Octave Band Center Frequency (Hz)
Octave Band Sound Pressure Level (0dB = 20μPa)
10 
20 
30 
40 
50 
60 
70 
80 
63 125 250 500 1000 2000 4000 8000 
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)
Octave Band Sound Pressure Level (0dB = 20μPa)
10 
20 
30 
40 
50 
60 
70 
80 
63 125 250 500 1000 2000 4000 8000 
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)
Octave Band Sound Pressure Level (0dB = 20μPa)
10 
20 
30 
40 
50 
60 
70 
80 
63 125 250 500 1000 2000 4000 8000 
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)
Octave Band Sound Pressure Level (0dB = 20μPa)
10 
20 
30 
40 
50 
60 
70 
80 
63 125 250 500 1000 2000 4000 8000 
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)
Octave Band Sound Pressure Level (dB re 20Pa)
10 
20 
30 
40 
50 
60 
70 
80 
63 125 250 500 1000 2000 4000 8000 
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)
Octave Band Sound Pressure Level (dB re 20Pa)
10 
20 
30 
40 
50 
60 
70 
80 
63 125 250 500 1000 2000 4000 8000 
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