set term png
set output "output.png"

fs = 16000.0
N_fft = 512.0

set xlabel "Frequency [kHz]"
set ylabel "Amplitude [dB]"

stats "output.txt" using 1 nooutput

set xrange [0:8]
set grid

plot "output.txt" using ($0 * fs / N_fft / 1000):(20 * log10(($1 > 1e-10 ? $1 : 1e-10) / STATS_max)) \
    with lines notitle