phones come with a lot of factory ringtones, notification tones and alarms, but this may not satisfy you. All-Ringtones.com provides various sound effects such as boing sound effect https://notification-sounds.com/54-boing-sound-effect.html in MP3 format. Feel free to use any sound, but keep in mind that the notification sound shouldn't be too long if you don't want it to get heavy. For ring tones or alarm tones, you have more options.