Smashtrax.com - Sound Tips and Techniques

Sound Tips and Techniques

Sound Tips and Techniques

Good audio can add so much to your video or film that it's worth devoting time or money to the process. Some people don't realize just how critical sound is to images. Studies have shown that an audience can tolerate poor image quality if the story is good. What the study also showed was that same audience does not tolerate poor audio for very long.

Sound 101

Rule #1
Rules are made to be broken, but if you value success and are starting out or wanting to break into the professional sound, you'll need to master the rules first. Once you master the rules and understand why they are rules, then you can concentrate on what to break, when and why. In the following rules, I'll include why the rule is important and possible reasons to break it.

Why is sound so imporant? We are highly visual and are extremely good at interpreting noisy video or grainy film. When you shoot in low light, it can even enhance the story or subject. But poor audio is very difficult to interpret and wears out your audience. The last thing they need to deal with is poorly recorded audio because it gets very tiring to hear what's important when so many other, unimportant sounds are competing for their attention.

Rule #2
Get the microphone as close as you can to the source of the sound. In almost all instances, you record three types of sound, usually only one of them is important (usually it's dialouge). The two sounds you want to avoid are ambient and reflections.
Ambient sound is a refrigerator, air conditioner, traffic, dogs, construction site, birds, airplanes, sirens, trains, buses, doors, footsteps ... you get the picture. There's tons of sounds around us, we just filter them out in real life. But the microphone can't filter them out.
Try this experiment: Take your camcorder, plug in a pair of good headphones (you do own a good pair of headphones, right? If not, I'll explain what you need in the next rule). Now walk around your house, step outside, go to the park, all the places where you'll be filming scenes or interviewing people. Notice what you hear. Turn the headphone volume up so you can hear background sounds. You may be surprised at what you can hear.
The good news is that sound decreases rapidly the further it is from the microphone. So if you put your microphone close to the source of your sound, your desired sound will be much louder than the ambient sound. Professional sound operators place microphones as close as possible to actors or people being interviewed. They want the microphone just out of frame or will plant the microphone somewhere in the scene, hidden, but close to the actors or interviewee. Reflections are sound that bounce off surfaces and arrive at the microphone a fraction of a second after the direct sound reaches the microphone. For instance, a person speaks into the microphone. The sound of their voice bounces off a hard wall nearby and arrives at the microphone after the sound from that person's mouth reaches the microphone. This is also called reverb and is highly prized among rockabilly guitarists.
But reflections are deadly for video and film. If you want reverb, your best bet is to record your sound with as little reflections as possible and create them in post-production. This is because reflections are impossible to remove in post while easy to add in post.
Hard surfaces like concrete, brick, sheetrock, wood, tile, you name it, create lots of reflections. Soft surfaces like carpet, drapery, upholstery, people, blankets, plants and the like are great at "absorbing" sound. Sound blankets (which are identical to the moving pads that movers use to protect furniture) are used to reduce reflections from hard floors and walls. One way to judge a room's reverberation is to clap your hands once and listen. If all you hear is the clap, you're probably in good shape. If you hear what sounds like a mechanical, wierd sound that tapers off then what you're hearing is definitely the reflections of your clap bouncing off all the hard surfaces.
When to break this rule: if you are REALLY good, you can place the microphone at the exact spot in the room to record reverberation at the amount desired. In wide shots, you want more reverberation and in closeups, you want very little. This is what the audience expects. But this is only if you are good AND the production can't spend the time to add reverb in post. It's very dangerous because you have to know what amount of reverb you need. You'll need really good headphones and headphone amplifier for this task.

Rule #3
Get a GOOD pair of headphones. They are expensive but sound is not something you should scrimp on. This is almost a separate rule, do not cut corners on sound. Pay for good sound operators, listen to them, listen to what they are hearing, and then fix it on location. Some sound problems are impossible to "fix in post." I could go on about this but this rule is about headphones.
A good pair of headphones will cost over $100. They will be "closed" in that ambient sound is muffled when you put them on. If you put them on, with them unplugged, and notice a BIG decrease in the sound around you, the headphones are probably closed. You can usually tell by looking at the cups. If there are no "vents" or holes on the back (outside) part and there is a cushion that either partially covers or completely covers the ears (the best kind), then it's most likely a closed pair. These shut out, or isolate ambient sound so you can concentrate on what's actually being recorded.
You can increase this isolation even further by pressing the ear cups to your ears. This blocks even more of the ambient sound and gets the speakers inside the ear cups closer to your ears.
Sony is a good brand for these types of headphones and so is Sennhieser. But there are lots of brands out there that make closed headphones. You don't need "studio monitor" quality although it helps. Mainly what you are looking for is isolation from ambient sound.
Also, close your eyes when listening. Humans are visual creatures and a large portion of our brain are devoted to processing visual information, much larger than the portions that process auditory information. When you close your eyes, you reduce all the visual distractions so you can concentrate on the sound you're recording.
One last and most important reason to use headphones: You may not be recording any sound. Many people have recorded video but no audio simply because they didn't have the microphone plugged in, it wasn't turned on, the battery was dead, or the cable was bad. Headphones will tell you right away if you're recording sound!
When to break this rule: The cheap walkman style headphones are easier to carry around, are less conspicuous, and better than nothing. If you wind up someplace and don't have your headphones, oh well ... remember Rule #2, get the microphone close to the source of sound and pay attention to ambient sound. Reduce the recorded ambient sound by getting your actor or subject as far away as you can from the source of any ambient sound. Headphones will tell you when you have this ambient sound at the right level. So always have at least an emergency pair of headphones tucked away inside your gadget or camera bag.

