Sony MDR-NC500D ユーザーマニュアル

Product Information

3-280-434-21(1)

MDR-NC500D

Noise Canceling

Headphones

CT

GB

KR

CS

2

GB

3

GB

Content

1. Introduction .......................................................................................................... 4

2. Principle of Operation of MDR-NC500D and Its Configuration ......................... 5

2.1. Feedback Type and Feedforward Type .......................................................................... 6

2.2. System configuration of MDR-NC500D ....................................................................... 7

2.3. Advantages of Digitization ............................................................................................ 8

3. AI Noise Canceling Function ............................................................................... 9

3.1. Operation of AI Noise Canceling function .................................................................. 10

4. Specialized Driver Unit ...................................................................................... 10

5. High-Quality Sound Unique to Digital .............................................................. 11

6. Weight saving mechanism .................................................................................. 12

7. Other Features .................................................................................................... 13

7.1. Monitor function .......................................................................................................... 13

7.2. Swivel mechanism ....................................................................................................... 13

7.3. Detachable connecting cord ........................................................................................ 13

7.4. Power supply ...............................................................................................................13

7.5. High-quality sound BTL headphone amplifier ............................................................ 13

Appendix: Indication of Canceling Performance

for Noise Canceling Headphones ....................................................................... 14

1.1. Total Noise Suppression Ratio .................................................................................... 14

4

GB

MDR-NC500D is the Digital Noise Canceling Headphones, which Sony developed as the

first of their kind in the world.

For this development, Sony put in all of its acoustical analysis technology, digital signal

processing technology and transducer technology.

By digitizing the noise canceling function, we succeeded in improving the performance in

the following points which, were difficult to be addressed with the conventional analog signal

processing:

• High canceling performance

• AI (Artificial Intelligence) Noise Canceling function

• Excellent sound quality

• Higher Signal to Noise ratio

1.Introduction

5

GB

2. Principle of Operation of MDR-NC500D

and Its Configuration

The noise canceling headphones make a canceling signal by analyzing with their noise

canceling circuit the surrounding noise collected by the small noise detection microphone built

in their main body.

With this canceling signal superimposed on the regenerative signal from the connected

equipment, reproduction from the driver unit reduces surrounding noise and makes it possible

to listen to music more clearly.

For the noise canceling, the following two methods are mainly used:

• Feedback type

• Feedforward type

1. Waveform of noise

(original sound)

Surrounding noise is collected by

the noise detection microphone

built in the headphones and its

signal is analyzed with the noise

canceling circuit.

2. Inverted sound

waveform

The inverted sound, which can

negate the analyzed noise, is

generated.

3. Sound waveform

canceled by

superimposition

By overlaying the original sound

with the inverted sound, the

original sound is negated. This

reduces noise at the eardrum.

Continued

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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

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GB

Comparison between Feedback Type and Feedforward Type

Noise canceling effect

Anti dependency of noise

canceling effect against

individual difference / fitting

difference

Miniaturization

2.2.

System configuration of MDR-NC500D

The Internal Block Diagram of MDR-NC500D is shown below:

The noise detection microphone of MDR-NC500D collects noise

around the ear.

The noise signal is digitized through the microphone amplifier and

high-speed A/D converter and is inputted in Digital Signal Processor

(DSP). Then the DNC software engine inside DSP generates the canceling

signal, which is inverted to the original noise.

Meanwhile, the regenerative signal of a music source supplied from

the audio input terminal is digitized by the high-speed A/D converter and is

inputted in DSP. Then, its frequency characteristic is adjusted by the digital

equalizer inside DSP. After the canceling signal is added, the regenerative

signal is reproduced as a sound by way of the high-speed D/A converter,

the headphone amplifier and the driver unit.

Mixing of the reproduced sound and the outside noise at the ear

negates only environmental noise, making it possible to enjoy music etc.

calmly.

