HTC One A9 notification sounds, how can I change the frequency?

[AC Question]

HTC One A9 notification sounds

Hi I have just recieved my A9 everytime I recieve a text or email, the phone gives my selected notification, then every 15 seconds I get a reminder sound to let me know I have a message waiting, how can I change this, both the sound and the notification frequency

many thanks in advance

 

[Roosterman]

If you are using the Gmail app, there is an item "settings" way at the bottom of the menu. For each account listed in General Settings, you can select various options, one being the sound.