MICROPHONE PLACEMENT

Understanding the pick up pattern of your microphone and the inverse-square law will help you to better understand where to properly place your microphones. When you are shooting video without the aid of a sound recordist, it often becomes necessary to mount the shotgun microphone onto the camera. This is convenient because you will not need to use a boom poll or other accessories. However, having the shotgun on the camera will require you to get physically closer to your audio source to ensure that you are recording a high- quality audio signal. You cannot stand far away from your subject without

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picking up all the ambient noise between you and the audio source. As discussed earlier, inverse-square law states that audio intensity is increased exponentially as the microphone is moved closer to the audio source.

In Chapter 3, I recommended that shooters get as many close up shots as possible. To get close ups, videographers should physically move the camera closer to the subject, rather than zoom. Zooming will magnify all your camera moves, and will make your footage appear shakier. More importantly, audio quality also benefits greatly when you physically move closer to your subject. If your camera is closer to the audio source, your shotgun microphone will be able to pick up a stronger audio signal and you will be able to avoid unwanted noise. Shotguns work best when they are less than 5 feet away from the audio source. You can increase the gain on your camera if you are farther than 5 feet away from your subject. But always remember that increasing gain increases the recorded volume of all the sounds, including ambient noise, in your shot.

Shotgun microphones can be used to collect ambient audio or vocals such as person-on-the-street interviews. Lavalier microphones are used specifically to capture high-quality vocal audio. Shotgun microphones have a pick up range of up to several feet, but lavalier microphones are designed to work best when they are placed close to your subject. Lavalier microphones should be placed 4 to 6 inches away from your subject’s mouth. Placing your lav microphone further away will require you to substantially increase the gain on your camera. This will result in the pick up of ambient noise such as room hum or clothing movement. Clipping your lavalier microphone too close to your source will result in unnaturally boomy or muffled audio.

Figure 4.7a The microphone is far away from the source and will pick up significant ambient noise.

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Figure 4.7b The microphone is closer to the source and will pick up a higher-quality audio signal.

Exercise

Place your camera and shotgun microphone 3 feet away from a constant audio source such as a radio, running water, or city traffic. Adjust your audio gain so that the audio meters are peaking at approximately −12db. Listen to the audio as you record. You should hear a very clean, clear audio signal. Next, move your camera 6 feet away from your audio source. Where do your audio meters read now? How much do you have to increase the audio gain on your camera to reach −12db again? As you increase your gain, do you hear other ambient noise more loudly?

On-camera microphones. Most cameras have a built-in microphone. You should avoid using the on-camera microphone unless you have no other options. These microphones, in general, do not produce high-quality audio:

The microphones are not of the highest quality. Camera manufacturers spend most of their design and manufacturing resources on the camera’s sensor, software, and build. Microphones are not generally a high priority.

Built-in microphones will pick up handling noise. Built-in microphones are a physical part of the body of the camera. These microphones will pick up any vibrations on the camera such as your fingers pushing buttons, as well as any mechanical movements inside the camera. These microphones tend to be omnidirectional and are also notorious for

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Figure 4.8 On-camera microphones should be avoided if possible. Always use external microphones when available.

On-camera microphones are poorly placed. You cannot adjust the placement of an on-camera microphone. Some manufacturers put their microphones in the center of the camera. Others put the microphone on the left or right side of the camera. The placement of built-in microphones is based on the overall design of the camera, and not on the ideal position for audio recording.

Recording multiple audio sources. Monitoring a single audio source while trying to expose and compose your shots is difficult. This takes intense focus and concentration. Trying to monitor two audio tracks makes your task exponentially more difficult. However, there are situations when you will want to record two audio signals simultaneously. For example, you may want to put a lavalier microphone on a scientist as she is giving you a tour of her lab. You may also want to put a shotgun microphone on your camera to capture the whirring of lab equipment or the chatter of lab workers.

To record multiple audio tracks, you must have a camera equipped with the ability to accept two microphone inputs. Typically, only high-end prosumer to professional cameras will have this capability. Cameras that allow two microphone inputs will allow you to adjust the gain levels of your microphones separately. For example, you may set the recording gain of the lavalier microphone on the scientist at 4. A setting of 4 may be too low for your shotgun microphone and you may want to set that at 6.

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Figure 4.9 XLR inputs are typically featured on high-end cameras, allowing videographers to use high- quality microphones.

After you have adjusted your audio levels for each microphone, it is import- ant to have the camera record each microphone onto a separate audio track. This will allow you to edit each audio track separately in post-production. Refer to your camera’s manual for instructions on how to set your recording tracks.

If your camera does not have built-in inputs for more than one microphone, you may want to use an external mixer that will accept multiple audio sources. You can send an audio signal from the mixer into your camera. Using an audio mixer will give you greater control of your audio, but it also adds another layer of complexity.

