Every record is made in WAV — so why do we listen in MP3?

The “original” created in a studio is, without exception, uncompressed WAV (PCM). Yet by the time it reaches you through streaming or download it is FLAC or ALAC — and usually MP3 or AAC. If the original is WAV, why do we not simply listen to that? Here is what happens along the way.

🎙️It always starts as WAV

After recording, mixing and mastering, the final master is uncompressed PCM — a WAV (or AIFF) file. Every stage of music production happens on top of that original, with nothing thrown away. Up to this point the loss is 0%. The question starts with what comes next: how to deliver it to people.

📦The problem is size

At CD quality (44.1 kHz, 16-bit, stereo) WAV runs about 10 MB per minute — 40–50 MB for a four-to-five-minute track, and over 500 MB for an album. When bandwidth and storage were expensive, streaming or downloading that was simply impractical. So the sound had to be compressed, and compression comes in two very different kinds.

🗜️Two kinds of compression — lossless vs lossy

Lossless compression (FLAC, ALAC) folds the data cleverly to shrink the file. Unfold it on playback and it is bit-for-bit identical to the original WAV — nothing is discarded. Lossy compression (MP3, AAC) instead deletes sound it judges you are unlikely to hear. The files get far smaller, but what was thrown away is gone for good.

📊The formats at a glance

WAV · PCMUncompressed original. Studio masters and archives. Roughly 40–50 MB per track. 0% loss — but large.
FLAC · ALACLossless compression. About half the size of WAV, yet bit-identical when unpacked. 0% loss. Used by Apple Music, Tidal, Qobuz and other hi-res services. (FLAC is open source; ALAC is Apple’s.)
MP3 · AACLossy compression. A psychoacoustic model discards sound deemed inaudible, shrinking files to about a tenth of the original. Not reversible. The default for mainstream streaming, downloads and YouTube. (AAC is the improved successor to MP3.)

💡 The analogy — ZIP vs JPEG

WAV is the original photograph. FLAC and ALAC are that photo in a ZIP file — unpack it and the original returns intact. MP3 and AAC are a reduced-quality JPEG — the file is small, but the detail you gave up cannot be recovered. That is precisely the difference between lossless and lossy.

📈Why the MP3 era came, and why lossless is returning

In the 1990s MP3 (Fraunhofer) cut songs to a tenth of their size and opened the digital music revolution — Napster, the iPod, downloads — because back then size was money. Now that storage and bandwidth are cheap, the market is moving back: Apple Music Lossless (2021), Amazon Music HD, Tidal and Qobuz. The goal has shifted from “make it small” to “keep it original”.

✅ So for training, WAV

For casual listening, good lossy audio (high-bitrate AAC) may be plenty. But speed listening and ear training lean on exactly the fine articulation and high frequencies MP3 discards. So that the brain does not spend learning energy patching over what was cut, BrainHz works from the same uncompressed WAV the master was made in, played back at speed.

Source

General audio-engineering knowledge compiled for education, based on public specifications for WAV/PCM, FLAC (Xiph.Org), ALAC (Apple), MP3 (Fraunhofer IIS) and AAC, plus the Apple Music Lossless announcement (2021).

※ This article summarizes and restructures the key points of the source above.

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