Octave Band Sound Pressure Level (0 dB = 20 μPa)
Octave Band Sound Pressure Level (0 dB = 20 μPa)
Octave Band Center Frequency (Hz)
10 
20 
30 
40 
50 
60 
70 
80 
63  125  250  500  1 000  2 000  4 000  8 000 
NC-15 
NC-20 
NC-25 
NC-30 
NC-35 
NC-40 
NC-45 
NC-50 
NC-55 
NC-60 
NC-65 
Approximate
Hearing
Threshold    
Octave Band Center Frequency (Hz)
10 
20 
30 
40 
50 
60 
70 
80 
63  125  250  500  1 000  2 000  4 000  8 000 
NC-15 
NC-20 
NC-25 
NC-30 
NC-35 
NC-40 
NC-45 
NC-50 
NC-55 
NC-60 
NC-65 
Approximate
Hearing
Threshold