Along with instrument level, mic level, and two flavors of line level, one of the analog signal levels encountered with pro audio and music equipment. The power output of an amplifier feeding a speaker is generally given in watts, which can be converted to voltage level using the formula volts = square root of power times resistance. So, for example, 1,000 watts feeding an 8-ohm load would require an 89.4 volt level (with a complementary current of 11.2 amps). An advantage to the comparatively high voltage and current levels of speaker signals and the fact that speaker-level signals are not amplified (once they are amplified to speaker level), speaker cables do not require shielding for protection against noise pickup.