Audio Recording Basics: Using Shotgun Microphones for Documentary Video Production

Audio is arguably the most important facet of any film or video production. There is a saying that goes: “Audio is 70% of what you see,” which means that sound makes up more of the experience than the visuals do. So while we may spend a lot of time planning for what our shot looks like, it’s even more important that we mic it properly for the best audio recording possible.

When it comes to filming interviews, there are two styles of microphone that are most often used: a lavalier and/or a shotgun mic. In the video above and article below, we’ll cover some of the basics you need to know about shotgun style microphones for capturing clean, usable audio for documentary style shoots.

Shotgun style microphones are long, cylindrical mics that are considered to be “directional.” This means that it will capture the most audio signal from whatever it is pointed at. How well it captures that sound is determined by a few different factors, including the microphones pickup pattern, room acoustics, and most importantly, the distance of the mic from the audio source.

Pickup Patterns

Shotgun mics will have varied polar (or "pickup") patterns, and it is important to understand which pattern will be best for what you plan to shoot. For interior interviews, we usually go with a hypercardiod, such as the Sennheiser MKH416. Here is a great video that explains polar patterns and gives some good examples of when to use each one:

Room Acoustics

Have you ever played racquetball and noticed how much sounds echoes in the court? It makes it hard to understand what someone is saying when they talk, doesn’t it? Flat walls that are parallel to one another will reflect audio very noticeably, therefore it is desirable to choose a location where audio reflections will be dampened. Soft materials like carpets and furniture help absorb rogue audio, and variations in surfaces from things like shelving units will break up sound waves. If you’re stuck in a room without furniture and thus sound with a lot of echo, hanging a few sound blankets can go a long way to lower the amount of audio bounce.

Get Your Mic as Close as Possible

Probably the most important thing you can do to get the strongest signal from the person speaking is to get the mic as close as you can. Off-axis noises will become less apparent, and the audio will sound rich and clean. Check your video to make sure your mic isn’t in the shot, but just outside of the frame. It’s a simple thing to do, but will have the most dramatic impact on your final results.

C-Stand or an Operator?

You’ve likely heard of shotgun mics being called “boom” mics, but that is in reference to a boom pole. These are lightweight, extendable poles that have shock mounts on the end which hold a shotgun mic.

For run and gun shoots or a quick interview setup, having a boom operator is an easy way to ensure you’re always getting the mic right where it needs to be. However, for sit down interviews we find that using a C-stand with a pole holder attachment works great.

Room Tone

One thing you’ll notice when using shotgun mics instead of lavalier mics is that they pickup room noises much easier. Low rumbles from nearby AC units, for example, can give your recordings a minor hum that doesn’t sound bad until you cut from one interview to another you shot that day when the AC unit wasn’t running. It is good practice to record something called “room tone,” especially when recording with a shotgun mic. Recording room tone means to roll audio for :30-:60 with no one speaking, and not having moved any equipment. This captures the rooms particular sound, and gives you a clean base to either add it in over edits (for a constant, consistent tone) or use it as a sample to do noise reduction with a program Adobe Audition.

Lav or Shotgun?

For seated interviews, why not both? Shotgun mics typically produce a richer sound than a similarly priced lav sound and I like to use a shotgun whenever possible. I will lav mic talent as a backup though. Sometimes there might be too much room noise and it becomes distracting, so I will end up using the lav audio track in the edit. (Don’t use both though, it sounds weird to cut back and forth from one mic style to the other on the same person.)

If you found this article helpful in your quest to learn more about filmmaking or video production, consider checking out our e-book, Tips for Shooting Professional Video Interviews, which includes an entire chapter on microphones and audio recording.