Is there any reason one should not whisper davening (besides shemoneh esrei)? Meaning as opposed to actually speaking it out loud?
What about bentching, brachos, or any other tefilos? Is it preferable to say it out loud or is whispering fine (as long as you can hear your whisper)?
Often, others nearby might be distracted if one actually says the words out loud. Is this a consideration?
Finally, if one is going with the m’haleich of saying Shnayim Mikrah together with the Baal Koreh on Shabbos, may one whisper this as well?
Whispering is fine, unless there are others who will want to say amen to your berachah, so that it is best to speak it out.
In shul, this matter depends on the custom and atmosphere of the shul in question. There are some places where many speak out the words, and therefore doing so does not amount to a distraction. However, there are places where most people are quiet, and speaking out the words can be distracting for others, so that it is better to whisper. This is certainly a valid consideration.
One may whisper shayim mikra with the ba’al korei, and many do so. However, in this case it is important that others should not hear you, for they should hear the ba’al korei alone.