Crossfade between songs
- Input
- Dois arquivos sobrepostos por 3 segundos
- Expected output
- Equal-power — potência constante na transição
Default curve for DJ mixes and podcast mixdowns.
what is equal-power fade audio
Equal-power vs. linear fade: what is the real difference in audio
The Weber-Fechner law describes that human perception of sound intensity is logarithmic — a linear reduction in amplitude does not result in a linear drop in perceived volume. The equal-power fade compensates for this by using the sine function for fade out and cosine for fade in, resulting in a constant power curve throughout the transition.
Continue in the tool
Open full toolMath behind equal-power fade
- For a fade out of duration T, the gain at each sample t is: g(t) = cos(t/T × π/2). For fade in: g(t) = sin(t/T × π/2). The key property is that sin²(x) + cos²(x) = 1 — so in a crossfade, the total power of the two combined signals is always constant.
- The linear fade uses g(t) = 1 - t/T for fade out. At the midpoint (t = T/2), the gain is 0.5, but the perceived power is proportional to 0.5² = 0.25 — only 25% of the original power, creating the characteristic volume "dip".
When to choose each curve
Simple fade at the start of narration
- Input
- Narração com entrada abrupta
- Expected output
- Linear — transição suave em 0.5 s
For very short fades, the difference between linear and equal-power is imperceptible.
Full tool FAQ
A linear fade reduces amplitude proportionally over time — simple, but can sound abrupt at the midpoint. Equal-power uses a sinusoidal curve that maintains a more constant perceived volume, ideal for professional mixdowns and crossfades.
Frequently asked questions
Is there an audible difference between the two fade types?
In long fades (5 s or more), the difference is clearly audible: equal-power sounds more uniform, while linear has a noticeable volume drop in the middle of the transition. In very short fades (less than 1 s), the difference is minimal or imperceptible.
Does this page replace official or professional review?
No. It helps explain the scenario and use the tool more safely, but real decisions should consider official sources, full context and qualified guidance when needed.