How to make ringtones louder so that I can hear it in a loud environment?
Though the is a little bit vague in nature, seems a very useful question for a larger community. You can use high pitched ringtones which are very common around the internet.

Also I came across this post at XDA which seems quite useful for you. (did not test them myself  though. even if me or anybody did, the level you require might be different.)

In the Google Play Market, there are apps like Super Loud Ringtones, Loud Ringtones, LOUD Ringtones

You must consider the suggestion made by Shywim as well.