> I wonder why this sort of vibration can't be addressed with shock absorbers in the seats?
Not at all naive, because it is addressed with shock absorbers in the seats; that is one of the very many tools NVH engineers use. :) But they're not 'shock absorbers' in the way you're thinking; the actual foams used in the car seats are specifically designed and selected to dampen certain frequencies. But, kind of like a speaker or headphones or even ear plugs, the dampening happens over a spectrum, and in general our organs resonate at lower frequencies, which are harder for foamlike materials to dampen.
NVH engineers view the entire road-vehicle-driver system as a huge, complex, spring-mass-damper system, and do a whole ton of partial differential equations to solve for the outputs.
Edit to add: so why not use traditional 'shock absorbers', the spring-damper kind that you're used to seeing? For passenger vehicles the answer is weight and complexity. But many trucks and tractors and so on do in fact have these.
Not at all naive, because it is addressed with shock absorbers in the seats; that is one of the very many tools NVH engineers use. :) But they're not 'shock absorbers' in the way you're thinking; the actual foams used in the car seats are specifically designed and selected to dampen certain frequencies. But, kind of like a speaker or headphones or even ear plugs, the dampening happens over a spectrum, and in general our organs resonate at lower frequencies, which are harder for foamlike materials to dampen.
NVH engineers view the entire road-vehicle-driver system as a huge, complex, spring-mass-damper system, and do a whole ton of partial differential equations to solve for the outputs.
Edit to add: so why not use traditional 'shock absorbers', the spring-damper kind that you're used to seeing? For passenger vehicles the answer is weight and complexity. But many trucks and tractors and so on do in fact have these.