When i set my alarm on my iphoneX it rings loud once then go very quiet. I want it to remain loud all the time

Go to Settings>Accessibility>Face ID & Attention and turn off "Attention Aware Features".

Hello patriciafromprescot, 

Apple Support Communities is a great place for help with the

alarms on your iPhone X. You mentioned the volume of the alert decreases. Does

this continue to happen if you change to a different sound? Also, have you

tried the steps outlined in the section titled If the alarm volume is too low

or quiet in the following article? 

How to set and change alarms on your iPhone

If not, complete the steps outlined there as they may help with

resolving this issue. If the issue continues, the next steps would be restarting

your iPhone and updating iOS if needed. Those steps can be found in the

following articles.

Restart your iPhone

Update your iPhone, iPad, or iPod touch

Let us know how that goes!