On C9Trader Stratus, each button has its own volume slider. Hover the mouse over the button you wish to adjust the volume and adjust the volume slider accordingly (Figure 1):
Figure 1 Volume slider
On the CloudHub, press Volume Mode and adjust the individual button volume for the Shout Down connections by pressing the right and left keys on either side of the Shout Down (Figure 2):
Figure 2 Volume Mode
Select Previous or Next to view more buttons and adjust as required.