Q&A for How to Hear Through Walls

Unlike light, which is reflected from an opaque wall and cannot travel through, some of the sound waves are not reflected but continue to move through the wall, causing the wall to vibrate and transmit the sound. However, what is inside the cavity of the wall can affect how much sound travels through to the other side of the wall; if the wall is fairly solid, there is little to disperse the sound waves and some of the sound will make it through. If the cavity contains cords, insulation batting, etc., the sound waves are more likely to be scattered, which can mean that little or no sound gets through to the other side. Hence, a soundproofed wall won’t let the sound waves pass through.

There is a "crime of eavesdropping" in many jurisdictions which involves intentionally overhearing, recording, amplifying or transmitting a private conversation in a private place without permission of the persons being listened to. Overhearing conversations in public is not usually covered by this, as people can expect to be overheard when in public. Using a listening device, wire-tapping, recording private conversations, etc., are generally activities considered to be illegal where consent is absent, although exceptions exist for law enforcement, employment and safety reasons. Since the laws vary by jurisdiction, it’s important to know your local legislation to get an accurate answer to this question in your location.

Medical stethoscopes are sensitive and may be able to hear through a wall, while the less sensitive mechanical stethoscopes might work for a thin wall but there’s no guarantee. If using an unmodified stethoscope, you’ll need to experiment a bit, such as having a friend talk in the other room and seeing if you can hear what they’re saying while moving the scope around until the sound is clearest. However, as explained in the above article, for a stethoscope to be most effective at hearing through walls, it requires modification by adding microphones to amplify sounds muffled by the wall. There are spy stethoscopes, which are expensive, but are modified already to hear through walls; do your research if getting one. Finally, the materials and thickness of the wall will make a difference to whether or not you can hear through it with a stethoscope, modified or not.

Choose a soda or beer glass, one that has a good, wide opening and some length to it. Put the rim of the glass against the wall of the room you wish to listen in on, keeping it flat against the wall. Rest your ear to the base of the glass to hear the amplified sound; if you hear better out of one ear than the other, use the better ear. It’s likely you’ll need to move it around a bit to find the right spot for the best sound reception (do so quietly though). You can also use an app to help amplify the sound if wished; this is explained above in the article.

Well, you can always try to make up a story if they find out. But if they still haven't found out, if they ask you anything about the conversation they had, just pretend you don't know anything. Keep in mind that this takes practice.

If an adult wants to be alone with your child (with the possible exception of a person in the medical field), tell them no and keep your child away from that person in the future.

If someone is being bullied, tell an adult you trust. Not everything can be solved by spying, and if you get in trouble, then you definitely won't be able to help the victim.

If they don't know that you know that they're spying on you, then you have the upper hand, my friend.

Tell the manager/landlord; he/she will deal with them. Or you could just ignore them.

Always tell a trusted adult or in some cases the authorities about bullying. If you are a minor and are noticing bullying, take action and tell someone! If you are an adult, contact the authorities.

If you want to communicate,you could just use a phone to call them (if you happen to know their number).

Call the police. This is break and enter and violations of privacy and might also be stalking and harassment. The police will inform the neighbors and may press charges if gets worse. If the person doing this is living in a rental property, then contact the owner (their landlord) or the estate agents who rented it. The council can help with these issues too. Also, just be sure you're not imagining any of this; if you are on medication, this can sometimes be an issue.

It depends on what you mean by tormenting and harassing; document incidents of what you consider to be such acts, so that there is evidence of actions and a pattern. Then, tell your landlord what is happening and ask them to intervene. If they won't, or they continue the behavior, see if there is a government-sponsored program or initiative for neighbor mediation. If not, contact the police; if they're not able to help, they'll know who to point you to for mediation or other help.

Yes, but ordinarily that's a big job and typically a messy job (probably more work than it's worth).