Generally, when you purchase songs from iTunes or Amazon you are buying MP3s, these are also known as “lossy” compressed files.
Audio Bit Rate is the term used to compare the amount of data. Kbps stands for kilobits per second (thousands of bits per second) and is a measure of bandwidth (the amount of data that can flow in a given time).
The Audio Bit Rate for a CD is 1411 kbps whereas the average mp3 download is only 256kbps. This can explain why you often feel that digital media files can feel flat and limp.
Hi-Res Audio downloads should always be around 4608kbps, allowing a lot more room for all of the digital information allowing a better, clearer, and true reproduction of the artist's music.
When you purchase high res downloads they often come in several formats, this is simply to ensure that your device is compatible to at least one of the types of files, the other selection will be lossless compressed or uncompressed. The general rule of thumb is that the lossless uncompressed will be 50% larger than the compressed and therefore take up more room on your hard drive or device.
Uncompressed files
PCM – the basic audio file format for digital music, whether it's MP3, CD-quality, or high-resolution.
WAV – the main audio format for Windows-based computers.
AIFF – the main audio file format for Apple® computers.
DSD – the only non-PCM-based file type listed here. This format stores audio in a fundamentally different way than PCM.
Lossless-compressed files
FLAC – a popular lossless audio option, however, it’s not compatible with some music playback software, including iTunes.
ALAC– aka Apple Lossless, the main lossless audio option for Apple computers.
WAV – the main audio format for Windows-based computers.
Resolution Options
Besides choosing the file format, you can also usually have a few resolution options.
For digital audio files, there are two key pieces of information: “word-length” and “sampling frequency.”
CD has a word length of 16 bits and a sampling frequency of 44,100 Hertz (a Hertz equals one cycle per second). You typically see resolution specs abbreviated so that CD-quality files are listed as 16-bit/44.1kHz.
You can achieve better-than-CD sound quality through higher word lengths, higher sampling frequencies, or both. High-res audio is typically 24-bit, with a sampling frequency of 88.2kHz or higher. Except for DSD, all of the file types we’ve mentioned so far use the same basic digital audio format, called PCM. PCM takes snapshots of the musical waveform – the word length measures how detailed the snapshot is, and the sampling frequency tells you how many snapshots per second. Taking more detailed snapshots, and many more of them, can produce a more accurate “picture” of the musical performance, but all that extra data creates a much bigger file. A 24-bit/96kHz music file will take up about three times more hard drive space than a CD-quality file.
DSD is a digital audio format that stores audio differently than PCM. It’s a “1-bit” system, which means that the music signal is processed as a stream of single bits rather than multi-bit chunks. A few websites offer DSD music downloads, and a small but growing number of components can play DSD files.
