Sony MDR-NC500D - Manual (Page 6)

6 GB
2.1. Feedback Type and Feedforward
Type
Feedback type
The noise canceling function of the “feedback type” is used in MDR-NC500D.
In the feedback type, the noise detection microphone is placed close to the ear.
By collecting noise in the position closer to the ear, a noise canceling effect with high
accuracy can be obtained.
The audio signal of noise collected by the noise detection microphone is analyzed on real
time with the noise canceling circuit (NC circuit), producing a canceling signal to always
minimize the noise at the eardrum. The canceling signal is reproduced from the driver unit.
Using this method enables the cancellation effect to be increased with the changing
environmental noise addressed.
Feedforward type
In the feedforward type, the noise detection microphone is attached outside the
headphones.
The NC circuit analyzes the noise signal collected by the noise detection microphone to
estimate what kind of sound the noise will become when it comes to the eardrum. And from
this estimated result, a canceling signal to minimize the noise is made and it is reproduced
from the driver unit.
This type enables miniaturization of the headphones since it is not necessary for the noise
detection microphone to be located near the ear where space is limited.
Feedback type Feedforward type
Noise
Driver unit
Noise detection
microphone
NC circuit
Noise
Driver unit
Noise detection
microphone
NC circuit