6 min read
Shotgun microphone guide: what the interference tube really does
A shotgun mic does not zoom. It rejects sound from the sides, and inside a small room that rejection turns against you.
The shotgun is the default film microphone, and the most misunderstood. The long tube in front of the capsule is an interference tube: sound arriving from the sides enters through slots and cancels itself out. Sound arriving from the front does not.
It narrows, it does not amplify
A shotgun does not bring distant sound closer. It reduces what comes from the sides, which raises the ratio of dialogue to room. Point it at an actor five metres away and you get a slightly cleaner version of a distant recording, not a close one.
Indoors, the tube fights you
In a small, reflective room, reflections arrive from every direction. The interference tube treats them unevenly and the result is a coloured, phasey background. This is why many mixers switch to a hypercardioid indoors and keep the long shotgun for exteriors.
- Short shotgun: versatile, usable indoors at a push, the common all rounder.
- Long shotgun: exteriors, sports, wide shots where you need maximum side rejection.
- Hypercardioid: small rooms, interviews, anywhere with hard walls close by.
Wind, handling and mounting
A shotgun outdoors needs a blimp and a fur cover, not a foam ball. Mount it in a proper suspension so pole handling noise does not travel into the capsule, and keep the cable strain relieved at the mount.
Checking what you captured
At the end of the day, verify the files rather than trusting the recorder screen. Sample rate, bit depth, channel count and timecode all matter to the assistant editor, and a mismatch found on set is a five minute fix instead of a day of conforming.
Drop a take into our audio inspector to read format, channel layout and embedded metadata locally, without uploading rushes anywhere.