Radio Audio Quality Explained: Bitrate, AAC vs MP3, and What 320kbps Means

Updated 11 September 2026

Bitrate is the amount of data a stream uses to describe each second of audio, measured in kilobits per second (kbps). More data means more sonic detail survives compression, so higher bitrates sound fuller and cleaner — especially through good headphones. Most free radio streams sit between 96 and 128kbps, which is fine for casual listening; 320kbps is the practical ceiling for MP3 and AAC streams, and it's where music starts to sound genuinely close to the source. That's the whole story in three sentences. The rest of this guide explains what's actually happening, and when the difference is worth caring about.

What bitrate actually measures

Live radio audio is far too large to send raw, so stations compress it before streaming — squeezing the audio into a smaller file by discarding the parts a codec judges you're least likely to notice. Bitrate is the budget for that compression. At 320kbps the codec can afford to keep almost everything. At 64kbps it has to make hard choices, and you hear them: cymbals turn to mush, reverb tails vanish, stereo space flattens.

A useful mental model: bitrate isn't "volume" or "clarity" as such — it's how much of the original performance survives the journey. (If you're new to how streams work end to end, start with what internet radio is and how it works.)

AAC vs MP3: does the codec matter?

Yes, more than most people expect. MP3 is the older format; AAC is its successor, designed to compress more intelligently. The practical upshot: at the same bitrate, AAC generally sounds better than MP3, and the gap is widest at low bitrates. A 96kbps AAC stream can sound respectable; a 96kbps MP3 stream usually sounds tired.

This is why bitrate alone doesn't tell you everything about a station's quality. A 128kbps AAC stream may comfortably outperform a 128kbps MP3 one. When you're comparing stations, the codec is the hidden second number.

Common bitrates and what they're good for

What 320kbps means in practice

320kbps is the highest bitrate in common use for MP3 and AAC radio streams. It isn't lossless — some data is still discarded — but at this level the losses are subtle enough that most listeners, on most equipment, can't reliably tell it apart from the original.

Whether you'll hear the difference from 128kbps depends on three things:

1. Your equipment. Through a phone speaker, you won't. Through decent wired headphones or proper speakers, you very likely will.
2. Your environment. On a loud train, compression artefacts hide behind the noise. In a quiet room, they don't.
3. The music. Dense, acoustic and atmospheric material — jazz cymbals, classical strings, ambient textures — shows compression first. Listen for the shimmer of a ride cymbal or the tail of a piano note fading into room sound; that's where low bitrates fall apart.

The honest summary: 128kbps is genuinely fine for background listening, and 320kbps is genuinely better for attentive listening. Neither claim cancels the other.

Why station bitrates vary so much

Bandwidth costs money, and a station pays for every listener-hour it streams. Doubling the bitrate roughly doubles the bill, so many independent broadcasters settle on 96–128kbps as the economic sweet spot. Higher bitrates also mean more data on your side — about which, see our breakdown of how much data internet radio uses.

Where 72FM fits in

Public-directory stations on 72FM stream at whatever quality their broadcasters choose — the directory links to official sources and can't change what a station sends. What 72FM controls is its own side of the fence: the player carries no ads or tracking on either tier, and 72FM Premium lifts the daily listening limit rather than changing the sound — the bitrate is always the broadcaster's. Premium is £4.99 for 30 days or £29 for a year (as listed on 72fm.com), with a 7-day money-back guarantee — and the honest test below costs nothing on either tier.

The honest test: play the same style of music at 128kbps and at 320kbps, through the best headphones you own, in a quiet room, and listen to the high end — cymbals, "s" sounds, reverb. If you hear the difference, it'll be there. If you don't, save your money and enjoy the free streams. There are more practical tweaks in our guide to getting better sound from radio streams.

In short

Bitrate is the data budget of a stream: 96–128kbps covers everyday listening, 320kbps is where streamed radio gets close to the source. AAC beats MP3 at equal bitrates, equipment and environment decide what you'll actually hear, and the only test that matters is your own ears.

Want the top end of the scale? Pick a 256–320kbps station — free on every tier. And if an hour a day isn't enough, try 72FM Premium: unlimited listening, unlimited favourites and every sleep-timer length, with a 7-day money-back guarantee.