Light Sensor: Light sensor is a transducer used for detecting light and creates a voltage difference equivalent to the light intensity falling on a light sensor. The two main light sensors used in robots are Photovoltaic cells and Photo resistors. Other kinds of light sensors like phototransistors and phototubes are rarely used.
Sound Sensor: Sound sensors are generally a microphone used to detect sound and return a voltage equivalent to the sound level. Using a sound sensor a simple robot can be designed to navigate based on the sound receives.Implementation of sound sensors is not easy as light sensors because it generates a very small voltage difference which will be amplified to generate measurable voltage change.