Amplified self-noise of the Zoom H4 recorder. There is a whine at 689 Hz, and a fainter whine at 251 Hz. Also a glitch every 1.1 Secs approx. when the SD card access LED is lit. The recorder was set to record in 16 bit 44.1 Kbps WAV via external mics., with nothing plugged into the ext. mic. sockets. 20 dB of amplification was applied to the resultant sample. I find the 689 Hz whine audible on quiet field recordings, but easily removed with a narrow notch filter.
Please log in to comment