How to soundproof a garage turned into a bedroom.?

High-frequency sounds penetrate by air and low frequency penetrates by solid. You need to provide acoustic insulation for both.  In my area, a garage cannot be part of a house unless it already has fire-resistant separation, including an (smoke and) air-tight barrier.  You can suggest that someone look into adding a layer of the necessary gypsum (wallboard) to the ceiling.

Do not add egg cartons to the ceiling (or walls) unless you enjoy the thought of dying in a flash fire, or you have a permit from the local fire marshal for properly fire-retardant interior surfaces.

I just red-tagged an entire house last week for having installed paper-faced insulation upside down in the basement ceiling without any flame-retardant barrier in an unpartitioned room having a propane-powered water heater.  We estimate that the three-story house would have been "fully involved" well before any smoke alarms upstairs went off, if a fire were to start in the basement for any reason.

Back in hippy days, the cheap solution was to staple empty egg cartons onto the ceiling to create a buffer. Depending on the size of the room, you'd have to eat a lot of eggs!

stick some sound proof tiles to the garage wall  or ban cars from the garage !!!

The simplest and surest solution is to use the wax ear plugs designed for swimmers. You can get them at most drug stores. My wife uses them all the time for her day time naps.

you may have to either remove the ceiling and Insulate it w/ sound proofing materials 

OR

Create a drop ceiling and insulate it with sound proofing materials.

Perhaps a padded area rug above will help as well.

The room above needs thick underlay and carpet. That will lessen any noise at source.

You are getting a lot of percussion from the floor above.  It is amplified and transmitted like a drum.  What I would suggest is a second ceiling if you have the head room and putting in some sound deadening materials. To do it right, you should talk to an acoustics company that does such work ( home theaters, music rooms, etc.)  You can also look up such things as "mass loaded vinyl" and get information on the internet.  Now, it is the combination of several sound dampening barriers that will work the best and knowing the combinations for your situation is why you need expert advice.

nothing possible cheaply ..soundproofing batts work well ..but this means existing ceiling removed ..another method is a suspended ceiling below existing ..but i doubt if you have headroom ..your garage conversion was poorly done 

Ear plugs. Get a job and move out.