1. the distortion of an audio amplifier is often specified in terms of "total harmonic distortion", or thd. to measure thd, the amplifier is driven by a pure sinusoidal input signal. if the amplifier is not linear, the amplifier output will include power at the harmonics of the test frequency. the thd is defined the ratio of the rms value of all distortion terms (2"nd harmonic and above) at the amplifier output to the rms value of the fundamental (thd is often specified as a percentage.) note: parseval's theorem implies that the power in the harmonics may be added together to get the total distor- tion power. (the rms voltages cannot be directly added to get a meaningful result.) assume that a system is being tested using a 300 hz test signal. a spectrum analyzer is used to measure the harmonic content of the output signal, giving the following measurements: frequency (hz)amplitude (dbv) 300 2.8 600 -19.2 900 -15.1 1200 -17.3 1500 -22.0 assume that harmonics higher than the 54h harmonic have negligible power. calculate the thd of the amplifier.