FFT Filter effect

The graphic nature of the Filter And EQ > FFT Filter effect makes it easy to draw curves or notches that reject or boost specific frequencies. FFT stands for Fast Fourier Transform, an algorithm that quickly analyzes frequency and amplitude.

 

This effect can produce broad high‑ or low‑pass filters (to maintain high or low frequencies), narrow band‑pass filters (to simulate the sound of a telephone call), or notch filters (to eliminate small, precise frequency bands).

Scale

Determines how frequencies are arranged along the horizontal x‑axis:

  • For finer control over low frequencies, select Logarithmic. A logarithmic scale more closely resembles how people hear sound.

  • For detailed, high‑frequency work with evenly spaced intervals in frequency, select Linear.

Spline Curves

Creates smoother, curved transitions between control points, rather than more abrupt, linear transitions. (See About spline curves for graphs.)

Reset 

Reverts the graph to the default state, removing filtering.

Advanced options

Click the triangle to access these settings:

FFT Size

Specifies the Fast Fourier Transform size, determining the tradeoff between frequency and time accuracy. For steep, precise frequency filters, choose higher values. For reduced transient artifacts in percussive audio, choose lower values. Values between 1024 and 8192 work well for most material.

Window

Determines the Fast Fourier Transform shape, with each option resulting in a different frequency response curve.

These functions are listed in order from narrowest to widest. Narrower functions include fewer surrounding, or sidelobe, frequencies but less precisely reflect center frequencies. Wider functions include more surrounding frequencies but more precisely reflect center frequencies. The Hamming and Blackman options provide excellent overall results.

Graphic Equalizer effect

The Filter And EQ > Graphic Equalizer effect boosts or cuts specific frequency bands and provides a visual representation of the resulting EQ curve. Unlike the Parametric Equalizer, the Graphic Equalizer uses preset frequency bands for quick and easy equalization.

You can space frequency bands at the following intervals:

  • One octave (10 bands)

  • One‑half octave (20 bands)

  • One‑third octave (30 bands)

Graphic equalizers with fewer bands provide quicker adjustment; more bands provide greater precision.

Gain sliders

Sets the exact boost or attenuation (measured in decibels) for the chosen band.

Range

Defines the range of the slider controls. Enter any value between 1.5 and 120 dB. (By comparison, standard hardware equalizers have a range of about 12 to 30 dB.)

Accuracy

Sets the accuracy level for equalization. Higher accuracy levels give better frequency response in the lower ranges, but they require more processing time. If you equalize only higher frequencies, you can use lower accuracy levels.

Note:

If you equalize extremely low frequencies, set Accuracy to between 500 and 5000 points.

Master Gain

Compensates for an overall volume level that is too soft or too loud after the EQ settings are adjusted. The default value of 0 dB represents no master gain adjustment.

Note:

The Graphic Equalizer is an FIR (Finite Impulse Response) filter. FIR filters better maintain phase accuracy but have slightly less frequency accuracy than IIR (Infinite Impulse Response) filters like the Parametric Equalizer.

Notch Filter effect  

The Filter and EQ > Notch Filter effect removes up to six user‑defined frequency bands. Use this effect to remove very narrow frequency bands, such as a 60 Hz hum, while leaving all surrounding frequencies untouched.

Note:

To remove shrill “ess” sounds, use the Sibilance Softener preset. Or use DTMF presets to remove standard tones for analog telephone systems.

Frequency

Specifies the center frequency for each notch.

Gain

Specifies the amplitude for each notch.

Notch width

Determines frequency range for all notches. The three options range from Narrow for a second order filter, which removes some adjacent frequencies, to Super Narrow for a sixth order filter, which is very specific.

Note:

Generally, use no more than 30 dB of attenuation for a Narrow setting, 60 dB for Very Narrow, and 90 dB for Super Narrow. Greater attenuation can remove a wide range of neighboring frequencies.

Ultra-Quiet

Virtually eliminates noise and artifacts, but requires more processing. This option is audible only on high-end headphones and monitoring systems.

Fix Attenuations To

Determines if notches have equal or individual attenuation levels.

Parametric Equalizer effect

The Filter And EQ > Parametric Equalizer effect provides maximum control over tonal equalization. Unlike the Graphic Equalizer, which provides a fixed number of frequencies and Q bandwidths, the Parametric Equalizer gives you total control over frequency, Q, and gain settings. For example, you can simultaneously reduce a small range of frequencies centered around 1000 Hz, boost a broad low‑frequency shelf centered around 80 Hz, and insert a 60 Hz notch filter.

 

The Parametric Equalizer uses second‑order IIR (Infinite Impulse Response) filters, which are very fast and provide very accurate frequency resolution. For example, you can precisely boost a range of 40 to 45 Hz. FIR (Finite Impulse Response) filters like the Graphic Equalizer provide slightly improved phase accuracy, however.

Master Gain

Compensates for an overall volume level that’s too loud or too soft after you adjust the EQ settings.

