SIGNAL TO NOISE: IMPROVING AUDIO FOR VIDEO PRODUCTION
Improving Audio for Video Production
It’s no secret that the world of video production has evolved exponentially over the last few years. With incredible filmmaking tools now available to everyone there is more quality video content being created and shared than ever before.
But how good is cinematic, high-definition video if the audio is lacking? Great audio can elevate and enhance the immersive qualities of a film or video, just as bad audio can ruin the experience, and distract the viewer. If you’ve ever filmed something and resorted to using the in-built microphone on your camera, you know exactly what I’m talking about!
Using a professional quality, external microphone will go a long way to improving the audio quality for your production. Choosing the right microphone however can be a daunting task to the uninitiated — just like camera lenses there is not really a “one size fits all” microphone (although some are quite versatile, just like lenses). Factors such as your location, recording equipment, framing and more will have an impact on which mic will best suit your needs.
The three most commonly used microphone categories in the broadcast world are ‘on-camera’ microphones, ‘shotgun’ microphones, and ‘wearable’ microphones (such as lapel and headset types).
The reason these microphones exist is to ensure that no matter where you are shooting, or what your chosen camera position and framing may be, you will always be able to follow the golden rule of audio engineering (and the single most important tip from this article) – to capture the best possible audio you always want to position the microphone as close as possible to your sound source. This is called achieving a good signal to noise ratio.
Signal to Noise Ratio
This is as important as knowing which direction to point the camera. In this term when we say ‘Signal’, we are referring to the sound you actually want to record (the actor delivering a line, the bride delivering her vows, the car door closing… whatever), while ‘Noise’ basically refers to everything else. The traffic in the background, other people on set, any reverb or environmental noise in the recording space and anything else that is secondary to your main source of sound is considered ‘Noise’.
When you position your microphone close to your sound source you are maximizing the ratio of Signal to Noise. If you back away from your sound source, your microphone is now picking up more of your environment, lowering your ratio of Signal to Noise. The resulting audio will be full of distracting and surrounding sounds, and not focused on your main source.
By having an understanding of this golden rule, selecting the best microphone for your production should be a much simpler process. I’ll quickly look at the positives and negatives of each below, along with what type of recording scenario they are best suited.
On-camera microphones are the simplest way to upgrade the audio quality of your camera. Models like the RØDE VideoMic Pro and Stereo VideoMic Pro have been designed specifically with DSLR cameras in mind, especially when used in a solo, run-and-gun type situation.
The VideoMic Pro is highly directional, which means it is very sensitive to sound directly in-front of the microphone, and less to the sides and rear, just like the shotgun microphones discussed next. This is perfect for interviews or any time you want to focus on a specific audio source. The Stereo VideoMic Pro is sensitive to sounds to the left and right, and is great for recording live sports, music, or natural outdoor ambience. We call this directional quality the microphone’s Polar Pattern — all microphones of all types will have one, and it is an important thing to consider when choosing your microphone.
On-camera mics are compact, lightweight, affordable, and feature universal connections such as a standard hot-shoe mount, and 3.5mm microphone jack, which makes them compatible with most DSLR cameras and camcorders on the market. Within the RØDE product range The ‘Pro’ models mentioned above will also give you audio sensitivity controls, and bass-roll-off switches, mounted on the rear of the microphone for easy access while shooting. No more navigating menus on your camera while recording!
As these microphones sit on top of your camera, this may not always give you the optimum signal to noise ratio. If your subject is close enough to the camera (roughly two meters or seven feet) or you’re simply recording the ambience of your environment, these microphones are perfect. For anything further away, you may achieve better results by getting your mic closer to your source using one of the following two microphone types.
Shotgun Microphones are very commonly used throughout all broadcast situations and are your most versatile option. They feature extremely tight and directional polar patterns, and are often mounted onto the end of a BoomPole, sometimes inside a Blimp for added protection from wind noise and vibration caused through movement. XLR is the common output connection for this type of mic, which is a more robust and secure connection used on more professional cameras.
It is common for shotgun microphones to require power, known as ‘phantom power’, which is typically supplied by the camera or recording device. A model such as the RØDE NTG2 is a self-powered microphone, using an internal AA battery. This allows for compatibility with a wider range of devices, including DSLR cameras. A professional grade model such as the NTG3 gives you superior audio quality, but does require phantom power from the device to operate.
The real advantage of a shotgun microphone is the ability to be positioned just outside of your shot, but much closer than you would otherwise be able to get if using an on camera mic. This increases your signal to noise ratio, and doesn’t force you to alter your perfect shot or framing. Used in conjunction with a boompole, shotgun mics are the preferred audio recording method for television, and most outdoor broadcast situations.
If your shotgun microphone does require phantom power, this means you will need either a separate phantom power supply, or camera with XLR inputs that does supply phantom power. This could mean additional or larger equipment to carry around on set. A boompole operator will also need to assist on location, so this adds another member to your crew. If you are tackling a project solo, or need to move around in a run-and-gun type situation, a shotgun mic might be too difficult to manage and position correctly. Lastly if your framing calls for a very wide shot, and you cannot discreetly position your shotgun mic close enough to your sound source, this will result in a poor signal to noise ratio.
But fear not, the last type of microphone we will discuss is great if you need high mobility while discreetly being close to your sound source.
The most commonly used self-worn microphones in a broadcast environment would be lavalier (or lapel) microphones, and headset microphones. They are designed to be small, discreet, positioned extremely close to your sound source and plug into a variety of devices such as wireless belt packs, or direct to your camera. The RØDE Lavalier, PinMic and HS1 mics currently give you eleven different choices of interchangeable connections via the MiCon system, to ensure you have full flexibility on set and can plug into pretty much any recording device or industry standard wireless unit available. The smartLav+ microphone was designed to plug directly into a smartphone (iPhone or Android) and give you a discreet, personal recording device in your pocket.
The key word for these microphones is discreet. Wearable mics are the ultimate solution for maximizing your signal to noise ratio and having total mobility at the same time. By placing the microphone and the recording device/wireless belt pack on the talent, they are not bound or restricted by long cables, and will sound crystal clear, no matter how far they are from the camera. This will add a level of professionalism to your videos that will make you stand out from your peers or competitors.
Wireless units, if you decide to pursue this option can be quite expensive and occasionally prone to interference or configuration issues. If you are a solo videographer or a small production team this can add considerable cost your budget. The smartLav+ microphone is an affordable solution but does come with one consideration; the audio will not be saved directly onto your camera, but rather on the smartphone itself. This means you will need to sync your audio and video recordings together in post-production. This may not seem like a big drawback to some, but if you are new to post production editing, this learning curve could add significant time to your production, which may also affect your budget.
Apart from signal-to-noise, no rules are really set in stone and you can of course bend them for a specific effect. Just like shooting video some decisions are made more from a creative standpoint than a technical one. Always try to monitor your audio on location to prevent any nasty surprises later, and if it sounds good to you, it probably is!
Mathew Piccolotto is a Product Specialist with RØDE Microphones with over ten years’ experience in the audio field. RØDE provides a wealth of educational content on their YouTube channel, and are always available @rodemics to help you with any questions.