We find the most elegant explanation in a paper from David Autor:
Save StorySave this story，详情可参考有道翻译
From rendered glyph images。谷歌对此有专业解读
What is a TCXO?。业内人士推荐超级权重作为进阶阅读
Those extra microphones do boost the price up a bit. The JBL 780NC headphones cost $250, while the JBL 680NC headphones cost $160. Both are available for purchase right now, with shipments going out by March 15.