What Is an Omnidirectional Microphone?

What Is an Omnidirectional Microphone

I think you all have seen the microphone. It is a device or a transducer that can convert acoustic energy into an electric signal. Various microphones are available in the market, like dynamic mics, condenser mics, ribbon diaphragm mics, and others. One of the key parameters by which one microphone differs from the other is a polar pattern. The microphone can have various polar patterns like cardioid, super-cardioid, and bidirectional or figure of eight patterns.

In this article, I will restrict only to omnidirectional polar pattern microphones. Now the question comes: what is an omnidirectional polar pattern? The word Omni comes from the Latin word all. So, it is a polar pattern that can capture sound from all directions. 

An omnidirectional polar pattern microphone can record the sound with equal strength if you are on the mic’s front, side, or backside. They have a diaphragm just like other microphones, but one side is exposed to sound waves. 

These microphones are beneficial for situations where you need to record the sound from numerous directions or locations. You usually find an omnidirectional polar pattern in lavalier mics or headset mics.

Well, in this article, I will elaborately discuss it in detail, which will help you answer any questions that arise in your mind regarding the omnidirectional polar pattern microphone.

Table of Contents

What Is A Polar Pattern?

It is one of the essential specifications of any microphone. The polar pattern means the response of the microphone to the direction of the sound. By knowing the polar pattern of any microphone, you can know which direction of your device captures the sound and which direction it will reject it. 

So, by selecting the proper polar pattern, you can avoid the unnecessary sound that comes from the direction, which can interfere with your performance on stage or while giving a presentation to your students in the classroom.

However, to understand the polar pattern of omnidirectional polar, you need to imagine a field of 360 degrees that covers your mic.

The portion of the microphone you look at and perform on the stage is the front-most portion of the microphone. It is at zero degrees, and the back of the microphone is at 180 degrees. The left and right edge of the microphone is at 270 and 90 degrees. The circumference of each circle from outside to inside represents 5 decibels decrease in sensitivity of sound.

The acceptance angle of an omnidirectional polar pattern microphone is 360 degrees because it can sense the sound from every direction.

The omnidirectional microphones work on the principle of pressure. The diaphragm is the main component of this microphone and is responsible for converting the sound waves into an electric signal. However, only one side is exposed to the pressure of sound.

We know the pressure is a scalar quality, which has only magnitude but no direction. The sound pressure acts on one side of the diaphragm of an omnidirectional microphone. So, we can say in theory that these mics don’t have any directivity.

Characteristics Of Omnidirectional Polar Pattern

Each microphone is different in its characteristics and uses. But the mics, which have an omnidirectional polar pattern, have almost similar features. So, you can decide using these mics or not if you know correctly almost all the essential characteristics of an omnidirectional polar pattern.

handheld microphone
Female speaker with a handheld microphone

So, let us look at some of the basics characteristics of an omnidirectional mic in detail.

#1. Sensitivity To Sound In All Directions

As we have discussed above, omnidirectional mics are sensitive to sound from all directions. It is one of the simple ways to describe the omnidirectional polar pattern. However, the diaphragm on one side of the microphone creates this polar pattern.

The omnidirectional microphones will behave just like unidirectional mics at higher frequencies. But it is usually not noticeable.

#2. Works On Pressure Principle

The omnidirectional mic works on the pressure principle. Here only one side of the diaphragm inside the microphone’s body exposes to the pressure of sound. The rear side is closed in a constant pressure chamber, and the pressure in it is almost equal to atmospheric pressure. Well, that chamber is not closed completely. 

They have miniature holes so that the chamber pressure matches the pressure of the atmosphere. However, the container will not be affected by the difference in atmospheric pressure that occurs by sound waves.

Now there is a difference in pressure on both sides of the diaphragm. When the pressure of the sound waves is more, then the diaphragm moves inward, but when the pressure of the sound wave is less, then the diaphragm moves outward. 

In this way, the sound pressure causes the diaphragm to move and finally converts the sound energy into an electric signal that is audible to everyone.

As pressure is a scalar quantity and one side of the diaphragm is exposed to sound pressure, it creates an omnidirectional polar pattern in the microphone.

