how does an audio signal work?

[[email protected]]

When I plug headphones into an ipod, I know that electricity of some kind
flows through the wire into the headphones, producing sound. What I don't
understand is, what exactly is done to the electricity to make an audible
signal?

I'm pretty sure the ipod controls the volume by changing the amplitude. If
you put a variable resistor between the ipod and the headphones, you can
reduce the volume. How does the ipod control the pitch of the sound? Does
it change the voltage, or the frequency (turning it rapidly on and off), or
what?

 

[[email protected]]

Without going through all the interim steps, the basic concept is that the
voltage coming out of the iPod (at any given volume control setting) is an
'analog' of the original vibrations of the source of the music.

Let's say that you're listening to somebody who was whistling into a
microphone, and let's also say that the person was whistling a pitch that
was a pure and simple sound (aka a sinusoid), and let's also say that the
whistling was vibrating the air (and microphone diaphram) 422 times per
second.

The voltage coming out of your iPod will be vibrating at the same rate,
that is at 422 times per second. When this vibrating voltage is then
applied to your headphones (because they're plugged into your iPod) then
the headphone's voice coil and diaphram will be shaking back and forth 422
times per second.

If you turn down the volume control on the iPod, or add resistance between
the iPod and headphone's wires, then the magnitude of the voltage
vibrations at your headphones will be reduced, but the rate at which the
voltage is vibrating is still 422 times per second.

The key thing to note is that the 'shape' or 'pattern' that the vibrations
take will always be similar, or an analog, of the vibrations of the
original whistler's microphone's diaphram. The relative size of these
vibrations will vary depending on the setting of the volume control, but
the shape of the vibrations will still be similar or analagous to the
original whistle.

So, in a nutshell, the iPod does not directly control the frequency of
what is fed to your headphones. It only is changing the voltage to the
headphones in an attempt to maintain a similar looking
pattern/shape/analog between that which has been recorded and the voltage
to the headphones.

If you want a more detailed explanation of how the entire process works
(i.e. analog-to-digital conversion, digital storage, digital-to-analog
conversion) then you'll need to do a lot of reading.

Bob

What is a "vibrating voltage"? Does that mean that, in your example, the
voltage is turning on and off or changing directions at 422 times per
second?

What exactly does it mean for voltage to "vibrate"?

Thanks for your time.

 

[[email protected]]

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Scope, Spectrum, Spectrogram, Sound Level Meter
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Does it work with ubuntu?

 

[Rich Grise]

When I plug headphones into an ipod, I know that electricity of some kind
flows through the wire into the headphones, producing sound. What I don't
understand is, what exactly is done to the electricity to make an audible
signal?

I'm pretty sure the ipod controls the volume by changing the amplitude. If
you put a variable resistor between the ipod and the headphones, you can
reduce the volume. How does the ipod control the pitch of the sound? Does
it change the voltage, or the frequency (turning it rapidly on and off), or
what?

Start reading here:
http://www.google.com/search?q=basic+electronics+tutorial
and all will be revealed to you.

Well, you might want to pick up a battery, a light bulb, a magnetic
compass, a bar magnet, and some hook-up wire.

When you've done some reading, if there's something you don't understand,
feel free to ask for clarification - we were all newbies once.

Have Fun!
Rich

 

[Jasen Betts]

Does it work with ubuntu?

for ubuntu use xoscope