Tip: If you have the option of recording audio to two separate channels on your camera, here is a trick that protects your audio from becoming overmodulated. When recording a single audio source, set your camera to record this signal to two separate audio channels. Set the audio gain of your second audio channel to record at a level lower than your first audio channel. You will get the same audio recording at different levels on different channels. If your audio becomes too loud in channel 1, the audio in channel 2 will be recorded at a lower level and will not be distorted. You can use the audio in channel 2 if the audio in channel 1 becomes unusable. This works well in situations such as rallies or sporting events when crowd noise is unpredictable.

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Figure 4.10 Audio mixers give video producers great control over recording levels and quality.

Figure 4.11 Audio mixers allow you to mix channels 1 and 2 separately.

Automatic Gain Control (AGC). Most cameras will offer an option for Auto Gain Control or AGC. Unless you are shooting in extreme situations such as violent weather or unruly protests, you should avoid using the AGC option. Automatic gain control behaves much like auto-exposure on your camera. Software in the camera will try to determine the best recording levels for your audio source. If the audio level is too low, the camera will automatically increase the gain. If the audio level is too high, the camera will decrease the gain. This initially sounds like an ideal solution. However, AGC can produce unwanted results or unusable audio. For example, during an interview, your subject may pause to contemplate a question or he may become emotional and must stop talking. AGC will detect that the audio has gone lower and adjust the gain. We want this moment of quiet, but AGC will begin to record at a higher gain and increase the ambient noise in the room. Conversely, if your audio source is sporad- ically loud, such as in the case of protest rallies or city traffic, then the AGC will decrease and increase the audio gain quickly and sharply. This will result in audio that fluctuates too quickly and sounds warbled.

Tools for recording audio. Just as there are seemingly many options for cameras and lenses, there are many tools for recording audio. We have discussed

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using shotgun and lavaliers with your cameras. Often, you will be required to record additional audio with an external audio recorder. External mixers and recorders come in a variety of models, features, sizes, and prices. Some recorders require external microphones, while others have built-in microphones. Smartphones have become great accessories to record audio as well as video. Manufacturers have made microphones and adapters specifically for use with the iPhone to collect and produced audio in the field.

Q&A with the Experts: Sarah Brady Voll, Audio Specialist

Figure 4.12 Sarah Brady Voll, Audio Specialist (holding boom).

What do you do?

I am an audio engineer. When I’m on set, my job is to record the audio so the Director of Photography (DP) can focus on getting the shot. If it’s a small shoot, I will mix the lavs and operate the boom. On larger shoots, I am the mixer that monitors all of the different audio feeds. I’m also an audio editor in post-production.

What is the role of audio in a video story?

The picture sets the scene but the sound is what sets the mood. Think about watching a really suspenseful scene in a movie. You can close your eyes and still know when someone is about to get attacked. You can also tell when the

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storm is about to end and the sun is going to come out. Every emotion you feel while watching a movie, video, or TV show has been considered and cre- ated by the sound supervisor.

Why can people watch poorly shot video, but they cannot bear to listen to poorly recorded audio?

Humans have a tendency to be able to forgive “bad” images. Think about how many times you’ve watched shaky, out-of-focus smartphone videos. We can watch bad video and fill in the gaps or make mental corrections for bad lighting or shakiness. Our ears have not developed the ability to make these corrections. Static, noise, hard to hear sounds are all difficult to modify in our brains.

What kind of audio gear should all videographers own?

Every videographer needs four things to be able to record sound: a wireless lav, a small directional shotgun mic, a small mixer, and a decent set of headphones. Your on-camera mic is crap.

Why is it better for a videographer to work with an audio field recordist?

If possible, you should always have both a videographer and an audio field recordist. Videographers are very talented people. They know how to set up shots for maximum impact. They can make the most boring rooms come alive by using smart angles and they are dedicated to making the project look as good as possible. Why would you want to interfere with that? Audio adds another layer of complexity that can be alleviated by the presence of an audio recordist.

What tips you would give any videographer working without an audio recordist?

First, know how to use all of your equipment. Don’t ignore your microphones and other audio gear. Practice with this gear. Second, record plenty of coverage. Record room tone and fill audio. If you are recording b-roll, you should be recording audio as well.

What is in your gear bag?

My gear kit changes depending on how large and complex the project. My “lightweight” travel kit includes a collapsible internally wired travel boom pole, a Sennheiser 416 shotgun mic, a zeppelin wind screen, a Sound Devices 744T 4-channel recorder, Sony 7506 headphones, four wireless Sennheiser 3G or Lectrosonics with Sanken Cos-11 mics, a Sound Devices Mix-Pre, a Comtek system, a lumbar support harness, a rain poncho, a bunch of high- quality XLR cables, plenty of extra rechargeable batteries for everything, a notebook, a few protein bars, and a bottle of Aleve.

CHAPTER 5

Field Production

MICROPHONE PLACEMENT