Science Buddies: "Ask an Expert"

Hello,

I would like to ask if it possible to block sound waves with sound waves? Most of us these days live in apartments surrounded by neighbours and their noise. The noise I’m talking about like foot noise in the middle of the night, music, vacuum sound, constantly through the day. You don't have a quiet moment left.

I could have option to soundproof my entire apartment including ceiling too which would cost dearly, never mind the time to install, the wall thickness lost and sore look it will have. I would like to look for another option.

Could I have a simpler solution for this? I would like to install a device that I plug in which generates sound waves which becomes mirrored or cancelled out effect to the sound waves incoming, this pushes back the sound waves to the direction they come from or to another direction .

For example can 25MHz wave generator block 25MHz wave’s incoming or do I need higher or lower frequency? What frequency will take to block a particular sound wave?

If not possible to do that what if I used higher spectrum like infrared waves and i had infrared generator will this possibly block the sound? Or electromagnetic waves not meant to be blocked by electromagnetic waves?

I have asked this question because I do not hear any noise when I listen to music or TV, it is blocking the noise waves coming to my ears and maybe I thought some waves below human hearing capacity (under 0dB example) can block as well.

Thank you.

The short answer is *yes*, it's possible. You can purchase active nose cancelling headphones which do exactly that. They have microphones on the outside of the earcups and bring an inverted copy of that sound into the cup so that you don't hear it. Some work great and some - not so much. It's a much harder problem when you're talking about an entire room since sounds will be louder in one part than another. Footsteps are a tough problem since they also vibrate the floor and you'll feel those in your feet.

Making a little gadget that simply cases your room to be silent is something that has never been done and is unlikely to ever exist. I've only done a little active noise cancelling myself and it's hard to do. Using higher frequencies to block the noise doesn't make any sense to me but perhaps someone else here has used (or tried) that technique and can comment on it. For now, I'd suggest a set of noise cancelling headphones while you come up with a better answer.

Howard