Answers to Readers' Questions on Sound. Also refer to physics, waveform, vibration, compression, matter, vacuum, characteristics, amplitude, volume, velocity, speed, air, frequency, pitch, wavelength, ear, microphone, Ron Kurtus, School for Champions. Copyright © Restrictions
Answers to Readers' Questions on Sound
The following 68 questions have been answered. They are listed according to date.
List of next 10 items
- Figuring out dB rating
- Making sounds with cardboard tubes
- Recording sound from a piano
- Can sound waves heat substances?
- Does shape determine how much is absorbed?
- Detecting stereo sound underwater
- Sound under water project
- Doing experiment with sound
- Underwater sound experiment
- Thank you soo much for your efforts
Figuring out dB rating
Question
December 27, 2005
My question is a rock band's music has an average sound intensity level of 123 dB.
What would the average level be if the intensity were reduced by 1/2 and reduced by a factor of 1/100?
- USA
9480
Answer
Figuring that out gets pretty hairy, since you need to use logarithms. Some scientific calculators have a log function.
See: http://www.phys.unsw.edu.au/~jw/dB.html for an explanation of how to calculate the difference in level.
Making sounds with cardboard tubes
Question
November 16, 2005
i am trying to come up with a way to make an experiment up by using cardboard tubes of diferrent sizes. each one has a long spring hanging from the bottom. each tube makes a differnt sound. (like thunder) i thought that this would be a good science fair project using vibration, but what i find is much more complex. i still want to use the card board tubes....i need help!
- USA
8979
Answer
You don't really need to explain the details in how something works. Some areas of vibration for making sounds can be very complex. The vibrations in a drum is a good example.
What you want to do is to perform an experiment in a good scientific manner. By varying the length of the tubes, you can show how the frequencies of the sounds change. But the length and type of the springs must be constant. If you change the springs, then you should keep the length of the tubes the same--at least for a single set of experiments.
The big thing is to measure the sounds you get to compare them with the changes in length. Doing it by ear may be OK, but it really is better to have a meter that will give you some numbers.
I hope those ideas help. Best wishes in your project.
Recording sound from a piano
Question
October 9, 2005
I'm fairly new to recording classical piano. If sound waves move in a straight paths, is there any reason to place microphones very high from the piano. In fact, any hints regarding miking pianos would be helpful.
Gret site.
Steve Halpern
stephen - USA
8465
Answer
Sound radiates in straight lines from the source. Thus it can be heard in all directions from the piano string. But you have to take into account reflections off hard objects and sound that is absorbed by softer objects.
Much of the sound from a piano goes upward, especially if it has an open top. That sound is probably the most pure, since it is not being reflected by furniture and other obstacles.
It is worth experimenting by placing the mic in different positions around the piano to see which gives the most pleasing sound to record.
Can sound waves heat substances?
Question
September 12, 2005
A question.
If sound travels through solids in waves, or vibrations.
And conduction of heat through solids is also vibrations of atoms in solids, then can sound waves heat substances. If not then why?
Fantastic site
Lynda - UK
8094
Answer
At any given temperature, the molecules in a material are moving randomly, bumping into each other, etc. In a solid, the movement is confined, but the movement is not really a vibration. As heat is added and the temperature goes up, the molecules speed up.
Sound is a regular vibration of the molecules in a material. This adds to the existing motion of the molecules in the direction of the sound. If the frequency and power of the suond wave is high enough, the temperature of the material can rise noticeably. Some ultrasounde devices are used to heat up materials.
Does shape determine how much is absorbed?
Question
January 8, 2005
Does the shape of a material( or the shapes that make it up) affect the volume of a sound through that object?
Timothy - USA
5546
Answer
The external shape and hardness determines how much sound is reflected. Then the internal material can determine how much sound is absorbed. Like, if the material is a loose mixture of particles or threads, the sound will bounce around internally and much more will be absorbed. That results in less sound coming through the material.
Detecting stereo sound underwater
Question
December 3, 2004
Thanks for the info on sound/audio. Would you please confirm the following with more specific, "Why is it so?"
I know that installing a stereo sound system in a swimming pool will not be effective (a mono system would be as good using just one speaker)because our ears under the water are virtually 'short-circuited' and in conjucion with the faster sound movement (about 5,000 feet p/sec.), loudness in either ear would be the same as well as time arrival in one ear in respect to the other and/or phase difference to both ears would inhibit stereo perception. I belive our heads are partly there to keep our ears a certain distance apart to appreciated from which direction sound is coming! (I would appreciate more technical reasons for the above, thanks)
Ted - Australia
5233
Answer
Actually, the reason people can't hear stereo under the water has more to do with the way the human hears the sounds. Underwter sound vibrations are detected and conducted by the skull, bypassing the individual ear drums. Also, the density of the ear drum is so close to water that it is not effective in detecting sound waves.
