Decibels Flashcards
What is the equation for finding watts?
dB=10log(P2/P1)
What is the equation for finding volts?
dB=20log(V2/V1)
What is the equation for finding sound pressure?
dB=20log(Pa2/Pa1)
How many dB is twice the voltage (volts)?
6dB
How many dB is half the voltage (volts)?
-6dB
In a dB equation, which part is the linear amount?
the ratio (ex. P2/P1, V2/V1, etc.)
What is the dB reference for 0dBW?
1 Watt
What is the dB reference for 0dBm?
.001 Watt (1 milliwatt)
What is the dB reference for 0dBV?
1 volt
What is the dB reference for 0dBu?
.775 Volts
What is the dB reference for 0dBμ?
.000001 Volts (1 microvolt)
What is the dB reference for 0dBSPL?
.00002 Pascals
How many dB is twice the power (watts)?
3dB
How many dB is half the power (watts)
-3dB
How many dB is near the just noticeable difference (JND)?
3dB
How many dB is 10x power?
10dB
What does 10x power sound like to the average listener?
twice as loud
What are the five types of dB problems you will encounter?
- expressing 2 measured linear values as dB
- solving for a missing linear value
- expressing V, power, or Pa as dB reference
- converting dB reference to linear amounts
- summing signals together (converting dB to linear amounts, then expressing V, power, or Pa as dB reference)
What are the 3 steps for expressing 2 measured linear values as dB?
- figure out what type of linear amount you will be using (volts, watts, or sound pressure)
- use the appropriate equation (10log for watts, 20log for volts and Pa
- solve for dB
What are the steps for solving a missing linear value?
- figure out what type of linear amount you will be using (volts, watts, or sound pressure)
- use the appropriate equation (10log for watts, 20log for volts and Pa)
- solve for output (ex. V2, P2, etc.)
What are the steps for expressing V, power, or Pa as a dB reference?
- use the equation dBref=(x)log(V/Vref) where V=measured amount compared to standard reference and x=either 10 or 20 depending on reference
- solve for dBref
What are the steps for converting dB references to linear amounts?
- figure out what type of linear amount you will be using (volts, watts, or sound pressure)
- use the equation dBref=(x)log(V/Vref) where V=measured amount compared to standard reference and x=either 10 or 20 depending on reference
- solve for V
What are the steps for summing signals?
- convert dB->reference (V, watts, or Pa)
- add together
- show results in dB
What is the equation for inverse square law?
NR=20log(D2/D1)
where NR=noise reduction, D2=second distance, and D1=first distance
