Why is my sofa making funny noises?

Yes, you are feeling (and hearing) the cardboard used in the arm. 

There is no evidence of a defect in your sofa that would trigger a manufacturer’s warranty, but you should complain anyway.

Pressing and releasing loose cardboard to hear the knocking sound can be addictive to some people and annoying to others.

It is not unusual for sofa manufacturers in this price range to use cardboard on the arms.

• It is also not unusual for furniture purchasers to experience exactly what you have described.

• Don't be surprised if you get the same sound eventually from the other arm.

The use of cardboard is a common cost-saving technique used in lower priced sofas. Cardboard is cheaper than cotton batting or meshed fabrics combined with foam, which is commonly used on more expensive seating.

Another cost saving technique is minimizing the amount of wood used in the arm. 

• Low cost sofas and chairs may have a sizeable gap (empty space) between the wood sticks or boards that make up the arm frames.

• Cardboard sheets, over the framework, can sometimes be pushed into the gap, resulting in the noise (and feel) you have described.

Cardboard covered arm frames may also have gaps at the top.

• The cardboard may be the primary support at the top of the arm.

• If someone sits on that arm, it may not be able to bear the weight. 

The repair procedure for this type of problem is described by The Furniture Specialist.

Technically, there is no defect. That's just the way your sofa was designed and built. Modern mass produced seating often cuts  costs in all the places you can't see.

If your sofa is new, the retailer may agree to have the arms reinforced to eliminate the annoying noise.

• If you are offered a choice between repair or replacement, choose repair.

• If the sofa is replaced, it will still have the same construction. Eventually, you may experience the same problem.