Sound Pressure Meter

Here is a simple circuit of “Sound Pressure Meter” to check the pressure of sound. An am-meter of few micro-amperes is used in its output in order to show the deflection corresponding to intensity of sound.

Circuit description

The circuit sound pressure meter utilizes a microphone, an operational amplifier, and a moving coil am-meter. Microphone pick-up the sound to be measured and change it into electrical signal corresponding to intensity of sound. The output of microphone is given to pin 2 of IC1 (TLC272) through bipolar capacitor C1, where IC1 is a 2-operational amplifier. Variable resistor VR1 is used to select the amplification power connected to pin 1 and 2. The reference voltage is given to non-inverting pin (pin 3) of IC1 through resistor R3 and R4. As TLC272 (IC1) is a combination of two individual operational amplifier, so for further amplification of half voltage of voltage at non-inverting input (pin 3) second operational amplifier is used.

A moving coil am-meter of 30 µA range having internal resistance of 6.5 KΩ is used in its output.

circuit diagram of sound pressure meter


Resistors (all ¼-watt, ± 5% Carbon)

R1 = 10 KΩ

R2 = 220 Ω

R3, R4 = 100 KΩ

R5 = 8.2 KΩ

VR1 = 500 KΩ (preset)


C1 = 10 µF/40V

C2 = 470 µF/16V

C3 = 4.7 µF/63V

C4 = 15 pF

C5 = 100 KpF


IC1 = TLC272 (2-operational amplifier)

D1 – D4 = BAT85

D5 = 1N4148


SW1 = On/Off switch

M1 = 30 µA/6.5 KΩ (am-meter)

MIC1 = MCE2000

3 thoughts on “Sound Pressure Meter”

  1. can we put an LED Meter in the circuit. it is like the LEDs will light up when the device receives sound pressure. but we still like to have the analog meter in it.

  2. can we use a transmitter and receiver to transmit this sound signal to any police station to inform whenever an accident takes place(accident prone areas)….

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