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
A volume knob or wheel is an example of a device called a *potentiometer*, which is a device that adjusts the voltage going down a wire by increasing or decreasing the electrical resistance.
If the resistance increases (if you turn the volume knob down), then less voltage makes it to the speaker, the cone vibrates less intensely, and the sound is quieter. The opposite is true if you turn the volume up.
A system consists of some signal source (tape player, radio etc), usually a preamp, an amplifier and a speaker.
The volume control sits between the preamp and the amplifier. The preamp produces a signal that is (generally) about 1 volt. The volume control has a long resistor, with a wiper that makes contact with the resistor at some point along its length. The preamp output is connected to one end of the resistor, and the other end is attached to the 0 volts point (‘ground’). The wiper is connected to the input of the main amp, which produces a signal with the voltage and power needed to drive the speaker.
When the volume is high, the wiper attaches to the resistor right beside the input. So the full 1volt signal appears at the input of the main amp. When the volume is fully down, it the wiper attaches to the resistor right down at the ground point – there’s no voltage there, as it is at 0 volts, so the main amp sees no signal and you get nothing out.
Anywhere between that, the wiper contacts the resistor somewhere along it’s length, and so the main amp sees somewhere between the full 1v signal and nothing, controlling the volume.
Nowadays the wheel or buttons generate pulses that control a computer that controls the D/A converter that controls the volume of the signal. To get increased dynamics, there can be one D/A converter for the volume and one (much more high resolution) for the signal, multiplied to get the end result, but it’s not a given. Also, the equalizer is completely digital, using digital (calculated) filters.
Sound travels through your electronic device as a very small electrical current. Think of this current as “flowing” like water.
When the volume knob is all the way up, all of the water is allowed to pass through it, but as you turn the knob down, less and less water is allowed through. The amount of “water” coming through = volume.
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Depends.
On purely analog devices audio is just an electric signal. When you adjust the gain you are controlling how much electricity you are letting through, like a water tap.
On digital devices this is more complicated but, generally speaking, when you press the volume buttons you are also controlling how much electricity is being sent to the speakers although not directly. Some code is interpreting your actions on the volume buttons and then this either results in the digital audio signal having less amplitude, or controlling the analog amplifier, or both.
An audio amplifier with a mechanical knob for attenuating the sound level accomplishes this with a variable resistance resistor called a potentiometer. Upon changing volume down, the extra sound that was there is sent to a parallel universe according to the laws of string theory. Energy is conserved due to the increase in volume elsewhere in the multiverse. In fact, it doesn’t matter whether you turn it up or down, even turning it to 11, since all possible outcomes exist in the multiverse, and the one you are experiencing now is just one of an infinite number of universes where another version of yourself is listening to the same song at different volumes. It’s all proven here:
See suggested for answers on analog devices. I just wanted to add that some devices save space and material by digitizing the input from a knob or wheel and converting the command to the audio section of a device.
On a digital wheel that you can keep spinning even when the volume is at 0 or 100, the input process is a two step assignment loop input, with short polling. Placing a finger on the wheel sets the start value (step 1). Then the direction the finger moves sets the positive or negative value (step 2). That value is sent to the audio “tap”, telling it to open or close a bit more. The value resets back to zero value of step 1, waiting for another directional input. It repeats that for as long as you’re tracing that finger along the track wheel.
Sound is sound waves, similar to waves in the water.
The device creates sound by sending electricity to a speaker. The electricity pushes the speaker inwards or outwards, creating a larger or smaller wave, depending on how much electricity you send through.
To make it quieter, the device simply sends less electricity. This can be done in multiple ways, e.g. changing the amplification in an amplifier circuit, or just taking the sound wave that it is trying to play, and multiplying it by the volume percentage.
A electronically recorded sound wave consists of a series of numbers. Each number says how much power to send to the speaker at a specific time. The is one number for (typically) every 1/44100th of a second. So if you set the volume to 10%, it simply multiplies each number with 10% (= 0.1) to determine how much power to actually send to the speaker.
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