Choosing the Best Sound Format for Production
There are many issues facing an audio professional who is considering getting into surround production, either for music, film, DVD, Internet, or multi-media. Whether you are recording, mixing, editing, or mastering, there is a lot of information that you need to be comfortable with before you can succeed in surround sound. Although this collection is a good start, it is by no means an exhaustive list or in-depth manual. Hopefully it will give you a well-rounded introduction and good foundation on which to build the pursuit of your goals.
There are a number of critical issues ...view middle of the document...
Some Dolby certified film stages alter this slightly and reference the surrounds to 82db. You would use pink noise and measure using C weighting and slow response. This is by no means a complete guide to setting up the monitoring in your room, but it's the basics to get you started.
5.1: spoken as "five point one". This refers to a surround sound format consisting of 5 full range channels and one LFE channel (see the next entry). It consists of Left, Center, Right, Left Surround, Right Surround.
7.1. This is reminiscent of, but not exactly the same as the old 70mm soundtracks. The current 7.1 has L, C, R, LS, RS, and LFE like 5.1, but adds 2 more speakers behind the screen between the center and left,
and between the center and right. These are referred to as LC and RC, or Left Center and Right Center. On large screens, this allows better tracking of dialog and effects, and more creative options for the mixers and director. The original 70mm 6-channel soundtrack had five across the front like 7.1, but no subwoofer and only mono surround. Some people have also suggested
LFE: Low Frequency Effects. Typically you use a subwoofer in this application, the "point one" of 5.1. The channel does not necessarily have to be band limited, as in the option to use it as a height channel in DVD-A, but when used as an LFE, it is of course for low frequency information. It is a discrete channel, not a crossover network to derive the low frequency information from the main program. However, in most end user systems, bass management is in use, which actually does divert the sub bass from the other 5 channels to the subwoofer along with the discrete LFE channel information.
THX: Tomlinson Holman experiment. Tomlinson Holman and Lucas film developed these guidelines for standardization of cinema sound systems and theater acoustics. There was later developed a standard for home playback systems and also a professional small room standard as well. The idea is that if your mix room and the playback theater are THX certified, the sound will be experienced by moviegoers as intended by the mixers and director by closely matching the sound of mix stage and movie theater.
PCM: Pulse Code Modulation. This is the sampling technique that is most familiar to us as it is the basis for the CD and for most uncompressed digital audio that we come into contact with. For the CD, we take 44,100 samples of the audio every second (44.1 kHz sample rate) and quintile it into one of the 65,536 steps in 16 bits of resolution. You definitely want to read the other three installments of "Tech Talk" if you want more information about this.
DSP: Digital Signal Processing. Every time you process digital audio in any way, perhaps by using EQ, dynamic range compression, or even volume adjustments, you are performing mathematical computations. The particular algorithms, dither practices involved, and other issues greatly affect the quality of the processing and resultant sound....