Many students want to know whether to buy an acoustic or digital piano, so I thought I'd summarise my thoughts here.
An acoustic piano has weighted keys - in other words it takes approximately 53 grams of weight to put down a key. There is also something called an escapement. You can find the escapement by slowly pushing a key down and feeling the point of friction (a little bump). This is where sound is made and it is approximately 2/3rds of the way down the key.
A digital piano almost always has weighted keys these days as well as many other functions such as different instruments, volume, metronome and sometimes fancy functions such as recording utilities, MIDI in and out, USB in and out and of course a headphone jack.
A digital piano does not have an escapement, which means that the point of sound occurs at the bottom of the key (the key bed).
If the digital piano and keyboard makers could make this one change - that is, that the point of sound was not made at the bottom of the keybed - then I'd have no concern about recommending students buy a digital piano.
However, since they do not, my preference is that students work on acoustic pianos. Aiming and playing at the bottom of the keybed, causes an impact back up the arm which over time can be a cause of pain and injury. I see it a lot in jazz, cabaret and musical theatre pianists who have to work on keyboards as part of their job.
The other thing is that digital pianos do not have the "ring" of the strings and students do not get to experience exactly how to create a beautiful, full and rich sound on a keyboard as they do on a piano.
That being said, I do understand that noise can be of concern, especially when living in an apartment. To this I say that if your child does become serious about playing the piano, learning long term on a keyboard is not an option, but might suffice for the first few years.
If you are going to buy a digital piano, make sure you do the following:
* Don't purchase anything too expensive. The expense is always the frills and extra functions that you will not need
* If I had to state a preference for digital pianos, I'd go with a Yamaha or Technics keyboard
* Note that the more expensive models do not sound any different
* Invest in a good set of headphones. This will make a big difference to the sound quality