LAS VEGAS — At a moment when Yahoo desperately needs to wow investors, the company unveiled a handful of enhancements to its mobile search service that are also being offered by rivals Google and Microsoft.

The announcement, made Wednesday at the CTIA wireless show in Las Vegas, includes a new voice-enabled search function that allows consumers to look up restaurants and websites by speaking into the phone. This could be a useful feature for people without QWERTY keypads on their phone, or for those who want to look up information while driving. The only problem is, Microsoft (MSFT) already offers a similar application on its Live Search mobile service.

Yahoo (YHOO) says its new voice recognition feature can adapt to a user’s voice over time and is now available for download on select Blackberry devices, including the Pearl and Curve. More compatible devices will be added in coming months.

Yahoo also unveiled a search box that will sit directly on a phone’s homepage, which will allow users to look up whatever they want without having to open their browser — a feature similar to a Google (GOOG) software “shortcut” for cell phones launched just last month.

On top of these features, Yahoo also plans to offer a downloadable application that tries to predict a user’s search as he or she starts typing. This is similar to the search assist function on Yahoo’s online homepage (accessible on a PC) but is the first such feature to become available on a mobile device. In other words, Microsoft and Google aren’t one step ahead on this one. Yahoo says its new recommendation tool can cut down on the amount of time it takes to conduct a search from a cell phone. Currently, this function is only available on Apple (AAPL) iPhones, which come loaded with Google applications like YouTube videos.

The new enhancements to Yahoo’s mobile search application will likely make it a smarter, faster and easier to use service. But, with the majority of the just-announced updates already available from the company’s rivals, it’s unlikely it will be enough to significantly differentiate Yahoo and deliver the much-needed pizazz investors are looking for as the company tries to fend off a takeover bid by Microsoft.