What Is A Directional Microphone?

If you are interested in audio recording, you may have come across the term “directional microphone”. But what does it mean, and why is it important? In this blog post, we will explain what a directional microphone is, how it works, and its advantages and disadvantages.

What is Microphone Directionality?

Before we go over what a directional microphone is, let us first go over what microphone directionality is. The directionality of a microphone is the direction(s) from which a microphone can pick up incoming sound. Sounds can come to a microphone from all directions – the front of the microphone, the back of the microphone, or the sides – and a microphone will pick up these sounds differently based on its directional characteristics or directionality. A microphone can pick up sounds with high sensitivity coming into the front of it but not sounds to the sides and rear. Another microphone may pick up sounds well from the front and rear but not the sides. Another may pick up sounds well from all sides. There are many different combinations.

The way that a microphone captures sounds from these different directions is called its pickup pattern.  Not sure what this is? Don’t worry! We’ve included a list below of the most common types of microphone pickup patterns.

• Omnidirectional Microphones
• Cardioid Microphones
• Super Cardioid / Hypercardioid Microphones
• Lobar Microphones
• Figure 8 or Bidirectional Microphones

For a more comprehensive explanation of these pickup patterns refer to our article: “What Are The 5 Most Common Microphone Pickup Patterns?”.

What is a Directional Microphone?

A directional microphone is a microphone that picks up sounds primarily from a specific direction.  An omnidirectional microphone is not considered to be directional.  The more focused a microphone is on one particular direction, the more directional it is.

Why Use a Directional Microphone?

There’s nothing more frustrating than picking up background noise, right? With this in mind, the main reason to use a directional microphone is to reduce and/or remove unwanted noise and focus on the desired sound source. For example, if you are recording an interview in a noisy environment, use a highly directional microphone that can reject sounds coming from behind or beside the speaker. This way, you can capture their voice more clearly and avoid picking up distracting background noises!

Another reason to use a directional microphone is to create a sense of space and depth in your recordings. For example, suppose you are recording a musical performance with multiple instruments. In that case, you can use different types of directional microphones to capture different aspects of the sound. You could use an omnidirectional microphone to record the overall ambiance of the room, a bidirectional microphone to record the stereo image of the main instrument, and a cardioid microphone to record the vocals or solo parts. By mixing these different tracks together, you can create a more realistic and immersive sound experience. Perfect!

How Does a Directional Microphone Work?

A directional microphone uses different techniques to manipulate how sound waves reach its diaphragm (the part that vibrates in response to sound). Depending on how the diaphragm is designed and positioned, it can be more or less sensitive to sounds coming from different directions.

One common technique is to add ports on both sides of the diaphragm. Sounds that come from both sides, which are most often background buzz, cancel each other out and allow the listener to concentrate on sounds coming from one direction. The most advanced directionality comes from using multiple microphones.

Another common technique is using an interference tube before the diaphragm. This long tube with slots along its length allows sound waves to enter at different angles. The sound waves interfere with each other inside the tube and create different patterns of pressure on the diaphragm depending on their direction. This way, sounds from directly in front of the tube are relatively unaffected (not amplified as some believe), while sounds coming from other directions are attenuated.  A microphone with an interference tube is commonly referred to as a “shotgun” microphone.

To learn more about the different types of microphone, please refer to our article, “What Are The 3 Most Common Types of Microphone Construction?”

To learn even more about directional microphones, we suggest Arthur Fox’s article, “A Complete Guide To Directional Microphones (With Pictures)”.

What are the Advantages and Disadvantages of a Directional Microphone?

As we have seen, a directional microphone can offer many benefits for audio recording, such as noise reduction, sound isolation, and spatial enhancement.  Another advantage of a directional microphone is that it can help to reduce feedback. Feedback is the annoying squealing sound that occurs when a microphone picks up its own output from a speaker or monitor.  Since a directional microphone is more sensitive to sounds coming from a specific direction, it can be located closer to a speaker or monitor without feedback as long as it is pointed AWAY from the speaker.

However, it also has some drawbacks you should know before choosing one.  A directional microphone can produce a less natural sound than an omnidirectional microphone. Since a directional microphone rejects sounds coming from certain directions, it can also lose some of the natural ambiance and reverberation of the recording environment. This can make the sound more dry and dull, especially if you are recording in a large or acoustically rich space. To compensate for this, you can use an omnidirectional microphone as a secondary source to capture the room sound and blend it with the directional microphone signal.

Conclusion

A directional microphone is a microphone that picks up sounds primarily from one specific direction and it can help reduce noise and isolate sound sources. However, it can also have some drawbacks, such as unnatural sound quality. Therefore, you should always consider your recording goals and environment before choosing a directional microphone.

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