If you get noise in the subs after adding an amp + sub when windows are up the issue is from the ANC (Active noise cancellation) see video : 


https://www.google.com/search?q=accord+2021+bypass+anc&rlz=1C1CHBD_enCA904CA904&biw=1920&bih=937&ei=Z3UBYo_5CKipptQP946vOA&ved=0ahUKEwjPyLSNrO71AhWolIkEHXfHCwc4ChDh1QMIDg&uact=5&oq=accord+2021+bypass+anc&gs_lcp=Cgdnd3Mtd2l6EAMyCAghEBYQHRAeMggIIRAWEB0QHjoHCAAQRxCwAzoKCAAQRxCwAxDJAzoFCAAQgAQ6BggAEBYQHjoFCCEQoAE6BwghEAoQoAFKBAhBGABKBAhGGABQ-QdYxSNg4CVoAXACeACAAaMBiAGWCZIBBDAuMTCYAQCgAQHIAQjAAQE&sclient=gws-wiz#kpvalbx=_gnUBYvD2E7KYptQPhbS5qAk28