5. Scientific concept :
The speed of sound is the distance
travelled during a unit of time by a sound
wave propagating through
an elastic medium.
In common everyday speech, speed of
sound refers to the speed of sound waves
in air.
However, the speed of sound varies
from substance to substance. Sound
travels faster in liquids and non-
porous solids than it does in air.
6. Last weekend, my family decide to go to Gua
Kelam in Perlis. As we walk through the cave there
is a lot of nice things to watch. Then, I notice
something interesting, when we talk in the cave, we
can hear our voice be reflect. We hear our own
voice echo. Why this happened? I also notice the
same phenomena occur when I talk in empty house
or when I shout in the tunnel. How can this happen
and what is the cause?
7. EMPOWER
Equipment required
2 microphones-crystal Mics were used since
they are cheap and give a large output
1 metre wooden rule
Fast digital storage oscilloscope-the ADC-212
was used
A balloon-to burst for a sudden loud sound
source
8. Experiment set up
The experiment was set up as shown below with two
crystal microphones placed 1 metre apart
9. 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.
10.
11. 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.
