Patent US 4,287,771

The disclosure is related to a sound level meter including unique features for measuring, storing and displaying a maximum sound level generated by a passing motor vehicle or the like. The meter operates as an ordinary sound level meter until a predetermined threshold noise level is reached, at which time a novel circuit continuously detects the incoming sound level and electrically stores the maximum value detected. A comparison means compares the incoming sound level with the maximum stored level. When the incoming sound level decreases by a predetermined amount below the maximum stored value, a circuit is energized to lock the maximum value detected in a memory device. Additional means are provided to visually display the stored value.