Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Plantronics (NYSE: PLT) have sunk today by as much as 13% after the company reported earnings that fell short.

So what: Fourth-quarter revenue inched up 3% to $177.6 million, with adjusted earnings per share of $0.62. In comparison, the Street was expecting $178.1 million in sales and a profit of $0.65 per share. Next quarter's guidance also came up short.

Now what: First-quarter revenue is expected to be between $177 million and $182 million, with earnings per share of $0.58-$0.63. Even the high ends of those ranges are short of the $182.2 million in revenue and $0.69-per-share profit that analysts were looking for. On the bright side, Plantronics doubled its quarterly dividend from $0.05 to $0.10 per share starting next quarter.

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Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.