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Sound Transducers

Sound is a type of energy generated from vibrations and can propagate as acoustic waves through a medium. Sound transducers convert sound energy into electrical energy or vice versa. Generally, the transducers that convert sound energy to electrical energy are input sound transducers such as microphone and those that transform electrical energy to sound are output sound transducers such as loudspeakers.

Sound Level Meter

sound transducer sound level meter working diagram
Sound Level Meter

It is a device that is used to display sound levels and expressed in decibels. A microphone is used to intercept the sound to be measured. The electrical signal produced by the microphone is very low and is made stronger by a pre-amplifier. The amplified signal is processed by a weighting network so as to be compatible with the perception of the human ear when exposed to certain frequencies. It is further boosted through another amplifier. The rectifier then converts the AC signal to DC signal so that the meter can display the sound pressure level in decibels. An output jack may exist so that the measured signal can be recorded or analysed whenever desired.


A microphone is a transducer that picks up sound and coverts into electrical energy. A microphone may use electromagnetic induction, capacitance variation or piezoelectricity to produce electrical energy from air pressure variations.

Moving Coil Microphone

The moving coil microphone or the dynamic microphone works on the principle that if a coil is moved which is placed in a magnetic field, and electric current is induced.

sound transducer  moving coil microphone diagram
Moving Coil Microphone

A moving coil microphone has a diaphragm to which a coil is attached which is surrounded by a magnet. When sound waves hit the diaphragm, the coil moves in the magnetic field to produce voltage. 

Other types of microphones include condenser microphones, which has a capacitor with one plate acting as a diaphragm and changes the capacitance according to vibrations. On the other hand, a ribbon microphone has a thin ribbon of sensing element to which sound waves are applied. Th ribbon is suspended  between poles of a magnet. When the ribbon vibrates a voltage is induced due to magnetic induction proportional to the sound energy.

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