Regarding the sound, it is good or even very good. I do not know if it is good or not, I just know he's good, he does his job. Clear, clean, no burrs, that's all we can ask and it runs well.
On the outer insulation, it is okay. I must say that I expected a further insulation coat. But it still remains in a quite good performance, which will also help to understand the different elements around us and hear the still, which is a good thing when driving in public transport or even pedestrians (crossing the road, etc.).
The main negatives are the noise made by the cord when walking (it is clearly heard in the ears and it is very unpleasant), and the fact that it is difficult to put it around the neck and continue to walk normally without seeming a robot: that is, you can not keep it around your neck long.
In summary, a very good helmet, which given its price represents an excellent investment. Surely not a professional helmet, but at approx. 35euros, this is normal. Moreover, if you just search a headset to listen to music or watch movies, pro quietly without use, then this headset is definitely worth. One also for the presence of the storage pouch for easy positioning in a bag, and protects quite well.