Spectrogram of marsh warbler song(= Mastersingers, Marsh warbler 2). Sv: Kärrsångare. Hålanda, Sweden, midnight, mid-June 2011. Telinga Pro 5 parabole with stereo DAT mic. Sonogram from Izotope RX, screen capture with Debut v. 1.83. There were few environmental sounds and few other bird sounds so the left and right channel are almost identical. A high pass filtering at 500 Hz was performed after the sonogram was made which explains why the low frequency artifact at 6.5 secs is hardly heard.