Volvo B9TLs sound I don't think it would be clear, if you sit
below, you will be able to hear the aircon sound...
MBO405, N113CRB maybe OK, some plys on low demand svc.
For MK2, maybe can try taking 103W, some ppl said that the demand
only 4, maybe can try.
VO3x, MK3, MK4 maybe can try svc plys on the 'forested'
area(Thomson, Lornie), may not have high demand but may not be very
clear because of the TVMoblie.
Dennis Trident can try on the non-peak hour, maybe svc 89, not many
ppl.
I am not sure about the demand for SMRTB, never go care and also
never take the bus frequently.