What is the simplest sound generating circuit?

Question

I'm relatively new to electronics, and have no formal training other that what I picked up through my electrical engineer father. I solder well, can read schematics, have assembled kit projects with a rough understanding of how all the parts work, and know basic electrical terminology and principles. Ohm's law is about as far as my electical math skills go.

So while this may seem like a very basic question to a more experienced and better trained person, please bear with me.

I spent a couple weeks messing around with some LEDs. I started by just hooking one up to my power source. Then, what happens when I add a resistor? What about a capacitor? what about resistors in parallel vs. series? From just playing with my breadboard, I now have an LED that blikcs randomly. Impressive? Nah...but I figured it out myself, and feel that I truly understand it.

Now, I want to design a synthesizer from scratch to give myself an understanding of how specific components affect sound. Starting from the most barebones circuit that can make a noise, I want to add a pot, then some capacitors, then some 555s...you get the idea. I just want to start with the basics and play around to see what happens.

Finding that circuit is proving to be quite difficult. I'm looking for a circuit more complex than hooking a speaker directly to a battery but less complex than http://www.musicfromouterspace.com 's Wacky Sound Generator (which, while simple compared to a real synth is still a lot more complex for me to truly understand what component A vs. compoent B does).

In essence, I want to find the sonic equivalent of Battery-to-Speaker and start playing with what can happen in between.

Electronics golf: what can produce sound with the minimal number of components?

Answer 1

The 555 is a good way to start making tones in a speaker. I suggest you make a simple oscillator using one, before you attack projects that use several of them.

Also, we had a question, What is the simplest way to make an oscillating signal? That turned out to be an inverter gate with feedback.

Answer 2

Super-simple solution: a Schmitt's trigger inverter like this:

and you create a simple square wave tone. You can also filter and manipulate it to make different waveforms.

Consider that with oscillators at different frequencies you can create virtually every sound: that's what the Hammond organ does.

A slightly more complicated but extremely more versatile solution is to use a microcontroller with a quick DAC and generate tones with it. Then you can do many things, from using pots to set frequency and volume, but also create loops or more sophisticated things.

Answer 3

Sound is just vibrations, vibrations are caused by "blinking" the speaker coil. The only difference is instead of blinking a few times a second, to blink a few hundred times a second. Whatever you did to make the LED blink, change out some capacitors with smaller ones, and stick the speaker in place of the LED. It might make noise.

Answer 4

If you want something where you can easily change the sound, I recommend the Atari Punk synthesizer, as published in Radio Shack's Engineer's Notebook, by Forrest Mims.

It certainly wouldn't qualify as "simplest", but it is the simplest circuit that can produce something approaching music. It's also a 1-IC circuit if you use the dual timer 556 package, instead of two 555's.

Answer 5

The simplest circuit, assuming it can be manually operated, can be just a battery and speaker with wire brush at one end. By short circuiting, by grinding the brush against other electrode, you will create audible noise.