Room Noise Detector: Build Your dB Threshold Circuit

One LED monitors three distinct noise levels: 50, 70 & 85 dB

Useful for identifying excessively noisy environments

Circuit diagram

Parts:

Device purpose:

This circuit is designed to signal through a flashing LED, the exceeding of a predetermined threshold in ambient room noise, chosen from three fixed levels: 50, 70 & 85 dB. Two operational amplifiers provide the necessary gain to amplify the sound signals captured by the miniature electret microphone, subsequently driving the LED. When SW1 is positioned in the first setting, the circuit is deactivated. Moving SW1 to the second, third and fourth positions activates the circuit and sets the input sensitivity threshold to 85, 70 & 50 dB, respectively. The current consumption is less than 1mA with the LED switched off, increasing to 12-15mA when the LED is consistently illuminated.

Use:

Place the compact enclosure containing the circuit within the room you intend to assess noise levels. The 50 dB setting is suitable for monitoring noise in bedrooms during nighttime. If the LED remains lit or flashes frequently, it indicates that the bedroom environment is unsuitable and excessively noisy for restful sleep. The 70 dB setting is appropriate for living rooms. If this level is frequently surpassed during daylight hours, your apartment is likely uncomfortable. Continuous noise levels exceeding 85 dB for 8 hours per day suggest a potentially hazardous environment.