Sony DIGITAL NOISE CANCELING HEADPHONES... User manual

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3-280-434-12(1)
MDR-NC500D
©2008 Sony Corporation
Noise Canceling
Headphones
FR
GB
ES
DE
PT
IT

2GB

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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

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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

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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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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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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

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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

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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

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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

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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

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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

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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 *1and 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
*1When the connecting cord with battery case is used. Two Alkaline LR03 (size AA) batteries are used.
*2Use 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

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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 / P0)
•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

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[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)

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Table des matières
1. Introduction .......................................................................................................... 4
2. Fonctionnement et configuration du MDR-NC500D ........................................... 5
2.1. Rétroaction négative et rétroaction positive ................................................................. 6
2.2. Configuration système du MDR-NC500D .................................................................. 7
2.3. Avantages de la numérisation ...................................................................................... 8
3. Fonction Anti-Bruit AI ......................................................................................... 9
3.1. Fonctionnement de la fonction Anti-Bruit AI ............................................................ 10
4. Transducteur spécialisé ...................................................................................... 10
5. Son d’une haute qualité unique en numérique ................................................... 11
6. Mécanisme de réduction du poids ...................................................................... 12
7. Autres caractéristiques ....................................................................................... 13
7.1. Fonction de contrôle .................................................................................................. 13
7.2. Mécanisme de pliage.................................................................................................. 13
7.3. Cordon de raccordement amovible ............................................................................ 13
7.4. Alimentation .............................................................................................................. 13
7.5. Amplificateur de casque BTL offrant un son de haute qualité .................................. 13
Annexe : Indication de la performance de réduction
du bruit du casque anti-bruit ............................................................................... 14
1.1. Taux total de réduction du bruit ................................................................................. 14

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Le casque MDR-NC500D est un Casque Anti-Bruit Numérique. Développé par Sony, il
s’agit du premier du genre dans le monde.
Pour ce faire, Sony a tiré profit de sa technologie d’analyse acoustique, de sa technologie
de traitement des signaux numériques et de sa technologie des transducteurs.
En numérisant la fonction anti-bruit, Sony a réussi à améliorer les performances sur les
points suivants, difficiles à traiter avec le système de traitement des signaux analogiques
conventionnel :
•Performance de réduction du bruit élevée
•Fonction Anti-Bruit AI (Intelligence Artificielle)
•Excellente qualité sonore
•Rapport signal/bruit supérieur
1.Introduction

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2. Fonctionnement et configuration du
MDR-NC500D
Le casque anti-bruit émet un signal de réduction du bruit après analyse du bruit
environnant, perçu par le microphone de détection du bruit intégré, grâce au circuit anti-bruit.
Ce signal de réduction superposé au signal régénérateur de l’appareil raccordé permet de
réduire le bruit environnant lors de la reproduction depuis le transducteur, offrant ainsi une
qualité de musique encore plus nette.
Les deux méthodes suivantes sont les plus utilisées pour anti-bruit :
•Rétroaction négative
•Rétroaction positive
1. Forme d’onde du bruit
(son original)
Le microphone de détection du bruit
intégré au casque capte le bruit
environnant, dont le signal est
ensuite analysé par le circuit anti-
bruit.
2. Forme d’onde du son
inversé
Un son inversé, capable
d’annuler le bruit analysé, est
généré.
3. Forme d’onde du son
annulé par
superposition
Le son original est recouvert par le
son inversé et annulé. Ceci réduit
le bruit au niveau du tympan.
Suite

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2.1. Rétroaction négative et rétroaction
positive
Rétroaction négative
Le MDR-NC500D utilise une fonction anti-bruit avec « rétroaction négative ».
Avec le type de rétroaction négative, le microphone de détection du bruit est placé près de
l’oreille.
En captant le bruit plus près de l’oreille, la précision de l’effet anti-bruit est accrue.
Le signal de bruit détecté par le microphone de détection du bruit est analysé en temps
réel par le circuit anti-bruit (circuit NC) et un signal d’annulation est généré en permanence
pour réduire le bruit au niveau du tympan. Le signal d’annulation est reproduit par le
transducteur.
Cette méthode permet d’augmenter l’effet anti-bruit selon les variations du bruit
environnant.
Rétroaction positive
Avec le type rétroaction positive, le microphone de détection du bruit est fixé à l’extérieur
du casque.
Le circuit NC analyse le signal de bruit détecté par le microphone de détection du bruit
pour estimer quel sera le type de bruit au niveau du tympan. A partir de cette estimation, un
signal d’annulation destiné à réduire le bruit est émis et reproduit par le transducteur.
Ce type permet de miniaturiser le casque étant donné qu’il n’est pas nécessaire que le
microphone de détection du bruit soit placé près de l’oreille où la place est limitée.
Rétroaction
négative Rétroaction positive
Bruit
Transducteur
Microphone de
détection du bruit
Circuit NC
Bruit
Transducteur
Microphone de
détection du bruit
Circuit NC