Feedback type

Excellent

Better

Less suitable

Feedforward type

Good

Average

More suitable

Continued

Internal Block Diagram of Noise Canceling

Headphones of MDR-NC500D

Audio In

A/D

converter

System

controller

DSP

Digital

equalizer

Digital block

DNC software

engine

D/A

converter

A/D

converter

Detection

microphone

Headphone

amplifier

Driver unit

Microphone

amplifier

High-speed A/D,

D/A converter

8

GB

2.3. Advantages of Digitization

The performance of noise canceling headphones greatly depends on the efficiency of the

filter circuit (NC filter) between the microphone to detect noise and the driver unit to

reproduce the canceling signal.

In MDR-NC500D, the filter circuit for noise canceling is realized on the DSP as the

digital signal processing of the newly developed “DNC software engine.”

In addition to general advantages such as accurate computation results, no theatrical

variation, and no electric noise, the digital signal processing has also the advantage of making

it possible to create special filter shapes, which were not able to be realized with existing

analog filters.

During the development of the DNC software engine, the architecture of internal filter

computation was thoroughly examined in order to implement a more effective noise canceling.

The know-how of Sony’s digital sound treatment was used to construct a software engine

specialized in the noise canceling treatment and the calculation accuracy was heightened.

Noise canceling with less residual noise and higher Signal to Noise ratio was made possible.

Example of the characteristic of

conventional NC filter

Response

Frequency

Example of the characteristic of

digital NC filter

Response

Frequency

9

GB

The characteristics of environmental noise vary with the scene to be used.

In an airplane, for example, low and midrange frequencies can have a large noise energy

and other frequency ranges have a smaller noise energy.

On the other hand, in the environment such as an office, the noise energy is small but

distributed over a wider range.

In MDR-NC500D, the filter circuit to control a noise canceling ratio was digitized and it

is controlled by software.

This enables the filter characteristic to be switched: AI Noise Canceling function with

which MDR-NC500D selects automatically the filter characteristic (noise canceling mode) that

is the most suitable for the user's environment.

3.AI Noise Canceling Function

NC MODE A

Noise mainly in an airplane is effectively

reduced.

Frequency

Noise canceling ratio

* Manual mode selection is also possible.

AI Noise Canceling function

Digital technology allows selection from multiple

noise canceling modes.

The headphones analyze the outside noise and

automatically select the optimal canceling mode.

NC MODE B

Noise mainly in a bus or a train is effectively

reduced.

NC MODE C

Noise mainly found in an office environment

(PC, copier, air ventilation, etc.) is effectively

reduced.

Continued

10

GB

In order that feedback type headphones obtain

a wider canceling range, it is necessary to minimize

the time delay between the output of the driver unit

and the input to the noise detection microphone.

By integrating the noise detection microphone

with the driver unit to minimize the time delay,

MDR-NC500D achieved a stable and wider range

canceling performance.

Moreover, the use of re-informed diaphragm

significantly improved the canceling performance

against environmental noise with a high sound

pressure that is generated in a very low frequency.

3.1.

Operation of AI Noise Canceling function

The operation of actual AI Noise Canceling function is as follows:

1. Press the AI NC MODE button to start the analysis program. *

2. Built-in DSP analyzes the sound information of noise from the noise detection

microphone.

Its specific value is extracted from the signal and the most effective noise canceling

mode is selected.

3. The noise canceling operation is started in the selected mode.

* During analysis, reproduction of music source and noise canceling function are temporarily stopped in order to

gather exact noise information.

MDR-NC500D completes the above-mentioned processing

in a short time of about 3 seconds.

The analysis algorithm of AI Noise Canceling (AINC)

developed a proprietary calculation technique based on the

Auditory psychology emphasizing the frequencies, which make

noise more audible to the ear.

It is the very realization of “smart headphones” which can

follow man's feeling.

With the AI Noise Canceling function only made possible

by Digital, please enjoy its comfortable canceling effect.

4.Specialized Driver Unit

DSP used in

MDR-NC500D

Driver unit

11

GB

MDR-NC500D digitized the NC circuit and used the digital equalizer in the playback

system.

The acoustical system of noise canceling headphones is generally based on the design,

which emphasizes low frequency in order to maximize the effect with limited electric power.

Moreover, in the case of the noise canceling headphones of feedback type, in principle

their music signal is impacted by the canceling function, so that the quality of the reproduced

sound is also impacted.

