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What's the Real Difference Between .wav, .aiff, .mp3, and .m4a?

by David Bawiec, iZotope Contributor October 9, 2019
File formats
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You’ve spent weeks working on the ultimate song, polishing the arrangement, and perfecting the mix. You’re finally ready to share your song with mom or to send it off to the studio for mastering. But before you can bounce it, you’re met with the ultimate head-scratcher: which audio format should you choose? WAV? AIFF? MP3? M4A?

In this article, you’ll learn the difference between the four popular audio formats, along with use cases for which one to choose when.

How to bounce a session

You want to send your friend your latest song. You could send your session file, but what if they don’t have your DAW? And on the off chance they can open the file, if they’re missing just one plug-in you used, your song won’t sound the same. How can you bypass all of this stress? 

You should bounce your session instead.

What is bouncing in audio?

Bouncing is the process of rendering your entire project as a single stereo audio file that can be played on any device. It’s the process of down-mixing all of your tracks into a two-channel (left speaker and right speaker) audio source. Unlike a session file, an audio bounce means you can send the audio file to your grandma and know that she’ll be able to listen to it without any special equipment.

When bouncing, you’re presented with multiple options: audio format, sample rate, bit depth, and sometimes even normalization. Each one of them is important, so I recommend you check out Griffin Brown’s great explanation of sample rate and bit depth in his Basics of Digital Audio article. 

The four gold standards

Today, we focus on the importance of choosing the right audio format, what they mean, and when you should use each one. What was once a single standardized audio format, quickly grew into a plethora of options. New formats appear and disappear to solve different problems and offer varying benefits. With time, four contenders have become the golden standards you find everywhere today. So let’s dive right into what the four standard audio formats are and when to use which one.

WAV files

What is a .WAV file?

File Extension: .wav
Format Type: Uncompressed Lossless

Waveform audio files (also called WAV files) are one of the more popular digital audio formats and a gold standard in studio recording. WAV was one of the first digital audio formats, and quickly became a staple across all platforms. Despite decades of progress, it still maintains its position as one of the world’s leading pro audio formats.

WAV files capture and recreate an original audio waveform at the highest quality without affecting or altering the sonic characteristics of the sound in any way. WAV uses PCM (Pulse Code Modulation) to encode the data by slicing it into small chunks to provide the highest quality possible. It’s a lossless file format, meaning that there is no data loss whatsoever. So what gets captured and recorded is the closest mathematical/digital representation of the original audio waveform—no noticeable audio quality loss happens in the process.

WAV files are also uncompressed, meaning that the data is stored as-is in full original format that doesn’t require decoding. This provides enormous versatility allowing for superb editing and manipulation.

AIFF files

What is an .AIFF file?

File Extension: .aif or .aiff
Format Type: Uncompressed Lossless

AIFF (Audio Interchange File Format) was created soon after WAV and works identically: it provides studio-grade audio recording and playback. Offering sample rate and bit depth options just like WAV files, AIFF registers the audio waveform as accurate samples (slices) using PCM to offer the highest possible audio recording quality and sound replication. Just like WAV, AIFF also stores data in uncompressed, lossless format, meaning you get no quality loss, just pure sonic happiness.

So what’s the difference between the two? It mainly boils down to history. WAV was created from a partnership between Microsoft Windows and IBM, so WAV files played back natively only on Windows machines. AIFF, on the other hand, was Macintosh’s response to WAV files, allowing full studio-quality audio recording and playback on Apple computers. Nowadays both formats can be recorded and played back natively on any operating system, so they’re easily interchangeable, offering the same high-quality audio, regardless of format.

MP3 files

What is an .MP3 file?

File Extension: .mp3
Format Type: Compressed Lossy

Uncompressed audio formats like WAV and AIFF provide gorgeous sound quality, but at the cost of high file size. With the boom of internet file-sharing in the mid-90s, people quickly realized sending uncompressed files over dial-up connections was impractical—and oftentimes impossible. Which is why MP3s (MPEG-2 Audio Layer III) were born. 

While a three-minute song would average 30MB in WAV or AIFF format, that same song converted to MP3 would take up a tenth of the space—only around 3MB. With compression algorithms that were capable of achieving impressively small file sizes, MP3 became a staple of the internet era and has maintained its strong position to date.

Like images, smaller audio files lose clarity and detail.

However, small file size came at the cost of sound quality. Take the pair of images above. On the left, you can see every little wrinkle and color vividly. A highly compressed image (on the right), however, becomes very pixelated and loses all of the clarity and detail. The same happens when you compress an audio file.

Different compression formats use varying methods to re-encode the data in a way that saves space. But this saving of space means some data has to get lost in the process. Usually, high frequencies are the first ones to go, as the majority of people can’t hear the details in really high frequencies. The lower the encoding quality, the more frequencies and details will get lost in your audio.

