Answers to Readers' Questions on Sound Detection. Also refer to physics, ear, hearing, microphone, vibration, process, electrical signals, amplified, music, loud sounds, spy devices, laser, Ron Kurtus, School for Champions. Copyright © Restrictions
Answers to Readers' Questions on Sound Detection
The following 11 questions have been answered. They are listed according to date.
List of first 10 items
- How to detect focused sound beam
- Someone it controlling my sound
- Detecting laser spy microphones
- Interested in digital signal processing
- Trying to see how loudness is affected by distance
- Experiment with wine glasses
- Why sounds are different
- Noisy neighbor sound system
- High frequency sound from airplanes
- Sounds from Hurricane Isabel
How to detect focused sound beam
Question
February 6, 2008
read of microwave hearing. audio spot i.e focussed sound beam. kindly explain
how to detect these sound signals and what equipment/detectors can be used to
detect these sound signals.
thanks,
Balraj - Bahrain
15290
Answer
I am not sure what microwave hearing is, unless you mean ultrasonic.
You can detect any sound beam with a microphone. But the frequency of the sound wave must be known to make sure the microphone will detect the sound. Often high frequency sounds must be detected with a laser device.
Someone it controlling my sound
Question
November 29, 2007
Thank you for great info. I have some unexplained occurences in my former and current home. I need a device that will help detect where sound is coming from in my home. I know it's some kind of sound device. Spoke with someone from the Pentagon who said based on my explanation what is occuring has to authorized by the United States Government but I told them I am not a terrorist. They said, they believe it's being conducted by an individual. I was almost killed. FBI said, they receive calls like the one I made looking for help but they do nothing so they are aware but refuse to help so I must help myself. I have a small child to support. My house, car is being remotely controlled because they sound can be turned off and on. The culprit former Lt. Col P. O., Sr. (currently an Air Marshal) and friends. We purchased a house from him due to a divorce and was angry to sell/move so he plotted to hurt/kill whoever moved into the house. If you can recommend devices to detect sound, electromagnetic waves, satellite.
- USA
14876
Answer
If this person was angry because of his divorce, why would he want to harm an innocent person who simply purchased the house? I would think he would be angry at his ex-wife and not some innocent person.
You said you had the problems in you former home too. Why would that happen before you bought the house from this Air Marshall? Did you know him then?
Sometimes the radio, TV and loud-speakers can be affected by strong signals from a CB transmitter. Usually, it is an innocent occurrence.
Detecting laser spy microphones
Question
January 22, 2007
Is there a way to detect if someone is using a laser to detect conversations in your house and is there an effective way to protect against these invasions?
edward - USA
12935
Answer
There are devices available that use invisible infrared laser beams to reflect off windows and detect conversations. But they cost about $50,000. So, they would most likely only be used by government agencies or for corporate espionage. It is unlikely such a device would be used to spy on an average citizen.
Less expensive devices use visible laser light and can be noticed inside the house. Turing on the radio or television can make conversations very difficult to record.
Interested in digital signal processing
Question
March 24, 2006
hello i m interested in doing a project in Digital signal processing for that i need to about the different Sound features that distinguish on sound from other can you plz help? if possible plz send some other data also that can be of some help for the DSP Field Sound section ,or any other refrenses you find useful,and yaa the site is amazing n found it really useful.
rahul - India
10586
Answer
A couple of good tutorials on digital signal processing can be seen at:
http://www.dsptutor.freeuk.com/
http://www.bores.com/courses/intro/
I hope that helps. It is an interesting subject that is an important technology.
Trying to see how loudness is affected by distance
Question
January 7, 2006
We are doing a science experiment in which we are trying to see how the loudness of one pitch is affected by distance and also how one pitch relates to another. I wanted to see if lower pitches measure to be louder at further distances than higher pitches of the same loudness at their origin. When I did this experiment, my results did show less loudness as I moved from 5,10, 15, 20, 25, to 30 ft for all the frequencies. But, I don't see a pattern when I compare pitches. Often, a lower pitch was softer at 5 feet than a higher pitch presented at the same intensity. I am having trouble figuring this out as my research told me that the opposite shoud happen. At 30 feet, I expected that a high pitched sound would not travel as far or as easily as a low pitched sound. ( I measured my hallway in five foot increments and used a portable audiometer with a speaker attached to present the tones. The tones I used were 500, 1000, 2000, 3000, 40000 and 8000.)I guess I was under the impression that the bigger soundwaves would travel further....Can you help me with this ...do you think I was doing something wrong? I used a sound level meter and recorded my data five times for each presentation level. I am looking forward to hearing from you. Thanks
Kileen - USA
9589
Answer
There are two reasons that the loudness of sound drops. One is that the sound spreads out as it travels from the source. The spreading is the same for all frequencies.
The other reason is that some of the sound energy is absorbed in the material through which it is traveling. Absorption is dependent on frequency or pitch of the sound. There isn't that much absorption in air.
