Perceived-loudness matching often needs separate listening tests to achieve

Evidence

The effect of loudness should typically be avoided in the tests, and equal loudness should be produced by the listening test signals. Depending on the case, the task may be simple or complex. In some cases, the equalization of the signal energies may be sufficient, while in others no computational metric available is sufficient, and separate listening tests have to be organized to set the perceived loudness levels to be equal. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 867

Categorization

• DEFINE: Distinguishes physical equal-loudness from perceptual equalization — a key methodological distinction.
• XREF: connects to: A human listener is needed to connect objective sound pressure with perceived loudness — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 650