Sound measurement has shifted from flat physical scales toward human-perception-weighted scales

Evidence

Just as the notation of music is now being replaced by the record player, the tape recorder is pushing the physical study of acoustics into the human area of psychoacoustics. And for general field work in measuring the intensity of sound, the flat response of the sound level meter (the so-called C scale) has given way to the contoured A scale, weighted along the lines of the equal loudness contours of the human ear. Similarly, the numerous refinements in measuring aircraft noise in recent years have tended more and more to take human response into consideration. Thus EPNdB (Effective Perceived Noise in Decibels) takes into account the particular tone components of aircraft as well as the duration of the noise, while NNI (Noise and Number Index) uses the EPNdB as a basis and additionally calculates the number of aircraft per day (or night) as a key annoyance factor. — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 440

Categorization

• DEFINE: Defines the C scale, A scale, EPNdB, and NNI measurement conventions crucial to cataloging soundscape intensity.
• QUESTION: Worth chasing which specific equal-loudness contours the A scale was weighted along, and how NNI handles night weighting.
• corroborated: 2 independent passages support this claim — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 440
• XREF: connects to: Perceived loudness and physical sound intensity follow different, non-intuitive mathematical scales — George Michelsen Foy, Zero Decibels: The Quest for Absolute…, 53; Human hearing perceives huge physical sound intensity changes as barely different — George Michelsen Foy, Zero Decibels: The Quest for Absolute…, 97; Human ear and voice are the standard modules for measuring soundscape — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 674 (+9 more)

Broader Connections

• Perceived loudness and physical sound intensity follow different, non-intuitive mathematical scales #expands (0.85) — George Michelsen Foy, Zero Decibels, 53
• Human hearing perceives huge physical sound intensity changes as barely different #exemplifies (0.80) — George Michelsen Foy, Zero Decibels, 97
• Human ear and voice are the standard modules for measuring soundscape #expands (0.65) — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 674