code: def quiet(f):
      """returns threshold in quiet measured in SPL at frequency f with an offset 12(in Hz)"""
      thresh = (
          3.64 * pow(f * 0.001, -0.8)
          - 6.5 * np.exp(-0.6 * pow(0.001 * f - 3.3, 2))
          + 0.001 * pow(0.001 * f, 4)
          - 12
      )
      return thresh
  
file_path: cleverhans/cleverhans_v3.1.0/examples/adversarial_asr/generate_masking_threshold.py
imports: import scipy.io.wavfile
  import numpy
  from scipy.fftpack import fft
  from scipy.fftpack import ifft
  from scipy import signal
  import scipy
  import librosa
label_desc: Use image node_id 3 for calling a global function with example usage: quiet(f) and returns: thresh