It falls into a category called “highly directional microphones”. It must be pointed directly at its target sound source for proper recording. Unidirectionality is the key for it to realize such a high concentration on the sound source to record the sound. The directional microphone rejects unwanted sounds coming from the sides and rear, thus allowing clearer pickup of the wanted sound source at which the microphone is pointed. Its naming comes from the fact that it is shaped like a shotgun barrel and it must be aimed directly at the target source so as to effectively pick up the sound.
Typically there are 3 kinds of shotgun mic pickup patterns:
1. Supercardioid: It is a narrow pickup pattern where the powered shotgun mic is sensitive right in front of the condenser and sounds off-axis are rejected.
2. Hypercardioid: It works like a supercardioid but carries a narrower pickup pattern and an extended rear pickup. SYNCO broadcast microphone D2 sets a typical example.
3. Ultracardioid: It might be the narrowest pickup pattern, not that excellent for use on a boom pole since it is so directional that even the slightest move has the subject go off-axis.
The main advantage of a shotgun microphone we have talked about so far is high directionality. A directional microphone is a great choice thanks to its narrow pickup pattern. It focuses directly on the sound source in front and picks up the sound with high gain, and records the noises (unwanted sounds) from sides and rear very low. This is advantageous for video makers and filmmakers who intend to pick up high-quality audio.
Other things to look for into shotgun mics include high sensitivity and low self-noise. A professional shotgun microphone is usually used to capture sound at a distance, meaning that the microphone is trying to pick up low-level signals. This is why a quality shotgun microphone needs to have sensitivity higher than those intended to pick up close sources. Then the low-level sound always needs to be amplified to a usable signal level. Hence, having a mic with low self-noise is very important.
A shotgun is commonly used in applications where only the sound in front of the microphone is expected to be captured and all other noises to be reduced. Such scenarios include talks or speeches in meetings, conferences, and lectures where the speaker does not need to hold a microphone and speak into it. The speaker can just stand and talk at a distance as long as he/she talks to the front of the microphone. This allows the speaker to just focus on talking during his/her lecture without being disturbed by the microphone held himself/herself. In this case, this type of unidirectional microphone is always used for DSLRs or cameras and becomes DSLR microphone or camera microphone. In a word, a shotgun directional microphone is an ideal choice when distance speaking is unavoidable and the speaker wants to set himself/herself free from holding or wiring a microphone.