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Fletcher Munson Curves, Equal Loudness Contours, What Are They And How To Use Them For Better Mixing

The Fletcher-Munson Curves
More commonly known as equal loudness contours.

Human hearing is a bizarre and magnificent thing. The section of psychophysics that deals with the way we perceive sound is psychoacoustics, it is where one would look to gain a better understanding and knowledge of how and why we hear as we do. When producing music as a sound engineer or hobbyist you should really familiarize yourself with how the ear deciphers sound to ensure the resulting production brings a clear and pleasant listening experience to your audience. Keep in mind our perceptions of sound are usually much different from what actually exits the speakers. Equal-loudness should be incorporated throughout the mix, which was first laid out in the Fletcher-Munson curve.What is a Fletcher-Munson curve?Harvey Fletcher and Wilden Munson were American physicists in the 1930’s. The two of them were the first to experience this psychoacoustic phenomenon. Through they’re combined efforts and extensive research, it was concluded that we perceive frequencies as louder or quieter when the actual amplitude of the sound is adjusted. The Fletcher-Munson curve or a collection of curves rather are a set of x/y graphed plots, where X represents frequency and Y is loudness in dB SPL.

• At lower volumes, midrange frequencies are perceived much louder, while lows and highs are heard at what seems to be quieter.

• At higher volumes, the low and high frequencies are brought to life, while our perception is now less sensitive to the midrange.

Most auido engineers and hobbiest today like to use the phrase “equal-loudness contours” in reference to the work of Fletcher and Munson..