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What Is a Cardioid Microphone? How Do They Work?

I often get asked about cardioid microphones and how they work. In this post, I'll answer these questions and more about cardioid microphones.

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The cardioid microphone is one of the most popular mics on the planet. It’s a great choice for recording interviews, speeches, or other audio recordings where quality is important. But what is a cardioid microphone, and how does it work?

This post will discuss how the cardioid microphone works and its benefits. We’ll also provide a few tips on how to use it effectively. So whether you’re looking to improve your audio recordings or want to know more about this popular microphone type, this post is for you.

Image of a black colored microphone with a stand. Source: dome dussadeechet takul, pexels
Image of a black colored microphone with a stand. Source: Dome Dussadeechet Takul, Pexels

What is a cardioid microphone? A cardioid microphone is one whose polar pattern and pickup direction are both in the center. Sounds directed in the direction of the microphone are picked up the best. The cardioid mic’s directional sound capture and rejection of ambient noise make it a popular choice.

What is a cardioid microphone?

A cardioid microphone is a mic that only picks up sounds in front of it. This front-focused pattern is great for live performances and other situations where noise reduction and feedback suppression are needed. It lets the microphone be pointed directly at the source of the sound while isolating it from background noise. Cardioid microphones vastly outshine mics with other polar patterns.

How does a cardioid microphone work?

A cardioid microphone captures sound in a single direction, or “cardioid.” This allows the microphone to pick up less sound from all directions, which makes it better for recording vocals, instruments, and other acoustic elements. This is because the cardioid microphone focuses its sound waves on a single point, so sounds coming from other directions don’t mess up or distort the sound.

For a cardioid polarization to occur, the diaphragm’s back side must be subjected to airborne sound waves. This results in a movable diaphragm that responds to changes in front-to-back sound pressure.

A cardioid microphone has a diaphragm that only moves in one direction, so sound can come in from any side. The diaphragm flexes and extends as the pressure on its front and back sides changes.

When there is more force on the front of the diaphragm, it will slide backward. Diaphragms move forward when there is more pressure behind them than in front of them. The diaphragm will not budge if the pressure on either side is the same. Therefore, the diaphragm of a cardioid microphone is open to sound pressure from all sides.

Manufacturers of microphones use clever ways to change the phase (and maybe the amplitude) of sound waves before they reach the back of the diaphragm. For example, they might put an acoustic labyrinth in the back of the capsule. So, if the same amount of sound pressure is put on both sides of the microphone diaphragm, as explained in the previous bullet points, the microphone won’t send a signal.

In a cardioid pattern, the rear null point is reached when sound from the back hits the diaphragm while sound from the front hits the diaphragm. For a sound wave to go from the back (180 degrees) of the acoustic labyrinth to the front of the diaphragm, it must take the same amount of time, T, to travel from the same place via the labyrinth to the back of the diaphragm.

Manufacturers get the unidirectional cardioid polar pattern with its very effective 180° rear null point by changing how sound travels to the back of the diaphragm. It’s important to remember that the delay is small since sound travels so swiftly. No matter how small, this phase offset causes unidirectional (and cardioid-type) polar patterns.

Characteristics of a cardioid microphone

Knowing the cardioid shotgun mic’s sound-recording capabilities is helpful if you plan on using it. For a general understanding, we have listed six common points below.

1. Exhibits proximity effect

For cardioid polarization to occur, the diaphragm’s back side must be subjected to airborne sound waves. This results in a movable diaphragm that responds to changes in front-to-back sound pressure.

Proximity effects are seen in pressure gradient microphones. However, the proximity effect is less pronounced in cardioid microphones than in bidirectional microphones with equal exposure on both sides of the diaphragm since the rear of the cardioid diaphragm is enclosed.

2. The null point at 180°

The 180-degree null point is a hallmark of the cardioid microphone pattern. The elimination of noise from behind aids in navigation. Easily block out unwanted sounds by directing the microphone to the desired source. The 180° null point is most often seen on stage monitors.

Cardioid mics work best when they are oriented away from the stage monitor. Vocalists can increase the gain on the mic pointed at them without getting feedback by pointing it away from the monitor.

3. Roughly 6 dB less sensitive at 90° & 270°

The on-axis cardioid pickup pattern is better because it is the most sensitive one-directional pattern. It also pays no attention to its hind end. As the cardioid polar pattern angle moves away from 0 degrees in either direction, the sensitivity decreases until the rear null point is reached. Its ideal cardioid configuration achieves a 6 dB attenuation at 90 and 270 degrees.

If we use -6 dB spots as our acceptance angle reference, the cardioid mic has a 180° acceptance angle. This means the microphone will always pick up sound in a 90-degree area on either side of its on-axis line.

4. Sensitive to vocal plosives

When sound pressure comes from all directions, the diaphragm is more sensitive to sharp sounds. Vocal plosives are short, sharp bursts of air produced by some consonant sounds. Explosive energy is short-lived and can make the sound pressure in the front and back of the diaphragm very different. When the diaphragm/capsule overloads because of the quick but significant change in pressure, loud “pops” can be heard in the mic.

