To understand what level of volume should be recorded, you should first get acquainted with some concepts and theory.
Sounds with low and high frequency appear quieter than average frequencies of the same intensity. With this in mind, the uneven sensitivity of the human ear to sounds of different frequencies is modulated using a special electronic frequency filter, resulting in the normalization of measurements, the so-called equivalent sound level.
Obtaining a vocal sound that is ideal for the whole song is one of the biggest problems in the entire mixing process. It takes a lot of practice and a well-sensitive hearing to make the vocals sound great and where it should be. Finally, we must also remember that there are no absolute rules, and if something sounds good, then it is good.
All extraneous noises will be heard on the record. If neighbors make repairs, neighbors swear under the windows on motorcycles or in the stairwell, your listeners will hear it, and it is not a fact that you will notice these noises during the recording process of the release – because you will be passionate about the conversation. You will definitely hear these noises when you edit or listen to the resulting record.
Use the level recommended by your console manufacturer. However, most often it is + 4 dB above the control level. It should be borne in mind that the technical characteristics of the recording equipment are very different. Therefore, a single rule simply exists, there is only a link to the most common technical capabilities of the equipment.
The main judge in recording and determining its quality will, of course, be your hearing. You should believe your feelings. Digital sound editing programs have a function named «Normalization», this is a semi-automatic way to adjust levels.
There is simply no single rule on which volume threshold to start mixing. It is necessary to be guided by your own feelings and experience in the field of sound recording.