Sound For Film
updated 12-31-08
Sound For Film can easily be thought of and treated as two distinct parts:Production and Post Production
Production sound involves recording the sound on the set or the location where the filming is taking place. This sound is to be syncronized with the film after is developed and before it is edited. The equipment needed for this is usually a stereo portable recorder (traditionally tape recorders, but hard disk systems are soon to replace them) a portable mixer and at least two microphones. The Mixer needs to be able to accomodate the number of microphones needed for any given shot and may need to have phantom power if condenser microphones are used. The microphone type will vary depending on aplication, but shotgun microphones are generally the best especially if noisy cameras are used for filming.If the noise of a camera is to excessive a Blimp may be used.
The word "Blimp" is actually used to denote two things. First it can be a large wind screen that completely encompasses the location microphone. It is called a blimp becuase it has the shape of an old zeplin. Second, it is a sound proof housing that a noise film camera is placed into. This is done so sound recordings can be made with the noise of the camera being recorded along with the intended sounds.
Production Technique
In General
There are many things that makes recording sound for motion pictures different than recording in a music studio. A major difference is production. Production audio is the sound recording done with the actors and camera on a set or location. For production audio the sound recordist is generally equipped with a portable recording device (recorder), one or a few microphones, a mixer if the recorder does not have a built-in mixer, headphones, and maybe some sort of portable sound baffling and/or sound absorptive material. The recorder, besides being battery powered and often having a small mixing section, phantom power, and limitors, is usually small enough to be worn by the recordist by means of a strap. Some times the recordist works with a boom operator, but often the recordist also operates the boom, so wearing the recorder is essential to moving around to properly operate the boom.
Dealing with Dynamic Audio
Many times the only production audio needed is the dialogue from the actors. Other incidental sounds like footsteps, doors opening and closing, passing car noise, and the whole host of ambient noises need to make a motion picture sound complete are generally more easily recreated in a foley studio than they are to be captured on set. Recorders used for production audio are usually stereo. But for dialogue only one channel is needed. (the left channel is the industry convention for using a single channel out of a stereo pair) It is a common occurrence that the actor's dialogue can is of such a dynamic range that it overloads the recorder's preamps or fades into the hiss of the bottom end of the recorder's low level recording ability. This problem can easily be solved by doubling the microphones and using both of the channels on the recorder. A pair of matched microphones should be physically attached, with gaffer's tape or the like, and done so, so that they have as close to the same pick-up area as possible. This would normally produce a phasing problem if both of the recorded microphone signals were played back together, but they won't so don't worry. Attach the mics to your boom, you will likely have to improvise something, and connect both mics to the recorder, each with the same length of cable. Now, the real trick is to set the mic preamps at different levels. One should be set high and other relatively low. When the sound source is loud the high gain mic will overload but the low gain mic should record the sound. And when the sound source is low the low gain mic will not pick up much but the high gain mic will pick up the sound fine and without having to have it's gain increased in post, producing all that hiss. The recordist will have to mix these two signals down to a mono signal before they can be synched with the image but the results are nothing short of a remarkable, and expert recording.
Synchronizing
When recording sound on a separate recorder from the camera there is the issue of synchronizing the recording (or taking) speeds so that the play back of the sound and image can be synchronized. This issue exists for both the film and video camera. The solutions are varied, only a few solutions will be covered in great detail here.
Crystal speed control motors
In the days before video motion picture cameras designed to be used for sound would generate a "pilot tone" that would be recorded on a special track on a tape recorder like a Nagra. This pilot tone was like a electronic sprocket that would allow the tape to be synchronized to the film image, using special time control equipment on the playback tape machine. However, these days many portable tape recorders and video cameras have precise recording speeds controlled by internal crystal clocks. Tobin Cinema Systems (TCS) makes a crystal clock controlled motor for several motion picture cameras like Arriflex, and Krasnogorsk. With both the camera and the audio recorder running at precise speeds a pilot tone system is no longer necessary.
Slate and Clap Sticks
Even if the camera and the audio recorder are running at exactly the same speed a reference will still be needed to indicate when the audio and image are to be started. An even larger issue is that of which audio track goes with which clip of image. This issue is solved with a "slate." In the old days of cinema a thin board of slate was marked on with chalk to indicate the scene, and shot being taken. This slate was held up in front of the camera each time the camera started rolling. Film shots could then easily be cut into manageable sections according to the slate images at the beginning of each clip. When sound was added to the mix the scene and shot would have to be called out loud by an assistance director (AD), so the audio recorder had a similar sort of audio slate that would match the actual slate. This allowed a specific image clip to be paired with a specific audio clip in post production. The clapper, or clap sticks where added to the top of the slate to give a frame accurate reference to synchronizing the image and the audio in post production. That is, on set the AD would call the audio "sound!" and would wait for the recordist to say "rolling," which meant the tape recorder was recording. Then hearing the sound reply the AD would call "camera!" to which the camera man would say "speed" when the cameras tachometer would indicate that the camera had reached operational speed. After hearing the camera reply the AD would then make sure that the slate with all the proper information was held for the camera to see and read out load the information on the slate for the audio recordist. After the scene is called out the clapper sticks are clapped together firmly to make a sharp sound. The sticks are then held together so as not to confuse the editor when aligning the visual image in post production. When this was all done the director should then finally call "action!"
