By understanding how bit rate and sampling frequency affect the quality and size of mp3 files you can control the quality and integrity of your whole album. By creating an mp3 file high enough in quality (also called fidelity) you can make it desirable enough to sell. But I'm getting ahead of myself. Let's start from the beginning.
Mp3 stands for "MPEG Audio Layer III". And MPEG stands for "Moving Picture Experts Group". So this is interesting: mp3, which is now accepted in the American-Heritage dictionary as the first word to contain a number, is also an acronym within an acronym. Hmmmm.
Mp3 files are audio files, but to be more exact, they are compressed audio files. The compression is what makes these files so popular as it allows audio data to be stored using much less space than previous file formats allowed. Space is very important on the internet. One always hears people talking about it, saying they're looking for "more megabytes" or "more gigabytes". So the size of your mp3 file is important as it relates to space available on the internet but also in how it relates to speed. The smaller the mp3 file, the faster it will stream over the internet.
The bit rate is the number of kilobytes streamed from the host computer to the receiving media player per second. Huh? Let's break that down. A "byte" is a computer term that means one unit of data such as the letter "A" or the number "1" or even a special character such as "%". The number "12" would be two bytes of data since it has two numbers. The word "cat" is made up of three bytes of data as it has three letters. Now here's the tricky part; each byte is made up of eight "bits", which are a series of ones and zeros that are unique to that byte and help the computer identify that character. So, a byte might look like the letter "M" to you, but a computer sees it as "01001101", or the letter "G" as "01000111". Each one and zero is a "bit". Taking the standard of the word "kilo" to mean one thousand, the word kilobyte means one thousand
Audio data in an mp3 file is also made up of bits and bytes. How fast the bits stream from the computer they're stored on to the computer requesting to play them is the "bit" rate. Although the proper term is "bit rate" it is usually referred to as being streamed in a certain number of "bytes". Why, we'll never know. Perhaps because it just doesn't sound right to say "byte rate". So an mp3 file streaming at 64 kb/s is capable of being sent at 64,000 bytes per second over the internet. That doesn't necessarily mean that it will go that fast, as the there can be many variables in how the data gets streamed that can cause "bottle-necking" or a slowing down of the data stream. But if nothing blocks it's way, it can go that fast.
So bit rate affects how fast the mp3 file traverses the internet, but it also affects the sound playback quality and the amount of space it will need to be stored. A really low bit rate will make a song sound very warbly and distorted, but too high a bit rate will create a too large file with no noticeable quality difference.
The sampling frequency of an mp3 file is the number of audio samples recorded per second. So an audio signal recorded digitally at 44.1 Hz would mean 44,100 samples (each sample may be many bytes in size) are being recorded per second. "Hz" stands for "Hertz" which means "cycles per second". Obviously the more samples recorded per second the more samples that will be played back per second, thus increasing the quality of the playback sound.
So sampling frequency is key to controlling the sound quality of your mp3 files. The standard sampling frequency for CD playback is 44.1 Hz. However, if you were to save your mp3 file at that sampling frequency it would be rather large in size and have long delays when streaming online. The very fact that you can change the sampling frequency to a lower rate and maintain rather good sound quality is the facet of mp3 technology that makes it so great.
One thing to keep in mind is that you can always lower the sampling frequency, but you can NEVER increase it. Even if your mp3 audio software allows you to save or convert an mp3 file from a low sampling frequency to a high sampling frequency the resulting file WILL NOT actually be better in quality. By converting an audio file to a lower sampling frequency you are essentially losing valuable data that adds to the integrity and overall quality of sound playback. That data cannot be restored or regained after it has been lost. When making mp3 files of varying sampling frequencies it is always best to start with an original source file that is already saved at the highest quality bit rate and sampling frequency possible.
Creating An Mp3 file
In this section I'm going to assume that you are starting out with your music on a CD. If not, then your music should at least be saved as a .wav file at the highest possible bit rate and sampling frequency. If you are starting out with another file format or are not sure of the quality of your starting file, the following steps will still apply equally the same with the one exception that you will not be able to improve the quality any better than it already is (see above).
You will need special software to do the creating and editing of your mp3 files and there is a lot of software to choose from. But not all audio editing software available will do what you need. If you want to download a free program, the only one I found that was good was on www.download.com called Blaze Media Pro (do a search). It's not professional grade software for running a recording studio or anything like that but it will rip CDs and convert .wav (and a few other formats) to mp3, as well as give you the ability to change the bit rate rate and sampling frequency. Surprisingly, almost all of the other programs I downloaded and tried do not give you this ability. Of course if you can purchase professional audio editing software for many varying prices. A program I use and highly recommend is Cool Edit Pro or Cool Edit 2000, but I'm sure you can peruse your nearest music store or website for something you think suits your needs. Just be sure it allows you to adjust both the sampling frequency and the bit rate when creating mp3 files.
To give you a quick run through on actually creating an mp3 file using Blaze Media Pro please follow the steps outlined below. NOTE that in Blaze Media Pro you can convert CD audio tracks directly to mp3 files but I do not have you do that. Instead you need to make a .wav file first as your original source file. This is important for a number of reasons. First, Blaze Media Pro has more options for creating mp3 files when converting from wav to mp3 than when ripping directly from CD. Not sure why, but 'tis always better to have more options. Second, wav files are not compressed like mp3 files so they contain all of the original sound data in it's entirety. This is good as we are going to want to make several different mp3 files from this one wav file and it is faster to have it handy on the hard drive.
1) Start Blaze Media Pro.
2) Put your music CD into your CD drive.
3) Click on "Convert Audio" then "CD Tracks".
4) At the bottom of the window select "WAV" and change the setting to the highest possible:
"48,000 kHz 16-bit Stereo".
5) Convert all the tracks on your audio CD to .wav files.
6) Close the "Convert Tracks" window, then click "Convert Audio" again.
7) This time click "Convert to Mp3".
8) In Blaze Media Pro it's called "conversion frequency" but it's also the sampling frequency. Go ahead and set it to 44.1 Hz (44,000 kHz).
9) Set the bit rate to 96 kbs.
10) Add and convert all the .wav files you created in step 5 to mp3 files.
TIP: After following these steps and listening to the mp3 files that resulted I think you'd be hard pressed to tell the difference from your CD. Try converting various .wav files to different, lower bit rates and sampling frequencies to create fast, streamlined mp3 files that you don't mind giving away. Also try making higher quality mp3 files that aren't too big in file size but are close enough to CD quality that they are nice enough to sell. I hope that this article on understanding mp3 files has helped you on your path to promoting your music online. Farewell!
More Resources On Mp3 files
History Of Mp3 Files
Audio File Format Types
Principles Of Digital Audio
Bit Rates And Sound Quality
Decide On The Quality Of Your Audio