Since the beginning of the 21st century, there has been a veritable sea change in the creation and playback of audio for the cinema. Part of this transformation has revolved around access — nearly anyone now has access to professional quality sound recording and mixing tools on the production end. On the presentation end, nearly all venues provide super-high-fidelity surround sound audio and even ordinary people are equipping their home theater units with surround sound audio. What this means for the filmmaker is that the audience can hear everything vividly! Yay! Everyone can hear all the subtleties you included in your complex sound design, BUT it also means that any audio imperfections and deficiencies are also glaringly apparent. So, no matter what our budget or level of production, we all must produce highly polished audio to accompany our carefully composed and exposed images. The first, and most important, step to this end is to gather the best possible sound in the field during production. Unfortunately, sound is often a blind spot for many filmmakers, especially those just starting out. All too often with inexperienced filmmakers, a lot of time, money, and preparation goes into the production of the images, but they begin to think seriously about sound only after they hear and try to work with the terrible audio they got during production. The production sound team — those people who record sound in the field — are the unsung heroes of the film world. When they do their job perfectly, no one notices them; when the sound is bad, they are cursed. Good sound people are invaluable, and smart film-makers understand that getting good sound in production means a stronger sound design in postproduction, more creative options in editing, and saving time and money. This is why good sound people work a lot and why I’ve devoted two chapters to the craft of sound recording in the field, it’s that important. A filmmaker must respect sound as much as image.
A simple sound (a) can be understood in terms of its wavelength (1), and its amplitude (2), or the degree to which it deviates from normal air pressure (3). The higher the number of cycles per second (b), also called Hertz, the higher the frequency or the sound. Sounds with very low frequencies have fewer cycles per second (c).Sounds are usually made up of complex combinations of harmonic and overtone sound waves accompanying the fundamental tone. These comprise the unique tone color characteristics of a sound’s timbre.Timbre is a feature of a sound’s unique character. Here are the waveforms for three different instruments producing the exact same note (middle C): a piano (a), a violin (b), and a human voice (c).Single-system sound uses the video camera (b) to record both picture and sound on the same record media. The addition of a dedicated sound person using a boom (a) can provide greater flexibility (see also Fig. 15-23).Double-system sound uses two devices: the camera to record the image (c), and a sound recorder to record the audio signal (b) coming from the boom op and their microphone (a). Because these two devices work independently, a slate (d) must be used to provide an audio/visual point of reference to sync picture with sound in post.A properly shot and recorded slate is the perfect audiovisual point of reference in postproduction. The frame where the slate is clapped is marked in the video file (a), and then the sound file is positioned so that the sound of the slate clapping (b) is aligned with the marker. Video and audio are now in sync.An acoustic signal (a) is translated into an electrical charge by a microphone (b) and is then converted into digital information via an analog-to-digital converter (c). These data are stored on memory cards or hard drive and later downloaded into a computer for syncing and editing (f). A digital-to-analog converter (d) reverses the process when we play the recorded sound (e).The process of converting analog sound (1) to a digital format involves sampling the signal at regular intervals. The lower the sampling rate (a), the less accurate the digital version will be; a higher sampling rate (b) creates a more faithful reproduction of the original sound.All professional sound recorders have these essential features: mic inputs and preamps (a), record level potentiometers (b), a peak meter (c), controls for record, play, and searching (d), headphone jack (e), audio/data outputs (f), and record media bay (here it’s compact flash) (g).A typical single-system sound configuration. Boom operator (a), sound recordist adjusting levels with field mixer (b), and audio recorded on camcorder (c).moving coil microphone (left) works by converting the movement of a diaphragm (a) into an electrical charge when the coil (b) attached to it moves up and down while suspended around magnets (c). A condenser microphone (right) uses a positively charged diaphragm (d) and the negatively charged back plate (e) to form a capacitor; the movement between these two electrically charged plates creates voltage fluctuations that are sent to a preamp (f).A frequency response graph plots how sensitive (measured in dB, on the x-axis) a microphone is to a range of frequencies (measured in Hz on the y-axis). Note that the AT803b, an omnidirectional lavaliere condenser microphone, has a “roll-off” option that affects its sensitivity to low frequencies (arrow).Some microphones have a “low-end roll-off” setting (b) that makes them less sensitive to low frequencies, usually caused by wind or machine noise. The flat response setting (a) is preferable for most situations.The pickup pattern of an omnidirectional microphone allows it to capture sound equally from all directions.A cardioid microphone has a pickup pattern that favors sound coming from the front and sides, but not from behind.Hypercardioid microphones have a narrow range of acceptance that greatly favors sound coming directly from the front, allowing them to be positioned somewhat further from the sound source.A sound recordist’s basic microphone arsenal covers all bases: sturdy dynamic cardioid microphone and modular condenser systems offering three interchangeable heads: omni, cardioid, and supercardioid (a); lavaliere mics (b); and a wireless microphone system (c).
