Understanding sound quality
Whether you’re a passionate listener or a passionate creator, you want to be sure that your music library offers the best possible quality for your favourite tracks. Audio compression is a technique used to reduce file size, making it easier to store music, but with a reduction in file size comes a reduction in quality.
When you’re building your music library, you shouldn’t let storage limitations get in the way of sound quality, and here we’ll explore a few tips for making sure your music is heard the way it’s meant to be heard.
There are a few different factors that will impact the quality of an audio file. Obviously, the higher the quality the better, but with high-fidelity audio can come issues with storage, as these files tend to be huge.
Audio quality is mostly measured by sample rate and bit depth, which we’ll summarise below. Another important term when considering sound quality is ‘lossless’ or, contrarily, ‘lossy’ audio. Each digital audio format will offer different capabilities in terms of sampling rate, bit depth and compression.
What is sampling rate and bit depth?
When we talk about the quality of an audio file, we’re usually talking about sampling rate and bit depth.
Audio is, at its core, analogue. Without sounding too flowery, audio is simply vibrations or waves travelling through the air. Those waves that create sounds must be converted – digitised – using what are known as transducers, like microphones and amplifiers, for example, which turn these sound waves into electrical signals.
A digital system can then record those electrical signals by ‘sampling’ them. The sample rate of an audio file is akin to the frame rate of a video file. Consider the fact that a video is a collection of stills, or frames, put together. A faster frame rate means the video moves from one frame to the next quicker, making for a smoother video. A song is the same, only rather than being a collection of frames, it’s a collection of samples of audio signals.
So the faster the sample rate, the smoother the audio. The average audio file, such as audio on a CD, would have a sample rate of 44.1kHz, or 44,100 samples per second, while a ‘high resolution’ file would typically have a sample rate of 96kHz, 96,000 samples per second, or higher.
Bit depth is akin to the resolution of a video. In a video, resolution is defined by the number of pixels in a frame, and in a song, bit depth represents how many bits create a sound. When an audio signal is sampled, sound information is extracted from it and stored in the form of bits. A higher bit rate means more information can be stored within each sample, so the higher the bit rate, the more accurately a digital audio file replicates the original.
These days, 24-bit, 96 kHz audio would be considered ‘high resolution’.
What is lossless audio?
Through the process of lossy audio compression, audio files are shrunk down, and in the process, they lose little pieces of data. If you compress an audio file in a lossy format and later decompress it, you won’t be able to recapture those lost details. Lossless compression allows you to compress an audio file without losing any of that important information.
You can listen to a lossy audio file and probably still hear every harmony and every bassline, but you’ll likely miss out on some of the finer details that go into the song’s production. If you consider yourself a bit of an audiophile, then the difference between a lossless and lossy audio file would likely be quite noticeable. If you’re recording your own music, lossless audio is absolutely essential.
MP3 and other compressed, lossy audio files are easier to handle on the hardware side of things, and of course, easier to store, which is why they’re more common. Streaming services like Spotify use lossy, compressed audio, even for Premium accounts, because with the millions and millions of songs available, lossless and uncompressed would use up way too much of your bandwidth.
Audio file formats
Aside from sound quality, other important factors when it comes to digital audio file types include file size and metadata support. Metadata refers to information stored within a file. In the context of music files, metadata can include cover art, artist, album, song title and any other information relating to the track. When you import an audio file to a music player like Apple’s Music app, it will be able to read this metadata and correctly categorise and tag it with all the relevant details.
You’ve probably heard of a lot of the file formats listed below. These are the most common audio formats, and each offers different sound quality, file size, metadata support and operating system compatibility.
Lossy audio formats
MP3
MP3 is the most popular audio file format. MP3s are compressed files, and are a preferred format because of their small file size. MP3 is ideal for storage reasons, particularly for keeping music on your smartphone, which can have quite limited space, but the sound quality isn’t great. Offering such low file sizes is what allowed MP3 players to triumph, paving the way for iPods, and later smartphones.
AAC
AAC files are also lossy and compressed, but offer better sound quality than MP3 files. AAC is the format used for streaming music on YouTube and Apple Music and on songs you download from iTunes. AAC is Apple’s answer to MP3.
WAV
WAV is the format that CD audio is usually encoded in. These are uncompressed, lossless files that offer tremendous sound quality, but take up a whole lot of space. WAV files are also limited in what kind of metadata it can support – and when you’re building your online music library, metadata can be quite important.
