The facts that your ears prop up your glasses and hold your hat on in the wind are totally secondary to their role in the music industry! Ears are the judge, jury, and executioner of everything.

Ears do funny things to sound before we interrupt how loud the sounds are. It is pretty important you understand this if you are in the 'sound business'. So what do we know about ears? Some useful bits of information include:

1. We do not judge the loudness of all frequencies the same! The ear canal resonates at about 3.8khz. It is most sensitive in the 1khz to 5khz region. This area is often called 'presence' and can get crowded if you are not careful resulting in an overall loss of clarity. You have to be careful of one instrument masking another (or the vocals) if it is too high in this area. Distorted guitar can dominate here. You can bring up or push back most instruments in the mix by altering their 1khz to 5khz levels.

2. You have a muscle in your ear called the malleus! Whoop de do! It squeezes up to protect the ear when the volume level gets high. This is referred to as acoustic reflex! It protects your ear from low frequencies but not high ones. It does not protect you from frequencies of 1khz and up! Once this muscle has tightened up it takes some hours before it relaxes and you can hear normally again. This is a really important thing to be aware of when you are mixing. It is why people tell you to monitor at low volume levels and take lots of breaks. If you do not keep this in mind you are likely to come in the morning and discover that yesterdays work does not sound like it did when you went home!
 

3. At low volume levels you lose bass response. Ears also have the ability to fill in the gaps when parts of the sound are missing as long as higher harmonics are present. This is why when you listen to sound on a little radio speaker which obviously is missing a lot of the bass component you can still recognise what you are listening to. This has significant impact on how you mix. You need to listen to your mix at different volume levels.

4. Your ears are very good at dealing with sound coming to them at the same time as reflections of the sound bouncing off the various surfaces around you. They are also very good at locating where the sound has come from. Altering where the reflections come from and the time delay of the reflection has significant impact on what you hear. In general terms a delay of 1-5 milliseconds will produce phase interference, 10-20 milliseconds produces what you think of as a small room reverb, 20-40 milliseconds is a large room or hall reverb, and over 40 milliseconds produces a distinct echo. Whether this is good or bad depends on what is in the recording. Above all listen to what your ears tell you!

LEARN MORE ABOUT SOUND

The Master Handbook of Acoustics
by F.Alton Everest
Complete coverage of the science of acoustics and the art of acoustic techniques including room resonances, reflection analysis, comb filters, and the design of audio/video rooms for almost any purpose on acoustical concepts and terminology.
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