Scientific concept : The speed of sound is the distancetravelled during a unit of time by a soundwave propagating throughan elastic medium. In common everyday speech, speed ofsound refers to the speed of sound wavesin air. However, the speed of sound variesfrom substance to substance. Soundtravels faster in liquids and non-porous solids than it does in air.
Last weekend, my family decide to go to GuaKelam in Perlis. As we walk through the cave thereis a lot of nice things to watch. Then, I noticesomething interesting, when we talk in the cave, wecan hear our voice be reflect. We hear our ownvoice echo. Why this happened? I also notice thesame phenomena occur when I talk in empty houseor when I shout in the tunnel. How can this happenand what is the cause?
EMPOWEREquipment required2 microphones-crystal Mics were used since they are cheap and give a large output1 metre wooden ruleFast digital storage oscilloscope-the ADC-212 was usedA balloon-to burst for a sudden loud sound source
Experiment set upThe experiment was set up as shown below with two crystal microphones placed 1 metre apart
Results : The balloon was burst approximately 2 m away from the foremost Mic. The plot below shows the results clearly. The lefthand “BLUE” trace is from the fpremost Mic (Mic 1) and the righthand “red” trace is from mic ( Mic 2) The waveform from Mic 1 between -164µs and 500 s is clearly visible in the trace from Mic 2 delayed by 2929 µs. There is second variation , in the waveform from Mic 1, around 1.5 ms caused by an echo from one wall or ceiling.
ENHANCE Telling how far away a person with a starter’s gun, at a running race, is by comparing the time difference from when you can see the gun’s smoke to when you hear the sound. Telling how far away a cliff is by making a sound and measuring how long it takes for the echo to return Telling where an enemies gun was fired. Telling how far away a lighting strike.