It's far. Under the condition of the same quality microphone core, the pickup effect of headset is obviously better than that of headset. I think the earphone microphone is
It's not very nice. You can choose contact headphones (flesh color), but this kind of headphones is more expensive.
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Supplementary answer:
1. What's the difference? This can't be described, because there is no standard of measurement.
2. Because the classroom is not big, should the collar clip be enough? This has nothing to do with the size of the classroom.