An SPL (Sound Pressure Level) meter, also known as a decibel meter, is a device that measures the sound pressure level in decibels (dB). It works by detecting the pressure variations in the air caused by sound waves.
The basic principle behind the SPL meter is to use a microphone to convert the sound wave's pressure variations into an electrical signal. This electrical signal is then processed by a circuit that amplifies and filters the signal to provide an accurate measurement of the sound pressure level.
The microphone in an SPL meter is typically a condenser microphone that is very sensitive to pressure variations in the air. It is designed to respond to a specific range of sound frequencies, typically between 20 Hz and 20 kHz, which is the range of human hearing. The microphone's diaphragm moves in response to the sound pressure variations, generating an electrical signal that is proportional to the sound pressure level.
The electrical signal is then passed through an amplifier circuit, which amplifies the signal to a level that can be measured by the meter's display. The display typically shows the sound pressure level in decibels (dB), which is a logarithmic scale that relates the measured sound pressure level to a reference level.
The SPL meter may also have various filters that can be applied to the electrical signal to adjust the measurement to different weighting curves, such as A, B, or C weighting, which are used to reflect how humans perceive sound at different frequencies.
In summary, an SPL meter measures sound pressure level by detecting the pressure variations in the air caused by sound waves using a sensitive microphone and then processing the electrical signal generated by the microphone to provide an accurate measurement of the sound pressure level in decibels (dB).