When you turn down or up the volume on devices with either a wheel or button, what actually happens that allows it to sound quieter or louder?
In: Technology
On electronic devices it’s easier to explain. It’s what the top comments say, but it’s a digital control.
Turn the knob marked volume to the right (or press the up arrow) to make it Too Damn Loud & turn it to the left to hide yourself from the monsters.
the amplifier that drives the speaker(s) is always “cranked to the max”. the volume knob normally stays in front of it and divides the quiet input signal into two parts – a proportion of the signal is sent to the amp to amplify, and the rest is consumed by something passive e.g. a simple resistor, and is never amplified. so the volume knob usually attenuates the signal so not all of it is amplified; that allows you quieter volume.
(preface: while only a hobbyist, I’m a self-taught electrical engineer focusing on audio amplifiers, and specifically guitar amplifiers, and specifically vacuum tube based audio and guitar amplifiers.)
Someone once told me “an amplifier is just a power supply that is modulated by its input.” So when you think of a power supply, think of the simplest one for a second: a battery. You have a positive voltage on one side, and a negative on the other (usually grounded, so the negative voltage is only relative to the positive voltage).
If you hook up a 9V battery to a speaker, guess what? The speaker moves. You don’t ‘hear’ the sound, but you’re able to visually SEE what a 9V signal ‘looks’ like. It doesn’t look like the sine-wave you think of when you think about ‘soundwaves’, right? Well, that flat-line can be thought of as a wave with a frequency and/or amplitude of 0. It’s useful to note that if you used a 4.5V battery, the speaker would move the same direction, but not with the same force. If you quickly switched the batteries back and forth, say, 60 times per second, you’d be creating an electrical soundwave. 60hz is (in North America anyway), the frequency that you hear humming from electronic devices. (and fluorescent lights? those are 120hz ‘buzz’. the why 60/120 is another topic for another time!)
If, that signal were wiggled (modulated) at a specific frequency (think pitch) and given an amplitude (this is effectively what becomes volume), you’d hear it out of the speaker. When you listen to a song, it’s not just one tone, it’s a whole lot of different tones being produced–but lets just focus on a single, simple, soundwave. I want you to visualize a sine wave for a moment. The closeness of the peaks/troughs is your frequency (the pitch), the HEIGHT of those peaks and troughs is your amplitude.
The specifics of the circuit will dictate how this is all achieved, but the volume control will either expand or restrict the maximum amplitude (the ‘height’ of that electric signal). Some amplifiers actually have fixed amplification (lets say 100x for a nice round number), but will allow you to limit the input signal on them through a simple resistive divider (a potentiometer, a “knob”). (note: the following is for illustrative purpose and intentionally simplified). So it may take up to 1V of signal coming in, and will shoot out 100V of signal on the other end. The potentiometer here divides the input signal, so say that 1v signal is dropped down to .25V, then that is still amplified 100 times, and comes out as a 25V signal. Other, newer, amplifiers work by raising or lowering the whole working voltage (or power) of the amplifier. So it may take a 1v signal, but the overall level of amplification of the amp is not fixed at 100x. (most do this through some type of power regulating circuitry which can be as simple as a very, very big potentiometer (known as a passive component, similarly a rheostat), or very elaborate involving digital and solid state active components (think transistors, IC chips, etc).
Whether done by active or passive components, this restriction, in turns, limits the electrical signal that is sent to your speakers. Speakers are an electro-motive device. They convert electromagnetic energy (your electric sine wave) into mechanical energy (by vibrating the air, they ‘wiggle’ the molecules in the air; the concept for overall volume is called ‘sound pressure level” or SPL and is measured in decibels, or dB. this last bit is unimportant, but thinking of sound waves you hear as literal pressure waves is neat).
There are various ways to do it. One is a potentiometer (if the knob has a hard low stop and hard high stop it may be like this), or it could use essentially micro switches to send pulses that the device uses to count up or down. There are probably other ways to do it as well.
Wildly simplified:
Imagine a strip or a rod, which has some electrical resistance.
One wire is connected to the end, the other slides up and down on the strip.
When you slide far away, the resistance between the 2 wires is bigger, and gets smaller as you slide the other way.
(Potentiometers are a bit more complex than this, but this is the overall simple concept of it)
I’ma tell you what I know, because I made quite a few of these circuits in the past year, someone more knowledgeable should critique me.
Your knob is a potentiometer, which is essentially a variable resistor. By turning the knob, you will either increase or decrease the resistance within the circuit. Due to ohm’s law, this will also affect your current and voltage.
By decreasing the resistance (turning up the volume) you are increasing the voltage and current. This increased voltage will go and power the electromagnetic vibrations within your speaker.
My question is, how does that speaker actually being “louder” happen? Is it just from the speaker operating at a higher or lower frequency? If someone could explain what’s happening within the speaker itself that makes us interpret the sound as louder I’d appreciate it.
The speaker holes get bigger or smaller depending on the buttons or direction of knob spinning and the phase of the moon
U/toxiclay had half the story: the other half are the buttons which are just momentary switches that tell the microcontroller to lower the volume by software. Like in your phone, you can program the input to be contextual, as well, so if you find your volume button it will bring up the power optima for sitting down/resetting the phone, or take a picture if you’re in the camera app.
Two different methods.
Analog devices are often continuous and involve the moving of a variable capacitor or resistor to change the electric makeup going to the speaker.
In a digital device nothing changes really, the knob is a user interface that tells a circuit to apply more or less voltage. However b/c it’s digital (all 1s and 0s) you never get continuous band control. Think if you’ve ever had a problem with a digital speaker that is too loud on one step and too quiet on the lower step
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