# Conversion from counts to dB

I have a sound signal, recorded by a hydrophone, which units are counts. I would like to convert the counts into dB re uPa (Decibels relative to microPascals), is that possible?

• um, dB is a relative measure. So, dB relative to what? – Marcus Müller Nov 21 '19 at 14:50
• counts? I never heard of this as a unit. Can you provide a definition? – Hilmar Nov 21 '19 at 14:56
• Excuse my lack of details, I am interested in counts relative to micripascals (uPa) since I have calibration data in the mentioned units. Counts are related to the bit depth. The hydrophone samples at 24 bit. – Berna Gomez Nov 21 '19 at 15:23
• @Hilmar when I've used "counts" as a unit it's been when an ADC or shaft encoder has been involved. 1 count = 1 LSB. – TimWescott Nov 21 '19 at 15:52
• It's not clear what your problem is. Do you understand what dB relative to something means? A voltage in dBv means take the voltage, divide by 1V (the reference, that's the 'v' on the end of dBv), then take $\log_{10}$, then multiply by 20 because it's a scalar quantity and not a power. So 10V is 20dBv, 100V is 40dBv, etc. So dBuP (assuming that's the notation you use) would mean take the sound pressure in $\mu\mathrm{Pa}$, divide by $1 \mu\mathrm{Pa}$, take $log_{10}$, multiply by 20 (I assume -- $\mu\mathrm{Pa}$ denotes a pressure, not power), and you're done. – TimWescott Nov 21 '19 at 18:17