On the back of the headset is the earpiece covered in Sound ID's Real Comfort Ear Loop. The rubbery ear loop is tapered to a narrow point like a spout, which is made to fit snugly in the ear. Attached to this is a round ear loop so that the entire earpiece fits securely within the folds of the ear. The Sound ID 300 comes with three different loop sizes for different sized ears. If you prefer, there's also an over-the-ear hook for additional stability. Indeed, the earpiece fits very comfortably in our ear and we could wear it all day without much discomfort. The earpiece can be swiveled either to the left or right to fit either ear.
Like on the SM100, the Sound ID 300 comes with three Personalized Sound modes to increase speech intelligibility depending on your preference. The three modes are Normal Listening Enhancement, Moderate, and Strong, and you can toggle through these with the aforementioned volume key. If you prefer a more natural sounding voice with not as much difference between the voice and the background, you would opt for Normal mode. If you prefer to really set the speech apart from the surrounding noise, you would opt for the Moderate or Strong Listening Enhancement modes. Do note that you would be sacrificing the "natural" quality of the speech the stronger the mode, resulting in a more machine-like voice.
We paired the Sound ID 300 with the Apple iPhone 3G. Because of the Noise Navigation technology plus the dual microphone noise cancellation, callers could hear us very clearly, even in a busy cafeteria. Call quality didn't fare so well with wind noise, though, with some static and echo at times. Still, we could hear our callers clearly enough, especially with the help of the Personalized Sound modes.
To really tell the significance of the Noise Navigation, we turned it off to compare the call quality with and without it. Indeed, having the noise cancellation on makes a huge difference--there was a lot more background noise without it. The automatic volume adjustment also did a great job in adjusting the incoming volume levels, depending on whether we were in a quiet environment or in a noisier one.
Other features of the Sound ID 300 include answering, ending, and rejecting calls, call-waiting support, voice-dial support, call mute, and a battery life indicator. The Sound ID 300 has a rated talk time of 6 hours and a standby time of 9 days.