What is the "wha" sound when you cover, uncover quickly your mouth,ears, or a speaker? I guess does it cause a doppler effect to sound? I have no idea what's going on
 A: These may not be just one thing.
If you uncover your ear you are almost certainly physically deforming your ear and creating pressure on the skin which may be generating some noise, and that close to your inner ear you'll notice tiny noises.
Uncovering your mouth to create that sound requires that you (again) be in contact with your skin and may be generating some low level noise (vibration) which is passed to your inner ear.  You may also be generating some rapid (but small) air pressure change which you can hear.
To consider possible causes try blocking and releasing at different speeds and with different force.  Even the very slightest rubbing of your ear will be audible to you.
Uncovering a speaker is likely to create a transient noise (if the speaker was active) or may simply be a pressure release (again depending on how you compress the air in the first place).  As speakers are designed to generate sound based on the vibration of the material, any sudden vibration you cause in the material could cause sound.
@Asher's comment about air rushing past your hand.  Yes you can probably hear this, but be careful to think about what you're actually hearing.  If you use a small rigid object to rapidly pass it near your ear without touching your ear, you will hear the air.  If you do with with you hand you may note that you'll detect other noises sometimes, which can be the physical contact of different parts of your hand with themselves.
A few quick experiments with a handy hand and ear (mine) suggest that just air movement is going to sound like a "woosh" (sort of no surprise there :-)) whereas a "wha" sound seems to require contact between surfaces and is a result of friction and/or physical deformation of something.
A: I might be misunderstanding your question, but to me it sounds (no pun intended) that the 'wha' you are referring to is purely from the sound that goes softer and softer as the thing blocking the sound blocks more sound from you ear and then harder and harder again as the thing blocking the sound blocks less sound from your ear. Thus, Creating a sense of an 'oeh' (on blocking sound) 'Wha' sound (on unblocking sound). 
Is it this 'Wha' you are referring to?
