Effective Response of ER•6i Earphones (measured at eardrum)

The above graph indicates that 6i earphones have 8 dB higher sound output and increased bass compared to the original ER-6 earphones. The dotted red line is the reference response of the open ear to live performances (CD equalization).

True high fidelity sound reproduction requires the reproduced sound to be as close as possible to the sound of a live performance. ER•6i Isolator Earphones are designed to match the acoustic response of the open ear.

How Etymotic Measure Response Accuracy
Earphone response was measured on a KEMAR® manikin that has the same acoustic properties as the average head and ear. 25-band accuracy scores are calculated by summing the difference between the earphone response and the target response in each 1/3-octave band from 50 Hz to 12.5 kHz.

The Isolator earphones reduce environmental sound levels 30-35 dB, allowing you to hear the full range of today's digital recordings without having to play them at unnaturally high and unsafe levels. Since you don't have to boost the volume to overcome external noise, ear overload distortion is minimized.

How Etymotic Measure Noise Reduction

Real-Ear-Attenuation-at-Threshold (REAT) Measurement Method
The ANSI standard method of measuring the noise attenuation of hearing protectors and earphones is to compare the quietest sound that can be heard with the earphone in place with the quietest sound that can be heard with the ears open. This Real-Ear-Attenuation-at-Threshold (REAT) method is the basis for all OSHA Noise Reduction Ratings called the NRR. ER-4 and ER-6 earphones were measured with the REAT method at E-A-R CAL Laboratories.

Probe Microphone Measurement Method
Active noise-canceling earphones cannot be measured with the REAT Method because their circuit noise interferes with the measurement. ER-4 and ER-6 earphones were compared to active noise-canceling earphones using a probe microphone method: A calibrated 84 dB SPL broad-band pink noise was generated in a reverberation room using four uncorrelated noise sources. The sound pressure developed in the ear was measured with a 2.5 mm microphone located deep in the ear canal. The noise reduction of each earphone was calculated as the difference between the noise level in the open ear and the noise level with the earphone in place.

Why You Don't Need Active Noise-Canceling
Active noise-canceling circuits add noise of their own when you are listening in quiet surroundings. ER•6i MicroPro Earphones reduce noise naturally by sealing your ear canals. The result:

• Clean, clear, undistorted music
• Rich detail that you miss with over-the-ear headphones
• Awesome, in-your-head sound
• Lightweight, comfortable fit
• More external noise isolation than any other earphone in the world, including active noise-canceling