Justin wrote:How can I convert decibels to pressure units, such as PSI, or vice versa? I've seen formulas such as dB = 10*log (P/Pref) or 20*log(V/Vref). Is this correct? How do I know what the reference P is? Thanks for your help!
Guest wrote:Justin wrote:How can I convert decibels to pressure units, such as PSI, or vice versa? I've seen formulas such as dB = 10*log (P/Pref) or 20*log(V/Vref). Is this correct? How do I know what the reference P is? Thanks for your help!
If P is power, the 10*log form is correct. However if P is pressure, db = 20*log(P/Pref) and Pref is 20 uPa (micropascals, I can't make a "mu" here). The assumption is that P is an rms pressure value, any static (dc) pressure is ignored. A 10 dB increase is always 10X in power or energy, but power is proportional to power, or to the square of voltage or pressure. That is where the factors of 10 or 20 come from.
Note that 20 Pa is 120 dB, painfully loud, while static atmospheric pressure is 101.325 kPa.
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For electrical signals, you have to find a reference to what the reference level is, but 1 mW of power (frequently into 600 ohms), or 1 V are common ones.