class_docstr: Implements psychoacoustic model of Lin and Abdulla (2015) following Qin et al. (2019) simplifications.
  
  | Paper link: Lin and Abdulla (2015), https://www.springer.com/gp/book/9783319079738
  | Paper link: Qin et al. (2019), http://proceedings.mlr.press/v97/qin19a.html
docstr: Calculate individual masking threshold with frequency denoted at bark scale.
  
  :param maskers: Masker PSD values.
  :param masker_idx: Masker indices.
  :return: Individual threshold vector of shape `(window_size // 2 + 1)`.
code: def calculate_individual_threshold(
      self, maskers: np.ndarray, masker_idx: np.ndarray
  ) -> np.ndarray:
      """
      Calculate individual masking threshold with frequency denoted at bark scale.
  
      :param maskers: Masker PSD values.
      :param masker_idx: Masker indices.
      :return: Individual threshold vector of shape `(window_size // 2 + 1)`.
      """
      delta_shift = -6.025 - 0.275 * self.bark
      threshold = np.zeros(masker_idx.shape + self.bark.shape)
      # TODO reduce for loop
      for k, (masker_j, masker) in enumerate(zip(masker_idx, maskers)):
          # critical band rate of the masker
          z_j = self.bark[masker_j]
          # distance maskees to masker in bark
          delta_z = self.bark - z_j
          # define two-slope spread function:
          #   if delta_z <= 0, spread_function = 27*delta_z
          #   if delta_z > 0, spread_function = [-27+0.37*max(PSD_masker-40,0]*delta_z
          spread_function = 27 * delta_z
          spread_function[delta_z > 0] = (
              -27 + 0.37 * max(masker - 40, 0)
          ) * delta_z[delta_z > 0]
  
          # calculate threshold
          threshold[k, :] = (
              masker + delta_shift[masker_j] + spread_function
          )
      return threshold
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  from typing import TYPE_CHECKING, Optional, Tuple, Union
  import numpy
  import scipy.signal
  from art.attacks.attack import EvasionAttack
  from art.estimators.estimator import BaseEstimator, LossGradientsMixin, NeuralNetworkMixin
  from art.estimators.pytorch import PyTorchEstimator
  from art.estimators.speech_recognition.speech_recognizer import SpeechRecognizerMixin
  from art.estimators.tensorflow import TensorFlowV2Estimator
  from art.utils import pad_sequence_input
label_desc: Use image node_id 12 for calling the PsychoacousticMasker obj's underlying member method code with example usage: obj.calculate_individual_threshold(maskers, masker_idx) and returns: threshold