An Analysis of EMI Noise Reducing Methods for Soundbar in HDMI Mode

This paper analyzes the effectiveness of reducing EMI noise in digital audio signals in the HDMI mode of a soundbar by using resistors and chip ferrite beads. To select the resistor value and the impedance of the chip ferrite bead that do not distort signals, an oscilloscope is used to measure the synchronization timing of the digital audio signals. For the verification of momentary synchronization timing errors between signals, a 1kHz audio signal is employed, and audio dropouts are detected through listening tests. The EMI noise levels at various frequencies embedded in the signals are confirmed by measuring the FFT of the 1MHz to 1GHz frequency range with a spectrum analyzer. By comparing test results measured in the EMI chamber, the paper proposes the use of the most effective component—either the resistor or the chip ferrite bead—for EMI noise reduction.