MICROPHONE POLAR PATTERNS

Just what are they?

All well designed and manufactured microphones exhibit at least one of these directional characteristics –

1. Uni-Directional (Cardioid/Super-Cardioid/Hyper-Cardioid)
2. Bi-Directional (or “Noise-Cancelling” for headset microphones)
3. Omni-Directional (or non-directional)
4. Lobar (Shotgun)

Microphone users would at some point come across these terms, but what do these different patterns mean, what are the advantages and disadvantages of each pattern and which pattern is suitable for which kinds of applications?

Let’s first look at how polar patterns are usually represented graphically in Figure 1 below.

 

Polar patterns are also commonly represented in polar charts, as shown in Figure 2 below.

 

1. Uni-Directional

These come in the three common variations:

• Cardioid – The sound pick up is mainly from the front of the microphone with only a slight drop in sensitivity at the sides. Pick up at the rear of the microphone is extremely low.
• Super-Cardioid – The sound pick up is mainly from the front of the microphone with a lower sensitivity at the sides compared to the Cardioid pattern. There is also now a low level pick-up sensitivity at the rear of the microphone.
• Hyper-Cardioid – Like the Super-Cardioid, the sound pick up is mainly from the front of the microphone but with an even lower sensitivity at the sides. The pick-up sensitivity at the rear of the microphone is also more pronounced than the Super-Cardioid.

2. Bi-Directional

Also known as “Noise-Cancelling” when used on headset type microphones, these exhibit an equal sensitivity on the front and rear of the microphone.  The pick-up sensitivity at both sides however is extremely low.

3. Omni-Directional

Also known as “Non-Directional”, these exhibit an equal sensitivity all around the microphone.

4. Lobar

Also known as “Shotgun”, these exhibit an extremely tight pick-up pattern at the front while having very low sensitivity at the sides and rear of the microphone.

1. Uni-Directional (Cardioid/Super-Cardioid/Hyper-Cardioid)

Uni-Directional microphones generally sound good for speech or singing applications.  If the surrounding is noisy, like on a loud music performance stage, Uni-Directional microphones will focus more on the voice and reject unwanted sounds. Thus, it will also be ideal for preventing potential acoustic feedback when loudspeakers are close by.

2. Bi-Directional (Noise-Cancelling)

Noise-Cancelling microphones are best suited for speech and communication type applications. As the name suggests, it will work very well in noisy environments such as in call centres, among large crowds of people, machine rooms, aircraft, etc.

3. Omni-Directional (Non-Directional)

These microphones are suitable for both speech and singing applications, especially where it needs to be look unobtrusive, as Omni-Directional microphones can be made very small. However, as they are sensitive to sounds from all directions, it is advised that such microphones be used in relatively quiet or well managed noise-controlled environments to prevent picking up unwanted sounds or acoustic feedback.

4. Lobar (Shotgun)

Shotgun microphones are ideal for speech type applications where the microphone cannot be positioned close to the person or on the person itself. As the pick-up pattern is very tight, it is great for focusing on a small area and reject unwanted surrounding sounds. Typically Shotguns are used in film or video sound capture where the microphone has to be kept out of the camera view but yet be able to capture speech clearly.