In this case, turn the noise reduction function ON or turn the noise reduction function and the ambient noise mode OFF. When the ambient noise mode is activated in a rather noisy environment, a noise may be heard. This is not a malfunction. You can use the Sony | Headphones Connect app to turn the noise reduction function on/off and change the settings of the noise reduction function and ambient noise mode. Note that if the headset is not properly seated in the ears, the noise cancellation function may not work correctly. Rotate the headset to place it properly in the ears.