Audio analyzers measure the noise and audio spectrum of output from an amplifier or a stereo. There are three basic product types: analog, digital, and converter-based. Analog audio analyzers use analog hardware to generate signals and analog filters to measure them. By contrast, digital audio analyzers use digital signal processing (DSP) algorithms to both generate and analyze signals in the digital domain. Today, most professional-grade audio analyzers are converter-based devices that generate and analyze signals in the digital domain, and use analog-to-digital converters (ADC) and digital-to-analog converters (DAC) for analog input and output. Basic format parameters include the number of channels, communications interface, operating system (OS), and dimensions or form factor.