Voith superlion.
Total and utter misinformation, the SMRT MAN
NL323Fs (A22) are powered by the twin-stage turbocharged (different
from being twin turbocharged) MAN D-2066
LUH-32 engine with a 6-speed ZF Ecolife 6AP 1700B, and
not with a Voith transmission. The whistling comes from the
twin-stage turbochargers of the D-2066 LUH-32 engine, which is very
prominent (and lovely). Other turbocharged buses such as the O405Gs
have whistling too but they sound different and much softer.
