Ive Been Planning This Garage Studio for 10 Years!

[gullfo]

the example has a simple turn versus a "twisted path". technically, simply blocking a direct path should be enough - but - if you have noise in the system (machine, other rooms etc) then the extra turns expose more insulation to the flow and thus more opportunities to attenuate it. otherwise if the system is quiet, little or no adjacent noise, and the air flow is slow, you can often use less "silencer", then if you're routing the air through a ceiling soffit + plenum, the amount of noise is also attenuated in the packing around the flex (or hard) duct.
as a general principle, i use duct board whenever possible - it has many benefits of both a hard duct and flex duct in terms of attenuation, air flow, some blocking. of course it's also pricy compared to flex duct, but often is the same or less than duct liner simply because more of it's used by hvac professionals vs duct liner.