The scientific name for the pitch in this image is B4. Scientific pitch is a way to define the specific frequencies of particular pitches as they are designated and written in text, and is often used to specify the range of an instrument in textual notation, rather than frequency.
The first part of the name, B, refers to the traditional tone, or musical note, name (A to G). The second part of the name, 4, describes which octave the tone is part of. So in this diagram, the tone of the pitch is B, and it is in the fourth octave.