Etymotic Was First
Etymotic Research introduced the ER•4B and ER•4S earphones in 1991. The ER•4 series earphones are in-the-ear, high-fidelity transducers developed specifically to combine flat frequency response with isolation from external noise. The isolation of outside sound makes it possible to listen at reduced levels, which prevents ear overload distortion and hearing damage from excessive volume levels.

ER Is Still The Leader
Other in-ear earphone designs have tried to match the ER•4 MicroPro earphones, but not one is comparable to the high fidelity, reference-quality sound or the isolation of the ER•4. The word "Etymotic" means "true-to-the-ear," and ER•4 MicroPro earphones produce the highest sound quality of any earphone available.