Sound

=Sound Sense - A Beginner's Guide to Sound=

How a little bit more thought about sound can add extra sparkle to your video productions
Virtually all new camcorders are able to record stereo sound of stunning quality, so it’s difficult to understand why many cam users ignore the full potential of their hardware. People, it would seem, will go to great lengths to acquire camcorders that have bucket-loads of visual gimmicks - like whopping great zoom ratios, image stabilisers and whacky digital effects - but how often do you hear a salesman hyperventilating over the fact that the model in his sweaty palms actually records 16-bit digital stereo sound? Not often - let’s be honest.

It’s a shame really, because we’re living in a world of Dolby Surround, Nicam, DAT, Mini-Disc, MIDI, the now-infamous MP3 and a whole raft of new developments designed to give our hearing the sensual pleasure it deserves. When we buy music, we buy it on CD; when we watch or record TV, the likelihood is that we’ll take advantage of Nicam digital stereo technology. It’s not good enough just to hear programme sound - now we have to experience it, too!


 * The built-in mic**

Most cam users rely upon their camcorder’s built-in mic for capturing sound, of course. That’s fine for recording the antics of kids in a paddling pool, and even a group of people chatting in a room. But when the object of the exercise is to capture a clean recording of someone’s dialogue, you need to think in terms of a more specialised set-up involving microphones, mixers and accessories.

The simplest way to achieve better sound quality is to put a microphone closer to the source of the sound. It may seem obvious, but it’s a simple technique that’s often overlooked! If you want a person to talk directly to camera, but you don’t have an external mic, then it’s no good expecting your audio to be crisp if the camcorder is six or seven feet away.


 * Laying on a spread**

If you’re shooting a set of landscapes, and all you want is an impressive stereo “spread”, the built-in stereo mic on your camcorder will usually capture good sound without the help of external sources - but make sure that it’s protected from wind and rain. Even a gentle summer breeze will create a buffeting on the mic which will, in turn, cause a horrible pop on the recorded track - and automatic level control (ALC) circuits will usually take a second or so to recover the previous auto level setting. A piece of foam rubber taped over the mic will help in these situations.

A good test of the camcorder’s stereo is to position the unit at right-angles to a busy railway line or motorway and play back the recording though a hi-fi stereo system or good pair of headphones. You’ll hear the effect as the train or traffic moves across the stereo “image”. Put the camcorder into an ambient church or large hall and you’ll get the same effect - and it can often be impressive. The problem with built-in mics is that their frequency responses (sensitivity ranges) are generally inferior to their independent counterparts, and they’re usually placed where it’s impossible to avoid knocking them - such as when you’re attempting to flick a switch on the front of the camcorder body or operate the zoom manually. So, for the serious cam user, the built-in mic should be regarded as a last resort or for recording secondary background audio only.


 * Combining close-up sound with long-shot picture**

Let’s say you’re recording an event in which you need to record someone addressing a large audience. It might be a concert, or even a wedding service. The plan is to shoot a long-shot of the person doing the talking, but as your camcorder is positioned some distance from the speaker, you’ll lose audio clarity as the microphone is moved away, too. This is where you’ll need a sound source that can operate independently of the camera. Yes - you need another microphone!


 * Choosing microphones**

The choice of microphone depends largely upon the nature of the work in hand. An omni-directional mic will be sensitive to sounds all around it, whereas a uni-directional mic will be more sensitive to sounds originated within a given field in front of it. In the latter category, a rifle mic is often a sensible choice - especially since their average cost is now coming down. A good rifle mic (alternatively referred to as a “gun mic” or “shot-gun” mic because of its appearance) gives a narrow field of sensitivity - usually enabling the recordist to eliminate sounds at each side of the mic much more effectively than a more general, cardioid, microphone (such as a general interview mic). It’s often thought that a rifle mic will pick up rather low-level sounds at a considerable distance whilst registering no trace of unwanted sounds. This isn’t actually true - but if you're recording dialogue in a busy street, a good rifle mic on a fishpole (telescopic microphone support) held cl! ose to the speaker will be your best chance of capturing speech clearly.

A Slik 6023 Monopod is a perfect low-cost mic fishpole, but don't forget the shock mount (supplied as an accessory to rifle mics) and a wind-shield. Rycote has, for many years, supplied wind-covers for mics such as these - and its “windjammer” is generally regarded by industry professionals as being the standard device for virtually eliminating wind-noise.


 * Personal mics**

A very common sight on TV presenters and reporters is the clip mic. Models in the Sony, Sennheiser and AKG professional ranges can cost a couple of hundred pounds each, and until recently the low-cost alternatives available to video-makers weren’t up to much in the quality stakes. A clip mic (also known as a tie mic, or even a “lavalier” mic, although the latter term has all but disappeared) is useful when shooting interviews with people, or where a person is presenting a so-called “piece-to-camera”.

Clip mics are useful for more than just attaching to people’s clothing during speech recording; when used in pairs and placed at either side of a piece of action or a performance, they’re extremely useful for recording the wide stereo spread of a scene (where dialogue or other audio will be close-miked and mixed into the stereo image). You’ll need a pair of long audio extension cables, though, and be careful not to run them alongside mains cables (lighting cable runs are the worst) or you’ll suffer terrible problems with hum.


 * Radio mics**

One way to eliminate cable runs is to use one or more radio mics. Up until recently, a good quality radio mic has been way beyond the reach of non-professional users on account of their high cost - and cheaper units haven’t been nearly good enough in quality terms. Now, that’s changed. There are at least a couple of low-cost (sub-£200) units that are designed for use with camcorders and produce extraordinarily good results. A good radio mic kit should consist of a clip mic and transmitter pack which is small enough to fit into a pocket or clip onto a belt. The receiver will either be a standalone unit or (better still) fit on the cam’s hot shoe, with a short cable plugging into the ext mic input of the camera via a 3.5mm mini-jack. Such mics will often transmit the mic signal over a distance of 50 metres - perhaps even further depending on local conditions. When obtaining a radio mic, make sure that it complies with current DTI Wireless Telegraphy regulations - otherwise you! might find your collar being felt during a recording session!


 * Maintaining a balance**

One of the main differences between professional and consumer camcorder systems is the lack of what many would call “proper” balanced audio connectors on today’s small VHS, Hi-8 and DV camcorders. If you want to exploit the recording potential of your camcorder, it’s best to acquire a good-quality professional microphone. Unfortunately, using one is often easier said than done, since pro mics have three-pin XLR balanced output connectors - whereas all consumer camcorders have measly little 3.5mm stereo jack inputs or RCA phono line connectors. Balanced lines, especially on long cable runs, help to minimise noise. Bob Tomalski’s feature, “Sound Solutions”, in CU, June 98, has useful tips on how to adapt mic cables to your needs. Better still, buy a professional stereo microphone adaptor like the VideoAge DXA-4 or the BeechTek Box.

Without a decent pair of headphones, of course, we won’t have much of a clue about the quality of sound that’s coming in, and that’s why they’re vital to the serious enthusiast. Like microphones, the dynamic range and frequency response of headphones is important, since you will want to have a clear representation of the sound you wish to make a key feature of your video production. Choose with care.

Sound is just as important as picture when shooting and editing video, and it’s really worth giving some serious thought to the way it’s recorded and edited. A good sound-track can make a huge difference to the impact of your production - especially if you’ve taken proper steps to look after the signal at every stage of the process. In the second part of this series, we’ll look at ways of mixing various sound sources - both during the recording stage and during editing. We’ll also find out how you can incorporate good quality music without paying a small fortune in royalties.