WAV and AIFF. If you want to carry your entire music library with you everywhere you go, or instantly stream your favorite songs without having to buffer, use a lossy format like AAC or MP3. And for the best of both worlds (high quality and compact file size), use a lossless file format such as FLAC or ALAC.
Keep this in mind during your next session when it comes time to bounce down the final track. It's important to make sure you're always listening to your music at the highest possible quality.