And this is still how it is done today. But a dry erase board is more commonly used and some very fancy slates actually have a digital read out indicating the time code on the camera and feed a similar signal to the tape recorder. However, if all you have is a dry erase slate/clapper you will need to call all the scenes and clap the sticks to indicate the reference frame. One other trick is at the end of a take before the camera and the audio recorder are stopped the slate should be held again in front of the camera but upside down to indicate the end of the shot. A clap reference can also be made hear for extreme precision.
Post Production
is sound that is added to the film while and after it is edited and is recorded independantly of the filming. (It is also the term used for the editing and mixing of orignal production recordings.) Post Production audio can be broken into the catagories of: Treatment of Origianl Sound, Foley , Sound Effects and, Music Sound Track. Equipment used in post production usually involves a full recording studio equiped to edit sound to film.
Treatment of Original Sound involves syncronizing the sound recording with the film, balancing the volume levels equalizing, and any other sort of treatment that may be necesary to blend the Original sound with any other sound that may be added, like Music.
Foley is the art of adding sound (most often environmental sounds) to the film while watching the film. These sounds are simultaneously recorded and mixed onto the film sound track. Foley is done when the original recording are lacking in some way or are non-existent. Foley these days can be more easily added to a sound mix using a Digital Audio Workstation (DAW). With the DAW the sounds to be added to the sound mix can be recorded independant of the film playback and lined up to perfect synchronization using the graphic interface of the DAW. For an example of extensive foley work check out: Glimpse, Coffin, and Gorilla Snomobilly . These short films had there sound entirely created in post production using dialogue replacement and foley.
Sound Effects are sounds that are added to the film to enhance the effect of the movie. Sound effects most often come from a sound effects library and are syncronized and with particular events in the film. These sounds are mixed onto the film sound track. Click here to go to owyheesound's sound effects library.
The Music Sound Track is just music that is chosen to emphisize a mood in the film. It is most often mixed into parts of the film that do not have much or any dialog.
Post Production Technique
Synchronization
The first significant job of post production is the synchronizing of the sound and image. This is done by loading the sound and image clips onto your editor. Whether you are working with film and a mag track or all and a digital editor the process is the same. The rough sync of each clip is done by aligning the visual and audio slates. Then the fine sync is done by aligning the moment the clapper stick make contact on the image with the sharp sound of the clapper sticks on the audio. This is very easy to do on a digital editor because the audio also has a visual representation. This makes frame accurate sync very quick and easy.
After the audio and the image are in synch then the two files should be married into a single file before they can be delivered to the picture editor. When the picture editor completes the edit of the film commits to 'Picture Lock' the film can come back to the sound editor for Foley, ADR and music mixing.
Foley
Adding the first pass of Foley is when the film can really come 'Alive' for the first time. It is important to make several passes at an entire film especially if it is a feature length or long film. Starting with by just recreating all of one type of sound like the body movement sounds (including footsteps) in the first pass then going back and adding another type of sound like all syncsounds like doors closing, guns cocking, drinks being poured, etc... keeps each type of sound consistent throughout the film and gives a good even quality to the picture. It also keeps the Foley artist from becoming to bogged down in one part of the film which could lead to delayed compleation dates.
ADR
Replacing the original dilogue recording durring production with dialogue recording in the studio can be a lot of fun, and it can be hilarious to see slight mismatches of lips and sound, but good ADR tries at all costs to avoid this. Unless a parody of poorly done ADR is being done Automatically Replaced Dialogue should be undectable to the average listener. The best ways to accomplish this are:
1.) to record the replaced dialogue in a location that has the same, or as similar as possible, sonic characteristics as the original production location
2.) use the same or as similar as possible the recording equipment as used in the original production
3.) use the same actor that did the performace in the original production
4.) elicit the same performance from the actor (this may require having the actor physically recreate the original performance in addition to the dialogue as physical movement dramitically affects the quality of an actors voice performance)
Sometime a visual playback of the actors performance is played back for the actor so they can see their motions but an original recording of the production audio is essential for the actor to mimick intonation and inflection. This original audio is called the 'Scratch track' and is usually not a great recording for some reason or other (which is why it is being replaced) but it is nearly imposible for an actor to simply read their own lips from a visual playback and recreate their performance. So, even if the audio is bad some kind of sound recording must be captured in production, even if, and especially if the dialogue is going to be replaced.
Music
Mixing the music to the film can be a bit of a trick. It takes real artistry to make the music loud enough without covering up the dialogue and the important Foley sounds. One way to get around mixing all the elements together is to mix all the dialogue into a single track and then dynamically compress it. And to do the same with the Foley and special effects sounds. This will result in three distinct tracks fo finall mixing: the dialogue, the Foely and sound effects, and the music. You will not likely need to dynamically compress the audio of the music since most commercial music and especially pop music tend to be heavely dynamically compressed.