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 Typical test index 
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 Frequency response 
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 It is an important parameter of power amplifier to reflect the processing ability of different frequency signals 
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 Distortion curve 
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 Total harmonic distortion, abbreviated as THD. The curve results are obtained by analyzing the higher harmonic distortion of the signal. 
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 Abnormal sound factor 
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 Abnormal sound refers to the squeaking or buzzing sound of the product during the working process, which can be judged by this indicator. 
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 Single point value 
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 The value at a certain frequency point in the result of the frequency response curve is generally used as a 
data point at 1kHz. It can effectively measure the working efficiency of the speaker under the same input power. 
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