If a picture is worth a thousand words, then a clip of audio must be worth at least a million. Here's the audio, by a newly-starting Audio Masterclass student, his diagnostic piece for analysis…
The recording is very good in many respects. The mic is a Rode K2 by the way – a true large-diaphragm mic. The student comments that he used an sE “vocal booth”, by which I assume he means the sE Electronics Reflexion Filter, which has achieved a certain level of popularity.
Now I have nothing against this device. I'm a firm believe in 'every little helps' and that small improvements in one's recording setup can lead to very useful improvements in audio quality.
However, the problem arises when people think that devices such as this can work miracles. To be fair, working miracles is nowhere to be found in sE's sales literature. But sometimes expectations can get carried away.
This device can help improve the dryness of a recording. A dry recording without ambience is always easier to work with than an ambient recording. This is most significant for speech and popular music vocals, and almost anything recorded in a small room.
Since much of the mic is surrounded by a sector of a kind of a Dyson Sphere, then ambient sound from these directions is attenuated. Some ambience will remain from parts of the mic not surrounded by the filter.
But noise is trickier. Noise will find a way around any barrier. Only if a barrier is totally surrounding, with no leakages, will noise be reduced to a truly significant extent. The sE Reflexion Filter can reduce ambience to a useful degree. Against noise it is less effective.
In this clip we can clearly hear the fan of the MacBook Pro used to make the recording. Basically, the computer needs to be in another room – that is the only complete solution.
You could ask the question why the filter should be better with ambience? After all, ambience and noise are both sound. How can the filter affect them differently?
The answer is that the ambience is to an extent masked by the direct sound. In contrast, during gaps between words, the noise isn't masked at all.
In summary, whatever you can do to control both ambience and noise is worthwhile. But miracles, well if they really did happen there would be a tax on them, wouldn't there?