Content

• To step
• Method 1 of 4: Using a glass
• Method 2 of 4: Using a hole in the wall
• Method 3 of 4: Using a spy stethoscope
• Method 4 of 4: Be aware of the consequences of spying
• Necessities

Wondering what that muffled conversation is about on the other side of the wall? Do you want to know what is being said? Whether it's a stranger or a loved one, in your own home or elsewhere, it's probably not a good idea to spy. But if you decide to go ahead and start eavesdropping, there are several ways to listen through walls with amazing clarity. As long as you are aware of the law and the legal risks you run if you want to do this.

To step

Method 1 of 4: Using a glass

1. Grab a glass. So you've decided to go for it. How do you start spying? One method is to hold an ordinary glass against the wall. The reason this works is that you create an “acoustic coupling” between the wall and the glass, allowing sound waves to travel from one side to the other. A soda or beer glass works best. Some eavesdroppers swear by disposable cups, but glass conducts sound better than other cups.
   • Experiment with different types and shapes of glasses to find which one works best.
   • If you have an iPhone, you can download the Amplitude Pro app and hold the iPhone against the glass that is pressed against the wall. With this app, you can better hear sounds that are at a distance, but it can also record the amplified sound.
2. Go on a scavenger hunt for the best spots. Some parts of the wall will transmit the sound more clearly than others due to the structure of the wall or the distance from the sound source. Experiment to test the sound quality until you find the best spot. Sometimes this can be difficult if the sound is coming from the ceiling. If you are too far from the sound on the wall, you will not be able to hear it that clearly.
3. Place the edge of the glass against the wall. Remember, for it to work, the glass and wall must be acoustically linked. You do this by laying the glass with the opening flat against the wall. Sound waves will now travel through the wall and glass, making it easier to detect.
   • Once you have placed the glass, hold your ear against the bottom of the glass. Keep moving the glass along the wall if you can't hear it properly.

Method 2 of 4: Using a hole in the wall

1. Drill a small hole. Another way to hear through a wall is through a hole and a plastic membrane, a method recently discovered by scientists in Japan and South Korea. First, drill a very small hole all the way through the wall. A drill with a thin and long chuck works best for this.
   • Don't expect to be able to hear much through the hole alone. In fact, a hole in a wall is a significant impediment to sound transmission.
   • Pick a time when other residents are not at home to drill the hole. Otherwise, they may notice the drilling noise or dust from drilling.
2. Cover the hole with a thin membrane. This should allow this method to work properly. Research has shown that by covering the hole with a thin membrane, the sound is transmitted almost as if there was no wall, because the membrane amplifies the pressure on both sides of the hole, allowing sound to pass through like a funnel.
   • Use normal household material for this, namely plastic foil. The scientists who conducted the study also used plastic wrap themselves.
3. Go ahead with eavesdropping. When you are done with the hole and the placement of the foil, you can start eavesdropping! If done correctly, you should be able to hear fairly clearly what is going on in the other room.
   • For an even better result, you can use this method along with the others. Place a glass over the hole and the plastic membrane.
   • Be warned that drilling a hole in the wall has some very big drawbacks, especially when it comes to secrecy. The other residents can hear the drilling; the hole can be discovered, or the grit from drilling that has landed on the floor, which can make them suspicious. Be very careful with this!

