Say there’s a ventilation system making noise from a certain direction. This can be useful for many aspects of production. For those of you looking for a decent omni mic on a budget, look at the studio projects c4 or the audio technica 4022.Ĭardioid mics have the characteristic of rejecting sound from the direction of the mic body. Omni mics come in various shapes, such as pencils, boundary mics (that you set on a large flat surface), or large diaphram condenser mics. Also, in orchestral recording for film and live productions you’ll often use omni microphones to capture the ambiance of the room as well as the orchestra. Common scenarios in production are wireless lavaliers and interview scenarios where you can’t get the handheld mic right in front of the interviewee’s mouth. So when should you use an omni mic? Anytime you want to capture sound from all angles. So what are the different types of polar patterns? This is due to interference from the microphone body and from how well the capsule responds to pressure from different directions. They become slightly directional in the forward region of the capsule. Even omni microphones are not truly “omni” at higher frequencies. Below is the pickup pattern of a Sanken shotgun microphone, varying with frequency. For example, a shotgun microphone has a lobar pattern at mid to high frequencies, but it is relatively hypercardioid at lower frequencies. The second misconception is that microphones keep the same polar pattern for all frequencies. The microphone body itself may block some high frequency content from being picked up from the rear due to it’s size. A well made omni microphone can also be made to capture all frequencies at the same level, meaning the bass and treble of your recording is accurate to what the subject actually sounded like. Sound impinging on an omni microphone is received from all angles – including perpendicular to the mic capsule and from the rear where the microphone body is. An accurate representation of an omni-directional pattern is shown below. It would make sense then, that polar patterns are actually spherical. Microphones are in-fact, 3 dimensional objects, and sound travels in 3 dimensions as well. The first common mistake is to think that microphones pickup sound in two-dimensions like most polar pattern diagrams show. You may have seen polar pattern diagrams online before. All rules can be broken of course, but you need to understand the basic principals of microphone polar patterns so that you understand what sound you are capturing and how that will affect your recording. Just as you wouldn’t use a bi-directional mic for vocals or dialog, you wouldn’t use a shotgun mic for an orchestra. Understanding microphone polar patterns is one of the first steps toward selecting the correct microphone for the job. Using the correct type of microphone to capture the sound you want is crucial whether you’re in the studio or in the field.