import pyfar as pf
sine1 = pf.signals.sine(1e3, 441, amplitude=2)
sine2 = pf.signals.sine(5e2, 441, amplitude=.5)
signal = sine1 + sine2
target_dB = 0
signal_norm = pf.dsp.normalize(signal, target=10**(target_dB/20),
    domain="freq", limits=(400, 600), unit="Hz")
ax = pf.plot.time_freq(signal_norm, label='Normalized Signal',
                       unit='ms')
pf.plot.time_freq(signal, label='Original Signal', unit='ms')
ax[1].set_ylim(-15, 15)
ax[1].legend()