A cardioid microphone is a unidirectional microphone whose sensitivity follows a heart-shaped polar pattern: it is most sensitive to sound arriving from the front, about 6 dB less sensitive at the sides, and least sensitive directly behind. Among Microphones, the cardioid pattern is the most widely used in recording, broadcasting and live sound, because it favors the intended source while reducing room sound and spill from other instruments.
The name comes from the Greek word for heart, describing the shape of the pattern when plotted around the microphone. Cardioid behavior is available in dynamic, condenser and some ribbon designs, so the pattern describes directionality, not the transducer type.
How a cardioid pattern is produced
A cardioid response is the sum of two basic responses in equal proportion: an omnidirectional pressure response and a figure-8 pressure-gradient response. In front, the two add; behind, the figure-8’s rear lobe has opposite polarity and cancels the omnidirectional component. Mathematically, the sensitivity is 0.5 + 0.5 cos θ, where θ is the angle from the front axis.
In a single-diaphragm microphone, this combination is achieved acoustically. Sound reaches the rear of the diaphragm through ports and an acoustic delay network, timed so that sound from directly behind arrives at both sides of the diaphragm simultaneously and produces no motion. Many large-diaphragm condensers instead use two back-to-back diaphragms, which also allows switchable patterns.
| Angle from front | Relative sensitivity | Level relative to on-axis |
|---|---|---|
| 0° | 1.0 | 0 dB |
| 45° | About 0.85 | About −1.4 dB |
| 90° | 0.5 | About −6 dB |
| 135° | About 0.15 | About −16.7 dB |
| 180° | 0 | Null, in theory complete rejection |
Real microphones deviate from the ideal. Rear rejection of about 15 to 25 dB is typical in the mid frequencies, and the pattern often widens at low frequencies and narrows at high frequencies.
Cardioid compared with other polar patterns
The cardioid belongs to a family of first-order patterns that differ in the mix of omnidirectional and figure-8 components. The table compares their key directional figures.
| Pattern | Null angle | Rear lobe level | Distance factor |
|---|---|---|---|
| Omnidirectional | None | Equal to front | 1.0 |
| Cardioid | 180° | None | About 1.7 |
| Supercardioid | About 126° | About −11.7 dB | About 1.9 |
| Hypercardioid | About 110° | About −6 dB | About 2.0 |
| Figure-8 | 90° | Equal to front, opposite polarity | About 1.7 |
The distance factor describes how much farther a directional microphone can be placed than an omni while capturing the same ratio of direct to reverberant sound. A cardioid rejects about two thirds of diffuse room sound, roughly 4.8 dB, compared with an omnidirectional microphone.
The choice involves a trade-off. Supercardioid and hypercardioid patterns reject more total room sound, but their rear lobes pick up sound from directly behind, whereas the cardioid offers the deepest rejection at 180° with a wider, more forgiving front.
Side effects of cardioid design
Because cardioid microphones rely partly on pressure-gradient operation, they show predictable side effects that experienced engineers use deliberately.
| Behavior | Cause | Practical consequence |
|---|---|---|
| Proximity effect | Gradient component rises at close distances | Bass boost when the source is within a few centimeters |
| Off-axis coloration | Pattern varies with frequency | Spill sounds duller or uneven |
| Handling noise sensitivity | Light, gradient-driven diaphragm | Needs shock mounting or internal isolation |
| Plosive sensitivity | Air blasts move the diaphragm strongly | Pop filters or distance required |
The proximity effect can add 10 dB or more of low-frequency boost at very short distances. Vocalists use it for a fuller tone, while speech engineers often counter it with a high-pass filter around 80 to 100 Hz.
Choosing and placing a cardioid microphone
Correct placement uses the null at the rear to point away from the strongest unwanted source. The decision table summarizes common situations.
| Situation | Recommended approach | Reason |
|---|---|---|
| Live vocals with floor monitors | Place wedges directly behind the microphone | Uses the 180° null to reduce feedback |
| Home podcast in an untreated room | Dynamic cardioid close to the mouth | Limits room reflections and noise |
| Drum kit spot miking | Aim the rear at neighboring drums | Reduces bleed between channels |
| Acoustic guitar in a good room | Condenser cardioid at moderate distance | Balances detail and ambience |
| Ensemble with surrounding sources | Consider omni or figure-8 instead | Cardioid off-axis coloration may suffer |
For stage use, the feedback rejection depends on where monitors sit. A cardioid works best with a single wedge behind it, whereas side-fill monitors at about 120° align better with the nulls of a supercardioid.
Distance is the other main control. Moving a cardioid closer to the source raises the direct sound relative to the room far more than any pattern change, because halving the distance adds about 6 dB of direct level. Engineers therefore set distance first for tone and ambience, then rotate the microphone so its null faces the loudest unwanted source.
Common misconceptions
Several assumptions about cardioid microphones lead to disappointing results:
- A cardioid does not remove room sound; it reduces diffuse sound by roughly 4.8 dB, which helps but does not replace acoustic treatment.
- The pattern is not uniform across frequency, so low-frequency rejection is usually weaker than published charts suggest.
- A cardioid is not automatically the best choice; omnidirectional microphones often sound more natural and have no proximity effect.
- Pointing the side at a noise source is weaker than pointing the rear at it, because side rejection is only about 6 dB.
Understanding these limits helps engineers pick the pattern for the situation rather than defaulting to cardioid out of habit, especially when natural off-axis sound or room character is part of the goal.
In simple terms
A cardioid microphone listens mostly to what is in front of it and largely ignores what is behind. If you drew its hearing area from above, it would look like a heart with the microphone at the dent.
That is why singers and podcasters often use one: it picks up the voice while keeping out much of the room and the noise behind it. Getting closer also makes the voice sound warmer and fuller.
A practical example
A singer in a small club band struggles with feedback whenever the monitor level rises. The sound engineer finds that the vocal microphone is a supercardioid and the floor wedge sits directly in front of the singer, which places it in the microphone’s rear lobe.
The engineer swaps to a dynamic cardioid microphone and keeps the wedge directly behind it, aligned with the 180° null. The singer is asked to stay within about 5 centimeters of the grille and to keep the microphone pointed at the mouth, and a high-pass filter at 100 Hz controls the proximity effect.
The monitor level can now be raised noticeably before feedback begins, and the vocal sounds fuller with less bleed from the drums. The improvement comes from matching the polar pattern to the monitor position, not from additional processing.