What is the science and engineering behind the volume control on a speaker?

There is something called a variable resistor which controls the volume.

@Tropical_Willie Thanks. I will sign out a book on variable resistors when my library goes out of lockdown.

The variable resistor that @Tropical_Willie talked about (sometimes called a rheostat) varies the flow of electricity (the signal) through a circuit without interrupting the circuit.

The strength of the signal changes the amplitude (not the frequency) of the vibrations of the speaker. By increasing or decreasing the amplitude of the sound wave generated by the speaker, it gets louder or softer.

@zenvelo Cool. Thanks.

It is like the “Cold” facet knob you twist it get more water or turn it the other way to stop the water.

It’s a potentiometer actually. Volume control depends on the circuit. Sometimes it controls the gain of an amplifier and other times it simply directs the percentage of output to the driver.

^ What @ru said.

This is my understanding of how it works. Someone correct me if I am mistaken.

Imagine two wires that complete a circuit when connected. One of the wires ends in a section having high resistance, and the other is connected to the speakers. If the second wire is attached to the end of the first, the current loses power when going all the resistance, reducing the loudness of the speakers. If the second wire attaches to the first away from the resistance then there is more power going to the second wire, and the speakers are louder.

The second wire is attached to the controller, which slides along the end of the first wire, allowing for variation in the amount of resistance included in the circuit.