I had only seen a review of this, and when it had debuted, it was around 600 dollars. Now for $495:
Etymotic ER-4 microPro Reference-Quality Earphones Manufacturer Id: ER4-P Manufacturer Name: Etymotic Noise isolation far surpassing that of active noise canceling earphonesTransparent, reference-quality sound Frequency response: 20Hz-16kHz, 4dBImpedance (ER-4P): 27 Ohms nominal.