How do MP3 and WAV Files Differ?

It's a question of quality

Digital audio is everywhere, with two major file standards (MP3 and WAV) - but how do MP3 and WAV files differ, and what are the benefits and drawbacks of each? Both MP3 and WAV files are used in all areas of audio, from portable players, and handheld recorders, to audio interfaces and more. The seemingly ubiquitous nature of both formats might suggest that both are interchangeable in all ways. There are massive differences between the two, however, many of which you’ll be aware of. Here, we’ll focus on exactly what the differences between the two are in a bit more detail.

The WAV file

The WAV file one of the simplest digital audio file formats. Microsoft and IBM originally developed WAV in 1991 for the use within Windows 3.1. Remember the first time you heard your PC making ‘chime’ noises, and not just beeps? Well, that’s courtesy of the WAV file. Without getting too geeky, the WAV was derived from the RIFF (resource interchange file format), which stored data in indexed chunks (interesting, eh?). Apple derived its own version of this file format in 1988: AIFF. Essentially, AIFFs are the apple equivalent of WAVs. They work by taking an audio signal and converting it to binary data. To do this, a device called an analogue to digital converter (AD) takes snapshot ‘slices’ thousands of times per second. For example, CD quality audio records at 44.1kHz, meaning it records at 44,100 slices per second. This makes it capable of recording the entire audible frequency range of 20hz-20khz.

Despite being an older format, the WAV file has several major advantages when it comes to professional, high fidelity recording applications.

• It is an accurate, lossless format – in a nutshell, this means that the format reproduced the recording accurately without losing audio quality due to the format itself.
• It is a very simple format – as a result of the files simplicity, files are relatively easy to process and edit. This has meant that easy to use editor software is available at all levels (from freeware to full, pro applications)
• Nowadays, astonishingly high recording rates can be achieved, with huge dynamic ranges (many ‘home’ audio interfaces offer up to 192kHz)

As a result, for studio recordings, mastering, and pro-audio applications, WAVs are an excellent format to work in. They do have drawbacks however.

• File size – WAV files are large. A stereo, CD quality recording (44.1khz, 16-bit), works out at 10.09 MB per minute. Moving up to 48kHz 24-bit stereo (which will improve both the frequency range and the available dynamic range) will increase file size to 16.48 MB per minute.
• Large file size makes WAVs impractical for portable devices and streaming

MP3 Files

It is fair to say that the MP3 has revolutionised (and some may say terrorised) the music world. MP3 is a shortened name for MPEG-2 audio layer III. The format was developed by the Moving Picture Experts Group, hence the (slightly conceited-sounding…!) name. Though it is still perceived as a modern format, MP3 files have their roots in ideas about psychoacoustics first conceived in the 1970s. Unlike WAV files, MP3s are a lossy format. This means that encoding audio to MP3 will reduce its quality, but also reduce its file size. It is the manner in which it achieves this that makes it so clever… Psychoacoustics is the study of how people perceive sound. There are many anomalies in the way we hear. It is these quirks in our hearing that are exploited by MP3 files. Firstly, the way in which an MP3 encodes knows that there will be certain frequencies that ear will not hear, and so it gets rid of this data. Secondly, it knows that if there are sounds that are loud, they will mask certain quieter sounds, so it gets rid of the ‘hidden’ sound. Finally, it exploits the fact that ear will hear some frequencies better than others. It's all tied in with the 'threshold of audibility'. Once the MP3 has decided which data to keep, this is then compressed again with more traditional data compression techniques. This gets the files down to a fraction of the size of WAV files- usually around 1/10th, but at the expense of some quality. The advantages of MP3 files are:

• Small file format – Because files are so small, they can be easily distributed over the Internet, and huge libraries stored on computers or handheld devices. Because of this, they have become the consumer standard for purchasing music.
• Compresses files with little perceivable difference to the overall sound quality.
• Easy to convert a WAV or CD to MP3 with free software

As you can see, the MP3 lends itself very well to distribution, streaming and promotion, due to its tiny file size.

However, this is at some cost.

• To compress the file, audio quality is sacrificed – though it's very clever, MP3 encoding is not perfect. Compression can sometimes result in odd audio ‘artefacts’ that are detrimental to audio quality, particularly to higher frequencies.
• This audio inaccuracy means that MP3s are not suitable for pro audio work. In addition, many DJs make sure that they use only higher quality 320kps files, as big sounds systems will tend to make lower rate files, sounds, er… lower rate.

So, for critical audio recording, mixing and mastering, use WAV, and for less critical work and distribution, MP3s are just the ticket. There is one key question, however…

How do MP3 and WAV Files Differ Audibly?

Well, there is a way of finding out. First, take a mono WAV recording, and covert a copy to MP3, then convert back to a WAV. Next invert this in an audio editor and save it under a new name. Select this new wave and copy it. Paste this into the original file, and export the two files as a single mono WAV. This is what an MP3 throws away. Have a listen below… Here's the original... Beats Original ...and the bits MP3 throws away. Beats MP3 Discarded Shocking, eh? However, both formats have their uses, so don’t be too harsh… ;-)