FM, DAB or internet radio: which actually sounds better

Ask three people which sounds better, FM or internet radio, and you will get three confident answers that contradict each other. The honest answer is that the question is badly posed. Each of these systems fails in a different place, and which one wins depends entirely on what you are listening to, where you are standing, and how much the broadcaster decided to spend.

FM: the analogue baseline

FM has been carrying music since the 1940s and the physics have not changed. A strong FM signal delivers roughly 15 kHz of audio bandwidth in stereo, which is below what a CD carries but comfortably above what most people can hear degradation in. More importantly, FM degrades gracefully. As you drive away from the transmitter the sound does not stop, it gets hissy, then it gets mono, then it gets noisy. You always know what is happening.

What people rarely mention is that most FM stations do not sound like clean FM at all, because they run heavy dynamic compression to seem louder than the station next to them on the dial. That loudness war has done far more damage to the sound of commercial FM than the transmission standard ever did.

DAB and DAB+: digital, but not automatically better

Digital radio was sold on a simple promise: no hiss, no fading, more stations. The first two are true. The third is the problem. A DAB multiplex carries a fixed amount of data, and every station added to it takes bitrate away from the others. Broadcasters, given the choice between fewer stations at good quality and more stations at poor quality, chose more stations almost everywhere.

The result is that plenty of DAB stations run at bitrates low enough that a good FM signal beats them audibly, particularly on music with cymbals or applause, where the artefacts are easiest to hear. DAB+ improved this a lot by switching to a more efficient codec, so a DAB+ station at 64 kbps can sound genuinely fine. But the standard did not guarantee quality; it only made quality affordable, and that is not the same thing.

One real drawback: digital radio does not degrade gracefully. It works, and then at some threshold it stops, bubbles, or cuts out entirely. In a tunnel or a valley, FM gives you a worse version of the programme while DAB gives you nothing.

Internet radio: the only one with no ceiling

Internet streaming is the only option here with no technical limit on quality. A station can stream at 320 kbps MP3 or lossless FLAC if it chooses to, and some do. It is also the only option where you can hear a station in Casablanca from a flat in Oslo, which no transmitter will ever manage.

The catch is that very few stations choose the ceiling. Most publish 64 or 128 kbps because bandwidth costs them money per listener, which is a cost FM and DAB simply do not have — a transmitter costs the same whether one person or a million are tuned in. So the medium with unlimited potential is, in practice, often the one running the lowest bitrate.

Side by side

So which should you use

• In the car, locally: FM, almost always. No data cost, no dropouts in tunnels, no delay. The sound is fine and the reliability is unmatched.

• At home on Wi-Fi: internet, and look for the highest bitrate the station publishes. This is where streaming actually wins.

• Live sport: FM, without hesitation. A thirty-second delay means you hear the goal from the neighbours before you hear it from the commentator.

• Anything not broadcast near you: internet, because there is no alternative, and that is the whole point of it.

The best-sounding radio is not a technology. It is a station that was mastered carefully and transmitted at a bitrate somebody was willing to pay for.

One test worth doing yourself

Find a station that broadcasts on both FM and online — most national broadcasters do. Play the same programme on a radio and on your phone, a few seconds apart so you can switch between them. Most people are surprised twice: first by how small the difference is, and then by how much of the difference comes from the speaker rather than the signal.