In psychoacoustics, loudness is a subjective perception of the intensity of sound. It is often described as the "strength" or "power" of a sound and can vary depending on factors such as frequency, duration, and background noise. The equal loudness curves represent the response of the human hearing mechanism as a function of frequency and loudness levels. The loudness level corresponds to [[sound pressure level (SPL)]] measured in [[deciBel]]s (dB), with higher dB levels indicating a louder sound. However, it is important to note that two sounds with the same dB level may not necessarily be perceived as equally loud by all listeners, due to individual differences in hearing sensitivity and other factors. The [[threshold of hearing]] for a frequency near 1 kHz is close to 0 dB SPL. ![[Lindos4-equal-loudness.svg]] Source: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Lindos4.svg) A pictorial representation of the loudness of different sounds: ![[pictorial-loudness.png]] The following pulses of different frequencies have the same intensity but are perceived with a different loudness. ![[constant-spl.wav]]