His theory is perfectly sound.

他的理论完全正确。

youdao

He seemed to me perfectly sound and able.

在我看来，他是十分精明能干的。

youdao

His reasoning is perfectly sound, but he misses the point.

他的推理完全正确，但是未切中肯綮。

youdao

Although an ill-repaired boat is more likely to sink, the force of powerful waves can cause even a perfectly sound vessel to founder.

ECONOMIST: Can capital controls stop poor countries crashing?

It made no difference that perfectly sound institutions (mainly banks) in normal times could lose their liquidity in a general panic situation that was no fault of their own.

FORBES: Fed Profits and Treasury Financing, the Good and the Bad

Well, it really hit the fan after those remarks, apparently, and now Bishop Carrasco has been forced to issue an apology to anyone offended by what looks to me like a perfectly sound complaint.

FORBES: Vatican Academy Struggles With Internal Dissent Over Outreach to Biomedical Researchers