Multi-tone signals are composed of multiple single sine waves or tones with unique amplitudes, phases, and frequencies. Multi-tone testing was initially implemented to increase the speed of immunity testing, but it also improves equipment efficiency, offers higher flexibility, and is fully compliant to standards. Multi-tones are used in measuring modern audio levels in consumer and professional audio devices, broadband devices, and in internet audio. This application note further discusses multi-tone testing, the theory of the science behind it, and how to put it into practice. For information on how AR’s vector network analyzers are ideal for multi-tone testing, download the full paper.