Was on sale a few months ago and seemed very popular with OzB users: https://www.ozbargain.com.au/node/258651
For only 20c I'm giving it a go.
Description:
The Official app of Noisli.com - The background noise and color generator for working and relaxing. High quality ambient sounds to help you focus while working and to boost your productivity.
Noisli is mainly used to drown out annoying noises in order to better concentrate and to enhance productivity, or to create a pleasant audio environment for relaxing or sleeping.
You’re working from an open office, have loud co workers and can’t focus? You’re working or studying from home or in a library and nothing gets you motivated? You’re continuous travelling on plane or train and need a quick power nap?
Noisli makes your life a little easier and keeps you sane during long office hours or intense study sessions.
HOW IT WORKS
Mix different sounds and create your perfect sound ambience tailored to your personal need and taste. Activate one or more sounds and adjust the volume slider to create an always different and pleasing sound environment. With Noisli you can boost your focus and enhance your productivity or just lay back, listen, and enjoy falling asleep.
SOUNDS
Rain, Thunderstorm, Wind, Forest with Birds, Leaves, Water stream, Seaside with seagulls and relaxing waves, Water, Fireplace, Summer night with owls and crickets, Fan, rumbling Train, Coffee Shop, White Noise, Pink Noise, Brown Noise.
ALWAYS WITH YOU - OFFLINE SOUNDS
The Noisli app lets you play all of the sounds offline and therefore you can always enjoy its features and benefits also while travelling on a plane or commuting on a train, or during any other activity with no need for an internet connection.
CREATE AND SAVE YOUR WONDERFUL COMBOS
Play and Mix the Sounds together and find your Favourite Combos - Save and Replay them whenever you like.
SYNC
Now you can sign up for a free Noisli account and have your wonderful Combos always in sync on all your devices. A network connection is required to synchronise.
TIMER WITH FADE OUT FUNCTION
With the Timer function you can take advantage of efficient time management methods, such as the Pomodoro Technique, to be more efficient and productive while cutting out distractions and prevent burnouts. Use the built-in countdown timer function during work, study or creativity sessions or simply use it as a sleeping timer for taking a relaxed nap or while falling asleep.
BACKGROUND AUDIO SUPPORT
You can enjoy the wonderful sounds also while using other apps or while surfing the web.
The app is also useful in many other situations, such as help during your meditation or yoga classes, helping with insomnia or to relax before going to sleep, relaxing while reading, reduce stress and relieve anxiety, soothe headaches and migraines or at the spa, during massaging sessions and for parents to help your baby fall asleep. Noisli is also used to mask Tinnitus and to help with ADD and ADHD. With Noisli you can improve your health and feel better.
Didn't know they had an app - I normally use the web version which is free on smartphone and PC, but would have happily paid $2.99 just to support them.