from matplotlib import pyplot as plt
a = slab.Sound.vowel(vowel='a')
e = slab.Sound.vowel(vowel='e')
i = slab.Sound.vowel(vowel='i')
signal = slab.Sound.sequence(a,e,i)
import matplotlib.pyplot as plt # preparing a 2-by-2 figure
_, [[ax1, ax2], [ax3, ax4]] = plt.subplots(
                nrows=2, ncols=2, constrained_layout=True)
signal.waveform(axis=ax1, show=False)
signal.waveform(end=0.05, axis=ax2, show=False) # first 50ms
signal.spectrogram(upper_frequency=5000, axis=ax3, show=False)
signal.spectrum(axis=ax4)