Combining sound levels - adding decibels 1/3 octave bands 1/1 octave band oct calculator calculation - sengpielaudio
 
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• Combining decibels of one-third octave bands
to level of octave band and vice versa •

Spectral data analysis − spectrum analyzer − one-third octave band = 1/3 octave band

Three adjacent one-third octave bands (1/3 octave bands) belong to one octave band.

Level of one-third octave band 1  dB
Level of one-third octave band 2  dB
Level of one-third octave band 3  dB
   
                        ↓
   
Combined octave band level  dB
Octave band level  dB
   
                        ↓
   
 Level of one-third octave band 1  dB
Level of one-third octave band 2  dB
Level of one-third octave band 3  dB
Should the level of an octave band be converted to one-third octave
bands, the energy of the octave band can be divided by three. This
corresponds to a reduction of (−)4.771 dB for each 1/3 octave band.

one-third octave

Regenbogenlinie

Calculator: Adding of equal levels of 1/3 octave bands

To use the calculator, simply enter a value. Then use the TAB key or
click the mouse in an empty area of the page to update the result.
Calculator works in both directions of the ↔ sign.

Number of 1/3 oct bands n:
 		  ↔  Increase of level Δ L:
dB
Formula1   Formula2
3 one-third octave bands are 1 octave band

The total level in dB is the level of one band plus the increase in level.

Octav bands     One-third octave bands
Octave bands                                      One-third octave bands

ISO
Band numbers		 Octave band
center frequency		 One-third octave band
center frequencies
11, 12, 13 16 Hz 12.5 Hz, 16 Hz, 20 Hz
14, 15, 16 31.5 Hz 25 Hz, 31.5 Hz, 40 Hz
17, 18, 19 63 Hz 50 Hz, 63 Hz, 80 Hz
20, 21, 22 125 Hz 100 Hz, 125 Hz, 160 Hz
23, 24, 25 250 Hz 200 Hz, 250 Hz, 315 Hz
26, 27, 28 500 Hz 400 Hz, 500 Hz, 630 Hz
29, 30, 31 1000 Hz 800 Hz, 1000 Hz, 1250 Hz
32, 33, 34 2000 Hz 1600 Hz, 2000 Hz, 2500 Hz
35, 36, 37 4000 Hz 3150 Hz, 4000 Hz, 5000 Hz
38, 39, 40 8000 Hz 6300 Hz, 8000 Hz, 10000 Hz
41, 42, 43 16000 Hz 12500 Hz, 16000 Hz, 20000 Hz

Standard frequencies for acoustic measurements according to EN ISO 266

1st octave cycle 31,5           63           125           250  
2nd octave cycle       45           90           180        
1st 1/3 octave cycle 31,5   40   50   63   80   100   125   160   200   250  
2nd 1/3 octave cycle   35,5   45   56   71   90   112   140   180   224   280
1st octave cycle         500           1000           2000      
2nd octave cycle   355           710           1400           2800
1st 1/3 octave cycle 315   400   500   630   800   1000   1250   1600   2000   2500  
2nd 1/3 octave cycle   355   450   560   710   900   1120   1400   1800   2240   2800
1st octave cycle     4000           8000           16000          
2nd octave cycle           5600           11200           22400    
1st 1/3 octave cycle 3150   4000   5000   6300   8000   10000   12500   16000   20000   25000  
2nd 1/3 octave cycle   3550   4500   5600   7100   9000   11200   14000   18000        

Adding decibels - combining up to ten acoustic levels
Adding decibels - combining up to thirty acoustic levels
Calculation of the center frequency of a frequency band - geometric mean
Calculator: Q Factor and center frequency - Find the −3 dB cutoff frequencies

Generation law for octave and third octave bands

Octave band 1/3 octave band


f1 = Lower cut-off frequency of the octave or 1/3 octave in Hz
f2 = Upper cut-off frequency of the octave or 1/3 octave in Hz
f0 = Center frequency of the octave or 1/3 octave in Hz
B = Bandwidth f2 − f1 in Hz		  

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