What is the main difference between LUFS and LU?

• A. LUFS is a relative unit; LU is an absolute unit.
• B. LUFS is the loudness unit with reference to full scale; LU is a general relative unit.
• C. LUFS and LU are both absolute units.
• D. LUFS is measured in decibels; LU is unitless.

Answer: (B)

Loudness measurements differ in what they use as their reference. LUFS uses a fixed reference tied to the full-scale digital level, so it gives an absolute loudness value you can compare across content and set targets for (for example, aiming for a specific LUFS level in broadcasts). LU is a relative unit; it expresses how much louder or softer something is compared to an unspecified reference, without providing an absolute loudness value. That makes LU useful for measuring changes or differences within a given reference frame, but it isn’t directly comparable as an absolute target across programs. So the main difference is that LUFS is absolute (reference to full scale), while LU is relative.