Background sound effects.
By David Mann
The three main types of sound effects we use in movies and television shows are referred to as hard effects, Foley, and backgrounds. The difference between them is mainly their length. Hard effects will usually be short sounds like gunshots, light switches, a slap on the face, glass breaking, etc. Backgrounds usually start at the beginning of the scene and continue all the way to the end of the scene. For example, if a scene we working on is staged at a park, we will almost always include sounds like birds chirping and singing from the beginning of the scene all the way to the end of it even though birds are not seen all of the time and in many cases, not seen at all.
Why do we need the background sound effects?
If you ever watch the footage of the movie as it was recorded on location you'll realize that it's somewhat dead as far as ambience sounds. For example, if you see a scene inside a bar you'll see a lot of people talking but you will only hear the dialogue of the main characters. The way this is done is that the people that you see talking are actually pretending to be talking or talking in very low voices. Of course, this is very unnatural for us to watch because in real bar there are a lot of people talking. If the people in the bar were talking normally, it would have made it hard for the mixer to mix it in a way that the viewers will easily understand the dialogue of the main character (which is always the most important).
In order to make it more natural, the sound editor will add in the sounds of people talking (sometimes called "Walla"). He will also add other sound effects to help the scenes seem more realistic such as glasses clinking, mixing drinks, room tones, maybe an off stage pool game and more.
What are room tones? In almost any room you enter you will hear some kind of noise. It can be from the air conditioning, it can be from traffic outside, it can be from a refrigerator or anything else. We don't always notice it but our brain is very use to hearing sounds all the time. So to make the movie as natural to our ears as real-life, we always add room tones on internal scenes. When scenes are external, we have the choice of adding traffic or wind. In addition to making the movie sound more natural by adding those sounds, they are also very helpful for the dialogue mixer since the dialogue coming to the stage might have times when the background noise in the dialogue recordings have noticeable changes or holes. The background sounds are helpful to mask those holes.
However, the main reason we add background sound effects is to make the movie or TV show richer. The backgrounds are great for setting the mood that the director would like the audience to experience. For example, you can have two different movies that are shot at the exact same location in a city, let's say one romantic movie and one suspenseful. In a romantic movie we can put light traffic sounds, almost no horns, wind in the trees, and birds. For the suspenseful movie we can add heavy traffic, people honking their horns, police sirens, nervous crowd voices, helicopters, etc. Together with the music, the background is a fantastic tool for setting the mood for a movie.
How do you edit backgrounds?
Cutting the backgrounds for a TV show or a movie can be a lot of work. I find that in order to be the most efficient, the first thing I do when I watch a movie is putting markers on every scene change and I recommend naming those markers with the location of the scene. Also, don't forget that any phone call between two people or more will be a location change, even if the two people talking are practically neighbors, it's important to create some kind of a difference between each home. After putting down the markers for any location change, you go to the first scene and start putting in tracts of backgrounds. Basically with backgrounds, the more the better, but when I say more I don't mean putting six tracks of similar backgrounds.
If what you add doesn't make a difference or only makes the scene noisier you shouldn't put it in. What you need to be very careful about is to choose the right sound to begin with and not trying to create the right sound by adding more and more tracks. For example, if you need heavy traffic, find a good track of heavy traffic and not bunch of light traffic tracks layered one on top of the other. Also, when you're choosing different tracks you can mute and solo to see which one is adding more substance and which one is adding more noise than substance. You need to have a very good library to cut an average movie; you can't keep re-using the same sounds on different locations. For example, if it's a movie about people going to different bars every night, every bar needs to have its own sounds. After you establish sound for each location you can use the "copy and paste" to save time and keep continuity in your movie. Of course, you also need to look for different things for the same location to cover different times of the day. For example, in office will be much busier during daytime as opposed to late at night when there are only few people left working.
Here is a warning for people who are new to this -- when you go to the theater to see a movie you cut background on, or even worse, watch a TV show you did, you will most likely not be happy about what you hear. You created beautiful ambiences but in most scenes, you will not be able to hear much of what you did. Don't feel you wasted your time. You still added a lot to the movie. One piece of advice that I got from an experience editor when I started was not to watch what you cut when it comes out. I myself do watch my movies and TV Shows as much as I can. It is a good way to learn.
Have fun cutting