Event Tracking and Virtual Page View Tracking Impacts the Bounce Rate

Enabling event tracking and virtual page view tracking impacts the bounce rate of the web pages. 

Example:
Page A has a bounce rate of 90% before implementing the event tracking for the video displayed in the webpage. Subsequent to the implementation of event tracking code, the page will show a declined bounce rate because Google Analytics started considering it as an interaction event contrary to the consideration of the video as an non-interaction event before event tracking implementation.

This would give an entirely different picture to the client, indeed a wrong notion that the page is performing better now compared to how it were earlier. Fix this the abnormal decline in bounce rate by telling Google to just consider the video as an non-interactive event. For that

Capitalize the fabulous feature in GA event tracking called "non-interaction events", wherein you can mark an event as a non-interaction by passing true as a fifth argument (or, 6th item in the array).

_gaq.push(["_trackEvent", "Category", "Action", "Label", 3, true]);

Adding the piece of code would facilitate Google Analytics to stop counting the event as an interaction and prohibit inclusion of the event metrics in bounce rate calculation.

From Google Analytics Help Page:

Non-Interaction Events

The term "Non-interaction" applies to the final, and optional, boolean parameter that you can use with the _trackEvent() method. This parameter allows you to determine how you want bounce rate defined for pages on your site that also include event tracking. For example, suppose you have a home page with a video embedded on it. It's quite natural that you will want to know the bounce rate for your home page, but how do you want to define that? Do you consider visitor interaction with the home page video an important engagement signal? If so, you would want interaction with the video to be included in the bounce rate calculation, so that sessions including only your home page with clicks on the video are not calculated as bounces. On the other hand, you might prefer a more strict calculation of bounce rate for your home page, in which you want to know the percentage of sessions including only your home page regardless of clicks on the video. In this case, you would want to exclude any interaction with the video from bounce rate calculation.

That's where the opt_noninteraction parameter steps in. Remember that a bounce is defined as a session containing only one interaction hit. By default, the event hit sent by _trackEvent() is considered an interaction hit, which means that it is included in bounce rate calculations. However, when this value is set totrue, the type of event hit is not considered an interaction hit. You can use this fact to adjust bounce rate calculations for pages that contain events. Setting this value to true means: a session containing a single page tagged with non-interaction events is counted as a bounce—even if the visitor also triggers the event during the session. Conversely, omitting this option means that a single-page session on a page that includes event tracking will not be counted as a bounce if the visitor also triggers the event during the same session.

Source: https://developers.google.com/analytics/devguides/collection/gajs/eventTrackerGuide#non-interaction