Method 3 of 4: Using a spy stethoscope

1. Gather your materials. Now we are going to work on the more advanced eavesdropping equipment. You can make a stethoscope yourself or buy one. Ready-made models will save you time, but can cost hundreds of dollars. A homemade stethoscope will cost around or under $ 25, assuming you already own a reasonably good MP3 player.
   • You can usually get a stethoscope at the drugstore for about $ 10. The quality will not differ very much.
   • You also need microphones. Stereo multimedia microphones are preferable because they are inexpensive (about $ 15) but at the same time have good sound quality. That means that you should be able to record sound with it quite well and without too many problems.
   • Finally, you also need an MP3 player to record sound, and a 3.5 mm (mini) Stereo Y adapter cable. The cable will be quite cheap, around € 3 or € 4. The MP3 player will be the most expensive item if you don't have one. Remember, you should be able to record with it, which probably means you need a newer model (many older models can only play, not record).
2. Take the microphones apart. You will need to cut the microphones in half to access the wiring, remove the connector pins, and disconnect the microphones. Then you place the bare microphones in the earplugs of the stethoscope.
   • A good tool for doing this is a hobby knife. This will make a neat cut in the outer parts of the microphone so that you can open it up. In the end you will have 2 microphones and 3.5 mm connectors (the cabling).
3. Disassemble and reassemble the earbuds from the stethoscope. Remove the earplugs from the stethoscope. This is fairly easy to do and they should come off right away. Don't throw them away, because you are going to attach them to the microphones.
   • Then drill shallow holes in each earbud to a diameter that matches the housing of the microphones. The size of these holes must be exact, because the microphones must fit exactly in them. A drill or grinder can give you the desired precision.
   • Glue the microphones into the earbuds. Apply some glue around the edges of the microphone housing, then insert the microphones into the holes you just drilled in the earbuds. Reattach the earplugs to the stethoscope and let the glue dry.
4. Connect the stethoscope to the MP3 player. Finally, connect the stethoscope and microphones to the MP3 player. Use the Y adapter cable to connect the microphones to the MP3 player. The sound you pick up through the wall is now picked up and amplified by the microphones, sent to the MP3 players for recording and storage.
   • Connect the stereo connector to the MP3 player. Your stethoscope is ready to use.
5. Start listening. Practice with your stethoscope. Just like with a simple glass, you will have to experiment with this to find a good place on the wall, or to get the hang of making a recording. However, you should now be able to hear what is being said on the other side of the wall, unless they are double or heavily insulated walls.

Method 4 of 4: Be aware of the consequences of spying

1. Ask yourself: do you really want to spy on someone, or do you need to? As soon as you start listening through a wall, you spy on another person and overhear your private conversations. This raises serious legal and ethical issues. Before you take action, it is wise to ask yourself whether you really want to do this. Is this worth the risk?
   • The situation is important. In England, for example, a man saved his elderly neighbor from a robbery because he could hear what was going on with a glass against the wall. In this situation, the wiretapping was clearly justifiable.
   • But most of the time it is not that clear. It is probably better not to do this if you are unsure about the situation. If you want to continue with it, make sure you are aware of the possible consequences of your actions.
2. Be aware of eavesdropping laws. Eavesdropping means listening in, recording, amplifying or sending (part of) a private conversation, without the consent of the person in question. Be aware that there are laws to deal with these types of practices. You may be breaking the law by eavesdropping. You may even be breaking the law just because you own a spy device.
   • In some states in the US there is something like a “one party consent” or a “two party consent”. In the former case, it is illegal to eavesdrop on a private conversation unless at least one of the intercepted parties has consented to it. In the second case, you need the permission of both parties to listen, record or amplify their communication.
   • Take Michigan. Michigan has a two-party consent law - you need permission from everyone involved to "eavesdrop, record, amplify, or broadcast a private conversation." This also applies in your own home. There, too, eavesdropping is a crime.
3. Consider all negative consequences. What happens if you eavesdrop and someone notices? What are the consequences for yourself? This is a good question and you should consider all possible outcomes, which in many cases can be very serious.
   • In Michigan, the penalty for illegal wiretapping is up to 2 years in prison, a fine of up to $ 2,000, or both. In California, wiretapping is a felony or crime. As a felony, you can face up to 364 days in prison and a fine of up to $ 2500, and as a crime, you can face up to 3 years in prison and a fine of $ 2500.
   • Conviction isn't the only bad outcome. You can also be sued for violating someone's privacy, which is extremely costly and can cost thousands of dollars. Even if you can avoid the legal consequences, you will still be dealing with a very angry person.

Necessities

For the method with the glass:

• A glass
• A wall
• An iPhone with the Amplitude Pro app (optional)

For the espionage stethoscope:

• A stethoscope
• Stereo multimedia microphones
• 3.5 mm (mini) stereo Y adapter cable
• X-Acto knife (or similar)
• Small drill
• Glue