By a stethoscope or a glass.
Termites in wall sound.
The loudest sound termites can make is called head banging.
When disturbed or threatened soldier termites create rattling noises by hitting their heads against the walls of tunnels.
If you hammer a piece of wood with termite galleries inside the sound will be hollow.
The pests use the vibrations caused by these movements to warn their colonies of danger.
Homeowners seldom see termites which in turn live in underground nests and eat the wood inside the walls.
The hollow sound heard when the wood is tapped.
The gnawing and nibbling sometimes can only be detected with magnification e g.
There re many animals beside termites that can make noises in the walls.
However there are ways to detect their presence.
While the first two sounds are physically caused by termites in action the latter stems from hollow voids left in the wood by termites as they eat through your home.