A shotgun microphone is a highly directional microphone that uses a long, slotted interference tube in front of its capsule to favor sound arriving along its axis and attenuate sound from the sides. Among microphones it is the standard tool for picking up dialogue from a distance, typically from a boom pole above the frame in film, television and video production.
Its typical polar pattern is called lobar or supercardioid-plus-tube: narrow at high frequencies, wider at low frequencies, with a small rear lobe. Most shotgun microphones are condenser microphones that need phantom power or an internal battery.
How the interference tube creates directivity
The tube is a hollow pipe with slots or holes along its length, placed in front of a supercardioid or hypercardioid capsule. Sound arriving on axis travels straight down the tube and reaches the diaphragm in phase. Sound arriving from the side enters through many slots at different points, so the parts of the wave travel different distances and arrive with different delays.
Those delayed parts partially cancel each other, which reduces off-axis pickup. Cancellation works only when the tube is long compared with the wavelength, so directivity is strong at high frequencies and fades toward low frequencies, where the microphone behaves much like its underlying capsule.
The frequency above which the tube becomes effective depends roughly on its length. The values below are approximate and vary with design.
| Microphone length class | Approximate length | Tube effective from roughly | Character |
|---|---|---|---|
| Short shotgun | 15-25 cm | 1.5-2 kHz upward | Moderate reach, forgiving aim |
| Medium shotgun | 25-35 cm | About 1 kHz upward | General film and video dialogue |
| Long shotgun | 40-60 cm | Several hundred Hz upward | Very narrow, needs precise aim |
Shotgun microphones compared with other microphones
A shotgun microphone is one choice among several for capturing speech. It does not “zoom” into a distant source; it only improves the ratio of direct to off-axis sound, which is equivalent to working somewhat closer with a less directional microphone.
| Microphone | Pickup pattern | Typical distance | Strength | Weakness |
|---|---|---|---|---|
| Shotgun microphone | Lobar, very directional | 0.5-1.5 m | Natural sound, invisible in frame | Colors reverberant rooms |
| Hypercardioid condenser | Hypercardioid | 0.3-1 m | Smooth off-axis sound indoors | Less reach outdoors |
| Lavalier | Usually omnidirectional | 15-25 cm on the chest | Consistent level, hidden | Clothing rustle, less natural tone |
| Dynamic handheld | Cardioid or supercardioid | 2-10 cm | Robust, rejects room | Visible, needs close use |
Many productions record a boom shotgun and lavaliers together. The boom provides natural perspective, while the lavaliers offer a backup when the boom cannot get close enough.
Specifications that matter
Shotgun microphone datasheets share a common set of parameters. Understanding their typical ranges helps compare models and match them to recorders.
| Parameter | Typical range | Why it matters |
|---|---|---|
| Sensitivity | About 15-50 mV/Pa | Higher values need less preamp gain |
| Self-noise | About 5-18 dB(A) | Lower values suit quiet scenes |
| Maximum SPL | About 125-140 dB | Headroom for shouting or effects |
| Powering | 48 V phantom, 12 V T-power or battery | Must match the recorder or camera |
| Output | Balanced XLR | Long cable runs without hum |
RF condenser designs are less sensitive to humidity and condensation than conventional DC-biased condensers, which is why they are popular for outdoor shooting in damp conditions.
Using a shotgun microphone well
Good results depend more on placement and aim than on the model. The boom operator positions the microphone just outside the frame, usually above and slightly in front of the speaker, pointed at the mouth or upper chest.
- Keep the distance short; every halving of distance gains about 6 dB of direct sound.
- Aim the null away from noise sources such as generators or traffic where possible.
- Overhead booming points the rear and sides toward floor and ceiling, which are often less noisy.
- Use a blimp and furry cover outdoors; wind noise can overwhelm dialogue.
- Apply a high-pass filter around 80-120 Hz to reduce handling and wind rumble.
Camera-mounted shotguns are convenient but compromise sound quality, because the camera is usually placed for the picture rather than for sound, often several meters away. They are best treated as reference audio or for run-and-gun work at short distances.
Limitations and common mistakes
The biggest limitation appears indoors. In a small, reflective room, sound from the sides reaches the microphone mainly as reflections that arrive from all directions, and the tube’s uneven off-axis response makes them sound hollow or phasey. Many sound recordists therefore prefer a hypercardioid microphone for interiors.
Other common mistakes include pointing at the speaker’s chin from too far away, ignoring the rear lobe that picks up noise behind the operator, and relying on the microphone’s directivity to fix a noisy location that should have been controlled.
A further pitfall is off-axis coloration on movement. Because the high frequencies are rejected first, a speaker who turns away from a narrow long shotgun becomes dull and distant almost immediately, while low frequencies stay. An operator who cannot follow quick movements should choose a shorter, less directional model, which keeps the tone consistent across the scene and is easier to match in the mix.
The simple explanation
A shotgun microphone is a long, narrow microphone that listens mostly in one direction. You often see it on a pole held above actors or on top of a camera. It hears the person it points at more clearly than the noise coming from the sides.
It is a bit like cupping your hands behind your ears to focus on one speaker in a noisy place. It does not pull sound from far away; it simply ignores more of the surroundings, so it still works best when it is fairly close.
How it is used in practice
A two-person crew films an outdoor interview on a city street for a documentary. The sound recordist mounts a medium shotgun microphone in a blimp with a furry cover on a boom pole and holds it about 60-80 cm above and in front of the interviewee, angled down toward the mouth.
The recorder supplies 48 V phantom power, a high-pass filter is set at 100 Hz, and the microphone is aimed so that its sides face the road. A wireless lavalier is recorded on a second track as a safety.
In the edit, the boom track provides clear, natural dialogue with traffic noticeably reduced, while the lavalier is needed only for one sentence when a bus passed close behind the crew.