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Audio characteristics

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Figure 4.

Harmonics

2.1.1

Total harmonic distortion

The Total Harmonic Distortion, THD, is a measure of the linearity or purity of the

amplification process and indicates to what extent the artifacts occur. A pure sine wave is

input to the amplifier and the spectrum of the output is determined. The THD figure is a

comparison of the output power or voltage levels of the harmonics to the fundamental.

The THD figure establishes the fraction of the output signal which is harmonics.

Figure 5.

Power output spectrum

There are two methods used to calculate the THD. The first method compares the power of

the harmonics to the fundamental.

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0

f

(V

F

0

f

F

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1

7

6

5

4

3

2

P

P

P

P

P

P

P

P

frequency

l

fundamenta

of

power

powers

harmonic

THD

L

+

+

+

+

+

+

=

=

∑