Fade-In — User Guide

Applies a configurable fade-in envelope to one Sound, with full-duration or partial fades, five curve shapes, optional whole-output gain adjustment, explicit normalization, playback, and visualization.

Author: Shai CohenVersion: 1.2 (2026)Category: DynamicsInput: exactly one SoundLicense: MIT

Contents:

What this does Quick start Fade curves Presets Parameters Processing details Visualization Output

What this does

The script copies the selected Sound and multiplies it by a fade-in gain envelope. The envelope rises from approximately zero at the beginning of the fade region to unity at its end. With a partial fade, all samples after the fade region are left at gain 1.0. With a full-duration fade, the curve spans the entire Sound.

Actual Sound time is preserved. Version 1.2 uses the Sound's real xmin/xmax. A Sound that begins at 5.0 s is faded from 5.0 s onward; the script does not assume that the object starts at time 0.

An optional gain adjustment named Apply_attenuation is applied to the whole copied Sound before the fade. Negative values attenuate; a positive custom value would amplify. Optional peak normalization is a separate final stage and is off by default.

Quick start

Select exactly one Sound object.
Run Linear_Fade-In.praat.
Choose a preset or Custom.
Choose the curve and whether the fade spans the full Sound or only its first N seconds.
Optionally apply whole-output attenuation and/or final peak normalization.
Leave Draw_visualization and Play_result enabled if desired, then click OK.

Fade curves

Let φ = (x − fadeStart) / fadeLen within the fade region, so φ runs from 0 to 1 in continuous time.

Curve	Envelope inside fade	Character
Linear	`φ`	Constant-rate rise.
Exponential	`(base^φ − 1) / (base − 1)`	For base > 1, slower beginning and faster approach to unity.
Logarithmic	`ln(1 + φ(base−1)) / ln(base)`	For base > 1, faster beginning and slower approach to unity.
S-Curve	`(1 − cos(πφ)) / 2`	Smooth slope at both ends.
Quarter-sine	`sin(πφ/2)`	Fast initial rise with a progressively gentler approach to unity.

Curve_base: used only for Exponential and Logarithmic. Values below 1 are rejected. Curve_base = 1 is handled explicitly as the exact linear limiting case, avoiding division by zero.

Presets

Preset selection overwrites the parameters listed below. Parameters not mentioned by a preset retain the form value.

Preset	Curve	Fade range	Whole-output gain adjustment
Custom	Form values	Form values	Form values
Gentle Entry	Logarithmic	Full duration	Off
Dramatic Rise	Exponential, base 20	Full duration	Off
Smooth Open	S-Curve	Full duration	Off
Quick Attack	Quarter-sine	First 20% of Sound duration	Off
Soft Intro	Linear	First 2 s, clamped to Sound duration	−12 dB applied to the entire output
Cinematic Swell	S-Curve	Full duration	−6 dB applied to the entire output

Normalize_output is not changed by presets. It remains whatever the user selected in the form; its default is off.

Parameters

Parameter	Default	Behavior
Preset	Custom	Selects one of the configurations above.
Curve_shape	S-Curve	Linear, Exponential, Logarithmic, S-Curve, or Quarter-sine.
Curve_base	10	Used only by Exponential/Logarithmic; must be ≥ 1. Base 1 gives a linear fade.
Full_duration	On	When on, the fade spans the complete Sound duration.
Fade_seconds	2.0 s	Used only when Full_duration is off. Values longer than the Sound are clamped to its duration; the effective fade is at least about 1 ms when possible.
Apply_attenuation	Off	Applies a constant gain to the whole copied Sound before fading.
Attenuation_dB	−6 dB	Converted to linear gain as `10^(dB/20)`. Negative values attenuate.
Normalize_output	Off	If enabled and output is non-silent, scales sample peak to 0.99 after all processing.
Draw_visualization	On	Draws the diagnostic page in Praat Picture.
Play_result	On	Plays the processed Sound.

Processing details

1. Copy source → <source>_fadeIn 2. If Apply_attenuation: sample *= 10^(Attenuation_dB/20) 3. Compute fade region [srcStart, srcStart + fadeLen] 4. Multiply samples inside region by selected curve 5. Samples after fadeEnd keep gain 1.0 6. If Normalize_output and output peak > 0: Scale peak to 0.99 7. Optionally visualize and play

The script processes all channels of the selected Sound together with the same time-varying gain law. It does not resample the audio, change duration, or create a mono downmix.

Normalization is intentionally explicit. With its default off, attenuation remains an actual level change. If normalization is enabled, it may undo some or all of that global attenuation by bringing the final sample peak to 0.99.

Praat Sound samples are located at sample-center times rather than exactly on xmin/xmax. The continuous envelope is defined to reach 0 and 1 at the mathematical region boundaries, but the first or last stored sample normally lies slightly inside those boundaries.

Visualization

The 8-inch Picture view contains:

Original waveform in gray.
Fade-in envelope on a 0–1 gain scale, with the fade region shaded blue; for a partial fade, a dotted marker identifies fadeEnd.
Processed waveform in blue.
Summary strip with source duration/sample rate, curve, absolute fade times, attenuation state, normalization state, output peak, and preset.

The Original and Output waveform panels use a shared amplitude range so their levels are directly comparable. The envelope panel describes the fade multiplier only; whole-output attenuation and final normalization are reported separately rather than folded into that curve.

Output

Object name: <source>_fadeIn
Channels: preserved from the source
Sampling frequency: preserved
Duration and time domain: preserved
Default normalization: off
Dependencies: Praat only