Breathing is a basic human function, but not everyone breathes effectively, especially during stressful times. By practicing proper breathing techniques, you can reduce stress and improve your body’s overall functioning. Some good techniques to use include diaphragmatic breathing, breathing through your nose, sighing as you exhale, and clenching your fists while breathing. There are also some lifestyle changes you can make that may improve your breathing.
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Water has different acoustic properties from those of air. Sound from an underwater source can propagate relatively freely through body tissues where there is contact with the water as the acoustic properties are similar. When the head is exposed to the water, some sound is transmitted by the eardrum and middle ear, but a significant part reaches the cochlea independently, by bone conduction.   Some sound localisation is possible, though difficult.  Human hearing underwater, in cases where the diver’s ear is wet, is less sensitive than in air.  Frequency sensitivity underwater also differs from that in air, with a consistently higher threshold of hearing underwater; sensitivity to higher frequency sounds is reduced the most.  The type of headgear affects noise sensitivity and noise hazard depending on whether transmission is wet or dry.  Human hearing underwater is less sensitive with wet ears than in air, and a neoprene hood causes substantial attenuation. When wearing a helmet, hearing sensitivity is similar to that in surface air, as it is not greatly affected by the breathing gas or chamber atmosphere composition or pressure.  Because sound travels faster in heliox than in air, voice formants are raised, making divers' speech high-pitched and distorted, and hard to understand for people not used to it.  The increased density of breathing gases under pressure has a similar and additive effect. 
Bodner: The main concerns are the power of the batteries I suppose and the water flow. The batteries are evolving in a very good rate and we don't expect any problems right now. As I said the water flow can be a problem, especially if using open systems, if you want I can elaborate better calculations.
Super, I love this article, thanks for the information.