Thanks guys! Terry, this is the set I bought which does say the DDC will control the speed, direction and lighting of two decoder-equipped locomotives. It does not mention sound even though the box says it does control sound. Thanks again

https://www.walmart.com/ip/Bachmann-Trains-Digital-Commander-HO-Scale-Ready-To-Run-Electric-Train-Set-With-GP40-and-FT-Diesel-Locomotives-Santa-Fe/37288551#read-more

I recently purchased the Model 501 GP40 and FT Diesel train set. The box states it has locomotive sound but I cannot find a function code that turns it on. Lights are F10 and work fine.
Can anybody tell me how to turn on he sound?