Intermodulation Distortion - Interacoustics Affinity 2.0 Additional Information

3.7.5

Intermodulation distortion

Distortion in moderate
-severe amounts will inevitably have a negative ef f ect on the quality of speech and speech intelligibility. To
assess the distortion product generated by the hearing aid, intermodulation distortion is measured.
Two tones equal in amplitude are presented to the hearing aid: one at the selected f requency dif f erence (f 1)
and one at the selected f requency (f 2). The HIT440 will make an FFT of the signal produced by the hearing
aid and the 2nd and 3rd intermodulation distortion is calculated.
2nd distortion: the signal at f 2 - f 1 in relation to the signal at f 2.
3rd distortion: the signal at 2*f 1 – f 2 in relation to the signal at f 2.
Below is an example:
3.7.6
Select test
D-0004576-Q – 2022/05
Affinity/Equinox2.0 – Additional Information
View test inf ormation
f or marked f requency
The three bars represent the
total distortion, 2 nd distortion, and
3 rd distortion
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