Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
sounding board n (MUS) де́ка
to use sb as a sounding board for one's ideas проверя́ть (прове́рить perf) свои́ иде́и на ком-н
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.