Appendix: Indication Of Canceling Performance For Noise Canceling Headphones; Total Noise Suppression Ratio - Sony MDR-NC500D Operating Instructions Manual

Appendix: Indication of Canceling Performance
for Noise Canceling Headphones
1.1. Total Noise Suppression Ratio
Total Noise Suppression Ratio (TNSR) of noise canceling headphones is expressed with
the following formula:
TNSR
=
10 log
(P I Po)
• Po
=
Energy of sound observed at the ear not wearing headphones
• P
=
Energy of sound observed at the ear wearing headphones
*
The above energy of sound measurements are weighted.
TNSR is the value measured using the noise signal based on a broad spectrum.
As compared with the method of measuring the noise canceling ratio at a certain point of
frequency, TNSR enables the canceling performance in the actual usage environment to be
more objectively evaluated.
Moreover, it can evaluate the canceling performance in each noise environment by using
the signals to simulate the spectrum distribution of real-world noise such as an airplane and a
train.