The linguistic resource being used is the metaphor.
Explanation:
The metaphor is an explicit comparison between two elements that have a strong similarity, which can be used in a poetic way by intensifying a meaning. An example of this can be seen in the text shown in the question above, where the author uses the metaphor to show how the audience was concentrated, but without showing emotion, when observing something, as well as a meaningless face staring at a place.
