How loud should a singer sing?
Sometime in the late 1960s, many singers found that they could get a rough, raw edge to their vocals by singing loud. Very loud in fact - as loud as they possibly could. This idea has persisted right up to the present day. But is it always the right thing to do, even in rock music?
One thing is for sure, if you sing loud for a long time, you will get a rough and raw edge on your vocal chords. This, to protect the writer from lawsuits, is not recommended. However, if you do this often enough, your vocal chords will become rough and irregular and this will indeed give your sound an 'edge'. It could also result in the total loss of your singing ability.
But singing louder doesn't necessarily make a 'bigger' sound. It doesn't even make a louder sound since the engineer will have to turn down the level to compensate. Often what happens is that the sound merely becomes thinner, and tuning often suffers.
Rather than singing louder, you can get a fuller sound by opening up the airway and singing with a wider passage through the vocal chords. With practice, a thin voice can be turned into a full 'fat' sounding voice, without having to sing louder. And without the physical risk that singing too loud incurs.
In any case, don't worry about the microphone. Dynamic mics, of professional quality of course, can handle all the level you can throw at them, and condenser mics usually have a 'pad' that can be switched in to prevent distortion.
Away from the topic of popular music, spare a thought for the poor old opera tenor. The female soprano opera voice is the loudest sound that humans can make. And he gets it right in the ear during the love duet!