The IC-M36 has Clear Voice and Voice Boost, Which has a sub-microphone on the rear panel that inverts phase and cancels out ambient noise from the main microphone. As a result, the IC-M36 reduces the affect of background noise (particularly trebly noise) from the transmitted signal and makes it easier to catch voice communication. When in an engine room or high noise environment, the sub-microphone detects the ambient noise and the IC-M36 automatically increases the volume output to suit the surrounding environment. When you need an instant “boost” in the volume, a simple push of the “LOUD” button gives you full volume immediately. In addition, holding the “LOUD” button mutes the audio output. The IC-M36 floats back up to the surface if dropped overboard, even if the optional speaker microphone, HM-165, is attached. Although the IC-M36 delivers a high 6W RF output and 700mW audio output, its current saving circuit offers a practical 8 hours of operating time with the supplied 980mAh Lithium-Ion battery pack. (Typical operation: 5% TX, 5% RX, 90% standby.) Thanks to the large, easy-to-operate buttons, the IC-M36 provides intuitive operation. A pinched-waist slender body makes it easy to hold and carry the radio, and is surprisingly compact for a floating radio. The IC-M36 is waterproof to IPX7 standards, has a 4-step battery indicator, NOAA weather and weather alert, 2-step power saver, and full Dual/Tri Watch and scan functions. Includes radio, battery pack, charger, AC adapter, belt clip, and hand strap. Three year warranty.