No single loudness meter can capture subjective loudness of varying program material across environments

Evidence

There has been a long quest for a perfect “loudness” meter that yields a single number perfectly representing the subjective loudness effect of any sound, as heard in any environment. The practical problem is that music, movies and mixed broadcast programs are not stable. The sounds continuously change in bandwidth, spectrum, level and transient/temporal structure. If we add the psychoacoustic complications of loudspeakers with different frequency responses and directivities located in different rooms, at different incident angles relative to listeners, at different distances, the situation becomes much more complicated. It is important to examine what matters and what does not matter. Even though the perfect solution may not exist, we do have measures that permit us to achieve our practical needs. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1172

Categorization

• DEFINE: Establishes the core challenge of loudness metering: signal non-stationarity compounded by listener-environment variability, the motivating problem for everything that follows in this chapter.