"The music that we are hearing is actually 8 seconds old."
That was my friend's claim.
My friends and I were about 13 years old, and we heard loud music coming from a big event about 3 kilometers away.
"The speed of sound is 340 meters per second, and the event is 3 kilometers away. So that means what we hear now is what they played 8 seconds ago at the stadium" our friend told us.
I found it hard to accept because I didn't know too much about sound and how it worked.
But my friend was really good at memorizing facts.
And he was right.
I, on the other hand, was more interested in understanding things.
So I was more interested in what sound is.
And more importantly: How could I create sounds myself?
Now, 20 years later, I know that sound is a variation in air pressure.
For example, if you move your hand back and forth really fast, you are creating a variation in the air pressure.
Humans can't hear anything below 20 Hz. So unless you're able to move your hand back and forth at least 20 times per second, you won't be able to hear any sound.
If you're like me, you're now frantically waving your hand to see if you can do it.
But I'm not even close to moving my hand that fast.
Instead, you can make sound with electronics. You just have to make "something" move back and forth at least 20 times per second (or 20 Hz).
(But it's only young people who can hear as low as 20 Hz, so if you're older, better make it 50-100 times per second)
This "something" could be the diaphragm of a speaker.
To make it move, you could, for example, create a circuit that alternates between 0V and 9V, and feed this voltage into the speaker.
Think back to yesterday's circuit.
What if you replaced the LED with a speaker?
Like this:
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Our LED-blinking circuit blinked an LED about one time per second.
Or 1 Hz.
That's too low to make sound.
But if we reduce the value of the capacitor in the circuit - meaning that it will charge and discharge significantly quicker - it can easily give out a few thousand hertz.
Replace the capacitor with one that is about 100-1000 times smaller, in value, and you should hear the sound.
NOTE: To build this circuit, also add a resistor (value 600 to 1000 ohms) in series with the speaker to avoid too much current being drawn from the chip.
And that's the basis of many electronics applications - for example the analog synthesizer which is one of the courses in our Ohmify community.
It's when you put these things together in real life - using actual components - that it all really comes to life. Our members do this all the time, and it's excellent fun!
If you want to build on your learning, understand precisely what others understand about electronics, and make all this second nature, then Ohmify is absolutely your quickest route to electronics success.
Tomorrow I'll send you some tips on learning electronics - but if you're ready to take this up a notch then you can learn a whole lot more about Ohmify by clicking here.
SUMMARY
We saw that the circuit that makes an LED blink makes other things happen too. You've learned the basis for a whole range of applications - many of which are explored and built at Ohmify.
Keep On Soldering!
Oyvind @ build-electronic-circuits.com
Ohmify is an online academy to learn electronics from scratch. Our members are hobbyists, teachers, inventors, artists, and more - from all walks of life. Our library of courses and project plans assume no prior knowledge. Get support, learn, build and chat with people like you - find out more here.
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