Academic articles are typically about abstract concepts interacting with observations, or other abstract concepts: the author does not play any role in the interaction, and the style of the language should reflect this. Hence, traditionally the role of the author in the study is downplayed by the use of an ‘impersonal tone’.
As the name suggests, this tone focusses on impersonal agents and obscures the ‘people’ involved in the research. For example, greater use is made of nominalisation and the passive voice. Compare:
- 1) I added the solvent to the substance.
- 2) The solvent was added to the substance.
- 3) The solvent dissolved the substance.
Sentence (1) talks about you as a researcher, number (2) focusses what you did (while obscuring the fact it was you) , while number (3) says what happened – you played no role in the process. Generally, speaking in the hard sciences, you should try to favour the style in (2) or (3) – or rather, the second two styles should be favoured. Or the best choices are (2) and (3).