Originally Posted by SilverEars
Shouldn't it be boosted at that region since we are less sensitive to it according to the curve? And, the heavy treble region seems to rise and that rise. The headphones should reverse the curve at average listening loudness level. Looks like 3k with a band around the region should be boosted to compensate for our sensitivity.
Wouldn't the dips around 3kHz have something to do with dealing with the natural resonances of the headphone cups? Naturally, if there are resonances at that frequency when the headphones are in place, then you would want to reduce the energy at those frequencies.
At 3kHz and assuming speed of sound is 330 m/s, the wavelength is 11 cm. That puts the 1/2 wavelength at 5.5 cm and the 1/4 wavelength at 2.75 cm (which would correspond to the first harmonics in open and closed headphones, respectively)
Those numbers sound like reasonable back of earcup-to-face lengths for circumaural headphones, don't they?
Here's a little java applet that illustrates acoustic resonance in various 1-D chambers of different boundary conditions. Unfortunately, it doesn't let one enter lengths less than 10 cm; however, by mathematical extension, you can see how the stated lengths above are accurate.
Edited by ab initio - 7/20/14 at 11:16pm