What Does Cardioid Mean? Microphone Polar Patterns Explained for Radio
Shop for a broadcast microphone and you'll hit the word cardioid within about thirty seconds. It's on nearly every mic marketed for radio and podcasting, usually with no explanation. Here's what it means, what the other patterns are, and why it matters for anyone putting a voice on the air.
A polar pattern is a map of sensitivity
Every microphone hears sound from some directions better than others. The polar pattern is simply a diagram of that: a circle around the mic showing how sensitive it is at each angle. Manufacturers publish these plots in their spec sheets, and Shure's educational guide to microphone techniques walks through the standard families of patterns and how each behaves in practice.
The main patterns, in plain English
- Omnidirectional — hears equally in all directions. Great for capturing a room or clipping to a lapel, bad for isolating one voice from a noisy environment.
- Cardioid — most sensitive directly in front, progressively less to the sides, and least sensitive directly behind. The plot is roughly heart-shaped, which is where the name comes from.
- Supercardioid / hypercardioid — even tighter at the front than cardioid, but with a small lobe of sensitivity poking out the back. More isolation, less forgiveness if you drift off-axis.
- Bidirectional (figure-8) — hears front and back equally, rejects the sides. Common in ribbon mics and useful for two people facing each other across one microphone.
Why radio work is cardioid country
A radio host wants one thing picked up — the voice — and everything else rejected: the computer fan, the keyboard, the room echo, the co-host's bleed. Cardioid does exactly that while staying forgiving about small movements. It's no accident that the classic broadcast microphones are cardioid dynamics; if you're comparing specific models, our guide to choosing a broadcast microphone covers the usual suspects.
The rear rejection has a practical bonus in home studios: point the back of a cardioid mic at your noisiest thing — a window, a computer, an air vent — and you get free noise reduction without touching a settings menu.
Two side effects worth knowing
Proximity effect. Directional patterns (cardioid and its tighter cousins) boost bass as you get closer to the sound source. That's the deep late-night-DJ effect — pleasant in moderation, boomy in excess. Omnidirectional mics don't do this. How you manage it is really a question of working distance, which we cover in radio mic technique basics.
Off-axis coloration. A cardioid mic doesn't just get quieter as you move to the side of it — it can also get duller or thinner, because the pattern isn't equally directional at all frequencies. This is why announcers are taught to keep talking into the mic even while turning to read notes, and why a tighter pattern (supercardioid) punishes sloppy technique more than a plain cardioid does.
Multi-pattern mics: worth it?
Some condenser microphones offer a switch to select among several patterns. For a solo broadcaster the honest answer is that you'll set it to cardioid on day one and never move it. Multi-pattern flexibility earns its cost when you record interviews across a table (figure-8), roundtables (omni), or music. For straight radio hosting, a fixed cardioid design — as NPR's microphone guide for broadcast work suggests — keeps things simple and removes one more way to have the wrong setting on air.
The short version: for radio, buy cardioid, aim the front at your mouth, aim the back at your noise, and let the pattern do quiet, constant work for you every show.