Perhaps you've been recording with a smartphone or a handheld recorder for some time now and
you'd like to up your game.
One of the best things you can do to improve the front end system is to attach a directional
microphone.
For wildlife recording, two types of directional microphones are commonly used.
The parabolic reflector system, or parabola, for short, and the shotgun microphone.
In this session we’ll focus on the shotgun microphone.
Specifically, we’ll talk about four things.
Why use a shotgun microphone?
How it functions.
How to aim a shotgun microphone.
And the Pros and Cons of why you'd use a shogun over, say, a parabolic reflector.
A shogun microphone is one of the most commonly used mics for recording bird and other wildlife
sounds.
It's a directional microphone.
A characteristic that helps reduce unwanted sounds in your recording and it’s relatively
inexpensive.
So how does it function?
What gives a shotgun microphone its, directional property, is the interference tube.
A hollow tube with precisely placed slits.
Sound pressure waves arriving directly at the front of the tube pass, unimpeded, to
the microphone’s diaphragm.
However, sound pressure waves arriving off-axis, are delayed in their arrival at the microphone’s
diaphragm.
When we look at the microphone's polar pattern, an illustration that roughly shows how the
microphone picks up sound, we can see the angle of acceptance and angle of rejection.
This is where the mic will be most effective and least effective for picking up sound.
At low frequencies it becomes ineffective and significantly less directional.
So how do you aim a shotgun microphone?
Aiming a shotgun microphone is intuitive.
Point the interference tube in the direction of the target sound, making sure to orientate
it both vertically and horizontally.
Wherever you illuminate with that conical beam, that is what the shotgun is most effectively
picking up.
However, not only does the shotgun accept sound in the forward plane, but to the rear
as well.
Therefore, when aiming a shotgun, the sides of the microphone should be toward the unwanted
or interfering sounds.
An important addition to a shotgun microphone setup, is a windscreen.
The point of a windscreen is to prevent gusts of wind from directly impacting the diaphragm
of the microphone.
On a windy day, your audio could sound something like this without a windscreen, like this
with an inexpensive foam screen, and like this with a blimp or thick fur wind screen.
It's best not to have the microphone perpendicular to the wind, but rather to face it head on
or have your back to the wind.
There are many pros in favor of using a shotgun microphone.
For one, it's directional property allows you to overcome the impact of unwanted sounds
such as, other birds or anthropogenic sound.
It is straight forward to aim, carry in the field, and to transport.
It is also easy to track a moving subject.
Lastly, the shotgun microphone offers a flatter frequency response that that of a parabola.
This is because the shotgun does not differentially amplify higher frequencies as the parabola does.
So what are the cons of a shotgun microphone?
One, it does not amplify sounds.
Two, there's no directionality at lower frequencies.
In short, a shotgun microphone is a great way to begin building your recording kit.
It can help you overcome unwanted sound in the environment and maximize the signal of
interest.