| 摘要 |
PURPOSE:To easily inspect a loudspeaker, by driving the loudspeaker in the vicinity of resonance frequency, converting its acoustic pressure level to an electric signal, Fourier-transforming its signal, and analyzing the frequency spectrum. CONSTITUTION:A loudspeaker 3 is driven by amplifying a signal from an oscillator 1 by an amplifying circuit 2. A sound in the vicinity of resonance frequency from the loudspeaker 3 is converted to an electric signal by a microphone 4, and its signal is inputted to a processing device 7 through an amplifying circuit 5 and an A/D converter 6. The processing device 7 is provided with an ROM 8 and an RAM 9, a wave number analyzer 10 is connected, and a waveform stored in the RAM 9 is Fourier-transformed. Whether a high-order higher harmonic wave exceeding a set value is incorporated in a frequency spectrum of an obtained acoustic pressure level or not is discriminated, and when it is a little, the loudspeaker is decided to be a nondefective product. As for a defective product, the cause of failure is analyzed by dividing the waveform into plural periods and driving a mutual correlation function. In this way, the loudspeaker 3 is inspected easily. |