But some mics work on the pressure gradient principle, i.e., the diaphragm on both sides partially exposes sound pressure. These pressure gradient microphones are found in ribbon diaphragm microphones or multidirectional condenser microphones (see What Is a Condenser Mic?). The design of these mics is a bit complex in comparison to pressure microphones. But it opens up to various polar patterns other than omnidirectional.

#3. There Is No Null Point

 The omnidirectional polar pattern microphone can capture the sound from any direction. So, it has no null point. However, that affects the capability of rejecting the unnecessary sound source.

#4. No Lobe Of Sensitivity

As these omnidirectional polar pattern microphones sense the sound from all directions, it has no lobe of sensitivity.

#5. Do not Have Proximity Effect

Proximity means exaggerating low-frequency sound when the mic is close to any source of the sound. When someone moves the mic closer to the sound source, there is an increase in bass response from the mic. Now you may be thinking, what is the bass response

Well, let me tell you, bass response is the response of your mic to low-frequency sound. The proximity effect can be a boon or bane, depending on its use. Suppose a singer is singing on the stage. Then if he sings close to the mic, the mic will produce an earthy sound. If he sings away from the mic and a bit louder, the mic has a penetrating sound.

This effect happens when both the sides of a diaphragm of the microphone are subject to external sound pressure. So you can say that you can observe the proximity effect only in directional microphones.

But in an omnidirectional microphone, one side of the diaphragm is subject to sound pressure, and the other sits in a fixed pressure chamber. So, these microphones do not have a proximity effect.

In other words, you can say the proximity effect is observed only in pressure gradient microphones and not in pressure microphones.

#6. Resistant To Vocal Plosives

The plosives occur when vital wind energy comes from the mouth of a performer or singer who is holding the mic. It occurs mainly with the use of heavy consonants.

empty conference room
Conference microphone

Mainly, if a person is giving a presentation or singing in English, six consonants usually produce plosives. They are as follows.

  • P and B from lip
  • T and D from the tip of the tongue
  • K and G from the middle portion of the tongue.

If you are going to speak in English in front of an audience, just try to pronounce these words and observe how your mouth opens and closes while pronouncing these letters. 

Well, let me tell you one thing while pronouncing these letters: a small amount of air is generated, and when they strike the microphone’s capsule, the mic produces a popping or a windy sound that is very bad to hear.

If I talk about an omnidirectional microphone, then one side of the diaphragm is only subject to external sound pressure—that is why these mics are better resistant to vocal plosives.

Now, if I talk about a pressure gradient microphone, then both sides of the diaphragm subject to sound pressure increase the risk of vocal plosives. 

So, you will often hear popping sounds from these mics. Well, there are various ways to eliminate the popping sound, like you can use a pop filter, or you need to place the mike at a farther distance from the mouth while performing, or you can use software to fix this problem.

#7. Resist To The Noise Of Wind

The omnidirectional microphones resist the noise of the wind, which is because one side of the diaphragm is subject to sound pressure.

#8. Natural Sound

As discussed above, omnidirectional mics can capture sound from any direction; they have no off-axis coloration. Now the question comes: what is an off-axis coloration? 

Well, the off-axis coloration means the incapability of a mic to capture the sound from all directions at the same frequency. Luckily the omnidirectional polar pattern doesn’t have this feature. So, they produce a much more natural and clear sound in comparison to other microphones.

#9. Prone to Feedback

The feedback effect is also known as the Larsen effect. It is an effect when the mic picks the sound from the speaker when the speaker is playing the microphone’s sound. In other words, I can say that there is a sound loop between the audio input and output. The microphone receives the signal from an acoustic or an electric guitar. After that, it amplifies and passes to the loudspeaker. Now the microphone picks some sound from the speaker, and then it amplifies and passes again to the speaker, which causes the feedback effect.

Most of the microphones produce feedback when they connect with the speaker and capture the output noise, which can create a ringing noise that is very irritating to hear.

The omnidirectional microphones don’t have a null point or any angle of decreasing sensitivity. Their nature is to pick sound from any direction—that is why these mics produce feedback, mainly in live performances.

