Which unit is used to express integrated loudness per ITU-R BS.1770?

• A. LU
• B. LUFS
• C. dB
• D. Phon

Answer: (B)

Integrated loudness from ITU-R BS.1770 is reported in LUFS, which stands for Loudness Units relative to Full Scale. This unit choice matters because BS.1770 specifies a method to weight and average audio over time to reflect how loud something sounds to human listeners, and it uses LUFS as the reporting unit. The plain unit LU is simply a generic loudness unit and can be ambiguous without a reference, while LUFS explicitly ties the measurement to a full-scale reference, giving a standardized, comparable value such as -23 LUFS for a program’s integrated loudness.

Decibels (dB) describe a relative level in a signal, not the standardized loudness measurement defined by BS.1770, so they’re not the accepted unit for integrated loudness. Phon measures perceptual loudness at a specific frequency, but it’s used for comparing loudness sensation across frequencies, not for the BS.1770 integrated loudness value.