Directivity is a microphone's directionality or polar pattern that indicates how sensitive it is to sounds arriving at different angles about its central axis. Understanding and choosing the appropriate polar pattern for an application is important. The sensitivity reduction of a microphone is the amount of gain that a microphone will lose if the voltage powering the microphone is decreased. This is important to engineers and applications that are focused on low power because it may be acceptable to lose some gain while realizing a voltage savings. The sensitivity of a microphone indicates the gain, based on a known signal level input. The signal to noise ratio is a ratio of the desired audio signal compared to the level of noise it receives from the background.