There are various ways to minimize the feedback, like you should never place the mic in Infront of the speaker or place the mic closer to the sound source.

But if I will talk about directional microphones like cardioid polar pattern mics, then they have a null point, i.e., at the rear side of the mic. So, you should always keep the loudspeaker at the back portion of these mics so that you can reject the unwanted sound.

Well, but in the omnidirectional mic, it is a bit harder to avoid the unwanted sound that enters the mic repeatedly.

#10 Becomes Directional At High Frequency

 The omnidirectional microphones behave like a directional microphone when they face sound waves of very high frequency.

It is so because the high frequency or short wavelength sound waves find it challenging to hit the rear portion of the diaphragm and move effectively.

#11. Larger The Body Of Microphone, Difficult To Achieve The Omnidirectional Polar Pattern

When the microphone is large, the high-frequency sound waves find it tough to reach the diaphragm of an omnidirectional microphone. So, this affects the directionality. At that time, the omnidirectional polar pattern does not remain in ideal condition.

But the miniature omnidirectional microphones like lavalier microphones are capable of maintaining ideal in most conditions compared to larger microphones. The sound waves of high frequency can easily move around the body of a small mic and hit the diaphragm. So, they can maintain their omnidirectional polar pattern most of the time.

What Are The Various Mics Where You Will Observe Omnidirectional Polar Pattern?

#1. Handheld Microphone

You will observe the omnidirectional polar pattern in handheld mics, especially those used for interviews and reporting. This polar pattern even reduces the need to move the microphone each time when someone new starts speaking.

#2. Conference Microphone

The conference microphone has an omnidirectional polar pattern so that everyone can hear the voice in an equal manner.

#3. Lavalier Microphone

Lavalier microphones are condenser microphones and work on the electrostatic principle. The plate capacitor plays a role in converting the audio signal into an electric signal. The upper plate acts as the diaphragm, and the backplate acts as another capacitor plate. The change in distance causes a change in the voltage of the parallel plates, resulting from converting audio into an electric signal.

lavalier microphone
Lavalier microphone

You will observe in the market that most of the lavalier mics have an omnidirectional polar pattern. They can capture wide frequencies of sound. Even they remain ideal most of the time in achieving the omnidirectional polar pattern.

#4. Pencil Microphone

The pencil microphones are condenser mics or dynamic mics (see What Is a Dynamic Microphone?) and have an omnidirectional polar pattern.

How To Achieve Omnidirectional Polar Pattern In A Multipattern Microphone?

The multipattern microphone has diaphragms or capsules back to back. The capsules usually have a cardioid polar pattern and are unidirectional.

So, to achieve the omnidirectional polar pattern, the mic signals produced by every diaphragm are summed up at equal amplitude. But you will not get an ideal omnidirectional polar pattern that works on the pressure principle. You will get a pattern similar to it.

Application Of Omnidirectional Polar pattern

  • Conference Call
  • Intercom
  • Wind reduction in the outdoor recording.
  • When you want to record a moving object
  • Lavalier recording
  • To avoid vocal plosives.
  • When you want to do natural recording

When Should You Avoid Using an Omnidirectional Polar Pattern Microphone?

  • Noisy Environment
  • Isolating any single sound source.

What Are The Various Polar Patterns Other Than omnidirectional?

#1. Bidirectional Polar Pattern

They can pick sound from the front and back of the mic, i.e., at zero and eighty degrees. They have a null point on sides, i.e., at 90 degrees and 270 degrees. The bidirectional polar pattern looks similar to figure 8 in the two-dimensional view.

#2. Cardioid Polar Pattern

They are unidirectional with a null point at 180 degrees. There are 6 decibels decrease in sensitivity from the sides of the microphone, i.e., at 90 degrees and 270 degrees, compared to zero degrees. See What is a Cardioid Microphone?

#3. Super Cardioid Polar Pattern

They have a unidirectional polar pattern with a null point at 127 and 233 degrees. Here you will observe that there are almost ten decibels decrease in sensitivity from the sides of the microphone (at 90 and 270 degrees), which has a super-cardioid polar pattern.

