code: def testSyntheticHum(self):
      # This test adds an artificial humming tone of 50 Hz.
      filename = join(
          testdata.audio_dir, "recorded/Vivaldi_Sonata_5_II_Allegro.wav"
      )
      audio = MonoLoader(filename=filename)()
  
      nSamples = len(audio)
  
      time = np.linspace(0, nSamples / 44100.0, nSamples)
  
      freq = 50.0
  
      hum = np.sin(2 * np.pi * freq * time)
  
      hum *= db2amp(-40.0)
  
      _, f, _, _, _ = HumDetector()(
          np.array(audio + hum, dtype=np.float32)
      )
  
      self.assertAlmostEqualVector(f, [freq], 1e1)
  
file_path: essentia/test/src/unittests/audioproblems/test_humdetector.py
imports: import numpy
  from math import *
  from essentia_test import *
  from essentia import array
label_desc: Use image node_id 4 for calling the TestHumDetector obj's underlying member method code with example usage: obj.testSyntheticHum() without return types