If you want the birds to go down to the lower floor of your farm you should try using the DIY Pvc Bazooka. It is very effective, point 45 dg angle place it at the Inter hole towards direction of the birds flying in. You can make it yourself and save money.
You could use with the external sound to guide them into the lower floor but make sure the volume is not too loud. Otherwise it would make the internal sound ineffective. Subsequently you could also use with the internal sound.
The best is to have 2 bazooka at the inter hole. You would see the different within few weeks. I have used it in my farms and it is very good. Many of my readers are using it.
Don’t forget get those thick PVC pipes because the sound rebound from a more solid surface would produce better sound.
Cost less than Rm 20.00 to make one.
Good Swiftlet Farming All. The BEST is to Share Not Envy!