is ABSOLUTELY necessary to record at 48 kHz that's not for film where the final audio will be bounced to 44.1 format anyway?
We know that at 44.1kHz we can accurately record and playback the frequencies that live in the human hearing threshold, so oversampling might seem an overkill. Most of the time this is the case, but some scenarios can benefit from higher sampling rates.
Ask yourself these questions:
Are you recording and/or working with ultrasonic frequencies? (above 20kHz)
You already knew this if you know about the Nyquist Frequency and Nyquist Rate.
A kind of exotic scenario, but it happens. If you are recording a sound that has frequencies (fundamental or overtones) above 20kHz, you need a higher sampling rate, which must be double the highest frequency you'll sample.
Even if you'll bounce at 44.1kHz, you might want to record ultrasonic sounds and then lower the pitch to a frequency range that 44.1kHz can handle.
Will you use a process that benefits from working with oversampled audio?
My DSP knowledge is very poor, so I need confirmation on this one. Is there a process that can benefit from working with oversampled audio? I don't know of any.
I know there are processes that benefit from working at higher sample rates (more on that later), but I'm not sure about the benefits of processing oversampled audio (which is not the same).
My first thought was about processes that use granular synthesis (like elastic audio). It at first makes sense that these would benefit from more resolution for the grains, making time and frequency manipulation smoother, but it might not be the case.
Anyway, if you find yourself using a process that can benefit from working with oversampled audio (if there's not such thing right now, there might be in the future, who knows), then that's a good reason to record at higher sample rates.
Will you use a process that benefits from working at higher sample rates?
Here's what I do know: some processes benefit from working at higher sampling rates. Some processes do the oversampling internally, though. To justify working at higher sample rates here, you would need to be working with a process that benefits from oversampling, but doesn't do the oversampling itself internally.
From article The Science of Sample Rates:
When you go beyond the mere recording and playback of sound and into the world of digital signal processing, it becomes clear that higher sampling rates actually can help. But the solution might be a different one than you’d expect.
When it comes to some non-linear audio processors like a super-fast compressor, a saturator, a super-high-frequency EQ, or a vintage synthesizer emulation, oversampling can be a major benefit. This in and of itself might seem like a great excuse to immediately jump up to 88.2 kHz or higher.
But not so fast: most plugin designers, knowing this full well, have written oversampling into their code. Even in a 44.1kHz session, plugins that benefit from oversampling automatically increase their internal sampling rate. To gain the full benefits of this, it’s important to note that the audio doesn’t have to be recorded at this higher sample rate, it’s just the processing that must happen at the higher rate.
So unless you are using plugins that have taken shortcuts and neglected to include oversampling in their code, then converting an entire audio session to a higher rate would make your mix take up more processing power without adding any sonic benefit.
Very few of the latter still exist. And thankfully so, because oversampling has led to huge improvements in the quality of digital processing. Finally, after decades of people trying, there are actually some software compressors that I like. A lot.
So, in short, it's only absolutely necessary to oversample if you plan to record and work with ultrasonic frequencies. It's not necessary but can improve your results if you find a process that can benefit from either oversampled audio or working at higher sampling rates (that doesn't already perform the oversampling itself internally).
These 3 are the only oversampling justifications I can think of in a recording, mixing, mastering, production, and processing context. Can anyone think of more?
Interesting articles on the subject: