Mine is not making the croaking sounds BUT thank you for asking WHY is "YOUR" sink=The reason mine does not make that sound is my venting is working properly and the drain lines have been water jetted a few years ago to establish full flow=
Many species of frogs and toads make rough, croaking sounds. There are also some birds, amphibians, and fish that are also capable of making similar sounds.
they have a sound sac in their throats
frogs and toads possibly burping
Egrets make croaking, gutteral sounds. As do most other herons.
Some fish make croaking sounds at the surface. Lol nice. {I'm the chick who asked this.} ^_^ I was bored.
Secretary birds are usually silent, but when displaying they will make a horse croaking sound, similar to wood being dragged over a wash board. They can occasionally be hear making mewing sounds at night.
One of the sounds a crane makes is like a low pitched frog croaking. The other sound it makes sounds like a group of sea gulls crying.
A frog gig will usually stop them from croaking.
They make very guttural croaking sounds and are sometimes mistaken for frogs. http://www.birdnote.org/birdnote-transcript.cfm?id=106
Probably because it draws/absorbs the heat making the heat "sink" into it
The great blue heron makes a gutteral, croaking series of sounds. Starts as a whining like screech, then descends to a "frahnk' sound.
The silence that surrounded the pond was only disturbed by one croaking frog.