96, 128, 160, 256, 320? These may seem like arbitrary numbers plucked from the air but in fact they are common “bit rates” for MP3 encoded music. Most often you will see a bit rate expressed as a number followed by “kbps”, meaning kilobytes per second. Essentially this is the amount of information stored in the file for each second of the song. So, following that, we know that a 3 minute long song encoded at 128kbps will be made of 23,040kb (kilobytes) of information. A song of the same length at 320kbps will be 57,600kb in size. This is great because you can store thousands of MP3 songs on an iPod, an 80gb model can store about 25,565 individual songs! If you wanted to store full CD quality music on the same device, you could only fit around 2,318.
You may be thinking, “So why does any of this matter? Surely the files with more data just take up more room on my MP3 player? Why would I want that!”. While it is true that higher bit rates will take up more storage space on your device, the pay off is more clarity in the sound of the music. MP3 encoded audio is compressed data, meaning it greatly reduces the over all size of the file by removing small pieces of data. The lower the bit rate (kbps) of the file, the more compressed it is – and the less data there is. It works by removing data that represents parts of the sound that most people can’t perceive. I’ll explain, don’t worry.
Digital audio is made of tiny slices of sound known as “samples” and most music you listen to plays back these samples at an incredible rate – 44,100 every second! Because of how our ears work, we can’t often tell one sample from the next so removing little pieces of information from a few is almost completely unnoticeable. This however isn’t a perfect process. If you are listening to a quiet piano piece MP3 you might notice a hiss in the background, or the beginning and end of a song might have a quiet sparkly glitch noise softly accompanying the music. These phenomena are known as Compression Artefacts. Most of the time they are only noticeable if you are listening on mid to high end headphones or speaker systems but they get more apparent with lower bit rates. It’s similar with how image resolution works: if you have a very small picture, it looks great on a very small screen – but not particularly great once it’s been blown up on a big screen.
The unfortunate thing is that not very many digital music vendors (iTunes, Spotify, eMusic, Amazon Music, etc.) don’t offer MP3 music at the highest quality – 320kbps. If you are listening on low to mid range quality speakers, headphones, or earphones this may not be a problem but for the audiophiles with expensive gear and a keen ear, this simply isn’t good enough. They would far prefer filling their digital storage with less music, not stored as MP3 and at a much higher quality, than a lot of lower quality music. It all depends entirely on the individual and their listening habits, but it is definitely worth talking about. Digital storage is becoming cheaper and cheaper, so perhaps small MP3 files are on their way out?