agreement in these sentences

she felt someone touch her shoulder.
they heard the dog bark in the middle of the night.
why should touch and bark??????????not barked??????
please help me to explain sentences above!!!!!!!!!!!!!!!!!!
thanks very much

“Felt” and “heard” in your examples are SENSE verbs. Sense verb has a 2nd actor (verb in the same sentence) which appears with a bare infinitive (infinitive without the “to” marker).

In “ She felt someone touch her shoulder,” “touch” is the 2nd verb, the infinitive. “Bark” is the infinitive in “they heard the dog bark in the middle of the night.”

Infinitive or the 1st auxiliary of an infinitive phrase must always be in its base or root form: “touch” not “touched”; “bark” not “barked”.

Some other verbs of sense are: see, watch, smell, seem & etc. The other group that shares the same characteristics is called the CAUSATIVE verbs and they are, for example, make, have, let, & etc.