The sound designer work starts in the pre-production of the project and continues in the post-production phase. However, sometimes screenwriters or directors take notes on how they imagine the sound of a certain scene: «bird’s eye view», «melancholic music», «start of rain with thunder».
We can then say that the process is carried out in parallel from the planning of the script.
Talking about film sound design is talking about dialogues, effects, atmospheres and music. The function that covers sound designing is to integrate all these elements in favor of the scenes and give a creative sound sense to the project.
Therefore, it is in the hands of the sound designer and his team* to create a sound world that fully involves the viewer in the film, a world that provides the listener with all kinds of sound experiences.
In large projects and in the post-production phase, the sound designer has the following team: dialogue editor, environment editor, effects editor and music composer.
His/her responsibility is to supervise all the tasks of this team, to make decisions about the material used and how it is used, to propose ideas, to anticipate problems, to set the criteria, to suggest to the director sound approaches for the improvement of the project…
The final decision to all this should be of the director, but a good sound designer will expose and defend his/her argument as an expert, even if he/she does not have the last word.
It should be noted that directors trust the figure of the sound designer; let us not forget that he is a person with trained ears, with analytical listening skills and critical listening.
He is someone who knows how to listen, who is trained and who, apart from having sound creativity, has a broad taste for music, nature recordings and, a broad knowledge of rhythm and silences.
In short
This means that when a video is being edited, small, short sounds are placed representing each thing that is seen. If for example a fast object passes by, a «whooosh» can be added. Sound design is usually done using sound packs that production companies buy.
These sound packs contain hundreds or thousands of sounds of the same theme. For example many types of steps, depending on if they step on glass, grass, there is an echo… So they can adapt the sound to the circumstance.
The best sound designer work should not be noticed. A trailer for example has many sounds, but you can hardly notice anything. It belongs to the moment and exalts the video experience. It adds an extra dimension and keeps the viewer more attentive (improves audio retention).
Depending on the video it is also less or more necessary. For example sound designing is essential in explainers and motion graphics. It would not be so much in a very long social network video as in a TED talk/conference. It is always ideal in any video but it takes work and time, also the licenses for the sounds have to be bought.