# Determine the Speed of Sound

5 Steps
I will go through a process that will allow you to determine the speed sound travels. This is a classic physics lab that in the past would have required lots of expensive equipment. The only expensive equipment involved here is a computer with a microphone input. Which by itself can be expensive, but most classrooms these days have at least one in the room.
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llanyort says: Jun 18, 2009. 1:18 PM
question(s) - 1)what if you wanted to measure the distance from the object(that created the sound) to the microphone that captured the sound ? 2)what if you placed two or three other microphones in the room in each corner, could you use them as well ? or would they cause any foreseeable problems in this project ? Im trying to pinpoint the distance and vector of an orignating sound. Is this possible ?
falconphysics (author) in reply to llanyortJun 18, 2009. 2:12 PM
I've not tried using multiple microphones with Audacity before. I'm not sure you could do that. What you could do would be to wire two mono microphones to the stereo input and record as a stereo track though.
llanyort in reply to falconphysicsJun 23, 2009. 8:03 AM
thats a good idea !!! thanks.. :-)
MAD LAB says: Aug 18, 2008. 6:44 PM
i am still a student taking up bs physics!! just want to ask wer can f find audacity program in our computer system! pls help me tanx
cowgomoo in reply to MAD LABMar 23, 2009. 9:37 PM
well i dont know what the hell you just asked but if i get what your saying, no audacity does not come standard on your computer. google "audacity download" and it should take you to the audacity homepage. just download the version that your system requirements meet.
Kiteman says: Jun 12, 2007. 11:24 AM
Why do people assume you need high-tech equipment to do decent science? You can calculate the speed of sound with two lumps of wood, a stopwatch and a convenient wall.
ewilhelm in reply to KitemanJun 12, 2007. 11:43 PM
How long do you think you can get away with having a comment like this and no Instructable showing us how?
Kiteman in reply to ewilhelmJun 13, 2007. 1:43 AM
Doh! OK, I know what I'm doing with my Science Clubbers tomorrow night...
falconphysics (author) in reply to KitemanJun 12, 2007. 11:50 AM
You're right, you don't need high-tech equipment to do decent science. In many cases I do very low tech labs. It all depends on what I'm trying to teach. The tech tools can often be more engaging for students, which is one of the reasons I use them. Additionally we use Audacity for some later labs and this provides a great introduction to the program.
mrmath says: Jun 12, 2007. 10:27 AM
Makes me wonder two things. 1) Is there anything open source can't do? :) 2) How'd they do it before the computer made it this darn easy?
Mister_Caipirinha in reply to mrmathJun 12, 2007. 1:29 PM
2) answer: Two microphones one meter apart connected to an oscilloscope. Do I get another prize??
falconphysics (author) in reply to Mister_CaipirinhaJun 12, 2007. 2:11 PM
Sure, if I win the laser cutter I'll send you not one, but two official prizes. ;)
Mister_Caipirinha says: Apr 14, 2013. 12:53 PM
It is also worth pointing out that the pulse comes back inverted - that first "down" peak comes back as an "up" peak - since the end of the air tube can be considered as fixed (cement has larger impedance than the air). If you can detect a reflection from the end just held up in the air it may be erect (assuming air not surrounded by the tube has a lower impedance that air in the tube). Neat!
falconphysics (author) in reply to Mister_CaipirinhaJun 12, 2007. 11:51 AM
Give the man a prize. The wave is indeed inverted when it reflects.