Phon Scale !full! May 2026

Author: [Your Name] Course: Psychoacoustics / Fundamentals of Acoustics Date: [Current Date] Abstract The perception of loudness is a subjective psychological phenomenon that does not correspond linearly with physical sound pressure level (SPL) measured in decibels (dB). The phon scale was developed to quantify this perception by equating the loudness of any sound to a reference 1 kHz tone. This paper reviews the historical development of the phon, its methodological foundation in equal-loudness contours (Fletcher-Munson curves), and its relationship with the more modern sone scale. While the phon successfully accounts for frequency-dependent sensitivity of human hearing, its limitations in representing non-sinusoidal and complex sounds are discussed. Understanding the phon scale remains fundamental for audio engineering, hearing conservation, and the design of auditory alarms. 1. Introduction Human hearing is notoriously nonlinear. A 50 dB SPL tone at 100 Hz sounds much quieter than a 50 dB SPL tone at 2,000 Hz, even though their physical pressures are identical. To create a metric that reflects how loud a sound actually appears to a listener , scientists introduced the phon .