A good study on the subject is at:
http://ccrma.stanford.edu/~blackrse/h2o.html
Sound under water project
Question
November 17, 2004
My friend and I are doing a science fair project on sound waves. How can you measure sound waves underwater? How do sound waves work underwater? Our idea is that sound waves are slower because of all the pressure. We are going to experiment. One of us will scream as loud as we can, and the other one of us will record using a timer how long it takes for us to hear it. We will do this from 10 feet, from 15 feet, and then from 20 feet. Then, we will do the same thing on land. We will record the data and then compare the two to see which ones are slower and wich ones are faster. Please help us to make our science fair project even better. Are there other ways to record sound waves underwater? Are there other ways to measure how long it takes? Please write back. We would love your input on this.
Thank you!
- USA
5066
Answer
Sound travels much faster under water than it does in air. If you put one ear under water and one ear out of the water and have someone click two clickers--one under and one above the water--at the same time, you will be able to show that sound travels faster under water.
You can use a stop watch to measure the speed of sound in air, if the distance is like 100 yards. But it goes too fast under water. The bes thing is to compare.
I hope that helps you with your project.
Doing experiment with sound
Question
November 8, 2004
hi! my name is matthew, and i am in the 7th grade at kamehameha schools hawaii campus. i am in a science fair club with my friend, and we are doing sound waves. our experiment is going to be trying to measure sound waves through different types of substances and solids, such as water, brick, wood, and moist air. i'm not exactly sure if our project will be the best because of the things we will have to record. i'm also not so sure if the results will turn out correct because of the circumstances of weather, outside noises, and temperature (if temperature affects the outcome of sound waves). i was wondering if you could help me to think up an excellent way to make this project work. also, i really like your site. it gives me a lot of information about my topic, and i'm glad that it is there for me when i need it. my teacher reccomended it for my type of project. i'm very glad that your site has so much detail on scientific subjects! anyway, please help my science fair project to be a success. i would really appreciate it.
thank you very much.
your humble "student",
matthew a.
p.s. do you think you could also include some other resources for my topic? you don't have to, but it would be very nice if you did, becuase my topic isn't too popular on the internet.
matthew - USA
4956
Answer
What you are trying to measure is how much the volume of sound decreases as it goes through various materials. That is called attenuation.
Your sound source must have the same volume for each test. A tuning fork is the best since it is constant and has a simple sound. But you could use some regular sound played on a tape recorder as your source.
When you do this, the thickness of each material should be the same. Moist air is not a good choice, because the decrease will be extremely small. You might make a tube and put the sound source on one end and the object on the other end. This would help to prevent sound from leaking around the edges.
To record the sound, it is best to use a tape recorder, so you can demonstrate it and play back the sounds for better measurements. Some tape recorders--like in stereo systems--have volume meters or a row of LEDs to indicate the volume of the sound. That is a good way to measure the volume.
The first test is just in air. Then you compare each material with the value for air.
I hope that helps you set up your experiment. Best wishes and let me know how it turns out.
Underwater sound experiment
Question
November 8, 2004
hi! i'm in the seventh grade and am in our school science fair. my partner and i are doing an experiment on sound waves underwater, and the following questions came up quiet a few times:
how can sound waves be transmited underwater? how can sound waves be recorded underwater?
please help us get some more information on these topics. we'd really appreciate it. thank you!
-kawena
kawena - USA
4954
Answer
The best sound source for underwater is something mechanical like a clicker or tuning fork. Of course, you can hear sounds under water, but it is more difficult to record and save them. If you use a battery powered tape recorder, you could wrap a mic in something like Saran wrap to keep the water from it. Don't use an expensive microphone, in case it gets wet. And especially, only use a battery powered tape recorder and keep it out of the water.
So you can create sound and record it under water. So what? There has to be some question you want to answer in your experiment.
Thank you soo much for your efforts
Question
October 27, 2004
thank you soo much for your efforts and knowledge has helped me very much. once again I would like to thank you for being such a help.
Steffan - USA
4811
Answer
I am glad the material was useful to you. Best wishes in excelling in what you do.
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Answers to Readers' Questions on Sound