text: import numpy as np
  
  
  def decibels_to_gain(decibels: float):
      """
      Change unit from decibels to gains.
      Args:
          decibels: value in decibels.
  
      Returns:
          value in gains.
      """
      return 10 ** (decibels / 20)
  
  
  def peak_norm(audio: np.ndarray):
      """
      Audio normalisation with respect to highest peak to obtain (-1, 1) amplitudes.
      Args:
          audio: signal to be normalised
  
      Returns:
          normalised signal
      """
      return audio / np.max(np.abs(audio))
  
  