AAC Vs. MP3: Which Is The Best Audio File Format?

Offline music is coming back with a vengeance, and if you're on the brink of shaking free from streaming platforms and storing your music locally (or just looking to use your soundbar's USB port to jam out some tunes), you might be confused about the different audio formats available and which is the best. At face value, the best audio files are those that sport higher bit depth and sampling frequency (16-bit/44.1-kilohertz and up). Lossless formats like FLAC (Free Lossless Audio Codec) and uncompressed audio such as WAV (Waveform Audio File Format) preserve all audio information, meaning they simply sound better than compressed files. Is that a done deal, then?

Not really. WAV and FLAC may be bustling with fidelity, but they're also heavy in terms of file size. As an example, take any song with a runtime of three minutes. A WAV file will come in anywhere between 30 and 50 megabytes (MB), while an MP3 compressed at 320 kilobits per second (kbps) will take up just 7 MB. Thus, compressed or lossy formats like MP3 or AAC (Advanced Audio Coding) may be more convenient if you'd rather have a barely perceivable drop in audio quality but much more hard drive space.

Which one of those is better, though? Well, when you dip your toes into the AAC-versus-MP3 conundrum, AAC has a significant edge. As a more efficient (and newer) format, it sounds better than MP3 even at a lower bit rate. However, MP3 is no slouch either if you don't go gung-ho on the compression and keep it at around 320 kbps, which is a standard quality you'll get from download stores.

MP3, or MPEG Audio Layer III, started life in a bygone era when storage space wasn't as widely available as it is today and download speeds moved at a snail's pace. So the best solution for moving files around the internet and between devices to essentially destroy the original audio and sacrifice parts of it in the name of reducing storage needs. By implementing lossy compression, MP3s eliminate parts of the audio that are less likely to be noticed by listeners in an effort to bring down the file size. For example, a 128 kbps MP3 axes away all frequencies above 16 kHz while also removing duplicate information from the left and right channels. A similar process applies to some of the lower-frequency information, too.

This is an exaggerated example, so to speak. With MP3, the damage is always there, but the sound quality ultimately depends on the bit rate. For instance, the loss of audio fidelity at 128 kbps is much more perceptible than it is with 320 kbps. In fact, many online users claim MP3 produces sound quality comparable to uncompressed audio at bit rates above 320 kbps, with differences being barely perceivable on high-end systems. Though MP3 remains popular because of its wide compatibility, it has fallen out of favor somewhat as superior lossy formats came into the picture.

The field of audio compression didn't stop at MP3. Apple engineered the AAC for efficiency, and one can argue they succeeded. With support for as many as 48 channels (MP3 is capped at 5.1 — five regular channels and one low-frequency channel), the new-and-improved algorithm squeezes out the maximum audio quality even at lower bit rates. Granted, if you compare them at high bitrates, you may not hear much of a difference. But the more you compress the audio (128 kbps and lower), the AAC versus MP3 practically turns into a heavyweight world champion versus a semi-professional boxer matchup.

To illustrate the demise of MP3, just consider that none of the major streaming platforms use it. Apple Music relies exclusively on AAC at a bitrate of 256 kbps. Similarly, Spotify mobile and desktop apps switched to Ogg Vorbis (up to 320 kbps for premium accounts), while Spotify's premium web player still runs AAC at 256 kbps.

With that said, if you're building a personal library, there's nothing wrong with opting for MP3 compressed at 320 kbps. Audio is a fickle entity, where the majority of people find it hard to tell the difference between lossless and high-res audio, and even between lossless and files compressed at 320 kbps. So, in short, if you have the storage space, target FLAC or WAV. Otherwise, both AAC and MP3 are solid contenders if you don't push them below the 320 kbps bracket.