I have a hidgon swimmer motion decoy. It seams fairly loud to me 25 yrds away in the water. Dose anyone know if drilling a hole in the top and shooting foam inside the decoy would help cut the sound? I don't want to hurt the action of the decoy or make it set weird in the water. If this seems like a good ideal then witch foam would be the best? I like the action of these but that hollow plastic is like a speaker. Maybe tha noise doesn't bother the birds. It's not as loud as as the mojo spinners I've listened to but these are best with very little wind and sound travels well.

Check your pump on the bottom, it may be going out. They will make a racket before seizing up. You can make your own swimmers with old decoys, bjlge pump and 6 volt feeder battery. I used to hunt when the water was calm with just 8 Swimmers and killed alot of Ducks

I've got a couple and haven't had any problems with noise? Is swimmer performing like it should?

No racket like a motor going out they are fairly new. Just the hum and vibration sound of a 800 gph bilge pump.
It might not be an issue. Just thought if I can hear it the ducks could. I don't have another one to compare it to.

The new pumps are loud. I noticed it also when I got a new one

Thanks Jeff. If you are hearing that noise at 25 yrds do you think that would scare circling birds? Thats why I was wondering if putting foam would muffle the pump noise?