The Orban 536A Dynamic Sibilance Controller has been designed as a universal de-esser for the recording, broadcast, and motion picture industries. It offers electrical specifications consistent with other state-of-the-art audio signal processing equipment, extremely simple setup and operation, and dynamic characteristics which have been optimized for sibilance control. The 536A incorporates a circuit which forces the threshold of de-essing to track the average input level, permitting constant amounts of de-essing and audibly consistent results over an input level range of approximately 15dB. De-essers have existed for years, usually as frequency-dependent sidechains in limiters or compressors. However, a compressor used as a de-esser cannot function optimally if one attempts to compress and de-ess with the same device, since optimum compression ratios, attack times, and release times are quite different for the two modes of operation. In addition, such devices are often insufficiently adjustable, and often contain simple filters whose selectivity cannot provide enough differentiation between sibilance frequencies and the lower frequencies where most of the voice energy is concentrated. Further, these devices cannot simultaneously de-ess voice and maintain natural dynamic range because their thresholds are fixed. A specialized de-esser is therefore necessary to perform sibilance control only. It is ordinarily the last piece of processing hardware in a chain which may include both an equalizer and a compressor or limiter. Both devices will tend to increase sibilance with reference to the energy of the lower-frequency vocal components; the de-esser then reduces sibilance levels until they are once again natural-sounding and do not cause overload in recording media employing high frequency preemphasis. Many voices, especially female, produce relatively high levels of sibilant energy. This can be exaggerated by close miking techniques (especially condenser mics), and by audio processing. Such exaggerated sibilance is not only annoying aesthetically, but also can cause saturation of slow-speed tape recordings (such as cassette), resulting in severe IM distortion on sibilance. Similar problems can occur in optical film recording. In disk recording, untrackably high velocities can be produced. The 536A controls the level of the sibilance to make it sound aesthetically natural and to avoid overload problems. When not de-essing, it acts like a high-quality amplifier. How It Works: When the level in the sibilance band (around 6kHz) attempts to exceed a certain fraction of the peak input level (determined by the THRESHOLD control), the channel gain is automatically reduced to hold the output at this threshold level. This gain reduction occurs only during sibilance. After each sibilant, the gain recovers so quickly that subsequent vocal sounds are audibly unaffected. Because the entire channel gain is reduced (as opposed to de-essers which operate as program-controlled filters), any residual IM distortion which accompanies the original sibilance is reduced along with the sibilance itself. Because the de-essing threshold automatically tracks the input level, the de-esser forces the balance between the sibilance and "voiced" speech to remain consistent over an input level range of more than 15dB. Thus recordings whose natural dynamic range has been preserved can be effectively de-essed.