Low sounds tend to be measure from 0 – 150 or so hertz. Many projects use a filtere to “roll offf 80hz and below, which is sometimes called rumble, which will help with the preception of a “muddy” recording. Sibilance tends to live at the other end of the spectrum, somewhere betwen 5,000 and 7,000 hertz, or more typically referred to as 5k – 7k. Often, using a compressor, tends to attenuate those frequencies and can make the “ess” even more pronounced. Special software or hardware algorithms, which themselves are also compressors (yeah it gets confusing), often referred to as de-essers are most often emplyed to cut the edge. It’s a bit of an art to get it to sound good, but with the help and guidance of a trained recording engineer, one can learn many of the basics of how to apply “just enough”

Some microphones have a scooped response, which means that by design some of the midrange, going into the “sibilance” range will be less pronounced. Other microphones tend to slope up at 2k and continue to do so util 8k or 10k. Those microphones, many of them expensive LDC’s or large diaphragm microphones, will often give even a more pronounced sibilance to recorded speech.

Some mic pre’s can also have an effect on speech, coloring it one way or the other.

Similarly, microphones have differenet capsules, may be solid state or tube and employ different headbaskets and design. One great idea, if for example you are working in a new studio and/ or a new microphone, is to askl for a few minutes to warm up. Tell the engineer that you would like to work the microphone from different distances and placement to get an idea of the response, and then ask to listen back. One way is to work it like a clock and start at 12 O’clock and move around until you finish at 11 o’clock. Listening back will give you an understanding of how your sound changes as you change position on microphone. It helps you develop a better trust in your relationship with the microphone.

Here is a really nice little blog from Michale Joly, world renowned microphone modder and expert on a few basic aspects of microphones.

http://www.oktavamod.com/node/26