old_contents: from __future__ import division
  
  import numpy as np
  
  
  def esum(levels, axis=1):
      """Energetic summation.
  
      :param x: Levels
      :param axis: 
      :returns: 
      :rtype: 
  
      """
      levels = _is_1d(levels)
      return 10 * np.log10(np.sum(10**(levels/10), axis=axis))
  
  
  def mean_tl(tl, surfaces):
      try:
          tau_axis = tl.ndim - 1
      except AttributeError:
          tau_axis = 0
      tau = 1 / (10**(tl/10))
      return 10 * np.log10(1 / np.average(tau, tau_axis, surfaces))
  
  
  def wavelength(freq, c=343):
      """
      Wavelength for one or more frequencies (as ``NumPy array``).
      """
      return c/freq
  
  
  def w(freq):
      """
      Angular frequency for one o more frequencies (as ``NumPy array``).
      """
      return 2 * np.pi * freq
  
  
  def _is_1d(input):
      if type(input) is int or type(input) is float:
          return input
      elif input.ndim == 1:
          return np.array([input])
      elif input.ndim == 2 and input.shape[0] == 1:
          return input[0]
      else:
          return input
  
new_contents: from __future__ import division
  
  import numpy as np
  
  
  def esum(levels, axis=1):
      """
      Energetic summation.
      """
      levels = _is_1d(levels)
      return 10 * np.log10(np.sum(10**(levels/10), axis=axis))
  
  
  def mean_tl(tl, surfaces):
      try:
          tau_axis = tl.ndim - 1
      except AttributeError:
          tau_axis = 0
      tau = 1 / (10**(tl/10))
      return 10 * np.log10(1 / np.average(tau, tau_axis, surfaces))
  
  
  def wavelength(freq, c=343):
      """
      Wavelength for one or more frequencies (as ``NumPy array``).
      """
      return c/freq
  
  
  def w(freq):
      """
      Angular frequency for one o more frequencies (as ``NumPy array``).
      """
      return 2 * np.pi * freq
  
  
  def _is_1d(input):
      if type(input) is int or type(input) is float:
          return input
      elif input.ndim == 1:
          return np.array([input])
      elif input.ndim == 2 and input.shape[0] == 1:
          return input[0]
      else:
          return input
  
subject: Fix docs