Sound Decibel Meter is a free online tool that allows users to measure noise levels directly in their browser without the need for an app. It provides live dB readings, including current, minimum, average, maximum, and peak dB levels. Users can conduct quick ambient sound checks for various environments such as rooms, traffic, appliances, and workplaces. The tool includes a noise reference chart to help users understand the context of their readings, comparing them to common noise sources like lawnmowers and conversations. The sound analysis is performed locally using the Web Audio API, ensuring that audio is not recorded or stored. Users need to allow microphone access to utilize the meter effectively.