A pair of
battery-powered headphones with little
microphones on the outside of each earpiece. The mikes pick up
constant noise in the 40-1500 Hz range, then quickly
reverse the polarity of the sound and feed it into your ear out of phase with the ambient noise, effectively cancelling out the background noise. You can also turn off the active circuit and listen to them like normal headphones.
These are still pretty hard to find. I wanted to test some out, but Sears, Office Depot, and even Circuit City didn't carry them. I had to end up going to Fry's for my set, so if you don't live on the West Coast, I'm not sure what you can do.
Product Review
What I bought
After spending about half an hour listening to two Sony sets at the Fry's listening station, I did something completely unlike my usual self and decided to spring for the ultra-top of the line $200 Sony MDR-NC20 set, over three models that were cheaper. I did this because...
- Sony's $100 MDR-NC5 set was more uncomfortable to wear, and they used the 'convex foam cushion' style of speakers, which I've gotten tired of. The NC20 is more like a studio set of headphones, and is more comfortable. Also, while the noise cancelling circuit was active, there was a slight hiss introduced to the sound that was played through them. I suppose others pay extra money for a white noise relaxation system, but not me. The NC20s also have a hiss, but it is quieter.
- Aiwa's $50 set also looked uncomfortable, and I was worried that it would have the same hissing problem as the $100 Sony. Also, I couldn't listen for myself.
- Koss's $150 Quiet Zone 2000 set looked intriguing, and the specifications were more impressive than the Sonys. However, Koss' regional representative hadn't coughed up enough money to Fry's for the store to put up a Koss listening station like the Sonys, so I couldn't listen for myself. Additionally,
- All the Koss boxes looked like they had been opened and taped shut again.
- The headphones looked kind of cheap.
- I spotted a couple of Koss set that had been returned and repackaged by Fry's.
All models required batteries (AAAs for the Sonys, AAs for the Aiwa, and two AAs for the Koss), and all had
adapters to the two-prong interface you find on
Airplanes. The Koss had a
proprietary jack for its headphones to its
battery pack, which was another reason I didn't want to get them (all other headphones fit the battery into the headset).
Specifications
Used as headphones, the MDR-NC20 acts like a $75 pair when noise canceling is off, and like a $150 pair when it is on. Here's what was listed:
- They only gave one spec for Frequency Response: 15-20,000. However, there is a marked improvement in mid-range and high response when the noise cancelling is activated. I suspect that Sony snuck an active filter into their set when they put in the noice canceling circuit. When I listen to my CD Player, I can appreciate this. However, when I play CDs in my computer, I tend to turn this feature off, because otherwise it can pick up and amplify the annoying interference I get from my fan and hard drive.
- They gave two specs for Impedance: 24 ohms when noise canceling is active, and 56(!) ohms when it is not. So you'll need some power to drive them.
- Noise cancelling: active for sounds between 40 and 1400 Hz. Maximum attenuation is about 10dB, or 70%. For the record, Koss' spec was 30dB max.
- Battery life: I'm up to about 24 hours of use and counting. Not bad for a single AAA battery.
So how do they work?
Pretty good, so far. In the store, both Sony models did a very good job of eliminating ambient noise. A
kiosk about 30 meters away was blaring some
ad for Microsoft Baseball 2000, and both models were very good at getting rid of most of the blare, as well as the omnipresent sound of the
HVAC. I found that a cool thing happened on the NC5 set when I cupped my hands around my ears....the mikes started picking up on the output from the speakers, and I got a weird digital
feedback effect that sounded like it came from an episode of
Dr. Who. Sadly, I could not repeat this on the set I now own.
When I got them back to my apartment, I tried them on again, not expecting much to happen. However, as soon as I switched them on, the traffic noise from the street and the sound of my computer's fan just disappeared. It was like I was living out in, say, Bakersfield rather than Pasadena. Here at work, the Air Conditioning sound is eliminated as well as that of my computer's fan, once again. I can still hear myself type as well as ever, and the most annoying aspect of my work environment--the conversations of other people in the office--are muffled no more than what is normal when you put on headphones.
The real test of these headphones came when I took them along with me on a plane trip from Los Angeles to Israel, which involved a 5 hour flight followed by a 11 hour flight. Here is where the headphones proved their true worth.
Warning: Using these headphones on a plane will result in increased expectations for all further flights. The low-frequency rumble is not cancelled, nor is the high frequency hiss of the wind cancelled, but the howl of the engines over the mid ranges is completely eliminated. It's like a first class upgrade. I took along some extra batteries expecting to have to change them midway through the flight, or at least on the return flight, but the issue never came up. I'm on my 24th hour of usage as I write this, and there is no sign of power loss, so I think this set will even be able to last through a DMan-style flight from New York to China (I'm still skeptical on the return flight in this case, though).
The biggest problems I had on the plane were that it was uncomfortable to lean my head against something to go to sleep, and that one of the planes had a poor input system, and the active filter of the headphones amplified the annoying hiss and static that was not noticable (or drowned out) when noise canceling was not on. Also, the two-prong adapter for use with the proprietary airplane headphone jacks was touchy and sometimes needed to be wiggled for the sound to come through right. This may have been a problem with the plane's hardware and not the adapter, however, since it was not always repeatable over different planes.
So should I buy a set?
Not if:
- You can ignore outside noise just by listening to music. When there is sound playing through these headphones, I can't tell the difference in noise attenuation at all. I'll have to check this again when I'm trying to listen to music on a vehicle attached to four jet engines.
- You're sensitive to labels like "Yuppie Scum". These things are still cool toys more than anything else. I feel like Patrick Bateman just wearing them.
- Your sound system introduces static or other interference, such as the fan noise on a laptop. This noise will be amplified on your headphones.
- You really hate white noise. Even the best models will put it out. Sony's instruction booklet tells you not to worry, it's normal. Incidentally, I didn't notice the noise when I was listening to music.
Yes if: