Introduction: DIY Homemade Passive Noise Reducing Headphones

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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.

Picture of 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.

Step 2: Dismantle the Donor Headset

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I used a headset designed to go on the outside of one's ears that had little foam pads.  I dismantled the headset taking note of the wire colors so I could reconnect them later after I had threaded them through the hole I drilled in the muff housings.

Step 3: Make the Spacers to Set the Speakers Back

Picture of Make the Spacers to Set the Speakers Back

I wanted to make sure the plastic speakers were not going to contact my ears.  I used foam weather stripping tape to offset the speaker about 1/2" further from my ears.  The stripping has adhesive backing, so it sticks to the back of the foam earpads from the muffs.  I used a knife to cut the weather stripping into two pieces about 1/4" wide and then simply stuck it on the back of the muff pads.  I learned that I could just bend it around the screws, there really wasn't a need to notch the foam around them.

Step 4: Modify Speaker Plastic (if Needed)

Picture of Modify Speaker Plastic (if Needed)


I picked up a cool tool at Harbor Freight (Item # 42804) that I used on this project.  A saw drill is like a roughing mill and it makes removing plastic that would interfere with the screws a snap.  I needed to make two crescent shaped cutouts around the location of the screws before I could glue to the speakers to the foam.

Step 5: Glue Speakers to Foam

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I sat the speaker on the back of the foam and was able to simply glue it right on.  It might be necessary for some headphones to make a wood or plastic ring to hold the speaker if there is too much space.  More foam tape to make an "igloo" to support the speaker would work fine too.

Step 6: Make Holes for Wires

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I took a piece of two conductor wire from an old wall transformer to conduct the audio signal from the muff we bring the original headphone cable into (left) to the opposite side of the headband (right).  It takes about 18" of wire.  One could also just peel a typical headset cable down further and cut the one to the left ear off shorter.   In mine, the wire goes from the music player to the left muff.  The wire is then extended by the two conductor wire and goes out the left muff, under the padded band on the top of the head, and into some holes in the right muff to feed the right speaker.

Step 7: Strain Relief the Wiring

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I brought my wires in by splitting the conductor and bringing each one in through it's own hole.  I tied and underwriter's knot in the loose ends that entered the headphone.  The knot keeps the wires from pulling out if they are stressed.  The cable that goes to the music player was brought in through its own hole.  I tied it into an overhead knot inside the headphone.  I also hot glued it inside the muff, and did a few rounds around the cable on the outside of the muff to form a poor man's strain relief.  It works and doesn't look too bad.  In the picture you can see the wire that comes in from the MP3 player (bottom) and the wire that conducts the signal for the right speaker back out of the muff.

Step 8: Complete Wiring and Reassemble

Picture of Complete Wiring and Reassemble

I routed the wire from the left muff housing through the padded headband and then into the right muff. I made sure all of the wires are long enough to reach when all of the adjustments are fully extended. I then soldered the speakers back onto the ends. I added a little electrical tape (pictured) to keep the wires close to the sliding plastic parts and out of the way when the headphones are adjusted. I put in the screws and I was done.

Thank you for the time you spent looking over my instructable. If you have read this far and are thinking, "This was great and totally worth a buck" You can help me continue to make more instructables by making a donation using this link to my ebay store. Thanks, and keep building! -- Yeltrow

Comments

Phil B (author)2011-09-28

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 (author)2011-09-27

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 (author)Phil B2011-09-28

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.

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