Bitrate is the most important parameter of any lossy codec. Bit rate is generally measured as the number of "bits per second" (bps) at which the data in a audio stream is being delivered. A higher bit rate means that the MP3 has more information. A 128kbps MP3 file pushes 128k bits per second at playback. The higher the bitrate, the more information is reproduced and so generally the higher quality the sound. There isn't really a recommended amount, it depends on your needs, but most people can't tell the difference if you increase quality once you have reached 256kbps.
You are looking to reduce the size of a large mp3 file or you just want to merge multiple MP3 files with different bitrate into one? It's easy enough. But please, never increase bitrate of existing MP3 file to get higher quality! It's not true, because bitrate can be changed only by re-encoding.
Audio Converter Plus can change MP3 bitrate, so you can easily send MP3 to your mobile device, or as an E-mail attachment.
Download Bitrate Converter from our site: http://www.abyssmedia.com/downloads/audioconverter.exe. Run the downloaded file audioconverter.exe to start installation, which is fast and requires no knowledge. After installation, double click on the new icon, you will see the user interface below.
Add the MP3 audio files from the "File" menu, select output folder and choose MP3 as output format. Next, open MP3 encoder options and select any bitrate what you need. Leave the other options by default. That's all! You can start conversion and get MP3 files with new bitrate.