I was given one of these as a baby present. .. see pics. It's a giraffe with in built sounds on a timer. 45 minutes. My daughter had right from birth. ..to hospital stays/surgery...everything. even the sleep specialist we see at the children's hospital suggested one for her..but she did say use it on all night.
We had az second sleep sheep on pram/in car.
Even recovering in PICU from surgery the white noise sound helped to calm her.
She doesn't use it anymore. ...but she does have a light up teddy bear that plays music. We taught her to turn it on and off herself so if she Wakes in the night she can turn it on to go back to sleep.