To solve these problems, an equalizer circuit is prepared in the audio input side.

The digital equalizer mounted in MDR-NC500D blocks the impact on the sound quality

and also brings about high-quality sound to maximize the intrinsic performance of the driver

unit.

By generously providing the digital equalizing technology accumulated with Sony’s AV

amplifiers and Hi-Fi audiovisual apparatus and using the newly developed computation

method optimized to the system, it was made possible to reproduce a music source with a

sense of realism from deep bass to silky highs.

5.

High-Quality Sound Unique to Digital

Desired

characteristic

Characteristic of

acoustical system

Characteristic of

digital equalizer

Total

characteristic

Response

Frequency

Response

Frequency

Response

Frequency

12

GB

Magnesium and 7075 aluminum are used as the material for the housing and the

headband, respectively.

By using these unstintingly, the mass is reduced to as small as 195 g or more than 10 %

weight reduction. *

* In comparison with MDR-NC60.

6.Weight saving mechanism

13

GB

7.1. Monitor function

MDR-NC500D is equipped with the monitor function to make the surrounding sound

more audible by muting music etc. during reproduction when you are spoken to, for example.

While wearing the headphones, you can hear an announcement etc. in an airplane or in a

train only by pressing the button.

During monitoring, disturbing noise can be reduced by the noise canceling function.

7.2. Swivel mechanism

A mechanism to reduce the storage thickness by rotation of the housing is used in order to

enhance portability. (Swivel mechanism)

7.3. Detachable connecting cord

The main body side of the headphones connecting cord is detachable.

According to the equipment in combination, you can select the connecting cord of optimal

length from accessories. When using the noise canceling function without any music playback,

etc., disconnect the cord for comfortable use.

Moreover, the connecting cord with battery case also serves as power source.

MDR-NC500D can be used longer in combination with the built-in lithium ion

rechargeable battery.

7.4. Power supply

MDR-NC500D supports three kinds of power supply methods: Built-in lithium-ion

rechargeable battery, Alkaline LR03 (size AA) battery *

1

and AC power adaptor.

The AC power adaptor is of 100 V to 240 V multi-voltage type.

It can be used almost all over the world. *

2

*

1

When the connecting cord with battery case is used. Two Alkaline LR03 (size AA) batteries are used.

*

2

Use with the outlet of a different shape needs an optional plug adapter.

7.5. High-quality sound BTL headphone

amplifier

The headphone amplifier is of BTL (Bridged Transformer-Less) type.

You can enjoy a powerful sound with a wide dynamic range.

7.Other Features

14

GB

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

/ P

0

)

•P

0

= 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.

Appendix: Indication of Canceling Performance

for Noise Canceling Headphones

15

GB

[Example of notation]

TNSR: 20 dB

[

Sony’s conventional method

]

Noise canceling ratio = Difference between ON and OFF

Largest value (one point)

Sound pressure

Frequency

Wearing (OFF)

Wearing (ON)

Noise before

wearing

[

Total Noise Suppression Ratio (TNSR)

]

Sound pressure

Total Noise Suppression Ratio = Difference in noise energy

when not wearing the

headphones and when the

Noise Canceling function is

active.

Frequency

Total Noise Suppression Ratio (typical values)

Unit: dB

NC MODE A

NC MODE B

NC MODE C

Train/Bus

18.0

20.3

15.0

Office

17.1

18.3

18.9

Airplane

20.0

17.0

14.9

• Based on Sony's one noise source simulations.

• Note: Noise canceling ratio (Sony’s conventional method) more than 25 dB (at MODE A)

3

CT

1. 4

2. MDR-NC500D 5

2.1. 6

2.2. MDR-NC500D 7

2.3. 8

3. AI 9

3.1. AI 10

4. 10

5. 11

6. 12

7. 13

7.1. 13

7.2. 13

7.3. 13

7.4. 13

7.5. BTL 13

14

1.1. 14

4

CT

MDR-NC500D Sony

Sony

•

•AI

•

1.

5

CT

GB

2. MDR-NC500D

•

1. 2. 3.

6

CT

2.1.

MDR-NC500D

NC

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