Ogg Vorbis
OGG, or Ogg Vorbis, is an open-source, lossy compression format, similar to MP3 and AAC, but more versatile without being tied to licences and patents. This is the file format used for music on Spotify.
Lossless audio formats
WAV
WAV is the format that CD audio is usually encoded in. These are uncompressed, lossless files that offer tremendous sound quality, but take up a whole lot of space. WAV files are also limited in what kind of metadata it can support – and when you’re building your online music library, metadata can be quite important.
AIFF
AIFF is Apple’s equivalent to WAV. This is a hi-res audio format, uncompressed and lossless, so you can expect great quality at the cost of storage space. AIFF offers better metadata support than WAV.
FLAC
FLAC files require about half the amount of space that WAV files require, while still offering hi-res, lossless audio. This is a royalty-free format that is used mostly for downloading high-quality albums, but for Apple users, FLAC files are only accessible through the Files app, and not supported by the Music app.
MQA
MQA is what allows Tidal to offer hi-res masters at phenomenal quality. It is a lossless format, but is compressed so it’s better suited for a streaming service.
ALAC
Apple’s answer to FLAC is ALAC. Like FLAC, this is a lossless compression format that can handle hi-res audio. It supports metadata and uses up about half the space that a WAV file does. What sets it apart from FLAC is that, as Apple’s own format, it is more compatible with iTunes and with iOS devices.
What happens during audio file compression?
When you download a song, you’re downloading a copy or reproduction of the original audio file. An uncompressed, lossless file is the closest reproduction you can get.
In order to reduce file size, compression algorithms are used to remove parts of a song that the system believes won’t be audible to the human ear. By making low-frequency sounds louder, the absence of high-frequency sounds becomes less noticeable. This process is called ‘masking’.
On the production side of things, audio compression can be a useful technique. In this context, the process of compression works by reducing dynamic range in audio signals. Dynamic range refers to breadth of loudness – the difference between the lowest and highest volume a piece of audio is capable of producing.
If a producer has a sound that is very loud at the beginning but tails off over time, they may want to compress it to reduce the difference in volume between the two parts. Compressing a sound will typically reduce its overall loudness at first, but this can be compensated for with make-up gain – which can ultimately make the sound much louder than it was initially. Both compression plug-ins and their analogue counterparts allow users control over the character of the sound that compression produces by manipulating attack time, release time and gain controls – make-up gain and gain reduction.
Audio compression is useful for mixing and mastering, but when it comes to actually saving and storing your music, compressing an audio file can do more harm than good.
What lossless audio formats are best?
It’s important to note that ‘lossless’ and ‘uncompressed’ are not one in the same. Take FLAC files, for example. These files are compressed to about half the size of a WAV or AIFF file, but are still lossless. Able to offer a resolution as high as 32-bit, 96 kHz, FLAC files can provide better audio than CD-quality (16-bit, 44.1 kHz).
So, if you’re looking for a way to store your music without any loss in quality, but you still need to be fairly conservative with space, FLAC would be the answer. If you’re a Mac or iOS user, ALAC is the best alternative to FLAC.
However, if you want truly uncompressed, lossless audio, then you’d want WAV or, for Mac or iOS users or those looking for better metadata support, AIFF. Lossless compression is great, but can never match the quality offered by a lossless, uncompressed format.
While you want the best possible audio quality for your favourite music, you still need to be careful when it comes to storage space. You won’t be able to find an audio format that is both space efficient and offers exceptional, lossless sound, so what do you do?
Lossless music cloud storage
Whether you’re a musician yourself or simply a keen listener, you want to make sure you can store all your music securely without compromising on quality. With that in mind, keeping everything saved on your device is probably not ideal.
With Dropbox cloud storage, you can store hi-res audio files of any format on the cloud, so you can access them from any device that can connect to the internet. Dropbox does not compress your files as you upload them, or alter them in any way, so you can be sure that if you’re uploading a WAV file, for instance, you can expect its high audio quality to remain intact.
Because everything is stored on the cloud, you don’t need to worry about disk space, giving you the freedom to enjoy an entire music library of lossless, uncompressed audio, the way it’s supposed to be heard. You can listen to your songs from Dropbox itself, so it can even act as your own personal streaming service.
It also makes sharing music easy – whether you’re sharing your new favourite song with friends and family, or collaborating with band mates. With Dropbox, you can quickly share large, high-quality audio files at the click of a button and again. Because everything’s in the cloud, everything is sent in an instant.
