Mask the sudden crack of the eggshell behind other, gentler noises.
For example, you could gradually turn on the water in the sink, slowly increase the stream until it's a loud (but gentle) hiss, and then crack the egg during that.
The sound should be about the same both in quality and volume, so the eggshell crack won't stand out as a sudden jarring noise.
(Disclaimer: I don't have children, so I don't know if this will be effective or if your daughter will just wake up because of the running water noise.)
lifehacks.stackexchange.com/users/4198/BrettFromLA
I'm a bit late to this question, but there's a solution that's non-technical that seems fairly obvious to me.
If you're able to take a shower without waking your daughter then it makes sense that you should be able to move to a separate room, softly close the door, break the egg, and then walk back.
Then you won't need a convoluted method to break your egg, or have to waste water in running a shower to cover the noise.
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Drill two holes--one on the top and the other on the bottom of an egg and then blow through one hole to push all the stuff from the other (if you can find a needle-pump [check the video], you can do this with one hole).
In this way, not only you make no sound, but you also save the whole intact eggshell for Easter egg decorating.
Keep in mind that most eggs have a air sac at the bottom of them, so it's usually better to blow out the bottom through the top.
I wouldn't say this is efficient, but I assume you are not cracking hundreds of eggs daily.
Other than that, this should be the quietest way of getting an egg out of its shell.
This video might be helpful: How to Blow Out an Egg
lifehacks.stackexchange.com/users/26452/Louie Lee
Crack some eggs the night before, put them in a container, use them in the morning.
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All you gotta do is use a butter knife and lightly hit the egg with it until it cracks enough for you to break it.
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The shell of an egg is predominantly calcium carbonate and will thus dissolve in acid.
There's a common kids experinebt that involves dissolving the shell of an egg in white vinegar to make it bouncy.
Leaving the egg in the vinegar for an extended period also pickles the egg white, making it increasingly rubbery and bouncy You could experiment with different household acidic liquids (vinegar, lemon juice, soda water) to find the time required to dissolve or weaken the shell sufficiently that it breaks silently or cuts with scissors, without being in the acid for so long that it becomes flavoured (though who knows, you may come to like lemon eggs!)
You probably only need to dip one end of the egg rather than immerse the entire thing You could additionally consider changing how you eat it (I'm presuming you fry, or scramble); boiling an egg then rolling it around in the base of the pan, under the water will quietly break the egg shell into fine pieces, squeezing one end then causes the boiled egg to pop out the other - it's a temporary measure; babies sleeping patterns don't remain fixed for long (in a few month's time things will be different).
There may also be periods where she is in a deep sleep and breaking an egg
normally doesn't disturb her.
Sleeping runs in cycles, and my experience is that a child's cycle is about 30 mins long whereas an adults is 45 to an hour.
People are most susceptible to being woken when in the lighter dreaming phases of sleep
lifehacks.stackexchange.com/users/25171/Caius Jard
Sometimes I have to break an egg while my baby daughter is asleep, and since her sleep is very light, the noise breaking an egg usually does (single sharp noise) sometimes wakes her up.  So my question is, how to break an egg silently, without making noise, and yet do it efficiently, without having the shell all mixed with the egg itself?
How to break an egg without making noise?
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lifehacks.stackexchange.com/users/1399/Shadow Wizard is Ear For You
There are a few different ways that you might be able to crack an egg without waking up a sleeping baby. One would be to simply crack the eggs in another room and another could be to mask the sound of the eeggshell behind other gentler noises, such as running water. Other techniques include piercing a hole in the top and bottom of the egg and blowing out the contents, or cracking the eggs the night before and storing them in the fridge. The options are to mask the noise behind a gentler noise, crack the egg in another room, drill holes in the top and bottom of the egg, crack the eggs the night before or soften the shells in vinegar first.
There are a few different ways that you might be able to crack an egg without waking up a sleeping baby. One would be to simply crack the eggs in another room and another could be to mask the sound of the eeggshell behind other gentler noises, such as running water. Other techniques include piercing a hole in the top and bottom of the egg and blowing out the contents, or cracking the eggs the night before and storing them in the fridge. You could mask the sudden crack of the eggshell behind other, gentler noises, or use a butter knife and lightly hit the egg with it until it cracks enough for you to break it. Alternately you could crack them the night before or simply walk into another room, crack them and then return.
Use a butter knife to lightly crack the egg, or go into another room to crack the egg. Alternatively, you could crack some eggs the night before and store them in a container. Eggs can also be pierced at each end, allowing the contents to be blown out. There are many different potential solutions to this problem, including cracking the egg in another room, or masking the sound behind other gentler noises. Alternatively, one popular method is to drill two holes in the egg and blow out the insides. You could also gently use a butter knife to crack the egg enough to break it. Finally, you could consider breaking the eggs at another time of day and then storing the insides in a container for later use.
Mask the noise behind a gentler noise like running water. Take the egg into another room to crack it. Drill holes in the top and bottom of the egg first. Crack the eggs the night before and put in a bowl. Hit the egg gently with a butter knife until it cracks. Dissolve the egg shell in vinegar first.
Mask the sudden crack of the eggshell behind other, gentler noises.   Move to a separate room, softly close the door, break the egg, and then walk back.   Crack some eggs the night before, put them in a container, use them in the morning. Use a butter knife and lightly hit the egg with it until it cracks enough for you to break it.
There are many different potential solutions to this problem, including cracking the egg in another room, or masking the sound behind other gentler noises. Alternatively, one popular method is to drill two holes in the egg and blow out the insides. You could also gently use a butter knife to crack the egg enough to break it. Finally, you could consider breaking the eggs at another time of day and then storing the insides in a container for later use.