In a bluetooth headset factory, the following steps can be taken to test the Active Noise Cancellation (ANC) function:
Prepare some noise sources, such as noise generators or speakers, to generate noises of various frequencies and intensities. Connect a bluetooth headset to a test device, such as a computer or a tone generator, and make sure the headset is properly paired with the test device. Play a noise audio on the test device. Enable the ANC function of the Bluetooth headset. This is usually accomplished with a button, switch, or a specific gesture on the headset. Check that the headphones are properly reducing external noise. You can use your ears to tell by listening and observing changes in external noise. If possible, you can also measure the effect of ANC by using an audio analysis tool. These tools can help you determine the level of noise reduction in the audio frequency range. Repeat the above steps and use noises of different frequencies and intensities to ensure that the ANC function of the Bluetooth headset can work normally in various environments.
Please note that the above steps are only for factory testing to verify whether the ANC function of the Bluetooth headset is normal. For more comprehensive ANC performance evaluation and certification, more detailed testing and analysis using professional audio test equipment and procedures are required.