#4. Hyper Cardioid Polar pattern

It is a unidirectional polar pattern and quite similar to a super-cardioid polar pattern. But it has null points at 110 and 250 degrees. Here you will observe that there are almost 12 decibels decrease in sensitivity from the sides (i.e., at 90 and 270 degrees) of the microphone. The rear lobe of this pattern is also 6 decibels less sensitive compared to zero degrees or on-axis.

Frequently Asked Questions

Which microphone polar pattern looks like an upside-down heart?

The cardioid microphone has an upside-down heart polar pattern. They capture the sound mainly from the front and reject the sound from the rear portion of the microphone. They pick the sound from the back portion but not in a proper manner. The shotgun mics focus on sound in front of the mic and reject the sound from the rear.

Which polar pattern is best for vocals?

The cardioid polar pattern microphone is best for vocals. They pick sound from the front of the mic and reject it at the rear. They also have the capability of reducing the noise of the ambient. These patterns color the sound more excellently in comparison to omnidirectional polar pattern microphones.

Which polar pattern does a ribbon microphone have?

Most of the ribbon microphones are bidirectional. So, they have a figure-eight polar pattern. Here the soundwaves which come from the sides of the mic cannot move the diaphragm of the ribbon microphone. It is so because the diaphragm is having pressure on both sides. See our guide‌ ‌to‌ ‌Ribbon‌ ‌Microphones‌

Do cell phones have microphones?

The cell phone uses an electret condenser microphone. In this microphone, you will find a dielectric material on one plate of the parallel plate capacitor. It has high resistance, is chemically stable, and contains negatively charged particles. 

The other plate of the capacitor comprises positively charged particles which are also called diaphragms. Both positive and negative charges create voltage in between the plates. 

When the acoustic energy strikes the diaphragm, there is a change in distance between the plates, which causes a change in capacitance and voltage. This voltage difference creates an electric signal.

But for all this process, the electret condenser requires significantly less power to function, which cell phones can easily supply.

Is phantom power AC or DC?

The phantom power is the DC electric power that transmits through the cables of the microphone to operate the condenser microphone.

How can I record my voice without a mic?

You can record voice without a mic in the following ways:
– Try to keep your camera close
– Shoot in a quiet environment.
– Protect the built-in microphone from wind
– You can use a free audio application.
– Do a sound check.

Does phantom power increase volume?

No phantom power does not increase volume. It provides DC electric current to the condenser microphone, which powers the amplifier and the diaphragm. Finally, it increases the volume of the sound.

Is it bad to use phantom power on a dynamic microphone?

It is the DC voltage that provides power to the condenser microphone. The dynamics mics do not need phantom power as an external power source. But if you use phantom power, then the dynamic mic will not get damaged, but there may be a chance that these mics won’t work correctly.

Is an omnidirectional mic good?

Yes, an omnidirectional mic can give you better performance as it has the sonic quality and lack of proximity effect.

What polar pattern does a lavalier have?

Lavalier microphones can be omnidirectional or unidirectional. The mic can pick sound from any direction in an omnidirectional polar pattern. 

Are condenser mics better than dynamic?

Condenser microphones are best for studio application and field recording. They are a bit more sensitive than dynamic mics and have a flat response that suits detailed capture audio.

Are condenser mics good for singing?

The condenser microphone is good to capture vocals at high frequencies. But they are not good at capturing louder sounds. The dynamic mics can be a good option if you wish to capture any loud sound.

Wrap Up

You may use the microphone in your day-to-day life to perform on stage or make the sound audible to the public. There are various microphones available in the market, and each differs in its characteristics.

The omnidirectional microphone picks sound from a 360-degree radius. So, the direction of the microphone is not that important here. You can use these mics for orchestra recordings, film shooting, or for recording acoustic guitar.

I hope this article has helped you understand omnidirectional polar patterns, which will help you purchase a microphone. 

Anyways, please do share your suggestions for this article. I would love to read your suggestions in the comment section. After reading this article, if you purchase an omnidirectional polar pattern mic, please share your feedback with me. I will be happy to read the feedback.

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