How many times per second audio gets digitally measured — 48 kHz is broadcast/film standard, 44.1 kHz for stereo CD. Higher rate captures higher frequencies.
Sampling Rate
On set, you quickly realize: the sampling rate determines which frequencies you can capture—and whether your sound can later be converted to other formats without issues. 48 kHz is the standard in professional film because the Nyquist theorem states that you can capture all audible frequencies up to 24 kHz with it. That's more than enough for the human ear. If, on the other hand, you work with 44.1 kHz (CD standard), it will work, but you'll force yourself into conversion problems later—and syncing with picture becomes critical because film timecode is based on 48 kHz.
In practice: Your recorder (Sennheiser MKE 600, Rode Wireless, any device) runs at 48 kHz, your mixer does too, your Final Cut Pro project does too. Everything harmonizes. If you need higher sampling rates later—for example, 96 kHz for immersive audio or Hi-Res projects—you do that consciously at the beginning, not as an emergency conversion. Because downsampling (from 96 to 48) works elegantly, upsampling (from 44.1 to 48) creates artifacts that will annoy you in the mix.
A common mistake: You think higher rate = better sound. That's not true. 48 kHz with a clean recording always beats 192 kHz with a bad preamp. The rate is an infrastructure decision, not a quality guarantee. What counts is the bit depth (usually 24-bit) and the microphones/equipment before it. Nevertheless: If post-production or deliverables demand 96 kHz, you need it from the start. When in doubt, ask early what sampling rate the editing suite needs—usually 48 kHz, sometimes 96 kHz for premium productions or surround mixes.
Synchronization tip: 48 kHz is coupled with the timecode logic of DCP and broadcast. If you start with 44.1 kHz, you'll be calculating yourself to death later. Saves you trouble: be consistent from the start. And yes, modern NLE software converts automatically, but a sample rate mismatch costs processing power and exacerbates sync problems during export.