What does bit depth determine in digital audio?

Bit depth in digital audio determines the number of distinct values that can represent the amplitude of the audio signal at any given moment. Essentially, it indicates how many bits are used to represent each audio sample. Higher bit depths allow for more precise representation of sound, leading to better dynamic range and lower noise levels, as there are more possible values to define the waveform's amplitude.

For instance, a bit depth of 16 bits means there are 65,536 possible amplitude values (from -32,768 to +32,767), while a bit depth of 24 bits offers over 16 million values (from -8,388,608 to +8,388,607). This rich gradation is crucial in delivering high-fidelity sound recording and playback, which is particularly important in professional audio applications.

The other options do not accurately describe the function of bit depth. While duration, type of audio file, and loudness are relevant factors in digital audio, they are not determined by bit depth. Duration corresponds to the length of the audio clip, the type of audio file relates to its format (e.g., WAV, MP3), and loudness is influenced by amplitude but not directly by bit depth itself.