There is much debate surrounding the subject of correct monitoring level, and the answer more often than not is down to individual preference, but there are some facts to be aware of. American physicists Harvey C. Fletcher and Wilden A. Munson found in the 1930s that human hearing is more sensitive in the 3 to 4kHz range and less sensitive in the ranges above and below this. This is thought to be because it is the frequency area that is crucial to the understanding of speech. The effect is exaggerated at lower volumes as you can see on the graph below: |
Fletcher-Munson (1933) - curves of equal-loudness level
Mixing at low volumes will often encourage you to increase bass and upper frequencies to compensate. At around 120dB the effect is at its minimum, but monitoring at this sort of level would definitely shorten your musical career! The ideal monitoring level is widely regarded as being around 85dB, but it is quite common to mix at much lower levels than this, turning the volume up occasionally to get an idea of what it sounds like played back loud. Always remember that your music will be listened to at a wide variety of levels, so it’s important to get this balance right.