Noise reduction and low cost but bulky

In my opinion, you can put on the QZ99 and "almost" be completely shut out from outside noises.

These headphones are designed for noisy environments such as an airport or racetrack. They are ideal for someone who has a radio scanner and also wants to listen to a stereo broadcast. They are not a complete isolation from outside noises, but they are very close. KOSS claims they provide about 12db of passive noise isolation.

They provide good insulation from surrounding sounds. Just put them on, and gently push them towards your head to complete the seal of the closed cup around your ears. They seem to be almost airtight, however, and this may cause some discomfort.

Without any audio playing, if I put my head back on the office chair and close my eyes, I am easily aware of my breathing and heartbeat. I can hear that same background noise as if I were to block my ears off by perhaps putting my fingers up tightly against the ear canal. In other words, I am hearing that "white-noise" type sound that you hear when it is completely quiet. At least I hear the sound. It could be that my ears have a problem of some kind, but I only hear the sound when it is absolutely quiet.

The QZ99 advertised a stereo/mono switch, which my pair does not have. It comes with a 1/8" stereo plug for use with portable players and a 1/4" adapter.

There is another KOSS model, QZ-5, that is $10 less has the same exact closed cup design. The difference is that QZ-5 has a strap across the top of the head and a metal clamp along the back of the head making it possible to wear a baseball hat.

As far as sound reproduction goes, I would rate them average. I think you would mainly purchase these for the noise reduction at a low cost.

They are also quite bulky and you cannot wear these things lying down unless you have a good pillow behind your head. It is virtually impossible to wear these while lying on your side.