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De-essing (also desibilizing) is any technique intended to reduce or eliminate the excessive prominence of sibilant consonants, such as the sounds normally represented in English by " s", "z", "ch", "j" and "sh", in recordings of the human voice. Sibilance lies in frequencies anywhere between 2 and 10 kHz, depending on the individual voice.
De-essing is a dynamic audio editing process, only working when the level of the
With this technique, the signal feeding the side-chain of a dynamic-range compressor is equalized or filtered so that the sibilant frequencies are most prominent. As a result, the compressor only reduces the level of the signal when there is a high level of sibilance. This reduces the level over the entire frequency range. Because of this, attack and release times are extremely important, and threshold settings cannot be placed as low as with other types of de-essing techniques without experiencing more blatant sound artifacts.
Here, the signal is split into two frequency ranges: a range that contains the sibilant frequencies, and a range that does not. The signal containing the sibilant frequencies is sent to a compressor. The other frequency range is not processed. Finally the two frequency ranges are combined back into one signal.
The original signal can either be split into high (sibilant) and low frequencies, or split so that the frequencies ''both'' below and above the sibilance are untouched. This technique is similar to multi-band compression.
The gain of a
Audio editing software, whether professional or amateur software such as Audacity, can use the built-in equalization effects to reduce or eliminate sibilance ess sounds that interfere with a recording. Described here is a common method with Audacity. The process is in two phases:
# Analyze the frequency of the voice's ess sound by sampling several instances and calculating the range of ess frequencies. Male voices sibilance range in 3–6 kHz, while female voice's typically range in 6–8 kHz.
# Apply an equalization filter to quiet the determined frequency band by −4 dB to −11 dB during ess-frequency time events.
The rise and fall time of filter should be fast (less than 10 ms) in order to clip the sibilance-specific instances only.
Causes
Excess sibilance can be caused bycompression
Compression may refer to:
Physical science
*Compression (physics), size reduction due to forces
*Compression member, a structural element such as a column
*Compressibility, susceptibility to compression
* Gas compression
*Compression ratio, of a ...
, microphone
A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...
choice and technique, and even simply the way a person's mouth anatomy is shaped. Ess sound frequencies can be irritating to the ear, especially with earbuds or headphones, and interfere with an otherwise modulated and pleasant audio stream.
Process of de-essing
De-essing is a dynamic audio editing process, only working when the level of the signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
in the sibilant range (the ess sound) exceeds a set threshold. De-essing temporarily reduces the level of high-frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
content in the signal when a sibilant ess sound is present. De-essing differs from equalization, which is a static change in level among many frequencies. However, equalization of the ess frequencies alone can be manipulated to reduce the level of sibilance.
There are several time- and frequency-based algorithms that can reduce sibilance or de-ess the sound. Time-domain approaches, such as bandpass filters, are more suited to real-time applications such as live radio due to less constraint on digital signal processor. Playback or offline applications incorporate methods based on fast Fourier transform (FFT).
Using a dedicated de-essing plugin
In the current digital stronghold of audio production, the most commonly used tool for reducing sibilance is a de-esser plugin. A dynamic equalizer can be used to achieve the same effects as a de-esser, however, plugin manufacturers have tailored these tools to operate efficiently within the mid-high to high frequencies. A de-essing plugin will compress the desired signal according to the amplitude of the selected frequency as it passes over a preset threshold. In the case of excessive sibilance anywhere from 4 to 10 kHz will often be where the problem resides. Certain plugins will shape the envelope of the compression to achieve a more musical effect. Over de-essing can result in the over-manipulation of transients, resulting in the softening or hardening of certain consonants, yielding undesirable effects.Side-chain compression or broadband de-essing
With this technique, the signal feeding the side-chain of a dynamic-range compressor is equalized or filtered so that the sibilant frequencies are most prominent. As a result, the compressor only reduces the level of the signal when there is a high level of sibilance. This reduces the level over the entire frequency range. Because of this, attack and release times are extremely important, and threshold settings cannot be placed as low as with other types of de-essing techniques without experiencing more blatant sound artifacts.
Split-band compression
Here, the signal is split into two frequency ranges: a range that contains the sibilant frequencies, and a range that does not. The signal containing the sibilant frequencies is sent to a compressor. The other frequency range is not processed. Finally the two frequency ranges are combined back into one signal.
The original signal can either be split into high (sibilant) and low frequencies, or split so that the frequencies ''both'' below and above the sibilance are untouched. This technique is similar to multi-band compression.
Dynamic equalization
The gain of a parametric equalizer
Equalization, or simply EQ, in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal. The circuit or equipment used to achieve this is called an equalizer.
Most hi-fi eq ...
is reduced as the level of the sibilance increases. The frequency range of the equalizer is centered on the sibilant frequencies.
De-essing with automation
A more recent method of de-essing involvesautomation
Automation describes a wide range of technologies that reduce human intervention in processes, namely by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machines ...
of the vocal level in a digital audio workstation
A digital audio workstation (DAW) is an electronic device or application software used for recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software program on a laptop, to an integrat ...
(DAW). Whenever problematic sibilance occurs, the level can be set to follow automation curves that are manually drawn in by the user.
This method is made feasible by editing automation points directly, as opposed to programming by manipulating gain sliders in a write-mode. An audio engineer would not be able to react fast enough to precisely reduce and restore vocal levels for the brief duration of sibilants during real-time playback.
De-essing without automation or with manual equalization
Audio editing software, whether professional or amateur software such as Audacity, can use the built-in equalization effects to reduce or eliminate sibilance ess sounds that interfere with a recording. Described here is a common method with Audacity. The process is in two phases:
# Analyze the frequency of the voice's ess sound by sampling several instances and calculating the range of ess frequencies. Male voices sibilance range in 3–6 kHz, while female voice's typically range in 6–8 kHz.
# Apply an equalization filter to quiet the determined frequency band by −4 dB to −11 dB during ess-frequency time events.
The rise and fall time of filter should be fast (less than 10 ms) in order to clip the sibilance-specific instances only.
See also
References
External links
* {{Music technology Dynamics processing Speech processing