Having said that, modern compression algorithms allow for higher bitrates, which, in turn, means that they’re able to achieve high compression ratios with little noticeable loss to the quality of the audio. Bitrate represents the amount of data conveyed per second of audio content, with the general rule of thumb being: smaller bitrates = smaller file sizes. So if you want to maintain good quality, yet still make use of the fact that MP3s are easy to share with friends and family, keep your bitrate above 128Kbps (kilobits per second).

M4A files

What’s an M4A/MP4 file?

File Extension: .m4a, .mp4
Format Type: Compressed Lossy

M4A (MPEG-4 Part 14) files were Apple’s response to MP3s. Often seen as the successor to the MP3, this Mac-centric compressed audio format found its true place with the birth of the iTunes Store, where it became the primary format for all music purchases made through the online music store. It is still the preferred format for all audio included in apps that are released on the Mac and iOS App Stores, as well as Nintendo and PlayStation products. With more and more developers including support for M4A, it’s quickly becoming the go-to audio format for compressed audio files.

M4A files are encoded with the lossy Advanced Audio Coding (AAC) codec, which is able to provide the same bitrates as MP3s, yet achieve tighter compression. This results in smaller file sizes, all while delivering higher audio quality. It’s like a golden unicorn, which is why it’s become such a popular format for light-weight audio deliveries.

Although many audio players can playback M4A files across various platforms, the audio format still can’t compete with MP3’s universal compatibility, which is why MP3s still rule the world due to their cross-platform adoption.

Choosing the right format for your project

When deciding which audio format is right for you, the first question you have to ask is whether the file needs to provide uncompressed audio or can it be in a compressed audio format?

Uncompressed lossless

If you’re working on releasing your song publicly, you’ll want to bounce it in an uncompressed audio format, that way your original master export is at the highest uncompromised quality possible. Additionally, following the Red Book standard to provide for the ultimate listening experience, CD-quality audio should use uncompressed audio files at 44.1kHz and 16-bit depth. The simple way to think of this is: if you need to share your music in a way that doesn’t jeopardize the quality of your music in any way, use an uncompressed audio format. So both WAV and AIFF will be your best friends here.

PROS: Studio audio quality without compromise
CONS: Large File Size that can be troublesome when trying to share digitally or via email

Compressed lossy

On the other hand, if your intent is to make sharing your music easy and fast, choose a compressed audio format that will provide you with small file size. Yes, it will mean you’ll have to trade perfect quality away, but if you know that the person you’re sending your song to is going to be listening on headphones on a bus or their car audio system, then you know that extreme audio quality won’t matter. At that point, convenience will always win. Additionally, since email providers limit attachment sizes and smartphones have limited storage space, any audio format that can offer smaller file sizes is going to be a winner. For all of those instances, choose a compressed audio format like MP3 or M4A.

PROS: Small file size, perfect for sending via email, direct messages, or storing on mobile devices
CONS: To achieve smaller files, audio quality is compromised. The smaller the file, the worse the audio quality will be.

WAV vs. AIFF

So if WAV and AIFF can both offer the same highest studio-quality audio, which one should you choose? Well, that will really depend on your use case. For starters, the historical prevalence still stands today. WAV files are more popular on Windows, whereas AIFF files keep their ground on Macs. If you’re planning to send your audio files to the studio for further overdubbing or mixing, consistency with your session is important, so talk with your sound engineer about what format they plan to use in the session, and make sure your audio bounces match. The great news is, regardless of which of the two formats you choose, you will achieve exactly the same superb audio quality.

MP3 vs. M4A

The majority of desktop and mobile devices sold nowadays come with native support for MP3 and M4A files alike. For higher quality results, I recommend you choose M4A, which can offer higher sonic results at the same settings, all while still resulting in smaller file sizes than MP3. On the other hand, if guaranteed compatibility is what you need most, MP3 will probably be the wiser choice of the two.

Conclusion

I hope that this guide was able to shine some light on the difference between the four basic audio formats and when to use them. Most modern DAWs allow you to bounce your song in multiple formats at once. As a general rule of thumb, I recommend you choose one Uncompressed Lossless audio format (AIFF or WAV) and one Compressed Lossy audio format (M4A or MP3). That way, regardless of what kind of format you need, you have it ready and you don’t have to re-open your session just to re-bounce the song in a new format. Additionally, if you have your song bounced in at least one Uncompressed Lossless format, there are plenty of great audio converters on the market that will allow you to convert your song into any of the other audio formats when you need them.

The audio world is filled with many options, and the four basic formats above are just a few of over a dozen different audio formats. Ultimately, whatever use case you may have, you’ll find an audio format that’s able to fulfill your needs—including a few Compressed Lossless file formats. Now that you know how to use the basics, I can’t wait to hear the music you create.

Learn more digital audio fundamentals:

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