Summary of Results
Comparison of Sound Isolating Earphones and Noise-Canceling Headphones Background As portable audio devices become increasingly common, people are often listening in noisy environments. A variety of headphone products on the market reduce the level of background noise heard by the listener, but with varying effectiveness. To learn more about how these products differ in performance, Shure commissioned a research study to compare the noisereducing performance of its sound isolating earphones to competitive headphones that utilize Active Noise Cancellation (generically referred to as Active Noise Reduction in the study). How These Technologies Work Sound isolating earphones prevent noise from entering the ear naturally. A foam, rubber, or plastic sleeve surrounding the earphone allows it to fit into the ear instead of resting outside of it. The snug fit and unique acoustic properties of the sleeve prevents outside noise from entering the ear. Sound isolating earphones do not require circuitry or batteries. Noise-canceling headphones use electronic circuitry to remove noise after it has entered the headphone earcup. Microphones inside each headphone earcup sample the noise field, and an electronic circuit creates an inverse or mirror-image of the noise signal and adds it to the music. The actual noise and the inverse noise cancel each other out. The microphones and circuitry require batteries in order to operate. Which Products Were Tested The testing lab purchased two examples each of popular noise-canceling headphones manufactured by Bose, Sony, and Sennheiser. These were compared to Shure E2c and E3c sound isolating earphones equipped with various types of sleeves. To insure accuracy, ten subjects were tested with each product on three separate occasions. Shure personnel were not present during testing. Products Tested
Manufacturer/Model Shure E2c Shure E3c Bose Quiet Comfort 2 Sennheiser PXC-250 Sony MDR-NC11 Sony MDR-NC20
Retail Price $ 99.00 $ 179.00 $ 299.00 $ 149.99 $ 149.99 $ 179.99
This model was deleted from the study because it could not be measured reliably using the measurement microphone mounted on the test subjects ears.
Testing Procedure The goal of the tests was to measure the amount of noise reduction (referred to as Insertion Loss in the study report) provided by each product. The sound isolating earphones were tested using a method called Real Ear Attenuation Threshold (REAT), in which the test subjects identified the sound level (or threshold) at which they could no longer hear the test noise signal, both with and without the earphones in place. The difference between the two measurements is the noise reduction (Insertion Loss) provided by the earphones. The REAT test method cannot be used for headphones that use electronic circuitry to cancel noise, so an alternate method called Microphone in Real-Ear (MIRE) was used for the noisecanceling headphones. With this method, a very small measurement microphone was placed in
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Comparison of Sound Isolating Earphones and Noise-Canceling Headphones each of the subjects ears, and the noise level inside the ear with the noise cancellation electronics turned on was measured and compared to the noise level outside of the headphones. Test Results The amount of noise reduction provided by each product was measured in nine standard frequency bands across the audible spectrum. The results are expressed in decibels.
Noise Reduction Performance
Noise Reduction (decibels) Product Shure E2c (foam sleeve) Shure E2c (clear sleeve) Shure E3c (foam sleeve) Shure E3c (gray sleeve) Bose QuietComfort2 Sony MDR-NC20 Sennheiser PXC-Hz 20 dB 21 dB 28 dB 26 dB 17 dB 4 dB 7 dB 250 Hz 20 dB 20 dB 29 dB 26 dB 17 dB 6 dB 7 dB 500 Hz 20 dB 20 dB 32 dB 27 dB 14 dB 5 dB 5 dB 1000 Hz 23 dB 23 dB 37 dB 27 dB 10 dB 4 dB 4 dB 2000 Hz 32 dB 32 dB 34 dB 32 dB 18 dB 8 dB 10 dB 3150 Hz 37 dB 36 dB 42 dB 36 dB 27 dB 12 dB 21 dB 4000 Hz 36 dB 33 dB 42 dB 32 dB 31 dB 16 dB 22 dB 6300 Hz 45 dB 39 dB 44 dB 32 dB 33 dB 16 dB 16 dB 8000 Hz 44 dB 38 dB 44 dB 33 dB 30 dB 22 dB 16 dB
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Comparison of Sound Isolating Earphones and Noise-Canceling Headphones Noise Reduction Performance
Noise Reduction (decibels)
Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 3150 Hz 4000 Hz 6300 Hz 8000 Hz

Frequency

Sony NC-20 Sennheiser PXC-250 Bose QuietComfort2 Shure E2c* Shure E3c*
* E2c and E3c earphones fitted with foam sleeves

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Comparison of Sound Isolating Earphones and Noise-Canceling Headphones Interpreting The Test Data The noise reduction performance of each product tested in the study is expressed in decibels at nine different points across the audible frequency spectrum. For easier comparison, Shure calculated a single average noise reduction figure for each product. These numbers represent the overall noise reduction that a user would experience. The average performance numbers were also converted into a noise reduction percentage (compared to not wearing any headphones at all). In addition, the relative performance difference between Shure sound isolating earphones and competitive noise-canceling headphones is stated as both a percentage improvement and a relative performance factor.
Product Shure E3c (with foam sleeves) Shure E3c (with gray soft-flex sleeves) Shure E2c (with foam sleeves) Shure E2c (with clear flex sleeves) Bose Quiet Comfort 2
Average Noise Reduction (dB) 37 dB 30 dB 31 dB 29 dB
Noise Reduction (%) 93% 90% 88% 87%
Shure Advantage (all figures for E3c with foam sleeves)
Shure blocks 16% more noise Shure blocks 34% more noise Shure blocks 42% more noise
Shure blocks 3.5 times as much noise Shure blocks 6.3 times as much noise Shure blocks 7.5 times as much noise

Sennheiser PXC-250

Sony MDR-NC20

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Comparison of Sound Isolating Earphones and Noise-Canceling Headphones
100% 90% Noise Heard by User 80% 70% 60% 50% 40% 30% 20% 10% 0%

49% 41% 22% 12%

es * E3 c* Sh u re 2
For More Information If you have questions regarding the test results discussed here, please contact Shure by phone or email. 888.88SHURE or visit www.shure.com or ask us a question by clicking below http://personalaudio.custhelp.com/cgibin/personalaudio.cfg/php/enduser/ask.php?p_sid=*WCTzo9i&p_lva=3306
*E2c and E3c fitted with foam sleeves

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