Abstract: A sound variation indication apparatus includes a comparison element, an interval checker, and an indication generator. The comparison element receives an audio signal and compares it to a check value to provide a status signal indicating a presence and absence of an expected sound input. The interval checker detects the status signal at predetermined intervals, to provide an interval output. The indication generator generates an indication if the interval output is an absence representation. A process of generating an indication on absence of a sound input includes providing an audio signal based on a sound input and comparing the audio signal to a check value, providing a status signal indicating a presence and absence of the sound input. A status signal value is determined at predetermined intervals, to provide an interval output. An indication is generated if the interval output is an absence representation.