Rule #4
Reduce ambient sound you don't want. Most of the time, you want to reduce or eliminate all ambient sounds that is in your control. Except in rare occassions and on high-budget projects, you have no control over the traffic, so reduce this source of sound by recording near a building or structure that blocks the sound of the traffic or get as far away from the road as is necessary. But most of the time, we can control ambient sound.
Always be polite and ask if you can turn something off. Most of the time, you'll be given permission but you can upset people if you just turn things off that don't belong to you. In which case, you may be told to turn it back on or at the least they will note your action and put it in the "reasons to not let you or any other filmmaker use this location in the future" column.
Usually, the noise from nearby refridgerators are always unwanted. These can be shut off by unplugging them or turning the thermostat temperature up or turning the thermostat to "Off." HOWEVER, don't forget to turn them back on when you are finished shooting. Leave car keys or something that you cannot leave behind inside or near the fridge. Car keys are the best, because you're not going to go anywhere without them.
Air conditioners can be turned off, but again, remember to turn them back on when you are finished. With hot lights, crew and actors, you may need to turn the A/C on between takes and off during takes. Ice makers, vending machines, florescent lights are all good candidates for turning off. But always remember to turn them back on. You don't want someone mad at you because all their ice melted or their frozen food thawed.
When to break this rule: You may want that ambient sound. You also need to consider what kind of ambient sound you want. It's inexpensive and quick to record sound effects in the field. Maybe you want to hear the actor's footsteps. Maybe you want the sound of the bus that just passed by, the sound of a closing door, a car starting up, or the sounds of the restaurant you're in. In most cases, you want to record "clean" sound with little or no ambient and then add sound effects in post. This is called "foley" and is very expensive to have done professionally because it takes an artist who knows all the tricks and has the right noise-making equipment. Or you can buy sound effect libraries and hope there's something in them you can use.

Sound in the Digital Age
Digital recording of sound is fantastic but comes with a particular disadvantage: Distortion from overdriving the audio inputs.
The Theory: A digital recorder converts sound into a series of numbers, which are recorded onto the tape, harddrive or minidisc. These numbers represent the amplitude of the sound. The numbers available to the recorder range from a minimum ot a maximum. If the amplitude exceeds the maximum number available, then the recorder has no choice except to the use the maximum number.
This is the problem. Even though the sound is louder than the maximum number available, that's all the recorder can assign it. So when you play the recording back, you get this horrible sounding, screechy, crackly, popping that can ruin your otherwise clean audio. It's impposible to clean this up without lots of money and even then it's impossible to fully clean up.
How to avoid it: Fortunately, there are several ways to ensure good audio without distortion. The first way is using you camera's built-in electronics that keep audio within limits. This is sometimes called "ALC," "AGC" or "Auto." The second method is hiring a good sound mixer who's will keep your sound within the recorder's limits. The third method is inserting a compressor/limiter into the signal path of your audio. The last method is setting the audio levels using the loudest sound you expect and then hoping that's good enough.
1. Use the camera or recorder's automatic level control
2. Hire a good sound mixer
3. Use a compressor/limiter
4. Set your audio manually using loudest sound expected
If you can't afford a dedicated sound mixer, an in-line portable compressor/limiter is your best bet. The built-in camera or recorder AGC does not do as good a job at controlling your sound levels, because when there is no sound, the AGC increases the gain. This either increases the background noise or, worse, when your actors or subject start talking, the first few syllables are distroted because the gain is too high.
With a compressor/limiter, you set the compression ratio very high, like 10:1 and the threshold high. This causes the compressor to act like a hard limiter when the sound level is higher than the threshold. Most of the time, you don't want any compression, but sometimes it's very handy, especially when you're shooting a training video. You want your talent's voice to be easy to understand and comprehend. A compressor can help achieve this. Set the ratio to something like 3:1 to 6:1, the attack time to 10 mSec and the release time to 100 mSec. "
"
Room Tone"
” Whenever you record in a particular location, you always want to record "room tone" or the ambient sound of the location. Everyone must stand still and make absolutely no sound while 30 seconds to 1 minute is recorded. This is crucial because invariably, you need silence during editing when you start tweaking the delivery and timing of dialouge. Or you need to cover up any accidental sounds made by the crew during a scene or interview. Use exactly the same microphone and leave all the lights that you used on. This way, the sound will be a better match to the sound you recorded during the scene when the actors or subject wasn't talking. If you move the lights or rearrange the scene, it's a good idea to record room tone before changing things around.

The Different Types of Microphones
· Condensor · Electret · Large-diaphragm · Omnidirectional · Directional · Shotgun · Lavalier (Lav) · All other types

Lavalier versus Boom and Shotgun
You'll usually use one of two mics for a scene, either a lavalier (the small mic you see clipped to someone's jacket) or a shotgun on a boom (a long, narrow mic at the end of a pole). There are pros and cons to each and it's important to know which is better in which situation. Lavaliers, or "lavs," are easier to use than booms. You clip the mic to the subject, run the cables and you have sound. With a boom, you need a boom operator and you have to worry about following the subject and hiding the mic from the camera. However, professionals prefer the sound of a boom over a lav. Of course, it depends on the mics being compared, but generally the boom will give a more natural and pleasing sound.
There are times when you need a lav over a boom. Wedding ceremonies require a wireless lav. Documentary interviews are less intimidating with a lav. When you don't have or can't afford a boom operator. When the subject will be in a long shot and you can't hide the boom from the camera.

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Article Added: Jan 25, 2006

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