Thanks for the easy medals.
You may want to put the audio file into an editor like WMM and lower its volume by at least half. The jump sound is fine. Though you may want to not have it play while in the air. And a mute button is always a good idea to have.
You should also consider expanding your game and adding upgrades and increasing the height significantly (Not physically but virtual height the camera can follow as you go higher) so you can have upgrades like higher jumps, a mid air jumps, faster coin spawns, better coin spawns (Adding high value coins). Things like that, it could significantly add to your games play length. Especially if you lower the value of the blue coin to 5 and take coins away when you purchase upgrades. The medals will give people a harder goal to get to the million coin medal. You could even add more medals this way depending how far you go with the upgrades. A gradual despawn would make things even harder if people can't just sit and wait for coins to flood the map.