Graph

Shows frequency along the horizontal ruler (x‑axis) and amplitude along the vertical ruler (y‑axis). Frequencies in the graph range from lowest to highest in a logarithmic fashion (evenly spaced by octaves).

Identifying band-pass and shelving filters in the Parametric Equalizer:

A. High- and low-pass filters B. High and low shelving filters 

Frequency

Sets the center frequency for bands 1-5, and the corner frequencies for the band-pass and shelving filters.

Note:

Use the low shelving filter to reduce low‑end rumble, hum, or other unwanted low‑frequency sounds. Use the high shelving filter to reduce hiss, amplifier noise, and the like.

Gain

Sets the boost or attenuation for frequency bands, and the per-octave slope of the band-pass filters.

Q / Width

Controls the width of the affected frequency band. Low Q values affect a larger range of frequencies. Very high Q values (close to 100) affect a very narrow band and are ideal for notch filters removing particular frequencies, like 60 Hz hum.

Note:

When a very narrow band is boosted, audio tends to ring or resonate at that frequency. Q values of 1-10 are best for general equalization.

Band

Enables up to five intermediate bands, as well as high-pass, low-pass, and shelving filters, giving you very fine control over the equalization curve. Click the band button to activate the corresponding settings above.

The low and high shelving filters provide slope buttons (, ) that adjust the low and high shelves by 12 dB per octave, rather than the default 6 dB per octave.

Note:

To visually adjust enabled bands in the graph, drag the related control points.

Constant Q, Constant Width

Describes a frequency band’s width as either a Q value (which is a ratio of width to center frequency) or an absolute width value in Hz. Constant Q is the most common setting.

Ultra-Quiet

Virtually eliminates noise and artifacts, but requires more processing. This option is audible only on high-end headphones and monitoring systems.

Range

Sets the graph to a 30 dB range for more precise adjustments, or a 96 dB range for more extreme adjustments.

Scientific Filter effect  

Use the Scientific Filter effect (Effects > Filter and EQ) for advanced manipulation of audio. You can also access the effect from the Effects Rack for single assets in the waveform editor, or for tracks and clips in the Multitrack editor.

Types

Specifies the type of scientific filter. The available options are as follows.

Bessel

Provides accurate phase response with no ringing or overshoot. However, the pass band slopes at its edges, where rejection of the stop band is the poorest of all filter types. These qualities make Bessel a good choice for percussive, pulse-like signals. For other filtering tasks, use Butterworth.

Butterworth

Provides a flat pass band with minimal phase shift, ringing, and overshoot. This filter type also rejects the stop band much better than Bessel and only slightly worse than Chebychev 1 or 2. These overall qualities make Butterworth the best choice for most filtering tasks.

Chebychev

Provides the best stop band rejection but the worst phase response, ringing, and overshoot in the pass band. Use this filter type only if rejecting the stop band is more important than maintaining an accurate pass band.

Elliptical

Provides a sharp cut-off and narrow transition width. It can also notch out frequencies, unlike the Butterworth and Chebychev filters. It can, however,introduce ripples in both the stop band and the pass band

Modes

Specify a mode for the filter. The available options are as follows.

Low Pass

Passes the low frequencies and removes high frequencies. You must specify the cutoff point at which the frequencies are removed.

High Pass

Passes high frequencies and removes low frequencies. You must specify the cutoff point at which the frequencies are removed.

Band Pass

Preserves a band, a range of frequencies, while removing all other frequencies. You must specify two cutoff points to define the edges of the band.

Band Stop

Rejects any frequencies within the specified range. Also known as a notch filter, Band Stop is the opposite of Band Pass. You must specify two cutoff points to define the edges of the band.

Master Gain

Compensates for an overall volume level that might be too loud or too soft after you adjust the filter settings.

Cutoff

Defines the frequency that serves as a border between passed and removed frequencies. At this point the filter switches from passing to attenuating, or vice versa. In filters requiring a range (Band Pass and Band Stop), Cutoff defines the low frequency border, while High Cutoff defines the high frequency border.

High Cutoff

Defines the high frequency border in filters that require a range (Band Pass and Band Stop).

Order

Determines the filter’s precision. The higher the order, the more precise the filter (with steeper slopes at the cutoff points, and so on). However, very high orders can also have high levels of phase distortion.

Transition Bandwidth

(Butterworth and Chebychev only) Sets the width of the transition band. (Lower values have steeper slopes.) If you specify a transition bandwidth, the Order setting is filled in automatically, and vice versa. In filters that require a range (Band Pass and Band Stop), this serves as the lower frequency transition, while High Width defines the higher frequency transition.

High Width

(Butterworth and Chebychev only) In filters that require a range (Band Pass and Band Stop), this option serves as the higher frequency transition, while Transition Bandwidth defines the lower frequency transition.

Stop Attn

(Butterworth and Chebychev only) Determines how much gain reduction to use when frequencies are removed.

Pass Ripple/ Actual Ripple

(Chebychev only) Determines the maximum allowable amount of ripple. Ripple is the effect of unwanted boosting and cutting of frequencies near the cutoff point.

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