Add a smooth audio fade-in in seconds
An audio fade-in raises the volume gradually from silence (or from a quieter level) to full volume, so a track starts gently instead of bursting in. This free tool adds a fade-in to MP3, WAV, M4A, FLAC and Ogg files: set the length, pick one of four curves, see the result drawn on the waveform, and download.
Use it for intros of songs cut from the middle, ringtones and alarm sounds that should not startle, background music for videos and presentations, podcast music beds, and voice clips that begin with a pop or a breath. You can also start the fade later in the file and cut away everything before it — a quick way to skip a noisy count-in.
Everything runs in your browser. The file is decoded, faded and encoded on your device with the open-source Mediabunny library (MPL-2.0) — plus LAME (LGPL) for MP3 or libFLAC (BSD) for FLAC — and nothing is uploaded.
How to use the Audio Fade In
- Drop an audio file on the box or click to choose one. Its format, duration, sample rate, channels and bitrate are shown with a waveform.
- Choose a fade curve — Linear, Exponential, Logarithmic or S-curve — and watch the curve change on the waveform.
- Set the Fade length in seconds, or drag the End handle. Drag Start, or type a time, to begin the fade later in the file.
- Optionally raise the Start volume above 0 %, and decide whether to cut the audio before the fade.
- Choose an output format and press Apply fade-in. Compare the original and result players, then download.
Audio Fade In features
Four fade curves
Linear, exponential, logarithmic and S-curve, each drawn as an icon and over your waveform so you can see the shape before applying it.
Live waveform preview
The faded part of the waveform is drawn at its new level over a faint copy of the original, with zoom for short fades.
Start anywhere
Begin the fade at any time in the file and either cut what comes before or leave it at the start volume.
Partial fades
Fade up from 10–95 % instead of silence for a softer lift, for example when a track should start quietly but audibly.
Sample-accurate
The gain is calculated for every single sample, so even 50 ms anti-click fades are smooth.
Keeps your format
Same as input by default; MP3, M4A, WAV, FLAC and Ogg are available too.
Which fade-in curve should I use?
Each curve maps progress through the fade, x from 0 to 1, to a gain from 0 to 1 that multiplies the audio:
| Curve | Gain formula | Gain at 25 % / 50 % / 75 % | Sounds like |
|---|---|---|---|
| Linear | x | 0.25 / 0.50 / 0.75 | Quick to become audible, then a slow final rise |
| Exponential | (10x − 1) ÷ 9 | 0.09 / 0.24 / 0.51 | An even rise in loudness — good for music intros |
| Logarithmic | log10(1 + 9x) | 0.51 / 0.74 / 0.89 | Audible almost at once — good for speech |
| S-curve | (1 − cos πx) ÷ 2 | 0.15 / 0.50 / 0.85 | Smooth at both ends — good for short fades |
Why the curve matters
We hear loudness roughly on a logarithmic scale: halving the amplitude lowers the level by about 6 dB, which sounds only moderately quieter. A linear fade-in therefore seems to jump up early and then hardly change. The exponential curve starts slowly in amplitude, which is heard as a steady swell — the usual choice for music. The logarithmic curve is its mirror image and makes speech intelligible from the first syllable.
For very short fades — 10 to 100 ms to remove a click at the start of a clip — the curve hardly matters, but the S-curve is the smoothest. For long cinematic swells of 5–15 seconds, try exponential.
Related tools
End the track gently with Audio Fade Out, cut it first with the Audio Cutter, or remove dead air at the start with the Audio Silence Remover. Joining several tracks? The Audio Joiner can crossfade them.
Audio Fade In FAQ
How do I add a fade-in to an MP3?
Drop the MP3 here, set the fade length (3 seconds is a good start), choose a curve and press Apply fade-in. Keep the output on Same as input to get an MP3 back.
How long should a fade-in be?
For songs, 2–5 seconds sounds natural; for ringtones and alarms 1–3 seconds; for voice clips 0.1–0.5 seconds is enough to remove a pop without hiding the first word.
Is this audio fade-in tool free and private?
Yes. There is no sign-up, limit or watermark, and your audio is processed in your browser — it never leaves your device.
Can I fade in from the middle of a song?
Yes. Type a start time or drag the Start handle. Tick “Cut the audio before the fade starts” to make the new file begin there.
Does adding a fade-in lower the quality?
Only the faded part changes volume. With WAV or FLAC output nothing else is touched; MP3, M4A and Ogg are re-encoded, so pick a bitrate at least as high as the original.
What is the difference between exponential and logarithmic fades?
An exponential fade-in starts slowly and rises faster at the end; a logarithmic one rises fast and then levels off. They are mirror images of each other.