Basic Sound Chamber Tests 75
3RD: Distortion present at the third harmonics, or three times the presented
frequency.
TOTAL: Distortion present at the second and third harmonics.
4. Press [EXIT].
5. Use [F5] to select a signal type of TONE NORMAL. (Press [F5]. Use [∨, ∧
]
to select TONE NORMAL. Use [>] to complete the selection and close the
pop-up menu.)
6. Press [START] to run normal frequency sweep.
After running a normal sweep, the harmonic distortion data will appear on the
measurement graph as a series of red bars. The scale for the bars is on the right
side of the graph
In general, you should ignore the harmonic distortion measurement when the
amplitude of the response curve measurement at the second harmonic is more
than 12 dB greater than the amplitude at the first harmonic. This is called the
12 dB rule and is part of the ANSI S3.22 standard.
Figure 3.4.7—Measuring Harmonic Distortion
