Most digital scales use a sensor called a load cell to convert a physical force (weight) into an electrical signal. This electrical signal is amplified and converted into a digital format so that it can be displayed as a weight value on the display. Sensors like load cells which convert a physical force into an electrical signal are called transducers. Speakers are another type of transducer which convert an electrical signal into a physical force by moving an electromagnet which then moves the the speaker's diaphragm to make sound. Both speakers and load cells deal with very small changes in electrical current which require a steady, noise-free power supply as well as amplification and sophisticated filtering methods to reduce electrical noise. Both speaker makers and scale makers take great care to reduce electrical noise in their circuits so that you get the most enjoyable experience out of your speaker, or measure just the right weight using your digital scale.