If you block the inlet on a vacuum cleaner no air can get in - the load on a vacuum cleaner motor is air. With no air to shift the motor has no work to do - runs faster - makes a louder and higher-pitched sound.
Many cleaners have a control that reduces the suction - the issue you have is with the rugs that block the inlet rather than with the cleaner itself - it appears to be working properly.
On a social note you very probably have an issue with the two boys - at their age they should really not be scared of a noisy vacuum - I suspect that they're fooling you and using the noise as an excuse to get out of housework.
Good luck...
April 2015