METHOD AND DEVICE FOR MEASURING HARMONIC DISTORTION OF SPEAKER

摘要

PURPOSE:To measure the harmonic distortion of a speaker with few data in a short time by converting a sound pressure signal into an electric signal by a microphone, converting this signal into a digital signal by an A/D converter, storing it and executing a prescribed interpolation. CONSTITUTION:As the sine wave of a frequency (f) is discreetly changed as an input signal within the measuring range, it is impressed on the speaker, an output sound pressure from the speaker is converted into the electric signal by the microphone, after that, it is made into a digital signal by an A/D conversion and data for one period of each frequency are cut out. After that, by the interpolation in each frequency, a sampling time DELTAt is changed, that is made into the data of an N point (N is the number of data of one period after the interpolation) to satisfy DELTAt*N=1/f and the harmonic distortion is obtained by a Fourier series approximation. Thus, it is sufficient to fetch the data of at least one period and a fetching time becomes much shorter in comparison with the case of using an FFT argorithm by an FFT analyzer.