Which noise color should I use for focus?
For masking speech, which is what usually breaks concentration in an office, pink noise is the best fit because its energy overlaps the 300Hz to 3kHz speech band without being as harsh as white. Brown noise is better for relaxing or sleeping, because it is weighted toward the low end and is less fatiguing over long periods.
How loud should I set it?
Loud enough that the distracting sound stops pulling your attention, and no louder. That is usually quieter than people expect. If you have to raise your voice to talk over it, it is too loud. Sustained exposure above roughly 70 to 85 dB carries hearing risk, and headphones make that easier to reach than speakers do.
Can I download the noise as an audio file?
No. The tool generates samples in real time with the Web Audio API and plays them straight to your output device. There is no encoder and no file. If you need an audio file, record the output with a desktop audio tool, or use a dedicated noise app that ships pre-rendered loops.
Will it keep playing if I lock my phone?
Probably not. Browsers suspend the audio context when a tab loses focus on mobile or when the screen locks, and this page has no background-audio session registered. For an overnight sound machine on a phone, use a native app. On a desktop with the tab open, it will run indefinitely.
Is the noise looped, and can I hear the loop?
It is a 3-second buffer played on repeat. You cannot hear the seam, because noise is unstructured: there is no melody or rhythm for your ear to lock onto and recognise as repeating. A looped rainfall recording, by contrast, has audible features that give the loop away.