The ER-4 provides extremely superb sound. It is very detailed, well-balanced, and gives deep, tight bass. Their 23db of isolation leave the ER-4 unrivaled by any other closed or sealed headphones. Prepare to enter musical nirvana…

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. Next Best Thing to Live Music

• Transparent, reference-quality sound
  
• For audiophiles, performing musicians and recording engineers
  
• For mixing, monitoring and critical listening
  
• Accurate real-ear response
  
• Unsurpassed isolation from outside sound

System Includes

• ER•4 MicroPro earphones
  
• 5 ft. cord with 3.5 mm stereo phone plug
  
• 1/4" stereo phone adapter plug
  
• Six 3-flange eartips
  
• 10 foam eartips
  
• Filter changing tool
  
• 4 replacement filters
  
• Shirt clip
  
• Zippered pouch
  
• Storage box

ER•4B (Binaural) earphones are for the binaural recording enthusiast. The ER•4B is an ideal earphone for use with material that has not been equalized for loudspeaker playback. It was developed from the ER-1 earphone that is referenced to a flat diffuse field and used primarily for speech reception research, where the goal is to produce the same frequency response at the eardrum as would be produced in the live situation.

ER•4S (Stereo) earphones were designed to compensate for the high frequency emphasis in all CD recordings, in order to provide accurate sound reproduction. Performing musicians often use them as in-ear monitors because the response of the ER•4S matches the response of most typical monitor loudspeakers. The high accuracy and exceptional sound isolation of the ER•4S have made these earphones popular with musicians, recording engineers and audiophiles. ER•4S earphones can be used with a headphone amplifier when using low power portable devices.

ER•4P (Portable) earphones can be used with portable CD, MP3, DVD and other players without requiring an additional amplifier. As compared to the ER•4S, the ER•4P has 10 dB greater output at high frequencies and 13 dB greater output at low frequencies. The higher sensitivity and enhanced bass of the ER•4P have made it the most popular earphone for most uses.

ER•4B	ER•4S	ER•4P	ER•4 Feature Comparison
•	•	•	Lightweight and portable
•	•	•	High accuracy
•	•	•	Noise isolation (20-25 dB)
		•	Enhanced bass response

Effective Response of ER•4 Earphones ER•4 Response Accuracy

ER•4 MicroPro Earphones are designed to match the acoustic response of the open ear. Music is naturally bright, but not harsh. The lack of coloration results in smooth treble, full bass, clear and natural piano, percussion and orchestral music.

Product Comparison Response Accuracy in Percent ER•4 MicroPro Earphones ER•6 Isolator Earphones Earbud $49.99 Active Noise-Canceling $149.99 Active Noise-Canceling $299.99   How We Measure Response Accuracy The accuracy score is perhaps the single most important tool for earphone design. A perfect recording of a live performance played through earphones with 100% accuracy would produce the same sound at the eardrum as the live performance. A complicating factor is that the acoustic resonance and horn effects of the ear change a flat signal entering the open ear to an eardrum signal with the approximate frequency characteristic of the target curve. A perfect earphone will create that same frequency characteristic at the eardrum. Target Curves Target curves on Etymotic Research graphs indicate 100% accuracy: The open ear diffuse-field response of the KEMAR® manikin modified to compensate for the high frequency boost added to high-quality recordings. This modification (approximately 5 dB at 10 kHz) is necessary to avoid earphones sounding too bright on commercial recordings. Commercial recordings have a high-frequency boost that compensates for the high frequency roll-off in studio monitor loudspeakers and high-quality stereo loudspeakers and earphones. 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. In the 1970s, Consumers Union used an "Accuracy Score" to rate loudspeakers. Consumer Reports reported that it was possible to predict listeners' loudspeaker ratings within 8% from a calculation based on one-third-octave frequency response measurements converted to loudness in sones. The average error in loudness from a perfect system, subtracted from 100%, gives the accuracy score. Etymotic Research extended this 21-band calculation to a 25-band calculation and routinely uses the 25-band accuracy score in all earphone designs. Other in-the-ear earphone manufacturers do not report accuracy scores, but Etymotic Research has tested all competitive products. The accuracy scores of Etymotic Research earphones are higher than those of most loudspeakers, and well above all competitive earphones, except electrostatic headphones that cost thousands of dollars. ER•4 Noise Reduction ER•4 MicroPro Earphones provide the highest isolation of any earphone: 35-41 dB (two to three times that of active noise-canceling earphones). ER•4 MicroPro earphones reduce sound naturally, without the added weight, bulk, or external power supply required for active noise-canceling. 3-flange eartips: 35 dB external noise isolation (NRR = 22dB) Black foam eartips: 41 dB external noise isolation (NRR = 32dB)   Product Comparison Noise Reduction in dB   Real-Ear-Attenuation-at-Threshold (REAT) Method ER•4 MicroPro (Foam) ER•4 MicroPro (3-flange)   Probe Microphone Measurement Method ER•4 MicroPro Earphones ER•6 Isolator Earphones Earbud $49.99 Active Noise-Canceling $149.99 Active Noise-Canceling $299.99 Earbud $199.99   How We 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•4 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 ER•4 Technical Specifications Frequency response: 20 Hz to 16 kHz ±4 dB Acoustic polarity: + electrical = + acoustic Transducer type: dynamic 1 kHz sensitivity (ER•4B/ER•4S): 108 dB SPL for a 1.0 volt input 1 kHz sensitivity (ER•4P): 108 dB SPL for a .25v input Impedance (ER•4B/ER•4S): 100 Ohms nominal Impedance (ER•4P): 27 Ohms nominal Maximum output: 122 dB SPL Maximum continuous input (ER•4B/ER•4S): 3.0 Vrms Maximum continuous input (ER•4P): .75 Vrms Weight: less than 1 oz.