wah-wah
Concise Oxford English Dictionary © 2008 Oxford University Press:
wah-wah /ˈwɑːwɑː/ (also wa-wa)
▶noun a musical effect achieved on brass instruments by alternately applying and removing a mute and on an electric guitar by use of a pedal.
■ a pedal for producing such an effect on an electric guitar.
– origin 1920s: imitative.
'wah-wah' also found in these Oxford entries:

