NOTICE: Etymotic earphones and accessories are out of stock and unavailable. We will update this page when the situation changes.

High Performance Insert Earphones for EP / ERP applications:

• Unique design minimizes interference with ERP / EP measurements
• Predictable frequency response
• High isolation between ears: reduces the need for masking sound (* when used with a source having separate grounds for each channel – eg NOT a standard PC sound card) 
• Eliminates collapsed ear canal problem
• 30+ dB external noise exclusion

Why do I need these special earphones for auditory EP / ERP applications?

• Calibratable – These insert earphones have optimally-flat frequency response. So, no matter the frequency of the sound you play, you can apply a single scale factor to achieve relatively accurate control of sound-pressure at the earphone.
• No stimulus artifact – The transducer is a few inches from the electrodes so you will not see a stimulus artifact in the recorded EEG.
• Predictable timing – The time it takes for sound to travel from the transducer to the ear is exactly one millisecond, and you can take that into account in your measurements.

Can I use standard earphones or speakers?

• Standard headphones will interfere with the EEG recording.

You can use loudspeakers, but we recommend against that because:

• Loudspeakers sometimes produce stimulus artifact
• Sound pressure levels depend on the exact head position relative to the speaker.
• Loudspeakers typically have irregular (not flat) pass bands, making calibration across frequencies a challenge.
• Time delay from speaker to ear depends on distance and head-position, so it is impossible to know the timing delay to the ear without carefully measuring the distance between the speaker and the ear.As
• 1 kHz sensitivity: 105 dB SPL for 1V rms drive
• Impedance: 10 Ohms nominal
• Acoustic Polarity: + Electrical = +Acoustic
• Typical Frequency Response (Zwislocki Coupler) at right

Copyright © Etymotic Research, Inc.