The Fletcher Munson curves are one of many sets of equal-loudness contours for the human ear, determined experimentally by Harvey Fletcher and Wilden A. Munson, and reported in a 1933 paper entitled “Loudness, its definition, measurement and calculation” in the Journal of the Acoustic Society of America. The first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933. In 1937 they created the first equal-loudness curves.

Humans don’t hear all frequencies of sound at the same level. That is, our ears are more sensitive to some frequencies and less sensitive to other frequencies. In the early 1930’s Dr. Fletcher and Dr. Munson, audio pioneers at Bell Labs discovered that the human ear hears differnetly at varioius loundness levels. At 130+ dB SPL we hear almost flat. But we hear lows and highs poorly at lower volumes (lower SPL) and it gets worse the softer the sound. To complicate matters further we all loose our hearing above 14,000 Hz as we age!

The important thing to understand about sound is the volume (in SPL) affects your perception of bass and treble response significantly. What sounds quiet one way, sounds different loud. The same thing is true for sources and microphones. A mic that sounds good at low level may sound terrible at high level! Fletcher-Munson also discovered that the dynamic range of the human ear was 120 dB!

How does this relate to Ham Radio After several years of experimenting and listening, the Heil Sound team discovered that most of the old line favorites have their frequency response in the wrong place. Just about every dynamic microphone has a mid-range response peak that is in the wrong place.

To fix this problem of audio quality and sound we use the knowledge of Fletcher Munson Curve.

  • Use an equalizer to equalize the sound to make the sound better
  • Get away from using a ham mic on rigs as almost all hand mics on rigs are made by the same two companies
  • Don’t just turn up your mic gain to get threw pileups during contest focus on audio quality studies have showed that during a pile up the operator will pick the best quality sound over the loudest call.