Dark Noise 3.0
The free version of Dark Noise includes eight sounds, continuous sound looping, Shortcuts support, Siri integration, and a timer. The Pro subscription increases the number of sounds to over 50 and adds custom sound mixes, alternate app icons, themes, and Family Sharing. The Pro features are also available as a one-time purchase.
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There are a lot of ambient sound apps on the App Store, but a lot aren’t very good. Dark Noise is excellent, and I expect having a free tier to show off what the app can do to new users will result in more paid users in the long run.
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Version 3.0 also introduces remastered Rain, Beach, Airplane Interior, and Thunderstorm sounds that sound better when used with stereo speakers.
I have been using Rain Rain for years, and both iOS and macOS now have built-in Background Sounds, which can be triggered from Control Center or Siri.
Update (2023-04-06): Craig Grannell:
I’ve long used White Noise+, with its straightforward mixing desk layout and one-hit price.
It’s easy to miss, but iOS and macOS both have this built in. On iOS, go to Settings ➙ Accessibility ➙ Audio/Visual ➙ Background Sounds (you can also add this to Control Centre). On macOS, go to System Settings ➙ Accessibility ➙ Audio.