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AUDIO Audio basics It is an absolutely true statement that the best way to improve the quality of your image is to improve the quality of your sound. Viewers will happily watch grainy, black- and-white images and consider it “art.” However, nothing you can say will keep them in their seats if the audio is too loud or unintelligible. Yet, far too often, video editors consider audio an after- thought; or something someone else will worry about when the “real work” of editing is complete. It doesn’t have to be that way. An understanding of basic audio concepts and terminology will help any editor improve their projects. Images show us what’s going on. Audio tells us how we should feel about it. Don’t think so? Watch any scene that’s heavy on effects with the sound turned off. The effects may be stunning, but they will feel lifeless and a bit hokey until you turn the sound back on. by Larry Jordan NOTE: To prevent bar fights, I need to establish that video editing systems display peak audio levels. Audio engineers generally work with average audio levels, which are about 20 dB lower than peak levels. Both are valid ways to measure audio, but the numbers are not the same and cause all kinds of confusion. In this article, I’m using peak values measured as dBFS (deciBels Full Scale). AUDIO 101 Let’s start with some basics. Everything we hear is caused by pulses of air pressure vibrating against our ear drums. These vibrations, called “Hertz (Hz),” vary in the number we hear per second. Low-pitched sounds vibrate slowly, while high-pitched sounds vary quickly. We describe “normal human hearing” as a range of pulses from 20 to 20,000 Hz, where 20 Hz feel more like a vibration than a tone and 20,000 Hertz sounds more like wind in a pine tree than a pitch. “Normal” is a relative term. A three-year-old will hear sounds far beyond both ends of this range. Older individuals often lose the ability to hear high frequencies. NOTE: For comparison, the base frequency of the lowest note on a piano vibrates at 27.5 Hz, while the highest note vibrates at 4,186 Hz. Overtones will extend into higher frequencies. What makes this frequency range even more interesting is that every sound we hear - speech, music and noise - falls somewhere within this vibration range. In fact, these overlap, which makes it really tricky to adjust one without affecting the other, because all sounds are intermixed within this single range of frequencies. Audio frequencies are logarithmic; which means that when frequency of a sound doubles the pitch goes up by an 48 | KITPLUS - THE TV-BAY MAGAZINE: ISSUE 101 MAY 2015