Sleep Sound Fade Timer
Play calming brown noise, rain, surf or fan hum that holds steady then fades to silence on a timer as you fall asleep.
About this tool
Sleep Sound Fade Timer
Play calming brown noise, rain, surf or fan hum that holds steady then fades to silence on a timer as you fall asleep.
Sleep Sound Fade Timer plays brown noise, rain, ocean surf or fan hum at a steady level while you fall asleep, then fades it to complete silence over a fade time you set. You choose the curve: a logarithmic fade drops an equal number of decibels each minute, which the ear hears as perfectly even, while linear and S-curve fades feel different in the last few minutes. Everything is synthesised in the browser, so it runs offline and no audio file is downloaded.
How to use Sleep Sound Fade Timer
- 1
Open Sleep Sound Fade Timer on AltFTool — it loads instantly in your browser.
- 2
Add your input to the workspace.
- 3
Adjust the options until the result looks right.
- 4
Copy or download the output and put it to work.
Why use Sleep Sound Fade Timer
Fades, never cuts
A sudden stop can wake you; the level slides to true silence instead.
Three fade curves
Logarithmic matches how hearing works, linear is faster at the end, S-curve is gentlest at both ends.
No files, no account
Sound is generated locally with the Web Audio API, so it works offline and uses no data.
Common use cases
- Fall asleep to brown noise that is completely silent 45 minutes later, instead of running all night.
- Mask a partner's snoring or street traffic for the 20 minutes it takes you to drop off.
- Give a baby or toddler a fan-hum wind-down that fades out rather than stopping abruptly.
- Set the start time and see the exact clock time the room will be quiet again.
Frequently asked questions
How long should a sleep sound timer run?
Most people fall asleep within 10 to 20 minutes, so a 30 to 60 minute timer with the last 10 to 15 minutes as a fade covers the whole sleep-onset window. Running sound all night is a personal choice, but a timer avoids it disturbing the lighter sleep stages later in the night.
Why does a logarithmic fade sound smoother than a linear one?
Because loudness is perceived roughly on a decibel scale, not a linear amplitude scale. A linear fade spends most of its time in the quiet region where changes are barely audible and then seems to disappear at the end, while a logarithmic fade drops an equal number of decibels per minute so each step sounds the same size.
Is brown noise good for sleep?
Many people find brown noise easier to sleep to than white noise because its energy falls about 6 dB per octave, removing the harsh high frequencies. Research on noise and sleep quality is mixed and results vary between individuals, so treat it as a comfort aid rather than a treatment.
Will the sound keep playing if my phone screen locks?
It may stop. Browsers can suspend audio in a backgrounded or locked tab, so keep the tab in the foreground, or add the page to your home screen and stop the screen from sleeping. On a laptop, sleep mode will also stop playback.