This is a bit ridiculous.

I can count out loud while reading (doing both at maximum speed for each separately). This means that the motor areas in the brain which generate signals to control muscles in my tongue, larynx, etc. compute the right nerve impulses for words 1, 2, 3, 4, 5 .... . This means that they are not computing the nerve impulses for vocalization of what ever I am reading.

Now, if during reading some little signals are present, that can mean all sorts of things. E.g. in a robot that would mean that the power supply's voltage stabilization is not perfect. Unless they actually decode words from the impulses they can't say if its some sort of noise or subvocalization.