If you're not a fan of the default iPhone notification sound, you can change it to something more your style. You can even set different notification sounds for specific apps, so you'll know right away which app is trying to get your attention. Here's how:
Open the Settings app on your iPhone and tap Sounds & Haptics. Under the Sound Effects section, tap on Notification Sounds. Here you'll see a list of all the available notification sounds. Tap on the one you want to use and it will start playing. When you hear the sound you like, tap Done in the top right corner of the screen.
Now that sound will be used whenever an app sends you a notification (unless you've specifically changed it for that app). If you want to change an app's notification sound separately from the others, go back to the main Settings page and tap Notifications. Select the app from the list and scroll down to where it says Sounds. Tap on that and then select your desired notification sound from the list.