SVL Scale Voltage to EU (1 Ch).vi - Sound Pressure Level: Why does it need a dB reference level?

[chassan]

Hello folks,

It appears that SVL Scale Voltage to EU (1 Ch).vi takes a raw ai voltage and converts it to a unit such as (in my case) Pa by dividing the ai voltage by the sensitivity of the microphone in mV/Pa.

1. Why, then, does SVL Scale Voltage to EU (1 Ch).vi require a dB reference (e.g. 20uPa)?

Best Regards,

Chris 

[mcleu]

Hi Chris,

dB values are taken with reference to another value. In air, it is ref to 20uPa, whereas in water is is ref 1uPa.

So your SPL value is = 20 * log10 ( Pressure measured / reference pressure )