You might try the experiment using different thicknesses of some material like water or even wood. People wonder why certain musical notes go through their walls but others don't.
Note that in your hallway, the sound is reflecting off the walls in a waveguide effect. This reduces the loss in amplitude from normal spreading of the sound wave. Also, some frequencies may bounce off the walls better than others.
At the very least, you can state all the conditions of your experiment and your results. Then your conclusions are that in this situation, you will get a certain set of results. You don't have to force your results to fit what you expect to happen.
Best wishes with your experiment. It seems like an interesting one.
Experiment with wine glasses
Question
August 24, 2005
hi..i'm just wondering if you could help me with my science project. well, i'm investigating the factors that affecting the sound produce by a wine glass. the sound is produce by rubbing your wet finger along the rim of the glass. some of the factors that had been identified is the diameter, the shape and the material used to make the wine glass. but, right now, i'm facing a problem in collecting the data. in oder to determine the different sound produce by different wine glass, i need to have a data. a quantitative data and not a qualitative data. is using an oscillooscope will be helpful for me? or do you have any other suggestion???please reply to me as soon as possible...thank you.
liyana - Malaysia
7865
Answer
Your experiment should not be simply investigating factors. Rather, you want to select one factor and see what happens when you vary it. Otherwise, the experiment can get out of control.
By rubbing your finger across the rim, you set up vibrations. The shape of the glass and amount of liquid determines which frequencies will resonate and increase in volume.
A big problem to consider is that the process of rubbing your finger along the rim can vary with wetness and other factors. It may or may not affect things too much, but you should be aware of the situation.
One experiment to do is to see how the pitch and volume changes with the amount of liquid in one type of wine glass.
If you try to compare materials in several wine glasses, you run into the problem of different shapes and amount of liquid. By keeping the level the same, you might be able to compare them.
As far as collecting quantitative data goes, you should make an audio tape of each trial. You can use the recording as a demonstration, as well as to repeat your measurements. A microphone and an oscilloscope could help to find the amplitude and frequency of the major wavlengths of the sound.
A question concerns your conclusions. What are you trying to prove? With the first simple example, you can plot frequency versus level of liquid. If you are trying the experiment with different types of glasses, then perhaps you could show how a combination could be used to create a whole spectrum of sound.
I hope these ideas help. Best wishes in your experiment, and let me know how things turn out.
Why sounds are different
Question
May 24, 2005
Could you please tell us why sounds are different.
Simon - Australia
7056
Answer
Sounds differ from the sources. A trumpet sounds different than a guitar. It is the combination of notes and amplitude. Notes vary by wavelength.
Noisy neighbor sound system
Question
November 10, 2003
My neighbor is using a sound system filling my house and striking me sometimes hurting but leaving hot spots like on my head. It makes everything either louder, vibrate, or echo. I have tried everything please advise so I can live in my house. I know it is going in a V shape around my house and also scans inside to follow me when I pass the two areas in the house going straight through. Please HELP I have been here so long in this I can hear ultrasonic sounds I never heard before.
Glenda - USA
1138
Answer
You might check to see if there are some ordinances on excess noise in your community. People should not have their sound system on so loud that it bothers their neighbors. It is bad enough in an apartment, but it really must be loud to affect people in another house.
Have you checked with your other neighbors to see if the noise bothers them?
Apparently, the shape of your house focuses and amplifies the sound. Although you should not have to use anti-noise earphones, they may help to give you some peace. See:
http://www.school-for-champions.com/science/noise.htm
You can buy noise reduction earphones for about $100. But still, check with the police to see if any laws are being broken with the noise.
Best wishes in solving this problem.
High frequency sound from airplanes
Question
October 6, 2003
Can planes give off high frequency sound waves that may be harmful to humans?
Vickie - USA
756
Answer
Not really. Sonic booms can startle people, but they are low frequency. High frequency noises from jet engines can be irritating to passengers. Sound from airplane engines outside can be harmful to hearing, due to their high volume.
Sounds from Hurricane Isabel
Question
September 15, 2003
Yes, we live on the NC coast. Emerald Isle. Area,
For the last three days we have heard a loud but faint at times roaring sound coming from the ocean, and it isn't the waves. you can here it as far as 3 miles from the sound. It sounds like a jet plane flying around and around in a big circle. And it is non-stop.
But you hear it more at night. Is it possible that we are hearing Hurricane Isabel? Isabel is over 700 mile away at this time. We are going back down to the water to record the sound tonight.
Love & Prayers
Lynn - USA
538
Answer
It certainly is possible that you are hearing sounds related to the hurricane. Low frequency sounds can travel great distances. 700 miles seems a long way, but much of the vibration causing the sounds is traveling through the water, so it moves much faster. Also, there is a tremendous amount of energy in that hurricane.
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Answers to Readers' Questions on Sound Detection