Sound Decisions: An Introduction to Audio for Filmmakers

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Please welcome our newest partner, Pro Moviemaker Magazine, to the team. We’d like to share with you an article from them on “Sound Decisions: An Introduction to Audio for Filmmakers.” Enjoy!

Sound decisions (1)

If you’re looking to produce a truly professional film then it’s crucial to be on top of your audio. Matt Bell looks at the challenges you’ll face and walks through a selection of the tools of the trade you’ll need.

If you’re looking to produce a film that resonates with professional values then it’s not just the footage that you need to think about. Audio will also make or break a production, and for many this can be a daunting area to enter and ultimately master. However, it doesn’t need to be quite so daunting: in reality it’s quite straightforward to acquire good quality sound once you know the basics.

The first thing to get your head around is the fact that your on-board camera mic is not going to be up to the job of delivering first class audio, although it might be able to give you a guide track that will be useful at the editing stage. The reason for this is simple: for a start all microphones generate very tiny electrical signals which need a lot of amplification to bring them to a usable level, and the so-called ‘preamplifiers’ or preamps used in built-in camera microphones are not of a very high quality, which means that the audio they capture is often hissy and unpleasant-sounding.

What’s more, although the idea of a microphone built into the camera casing seems great for ease of use and portability, in practice the microphone’s location ensures that it will pick up all manner of other unwanted noise. As the user adjusts zoom or focus manually or automatically, the body will probably convey and capture some motor and casing noise in the form of intrusive taps, whirrs and thumps.

This is a particular problem with handheld work. The resulting video may have that exciting, on-the-fly documentary feel, but the chances are that the audio captured at the same time will be unusable: noisy and/or unintelligible, like an amateur home movie. The location of the built in microphone on most cameras, namely on the front facing forward, also makes them prone to picking up wind noise when working outdoors, which can be a huge problem that can render the entire audio track unusable.

Moving on to the idea of using an external microphone but still recording audio on camera, this approach allows a good deal more flexibility. Purpose-built, professional-quality external microphones tend to produce more pleasing sound than affordable built-in models, and users can also gain an extra degree of control over what is recorded. Some external microphones — known as omnidirectional or just omni mics — pick up sound with equal sensitivity in all directions, while others — directional microphones — pick up sound more efficiently in some areas than others. The long, thin shotgun microphones seen mounted on video camcorders tend to be much more sensitive in front on the microphone, along the axis of the body, and less sensitive off-axis.

Using mics of this kind can help to ‘focus’ an audio recording on what the videomaker requires at the expense of what they don’t — provided the user is aware of where their microphone is most and less sensitive, and positions the main subject of the recording accordingly when capturing a take. A graph showing the areas around a microphone where it is more and less sensitive is called a polar pattern, and there are several types. When choosing and using a microphone, it pays to consider its polar pattern; positioned carefully, a directional mic can, for example, reduce the amount of background noise recorded, and increase the level of the subject.

Different types of microphone polar pattern. The area of maximum sensitivity in each case is within the dotted line. Cardioid just means ‘heart-shaped’; in practice these mics and shotguns are good for interviews, as they pick up what’s in front of the mic, but are less sensitive at the sides and rear. Shotgun mics are even less sensitive at their sides.

Different types of microphone polar pattern. The area of maximum sensitivity in each case is within the dotted line. Cardioid just means ‘heart-shaped’; in practice these mics and shotguns are good for interviews, as they pick up what’s in front of the mic, but are less sensitive at the sides and rear. Shotgun mics are even less sensitive at their sides.

Reducing distractions

Depending on the directionality of an external microphone and how it’s mounted on the camera, body, casing and motor noise can also be much reduced or eliminated. Some external microphone mounts attach the mic to the camera’s hot shoe or tripod thread; however, unless these mounts are somehow deadened, they can convey camera body noise to the mic just as the casing does to a built-in mic. The best microphone mounts suspend the microphone in some way, either in an elasticated cradle or other vibration-reducing construction, to decouple it from the body of the camera and prevent body noise from passing through to the microphone. A decoupled microphone cradle mount like this is a must if an on-camera mic is going to be the primary audio source on your video footage.

Of course, you can avoid camera body noise by not mounting the mic on the camera at all. However, if you’re still ultimately recording the audio on the camera, some means of getting the audio back from the remotely positioned mic to the camera will still be needed, which can mean unwieldy trailing cables. It’s possible instead to use wireless microphones, which transmit the audio they capture via radio waves back to a receiver pack that you then plug into the camera. However, these systems tend to be more expensive than cabled microphones, can be susceptible to interference from other radio-frequency devices in the area where you’re working, and may even require an official licence for legal use.

Despite such complexities, however, wireless microphones can be an excellent solution for capturing audio when circumstances dictate that the camera has to remain at a distance from a subject. You could, for example, use a discreet microphone close to your subjects when capturing the sotto voce marriage vows from the happy couple on a wedding video.

Power and connectivity are complicating factors. External pro microphones tend to plug into a three-pin connector called an XLR, whereas if you’re working with a DSLR it’s likely that you’ll find, at best, the ‘iPod headphone-style’ 3.5mm-jack socket as an input. This ensures that some sort of plug adaptor is usually necessary, which, when hanging off the side of y­­­our camera, can further add to the unwieldiness of your setup. Furthermore, many professional microphones need to be separately powered, and very few DSLRs have the ability to supply the right kind of power, meaning you’ll have to use batteries.

Taking care of both of the above issues, it’s possible to buy dedicated XLR-to-jack interface boxes that can be fitted under your camera, and these will often also supply microphone power.

The third main audio capture option is to use a stand-alone audio recorder, or recorders. Even 15 years ago, this would have required costly, bulky recording hardware, and lots of tape, but with today’s high-quality digital pocket audio recorders, most of which record like cameras on to low-cost SD storage cards, this is a very affordable, flexible approach. Capturing several different audio sources simultaneously is also much easier; each source simply gets its own recorder, and the audio from the relevant recorder is chosen to match the appropriate video footage in post-production. It means that all of the camera’s vibration-related audio problems are solved at a stroke, and recording an audio source at a great distance from the camera is also much more straightforward.

The post-production audio sync approach may be unpopular with videomakers who are used to capturing as much ‘live in camera’ as possible. But given that for all but the most basic of Youtube video content some degree of post-production is going to be needed after camerawork is complete anyway, even if only to add titles and credits, many feel the added flexibility and simplicity at the capture stage is worth a little extra work in post-production.

For more features, product reviews and news download your free issue of the Pro Moviemaker magazine at www.promoviemaker.net


Equipment: A Few Starting Points

We’ll look in more detail at equipment choices in a future installment of this series, but here are a few manufacturers to check out in the key equipment areas mentioned this month.



Rode: www.rodemic.com

Sennheiser: http://en-uk.sennheiser.com/mics

Shure: www.shure.co.uk/products/microphones

Sony: www.sony.co.uk/pro/products/broadcast-products-professional-audio



Rycote: www.rycote.co.uk



Beachtek: http://beachtek.com

Juiced Link: www.juicedlink.com



Olympus: www.olympus.co.uk/site/en/a/audio_systems/audio_recording/index.html

Roland: www.roland.co.uk/products/subcategories.aspx?c=109

Tascam: www.tascam.eu/en/cat/4

Zoom: www.zoom.co.jp/products

Jasmine Moore

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