5. Excellent sound isolation

Because the cardioid mic only picks up sound from one direction and doesn’t have feedback, it is great for isolating individual sound sources. The wide acceptance angle of 180 degrees of a conventional cardioid microphone provides significant wiggle room when positioning or repositioning the microphone about the sound source. If we place a cardioid microphone in the right spot, we can pick up only the sound from one direction.

This method can get a close mic on a single source when there are no other sounds nearby or behind it. If you can, put the “unwanted” sound sources behind the microphone, close to the point where the cardioid pattern stops picking up sound from the back.

6. High gain-before-feedback

When the cardioid microphone is put in the right place for live sound reinforcement, it can have a high gain-before-feedback. This is because the microphone has to be pointed away from any speakers or monitors to make use of the rear null point.

This is called a feedback loop when a microphone boosts the signal from a speaker and then boosts the signal from the same microphone. Turning the cardioid at an angle away from a live speaker increases gain-before-feedback significantly.

What are the benefits of using a cardioid microphone?

Using a cardioid microphone has several advantages. Among them are:

  • The quality of recorded sound is unaffected by background noise. This is because they are less susceptible to picking up outside noise than microphones with a wider frequency range, such as omnidirectional or figure-eight mics.
  • Because they pick up sound only from the front of the mic and cancel out sound from the rear, they are ideal for recording vocals and acoustic instruments.
  • Cardioid microphones is that they are less likely to pick up unwanted feedback.
  • Their compact size and lightweight enhance their portability and simplicity of setup compared to more conventional microphones.
Image of a gray and black colored microphone on a stand. Source: hrayr movsisyan, pexels
Image of a gray and black colored microphone on a stand. Source: Hrayr Movsisyan, Pexels

When should you use a subcardioid microphone?

The cardioid shotgun mic’s unidirectionality and rear-side rejection make it useful in many applications.

  • When using live sound reinforcement in front of the monitor speakers.
  • If a lot of benefits are needed from the response
  • Silence the surrounding din of a busy place
  • Intended Use: To record one’s own very localized sound source
  • Record high-quality sound even in challenging settings.
  • When an impact of proximity is necessary
  • That rear-end noise be kept to a minimum

When should you avoid using a cardioid microphone?

While there are many reasons you would want to use a cardioid microphone, there are some circumstances where you’d want to avoid it.

  • What happens if the sound source travels away from the mic?
  • To avoid the effects of closeness when.
  • To capture the purest possible ambiance.

If you want even more tips and insights, watch this video called “What is a Cardioid Microphone [What you Should Know About Cardioid Mics]” from the Zim Mics YouTube channel.

A video called “What is a Cardioid Microphone [What you Should Know About Cardioid Mics]” from the Zim Mics YouTube channel.
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Frequently asked questions (FAQ)

Do you still have questions? Below are some of the most commonly asked questions about cardioid microphones.

Is a cardioid microphone good for vocals?

Yes! The advanced cardioid pickup pattern will help keep the background noises from getting in and causing feedback. These characteristics are necessary for a live mic, so if you’re searching for a voice mic for the stage, this is probably the best option.

Where should I place my cardioid mic?

To find the optimal placement for a cardioid microphone, cup your hands over one ear to create a stereo headset while listening tot he playback. You’ll want to move around the player or sound source to locate the sweet spot where the instrument’s frequencies are evenly distributed.

What is an acoustic labyrinth

The acoustic labyrinth is an open-ended tuned pipe in a microphone. When the wave from the speaker reaches the end of the pipe, it expands into the listening area, generating an abrupt pressure drop that reflects back through the pipe as a rarefaction to the speaker.

Conclusion

We hope this blog has helped you understand a cardioid microphone. As well as how to use it effectively.

This article covered what a cardioid microphone is, how it works, and the characteristics of a cardioid mic. Here are some key takeaways:

Key takeaways

  • Cardioid microphones only pick up sound coming from in front of them.
  • For a cardioid polarization to occur, the diaphragm’s back side must be subjected to airborne sound waves.
  • The 180-degree null point is a hallmark of the cardioid microphone pattern
  • Extra tips:
    • Although ribbon microphones are a subset of the dynamic microphone family, they are often considered to be an independent design due to their distinctive operation and sound.
    • The sensitivity of condenser microphones much exceeds that of a dynamic microphone.
    • To capture sound from any direction, an omnidirectional microphone is required.

So, do you find cardioid microphones convenient to use? And did I cover everything you wanted to know? Let me know in the comments section below (I read and reply to every comment). If you found this article helpful, share it with a friend, and check out my full blog for more tips and tricks on music production. Thanks for reading, and never stop making music.

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Audio Apartment Author
Written By Andrew Ash
Hey there! My name is Andrew, and I've been making music since I was a kid. I now run this blog all about home studios and music production. If you want to improve your home studio setup, this is the place for you!

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