Calculate dB per octave slope from two frequencies and a level change, or convert dB per octave, dB per decade, and filter order values.
dB Per Octave Formula
The following formula is used to calculate the dB per octave.
dB/Octave = (End Level – Start Level) / log2(End Frequency / Start Frequency)
Variables:
- Start Frequency (Hz) – The frequency at the beginning of the range.
- End Frequency (Hz) – The frequency at the end of the range.
- Start Level (dB) – The level in decibels at the start frequency.
- End Level (dB) – The level in decibels at the end frequency.
- dB/Octave – The change in level for each octave between the start and end frequencies.
To calculate the dB per octave, subtract the start level from the end level, then divide by the logarithm base 2 of the end frequency divided by the start frequency.
What is dB Per Octave?
dB per octave is a measure of how much the level in decibels changes for each octave in frequency. An octave is a doubling of frequency, and this calculation is often used in audio engineering to describe the behavior of filters, amplifiers, and other audio equipment across the frequency spectrum.
How to Calculate dB Per Octave?
The following steps outline how to calculate the dB per Octave.
- First, determine the start frequency (Hz).
- Next, determine the end frequency (Hz).
- Then, determine the start level (dB).
- After that, determine the end level (dB).
- Use the formula to calculate the dB per Octave.
- Finally, compare your result with the calculator above to verify your calculation.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Start Frequency (Hz) = 100 Hz
End Frequency (Hz) = 200 Hz (one octave above)
Start Level (dB) = 90 dB
End Level (dB) = 85 dB
