The Rode VideoMic is a good choice when shooting documentaries or budget short films. This microphone comes with the Rycote Lyre suspension system that reduces unwanted vibrations as well as handling and cable-borne noise. The line and gradient microphone with a super-cardioid pattern captures sound coming from the front while canceling side noise. With the built-in attenuation, you can select 10 or 20 dB pad to minimize the microphone sensitivity to handle higher SPL levels. The high-pass filter switch filters out ambient sounds and noise below 80 Hz. This microphone has an internal battery of 9 V that can last up to 100 hours approximately.
The signal to noise ratio (SNR) is a useful and universal way of comparing the relative amounts of signal and noise for any electronic system; high ratios will have very little visible noise whereas the opposite is true for low ratios.