Personal Audio > Resources > Sound Advice > Best Bit Rate for Your MP3

Bit Rate Matters Quite A Bit
Digital audio files are NOT all created equal.  Technical characteristics like bit rate, sample size, and sampling frequency can have a big impact on sound quality.  One of the most common – and easily controllable – settings in the CD-ripping process is the bit rate.  When you convert CD’s to MP3’s using a bit rate that is too low, high frequency content – cymbals for example – can take on a distorted, shimmering sound.  Midrange content (like vocals) can also sound “squashed” or artificial.  But just a little knowledge about the MP3 conversion process can help you pick the right bit rate to deliver great sound quality.

CD Quality and Bit Rate
Let’s start from the top down in terms of quality. “CD quality” is 16 bits of pure high-energy audio at a sampling rate of 44.1 kHz. We will use “CD quality” as the benchmark.  CD files are called WAV files (.wav) These don’t use any compression or conversion from the original source - which is why they are so large and have such great sound.

Remember though, that any MP3 converter is “lossy”, meaning it is eliminating some information that can’t be recovered. You will never have actual CD quality music on your MP3 player, but your ear probably won’t know the difference.

Some other acronyms to be aware of are MP3 and MPEG.  The term MP3 is a shortened word for MPEG audio layer 3. MPEG stands for Motion Picture Experts Group.  This is the organization that created the encoding process that takes large CD files and converts them into smaller packages of music to enjoy on-the-go.  The MP3 encoding process throws out all of the redundant information in your music that your ear (hopefully) won’t miss. It then packages it in a smaller and more convenient file, enabling you to hear basically CD quality music for about 1/12 of the size.

A benefit of using MP3 files is that it allows you to control the Bit Rate. Bit rate tells us how fast the data in an audio file is sent through the converter into your storage device.  It’s akin to taking a hundreds of thousands of nano pictures of the audio information in one second. The most common bit rate is 128kbps (or 128,000 nano pictures of audio in one second). The higher the bit rate, the better the “resolution” or sound quality is compared to the original CD quality file.

While downloading music, consider the bandwidth of your connection (i.e. Cable connection, DSL, dial up modem). Attempting to download a larger file will slow your Internet connection and may result in a fragmented audio file.  MP3 files were created to combat the lack of bandwidth on the Internet. If you’re still using dial up to download your music, stay away from higher quality conversion files (above 128kbs).

Variable Bit Rate
Thus far, we have been discussing constant bit rates, meaning that the bit rate stays the same throughout the song.  There is a fairly new process of converting MP3 files called Variable Bit Rate (VBR). A VBR converter analyzes the file before converting it and decides what rate to convert and at what point in the song that it should change. With VBR, a denser file (one with a lot of instruments or sounds occurring simultaneously) will convert at a lower overall bit rate but sound just as good if it was converted at a higher rate. The result is consistent quality no matter what type of file is being converted and is great if you have a wide-ranging collection of music.

With Constant Bit Rate (CBR), you will have consistent file sizes but possibly inconsistent quality depending on your music selections. Most new players support VBR but you should read the specs on your player and the software you are using before you start converting your entire library.

How to Set the Bit Rate
In order to determine how to set your bit rate, you will need to balance your need for hard drive space and sound quality with the type of music you will be listening to – only you can decide what works best. 128kbps is a common default converter, but for some people, it is not acceptable quality. The higher the bit rate, the better your music will sound, but you will cramp the space on your hard drive.  If half of your library happens to be audio books, converting or downloading the audio at a high bit rate as opposed to a low bit rate will have very little effect on the quality, but will take up more space.

The table below gives you some perspective on quality to size ratio.

There are roughly 1,000 kilobytes (kB) in 1 megabyte (MB), and 1,000 megabytes in 1 gigabyte (GB). Assuming a fixed bit rate of 128 kbps and 4 minutes per song, 250 songs would take up about 1 gigabyte of space. This is a good equation to use when taking a look at your entire music collection to determine changing your bit rates or upgrading your music player.

There are hundreds of MP3 software players out there. If you search in the preferences or options section, you’ll most likely come across converting or an importing tab. In Apple’s iTunesÓ on a PC it is located In Edit/Preferences/Advanced Tab/Importing Tab, and in iTunes > Preferences > Advanced > Importing on the Mac.

Now choose your encoder. If you choose “MP3 encoder” in the “Import Using” Field, it will let you choose a fixed rate from 16kbps to 320kbps by clicking the “Custom” option in the Setting Field. Your file will then be converted to the popular MP3 format.  In the custom screen you can also choose your fixed bit rate or check the VBR box to make it a variable bit rate converter. If you choose VBR you can then change the spectrum of quality that the VBR converter will use from Lowest to Highest.

Please note that these conversion settings do not apply to music downloaded from Apple’s iTunesÓ, just music that you import from your own CD collection.

You may also notice other converter options in the encoder tab like Apple Lossless, AAC MP4 and AIFF. These are just more options for converting your music to an MP3 like file.  A format other than MP3 may not play on your player. Apple lossless, AAC, MP4 and AIFF formats are supported by Apple products but may not be supported by other manufacturers’ players or software. If you are not sure if your player supports these file formats, stick with converting to MP3 files.

For more info on AAC and AIFF files please click here.

Hear for Yourself
The test is to convert a few songs at different bit rates.  Then listen carefully, and see what differences you notice between the different versions of the same song.  Your ears will tell you what really matters. 

Of course, the type of earphones you use can also make a huge difference in the way you hear your music.  Shure’s goal is to create products that accurately capture or reproduce the sounds the way the artists intend them to sound.  Many people who make the move to using higher quality earphones begin to download their music at higher bit rates because you will notice the defects and nuances that were not apparent before.  

Experiment with bit rates and songs to experience the difference Shure earphones can make.