Bit depth and sample rate are completely separable. If you are recording something important, it may well be worth the higher SR just in case some technology co

Bit depth and sample rate are completely separable. If you are recording something important, it may well be worth the higher SR just in case some technology comes along that can exploit it. But the 20-20kHz bandlimit is a pretty well-entrenched thing. People are working in it. It's tough sledding. So the rule of thumb is that each bit gives -6dB more noise floor. This gives us a rough digital noise floor of -96dB for 16 bit or -144dB for 24 bit. But you can add dither to randomize the digital noise, and turn it into "white noise" or the like. Aliasing is taken care of by the "reconstruction filter" ( named for the "reconstruction" part of the Shannon-Nyquist theorem). This has been a solved problem for some time now. There's a super-high speed digital filter in the DAC phase that can be measured to eliminate all aliasing products. Implementation quality varies, but even cheap stuff now does a good job of it. Yes; it's unusual to have a room for recording that gets to -70dB much less -96dB. -40 to -50 is much more typical for, say acoustic guitar. Noise doesn't add like you'd think; the dominant noise wins, basically. Combined waveforms make for another waveform. They add brilliantly and this isn't lossy at all. There are pathological cases, but they're not likely found in nature. Transducers - headphones, speakers, microphones - all impart much more error than the electronics in the middle.