Sound

Sound

By: Chris Gamel

This article first appears in the 2011 Summer Issue of Currents, the quarterly publication of the North American Nature Photography Association (NANPA)


Capturing great video imagery is only half the battle when producing documentaries or other video productions.  The other half is sound.  Sound has been a part of movies for the past 90 years and if you want your movies to be taken seriously, you have to capture good sound.  Sadly, if your movie has good sound, no one will pay any attention to it (the sounds that is.  I hope they will pay attention to the movie).  If the sound is bad, however, that’s the only thing they will remember.  Quality audio has the potential to transform a good movie into something great.  By the same token, bad audio will destroy an otherwise good film.

Sound recording is a huge field and takes years to master.  Fortunately there are some basic steps that you can take which will greatly improve the quality of your audio.

A WARNING TO DSLR USERS

DSLR cameras are amazing tools and capture stunning still and motion images.  Unfortunately, their main weakness is sound.  From tiny built-in microphones to non-existent audio controls, DSLR cameras make it extremely difficult to capture good quality sound.  While overcoming these challenges is not impossible, the DSLR’s sound recording limitations are the number one reason why many videographers opt to use dedicated video cameras instead.  This is not meant to discourage you from using a DSLR to record video.  Rather, you need to be sure that you start your exploration of audio with an understanding of the limitations these cameras present.

LISTEN TO YOUR AUDIO

Poor quality audio is often a result of minor diffi­culties that can be easily fixed.  Loose cables, poor connections, or loud background noises can all ruin otherwise good sound.  The key is being aware that a problem exists.  You do not want to be surprised by audio problems after you return home.  To avoid those, it is essential that you listen to your audio as it is being recorded.

In the field, audio is monitored using quality headphones.  While a small set of ear buds will work in a pinch, you are much better off using headphones that fully cover the ears and eliminate background noises.  While dedicated video cameras easily accept headphones, DSLR cameras do not.  This is a major limitation, as they do not permit you to hear your sound as it is recorded.

USE THE RIGHT EQUIPMENT

All video cameras, including DSLRs, contain a microphone.  Unfortunately, recorded sound is not the same as the sound we hear.  The human ear is very good at filtering out background noise.  The camera is not.  The camera records every sound within range, without context or priority.  This means we must be very careful about which sounds we record.

While the convenience of a built-in microphone can’t be denied, its use is somewhat limited.  Like a built-in flash, a built-in microphone cannot be taken off the camera.  This presents challenges.  One of the keys to capturing good audio is to get the micro­phone as close as possible to the sound source.  This is difficult to do if the camera and the microphone are a single unit.  As the distance between the microphone and the subject increases, so does the prevalence of distracting background noises.

External microphones provide a number of benefits when recording sound, assuming that the correct type of microphone is employed.  Knowing the types of microphones that are available and using the best microphone for the job is a big step in the process of recording good audio.  It is also helpful that external microphones can be used with both DSLRs and dedicated video cameras.

Omni-directional microphones (mics)—The most common type of microphones are called omni-direc­tional mics, meaning they record sound equally well in all directions.  They can be found both on camera (the built-in mic) and off camera (as commonly seen on the evening news).  While recording sound in every direction might sound like a good thing, omni-directional mics offer no selectivity in what they record.  Recording sound in every direction means both you and the subject are being recorded equally, and guess which one of you is closer to the mic?  Omni-directional microphones are best suited for situations when the microphone does not need to be hidden from the camera.  Unfortunately, the need to get them close to the subject severely limits the use of omni-directional mics for nature subjects.

Shotgun microphones—Shotgun mics record sound in a specific direction.  With their narrow angle of view, shotgun mics make it possible to isolate important sounds while eliminating others.  Like telephoto lenses, which are used to isolate the subject visually, shotgun mics isolate sounds from a single direction and are ideally suited for nature films.

Lavaliere microphones—Also called lapel mics, lavaliere mics are small mics designed to clip onto a person’s shirt.  The range of these mics is limited.  By placing them close to the subject (6-12 inches), it is possible to record good sound while eliminating background noise.  Lavaliere mics come in both wired and wireless versions.  As would be expected, wireless mics are more expensive.  They can also run into problems in heavily populated areas where the airwaves are full of signals.  Lavaliere mics are ideally suited for recording people and are commonly used for interviews.

CONTROLLING THE AUDIO

Recording audio is not enough.  You must be able to modify and manipulate the audio settings during the recording process.  Two controls are especially important when recording audio in the field: volume and gain.

Volume lets you modify the sound recording levels to ensure that the sound is recorded at the sweet spot.  Too low and no one will hear the sounds you worked so hard to record.  Too high and digital distor­tion will make your audience cringe.  Judicious use of headphones, sound level meters, and volume control make it possible to capture good quality sound.

Audio gain is equally important.  Gain is the audio equivalent of your camera’s ISO.  Increasing the gain amplifies the sound levels, but with a price of greater audio interference.  At high gain levels, audio becomes almost unusable.  Audio gain can prove useful at times, but it is essential that your camera let you turn the gain off when it is not needed.

Automatic gain control (AGC) can present a major problem.  In an attempt to help, the camera automati­cally increases the audio gain anytime the sound levels drop (like when you are waiting for an animal to start doing something).  In effect, the camera is listening really hard for any sound that might be out there.  The problem comes when sound levels return to normal, but the gain is still elevated.  This results in a recorded noise starting off very loud and then dropping down to a more reasonable level.  Imagine turning on your car stereo and forgetting you had the volume set to the maximum level and you get the idea.  This plays havoc with the quality of your sound and is very difficult to fix in post-production.  Dedicated video cameras provide the option of turning off AGC.  Unfortunately, manual override is not available on most DSLR cameras, which also have AGC.

As photographers, we are visual creatures.  As videographers, we don’t have that luxury.  Fail to capture good audio and all of your hard work will be wasted.  By listening to your audio as it is being recorded in the field, using the correct type of microphone for the sound you are recording, and maintaining control over the audio settings as sound enters the camera, your audio will be several steps ahead of the competition.