I am not sure sometimes I hear a quack and some times it just a noise this is our first time with ducks so I guess I dont know the difference may be i can post a short video of the sounds
The drake(male) is a very raspy voicing, the duck(female) is a genuine quack exactly what you'd think of as a quack lol the only video i have is of my calls and they are real loud so a poor comparison...
Here not in English BUT you can hear the raspy undertones of the drakes vs the solid sound of the females..