Did You Hear That?

Did You Hear That?
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PickupPatterns:

No, this doesn't relate to your best bar line or behavior. It's a description of how the mic 'hears' sound, based on the direction it's facing.

Omni-directional pickup pattern

Omni-directional mics have a pattern just as their name implies; Omni (all) directional. These are rarely used in settings where the audio input to the mic will also be reproduced simultaneously through loudspeakers. In other words, you won’t find omnidirectional mics on your favorite band’s stage during a live performance. There are two reasons for this. First, because omni’s pick up or hear everything in all directions, the sound coming from the speakers may also be picked up, and cause feedback where the mic hears the speakers and in turn feeds more sound to the speakers which the speakers reproduce and the mic hears... and so on. Secondly, bleed from other instruments on a stage make it difficult to control what the mic hears, so if you have a person being interviewed on a rock stage, whether they are in front of or behind the drummer, it won’t matter because the mic hears the drummer regardless of what is done. The pickup pattern of an omni directional mic is drawn as rounded. Omni’s are good for interviews in a quiet stage setting, good for broadcast use, and good for recording studios where the setting is controlled and reflections from walls, ceilings, floors, and instruments is a consideration for capturing the optimum sound.


	Omni-directional	Sub-cardiod	Cardiod	Hyper-cardiod	Line	Bi-directional

Acceptance Angle (3 db down)	--	170°	120°	100°	90°	90°
Null (angle of minimum sensitivity)	none	100°	180°	110°	120°	90°
Distance Factor (DF)	1.0	1.2	1.7	2.0	2.5	1.7

Unidirectional Pickup pattern

Uni-directional mics are probably the most common form of microphone. The example of the Shure SM58 is a good example of a uni or ‘one’ directional mic. These mikes have a pickup pattern that is somewhat heart-shaped, leading many engineers to call them "cardiod" mics. The tighter the pattern is, the less sound is picked up from areas away from the mic element, or part of the mic that hears sound. Extremely tight patterns are known as Hyper-Cardiod or Super-Cardiod mics because of their very tight pickup pattern. These mics are extremely useful in most stage settings where a singer needs to have maximum mic sensitivity and yet have maximum rejection of farther away audio to minimize bleed into the house sound system, and to minimize the concern for feedback in the PA system. Typically, these are stick mics, but by no means are all uni-directional mics stick mics.

Shotgun mics come in a wide number of makes, models, patterns, and price ranges. These are the mics seen on the end of long booms, generally 8-16 inches in length, often covered over by fur windscreens or large acoustically transparent housings known as a "blimp." Shotguns are great and usually necessary in video shots where a stick or lavalier microphone would be intrusive to the shot. Watch Jay Leno, Saturday Night Live, or David Letterman long enough, at some point you’ll see the shotgun mike mounted on a boom drift into the picture at least once. (bit of trivia, the mic on the desktop of these late night talk show hosts is mostly for show, but in some moments of system failure, have saved the day) Shotguns are also exceptionally good for voice over work, and many V/O pro’s use shotgun mics in their work. Shotgun mics generally have a fairly narrow field in which they’ll pick up audio. The further away from the source the mic is, the less audio will be picked up with clarity. However, shotgun mics are electronically and physically tuned to work a narrow ‘corridor’ to pick up audio from the source. This ‘corridor’ is known as a pattern, which is often variable in a microphone. Some shotgun mics have a narrow pattern, others may be switched to be a wide field mic, and yet others may be switched from mono to stereo with mid/side or wide midside recording abilities. The pattern is a characteristic of the mic’s build. The long, narrow physical housing of a shotgun mic allows frequency filtering and

phasing to be used to narrow the mic’s pattern. The mic is pointed at a source, and audio is picked up while sounds not relevant to the source are rejected. This doesn’t mean that a shotgun mic may be taken into an exceptionally noisy environ and used to record a whispering interview and that the mic will reject the noise. It will give priority to the source it’s pointed at, but the mic cannot reject out of hand, sounds that are coming from its sides. (ambient sound) It merely hears the sounds with lesser volume. Many require phantom power, or power from a device such as a battery or output from a camera or mixing device that provides voltage to the microphone. This is known as a condenser mic. Phantom power typically raises the sensitivity level of a microphone, so that the mic can ‘hear’ better. It also allows for the plates that make up the ‘ears’ of the microphone to be more refined, to reproduce sounds more accurately. Shotgun mics fall into the category (usually) of uni-directional or stereo directional. If there is such an animal as an omni directional shotgun, I’ve never seen it, but it may exist somewhere in this world. It would defeat the purpose of a shotgun however, to have omni characteristics.[an error occurred while processing this directive]

Shotguns may be mounted on a camera for the ‘run-and-gun’ videographer, but it is better utilized on it’s own stand, or better yet, on a boom managed by an experienced boom operator. Your next door neighbor is probably not the best choice for a boom operator. Good boom operators are rare, and usually somewhat expensive. And worth every dime. If your master camera is mounted on a tripod, the shotgun may live on the camera if no other option is available. However, sometimes it’s easier to carry a mic stand that might sit next to the camera, so that any camera movement might not interfere with the directional audio of the shotgun. If the shotgun is on a roving camera, be aware that a fast pan with the camera across a far reaching shot will play havoc with listeners ears, particularly if there is information that requires viewers attention. As an example, if you have someone on camera describing the beautiful cement floor they just poured, and the mic is pointing at them describing it, don’t pan the camera across the floor as they describe the process, or the mic is no longer pointed at the audio source that the viewer should be hearing.

Having the mic on a stand provides a little more freedom for the videographer. In searching for a shotgun, look for mics that are metal bodied. Avoid plastic mic’s like the plague. Plastic usually resonates at higher frequencies than metal, breaks more easily than metal, and plastic mics generally sound poor. Look for a mic that has a fairly tight pattern for most video uses. Look for a mic that has not only a solid housing, but a good mount, potentially switching ability for stereo to mono, stereo to mid/side, or wide stereo. Make sure the mic comes with a decent foam windscreen that covers the entire length of the mic excepting for where the mic clip or mount might be. The mic should come with any special cables, and should be clearly described to pattern and style. Personal preferences run towards the Audio Technica AT##### for long range use and the AT ### for short range use. Sennheiser, Shoeps, and EV all make good shotgun mics as well.

Source: © 2003 Sundance Media Group

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