If you’re bored of your default notification noise, you can change it very quickly. To change Gmail notification sound iPhone, first, opens the Gmail app on your iPhone device and tap the three bars at the left. Then, scroll down to “Settings” and tap it. Select the email address you use from the list that appears. Then, scroll down to “Inbox Notifications,” then tap “Sound” and change the notification to a sound you find more pleasing.
Read also - Why is my Gmail Not working