And as your sleep deepens, your brain moves to longer delta waves.

随着睡眠加深脑波会变成更长的波。

youdao

It is called delta sleep because of the presence of high amplitude, low frequency delta waves that are seen to occur in the EEG.

这个阶段的脑电图以高幅低频的三角形delta波为主，所以被称为Delta睡眠。

youdao

Then you get successively deeper, II through IV, slow, irregular, high amplitude delta waves, and then once you reach stage IV you start going up again, up through stage III and II.

然后睡得越来越深，从第二到第四阶段，慢，不规则，高振幅的δ波，等你到达第四阶段，你又开始返回，第三阶段和第二阶段。

youdao

Then you get successively deeper, II through IV, slow, irregular, high amplitude delta waves, and then once you reach stage IV you start going up again, up through stage III and II.

然后睡得越来越深，从第二到第四阶段，慢，不规则，高振幅的δ波，等你到达第四阶段，你又开始返回，第三阶段和第二阶段。

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