Error and slow response in specgram matplitlib

I've been working on an audio spectrum analyzer in pyqt with python,

I have almost finished just that I have 3 last situations,

1.- It is very slow when making the representation of the file, that is to say in general the program is slow

2.- It throws me an error when I try to read other audio formats like (mp3) and I need you to read all or most of the audio formats.

3.- It throws me an error after loading a file that is in a different route from the path of the first file I show.

this is the error:

This is my code:

import sys
import matplotlib

matplotlib.use('Qt5Agg')
from PyQt5 import QtCore, QtWidgets

import matplotlib.pyplot as plt
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure

import soundfile as sf




class Spectrograph(FigureCanvas):
    def __init__(self, parent=None, width=5, height=4, dpi=100):
        plt.style.use('dark_background')

        self.fig = Figure(figsize=(width, height), dpi=dpi)
        self.axes = self.fig.add_subplot(111)
        self.cbar = None
        self.compute_initial_figure()

        super(Spectrograph, self).__init__(self.fig)
        self.setParent(parent)
        FigureCanvas.setSizePolicy(self,
                                   QtWidgets.QSizePolicy.Expanding,
                                   QtWidgets.QSizePolicy.Expanding)
        FigureCanvas.updateGeometry(self)
        self.setAcceptDrops(True)


    def dragEnterEvent(self, e):
        if e.mimeData().hasFormat('text/uri-list'):
            e.accept()
        else:
            e.ignore()


    def dropEvent(self, e):
        if e.mimeData().hasUrls:
            for url in e.mimeData().urls():
                e.setDropAction(QtCore.Qt.CopyAction)
                e.accept()
                file = str(url.toLocalFile())
                self.update_graph(file)
        else:
            e.ignore()


    def update_graph(self, file):
        self.axes.cla()
        if self.cbar:
            self.cbar.remove()

        data, samplerate = sf.read(file)
        y = data.sum(axis=1)/2
        Pxx, freqs, bins, im = self.axes.specgram(y, NFFT=256, Fs=samplerate, cmap='jet')
        plt.gcf().set_size_inches(10,5)
        self.axes.set_xlim(0, len(y) / samplerate)
        self.axes.set_ylim(0, 23000)
        self.cbar = self.fig.colorbar(im)
        self.cbar.set_label('Intensidad (dB)')
        self.axes.set_xlabel('Tiempo (s)')
        self.axes.set_ylabel('Frecuencia (Hz)')
        self.a = 0
        self.draw()


    def compute_initial_figure(self):
        pass


class ApplicationWindow(QtWidgets.QMainWindow):
    def __init__(self):
        QtWidgets.QMainWindow.__init__(self)
        self.setAttribute(QtCore.Qt.WA_DeleteOnClose)
        self.setWindowTitle("Audio Spectrograph")

        self.main_widget = QtWidgets.QWidget(self)
        self.graph = Spectrograph(self.main_widget, width=5, height=4, dpi=100)

        layout = QtWidgets.QVBoxLayout(self.main_widget)
        layout.addWidget(self.graph)

        self.main_widget.setStyleSheet("QWidget {background-color:   black}")

        self.main_widget.setFocus()
        self.setCentralWidget(self.main_widget)



if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    window = ApplicationWindow()
    window.show()
    sys.exit(app.exec_())