2012 Honda Accord Sdn - Many questions

  1. Why is there a sound from one of the fan of the car?
  2. Why my car mileage is not good enough?
  3. While acclerating why is there a sound?
  4. On highway, on a little higher speed why is there a sound?

Fans make noise. Ever hear a propellor airplane? Most of the sound your hear is from the prop, not the motor. Some cars have more than one fan.
Mileage, maybe you expect too much.
On acceleration engine is under more strain and going to higher RPMs, therefore more noise.
Higher speed =higher RPMs.

All in all, maybe a pure electric would suit you better.

Thank you for your response.
On mileage, I am at least expecting 24 or 25 mpg but it seems the car is giving just 20mpg. Any views or suggestions on this? It would be really helpful to me.

Cars are so sophisticated now there is not much you can do other than make sure all maintenance is up to date. At 8 years, depending on miles on your car, May be time for new spark plugs. The temperature gauge usually should be around the middle of ‘normal’ range, if running on the cool end, that will affect mileage. Use TopTier certified gas, check their website for brands of gas. This will help to keep the fuel system clean. Under maintenance—make sure your air filter is clean, I tend to replace mine earlier than recommended.
Other than that, driving techniques affect MPG.

One more thing, tires need to be inflated to pressure indicated on your door jam.
When you replace your tire you can look at low rolling resistant tires, but these may not suit your driving needs.