Apple MA261Z/A User Manual - Page 641

Frequency Ranges and Equalization The entire range of human hearing, from 20 Hz to 20,000 Hz, can be broken into a spectrum of frequency bands: low, midrange, and high. VIII Note: Different devices define these ranges differently; the following ranges are approximate. Low (20-250 Hz) Audible bass frequencies start around 20 Hz, though many speakers cannot reproduce frequencies this low. This is an example of where audio meters can be deceiving because the meters may show very high signals but the speakers are not capable of making sounds that low. The lowest frequencies are felt as well as heard, and require the most power to amplify. Often, subwoofer speakers are used just to handle the low frequencies in the mix (the 0.1 channel in a 5.1 surround sound mix is a dedicated lowfrequency effects channel). If you are trying to increase the impact of sounds like kick drums or explosions, add gain around 30 Hz or so. Filtering out 60-80 Hz removes a lot of low end noise and rumble from wind or microphone handling. Between 150-250 Hz, you can add "warmth" to the audio signal (or subtract it). Midrange (250-4,000 Hz) Humans are most sensitive to this part of the audio spectrum. Most of the frequencies that make speech intelligible are in this range. You can make audio tracks stand out more in the mix by subtly increasing the frequencies in this range. At the top of this range, around 4 kHz, is where vocal sibilance occurs. Too much sibilance can be grating, but a little bit can make the voice sound crisp and detailed. If your track has too much sibilance, try reducing the 4 kHz range. High (4,000-20,000 Hz) The high end of the frequency spectrum adds "brightness" or "brilliance" to a mix, but no longer affects factors such as impact (bass) or speech intelligibility. High-end frequencies can be grating, so don't boost these frequencies too much. Chapter 46 Using Audio Filters 641