code: def melspectrogram(self, y):
      if self.preemphasis != 0:
          D = self._stft(self.apply_preemphasis(y))
      else:
          D = self._stft(y)
      S = self._amp_to_db(self._linear_to_mel(np.abs(D)))
      return self.normalize(S)
  
imports: import librosa
  import soundfile
  import numpy
  import scipy.io.wavfile
  import scipy.signal
  from TTS.tts.utils.data import StandardScaler
label_desc: Use image node_id 15 for calling the AudioProcessor obj's underlying member method code with example usage: obj.melspectrogram(y) and returns: self