The MP3 format is the most popular lossy audio format in use today and has been around since the early 1990s. Its success is mainly attributed to its universal compatibility. Despite its ubiquity, there are a number of factors that determine the quality of an MP3 file, as well as how it is encoded. Pay attention to these settings when converting a file to the MP3 format.
Audio Source Quality
In order to select the optimum encoding values, consider the nature of the audio source. For example, when a low-quality voice recording is encoded from an analog tape using the highest possible encoding settings, the converted file takes up a lot of storage space. If an MP3 file that has a bitrate of 96 kbps is converted into one with a 192 kbps bitrate, there's no improvement in the quality. This is because the original is only 32 kbps and anything higher than this increases the file size but does not improve sound resolution; that data has already been lost.
Here are some typical bitrate settings you may want to experiment with:32 kbps: Voice and analog tape recordings.128 to 192 kbps: Tracks ripped from a CD.192 to 320 kbps: Complex audio source recordings, like classical music, that contain a broad spectrum of frequencies.
Lossy to Lossy
The MP3 format is a lossy format, so converting to another lossy format (including another MP3) is not recommended. Even if you try to convert to a higher bitrate, the audio file still loses quality. It is usually best to leave the original as it is, unless you want to reduce storage space and don't mind a reduction in audio resolution.
Lossy audio formats are compressed by an algorithm that discards some sound data from a digital recording and shrinks the file size. This loss is often imperceptible to most listeners.
CBR and VBR
Constant bitrate (CBR) and variable bitrate (VBR) are two options you can select when encoding an MP3 file. They both have their strengths and weaknesses. Before you make a decision on whether to use CBR or VBR, first think about how you are going to listen to the audio.
CBR is the default setting that is universally compatible with all MP3 decoders and hardware devices but does not produce the most optimized MP3 file. Alternatively, VBR produces an MP3 file that is optimized for both file size and quality. VBR remains the best solution but it is not always compatible with older hardware and certain MP3 decoders.