Room Noise Detectors

Published:2013/7/28 20:09:00 Author:muriel | Keyword: Room Noise Detectors | From:SeekIC

Parts:R1 10K 1/4W ResistorR2,R3 22K 1/4W ResistorsR4 100K 1/4W ResistorR5,R9,R10 56K 1/4W ResistorsR6 5K6 1/4W ResistorR7 560R 1/4W ResistorR8 2K2 1/4W ResistorR11 1K 1/4W ResistorR12 33K 1/4W ResistorR13 330R 1/4W ResistorC1 100nF 63V Polyester CapacitorC2 10µF 25V Electrolytic CapacitorC3 470µF 25V Electrolytic CapacitorC4 47µF 25V Electrolytic CapacitorD1 5mm. Red LEDIC1 LM358 Low Power Dual Op-ampQ1 BC327 45V 800mA PNP TransistorMIC1 Miniature electret microphoneSW1 2 poles 4 ways rotary switchB1 9V PP3 BatteryClip for PP3 Battery Device purpose:This circuit is intended to signal through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electret microphone to drive a LED. With SW1 in the first position the circuit is off. Second, third and fourth positions power the circuit and set the input sensitivity threshold to 85, 70 & 50 dB respectively.Current drawing is <1mA with LED off and 12-15mA when the LED is steady on. Use:Place the small box containing the circuit in the room you intend to measure ambient noise.The 50 dB setting is provided to monitor the noise in the bedroom at night. If the LED is steady on, or flashes bright often, then your bedroom is inadequate and too noisy for sleep.The 70 dB setting is for living-rooms. If this level is often exceeded during the day, your apartment is rather uncomfortable.If noise level is constantly over 85 dB, 8 hours a day, then you live in a dangerous environment. dB Example of sound sources20 Quiet garden, electric-clock ticking, drizzling rain30 Blast of wind, whisper @ 1 m.40 Countryside areas, quiet apartment, wrinkling paper @ 1 m.50 Residential areas, quiet streets, fridges, conversation @ 1 m.55 Offices, air-conditioners60 Alarm-clocks, radio & TV sets at normal volume64 Washing machines, quiet typewriters67 Hair-dryers, crowded restaurants69 Dish-washers, floor-polishers70 Loud conversation, noisy street, radio & TV sets at high volume72 Vacuum cleaners78 Telephone ring, mechanical workshop80 Passing trucks, noisy hall or plant, shuffling @ 1 m.90 Passing train, pneumatic hammer, car hooter @ 1 m.95 Mega disco , circular saw100 Motorcycle without silencer



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