There are times when being able to amplify your voice is beneficial in a classroom or in a video conference scenario. An iPhone app that uses the phone built-in mic and creates a pass-through to the phone output may do the trick without enlisting the help of the A/V squad. In this entry, we'll take a look at a couple of apps that convert the iPhone into a simple and inexpensive PA system.

Let's first take a look at the requirements to make the microphone work. In the classroom scenario, we have to assume the typical 3.5-mm (1/8") stereo miniplug cable that is usually designated to provide audio output for the instructor's laptop exists and is amplified to the room's speakers. This cable would connect to the iPhone's headphone jack. If the provided cable does not have much slack, an extender male-female cable, available at various lengths, can be purchased for under $10 at an electronics store.

In the video conference situation, let's assume you are using a computer to hold a video conference with at least one other participant sitting alongside you. Rather than depending on the computer's built-in mic to pick up the multiple voices, you can attach the iPhone to the computer's audio-in port using a male-to-male 3.5-mm stereo cable so that the iPhone can be passed around to the various participants for a more localized sound source.

The iTunes Store offers numerous microphone apps. We bought and tested two of them, the Von Bruno Microphone and Microphone Pro. We also bought SmuleVox, but it turned out to be a novelty app that did not suit our purposes. There are dozens of other choices with prices ranging from 99¢ to $3.99. The apps we purchased were all 99¢. The iTunes Store user comments were useful to whittle down the selection since many of the microphone apps were given poor ratings.

Von Bruno Microphone

Microphone Pro

Both the Von Bruno Microphone and Microphone Pro performed well and would suit most users. The Von Bruno Microphone is the simpler app, offering just a simple on/off switch that is a little hard to locate during stressful situations. Von Bruno Microphone does not offer any volume control, which must be done using the iPhone's volume control or via the amplification system. Under some situations, the output from the Von Bruno Microphone was not sufficiently strong to send out a loud output.

The Microphone Pro app, on the other hands, offers additional on-screen buttons, including a very handy, large on/off button that does double duty as a mute button. This app also includes a volume slider that comes in very handy to drive the audio output to acceptable levels.

Choosing between the two apps was fairly easy, with the Microphone Pro coming out on top because of the chunkier controls and the volume gain slider, but both performed as expected. Holding the iPhone upside down like a microphone was an easy adjustment, you just had to take care not to accidentally tap one of the buttons. Neither app supports a wireless connection via Bluetooth, which would be a useful feature in the computer-based video conference scenario presented earlier.

The novelty app mentioned earlier, SmuleVox, does the same thing but also modifies the pitch of your voice and adds an echo. This app would only be useful in a classroom situation if it was necessary to use your best Darth Vader voice to get the student's attention.

One last note, it is important to take time to ensure this kind of setup works as expected prior to the class or conference session. The testing period will allow for setting appropriate volume levels on the iPhone and on the amplification system. The testing also breeds familiarity with the app so that during actual use there is no fumbling and the use of the technology will feel more natural and transparent.