DIY Homemade Passive Noise Reducing Headphones

In this instructable, I'll document how I modified a pair of Harbor Freight item # 94334 hearing protection ear muffs to get the sound blocking benefits of the hearing protection, plus be able to listen to music or a scanner.  I have tried using ear buds under the muffs, but they hurt my ears after a while and were always getting knocked out.  Now I can listen to music at the same volume level I normally would, even while cutting the grass without hurting my ears.  The Harbor Freight muffs are comfortable enough to wear for hours of use.  

Step 1: Pull back the pad to reveal the hidden screws inside the muffs.

Pull back the pad to reveal the hidden screws inside the muffs. Then use a phillips screw driver to back the screws out.  Pull off the pad and set it aside.  Remove the foam from inside the muff.

Comments

[Phil B]

Thank you very much for your detailed response. If you mentioned impedance and I missed it, I apologize. I do have some old player headphones of varying quality. Probably one or the other would work.

I would like to share my test for how well a noise limiting apparatus works. I put the phones onto my head and turn on the player while cozying up to to vacuum cleaner while it is operating. If I can hear a podcast over the whine of the vacuum, I figure I have made progress and have a test comparable to sitting on a jet airplane.

[Phil B]

This is an interesting concept I would like to try. I have tried just about every variation but this one (or spending big dollars for a really nice Bose noise reducing headset). Was there anything special about the headphones you sacrificed? Would some small speakers off the shelf or from a couple of old battery radios work as well? Thank you for the idea. (I would like to have something that works better on jet passenger airplanes than what I have used so far.)

[yeltrow]

Dear Phil B,
The headphones I used were airline freebies. They weren't anything special. Speakers from battery operated radios may not work very well. Typically, headphones have an impedance (resistance for AC signals) of 20-100ohms. These http://www.radioshack.com/product/index.jsp?productId=2271508 are 32 ohms. The problem is that the most power is delivered to the headphones when they are a good match for the output impedance of the music player used. Typical speakers are in the 4-8 ohm impedance. This would mean that the amplifier in the MP3 player (if designed for 32 ohms) would be dissipating most (80%) of the heat instead of it's typical 50% and could either produce distorted output or damage itself. Any old yard sale headphones should work okay, as long as they aren't the type that go inside the ear. You will probably want to avoid using regular old speakers.