Noise-Cancelling Headphones

You must have noticed from my first blog post that I am a huge fan of music and hence I like to enjoy my music to the fullest. Unfortunately, background noise is heard when I listen to music on the go. For example, when I am travelling in a bus, I hear phone conversations and sometimes loud crying of babies, which is very disturbing. There is a solution to this, which is noise-cancelling headphones but unfortunately I do not own one because they are very expensive. But I will tell you how they work.

There are two types of noise-cancelling headphones, namely active and passive. The latter are manufactured to maximise filtering of noise of about 15 to 20 dB by using material such as layers of high-density foam or other material that absorb sound. Due to this reason, these headphones tend to be heavier than ordinary headphones. Active noise-cancelling headphones perform the same task as passive ones but they have some extra features. Sound waves with high frequencies can be blocked because of the structure of these headphones. The incoming noise is in anti-phase with the sound waves produced by the speakers in the headphones. In other words, destructive interference takes place, which is shown in the figure given below.

Inside noise-canceling headphones

Figure : Cross-section of a set of noise-cancelling headphones

Let’s look at the components found inside these headphones.

  • Microphone – The embedded microphone receives external sound waves, which cannot be blocked passively.
  • Noise-cancelling circuitry – The electronics fitted inside the ear cup sense and generate a model of the incoming sound wave and stores information such as the frequency and the amplitude. An anti-phase wave is then created to cancel the noise.
  • Speaker – The anti-phase wave of sound produced by the circuitry is fed into the speakers along with the audio produced by music; destructive interference takes place erasing the noise and the desired sound is produced in return.
  • Battery – This provides the energy required for the noise-cancellation process. The battery found in modern active noise-cancelling headphones (eg. new Beats Studio) can be recharged by plugging the headphones to the computer using the USB cable provided with the headphones.

 

References :

HowStuffWorks “Noise-canceling Headphones”. 2014. HowStuffWorks “Noise-canceling Headphones”. [ONLINE] Available at: http://electronics.howstuffworks.com/gadgets/audio-music/noise-canceling-headphone3.htm. [Accessed 24 March 2014].

 

The Freescale DSP56321 – An Overview

Today, I would like to share something that I have learnt when I was following my Undergraduate degree in Electrical and Electronic Engineering at University of Manchester. It is about the Freescale DSP56321.

The DSP56321 is the fastest member of the DSP563xx family and is ideal for systems requiring a minimum cheap count. Below is a block diagram showing the internal architecture of the device.

DSP56321 block diagram

Figure : Internal architecture of the Freescale DSP56321[1]

Let’s look at the hardware components briefly.

Memory

The DSP56321 has three internal memory areas, namely program memory (which contains the coding or instructions), x-data memory and y-data memory, and each area of memory has its own data and address bus. These communicate with the outside world using bus multiplexers. The program memory is sub-divided into 32768 words of user programmable RAM and 192 words of bootstrap ROM. This ROM holds a special program that is automatically invoked when the device is reset. The x and y areas of data memory can store up to 40,960 words of user data. This is an extension of the Harvard architecture because many algorithms used in signal processing utilise two distinct signal vectors. For example, FIR (finite impulse response) filters require memory to store the incoming signal and memory to hold filter coefficients and FFT (fast Fourier transform) routines require memory to hold the real and imaginary Fourier components.

The Data ALU

The Arithmetic and Logic Unit (ALU) of the DSP56321 has the task of carrying out the mathematical and logical processing of the data stored in x and y-data memories and contains an enhanced 24-bit fixed-point filter co-processor, which processes using values between -1  and +1. The ALU comprises four 24-bit input registers.

Processor ports

There are five logical ports (A to E) in the DSP56321 which are used for communication with external devices such as memory and interfaces. Each port has a particular designated operation of communication. For example, port A is the memory expansion port that is used when external memory is connected to the processor.

Register control of peripheral systems

This device also contains separate registers that control various peripheral systems. It is possible to modify the operation of a peripheral by loading different control words to these registers.

References

[1] DSP56321 Internal Architecture [ONLINE] Available at:http://cache.freescale.com/files/graphic/block_diagram/DSP56321BD.jpg. [Accessed 19 March 2014].

[2] Lecture Notes by Prof. P. Gaydecki (2013)

Theory Behind Soundbars

Modern houses are equipped with various consumer electrical devices such as smart televisions and home theatre systems. If you look at home theatre systems, careful wiring should be done, so that the living room is tidy without any wires trailing on the floor, and this is clearly not an easy task. The solution to this would be having a soundbar instead because one only needs to connect the soundbar to the “optical out” port of the television using one cable. A soundbar can also save space if you are living in a small room because it is not necessary to have so many speakers : The sound emitted from a set of speakers can be delivered from one device. Let me explain the theory behind this compact yet incredible  device.

A soundbar is a long slender device, which consists of seven speakers and each speaker is integrated in such a way that surround sound can be achieved. It has been designed to reflect the sound emitted from the device by the walls. The walls have to be reflective surfaces for this feature to be effective. If there are a lot of absorbers such as curtains and cushions, a soundbar will not be a good choice.

Soundbar

The figure above shows how surround sound effect is created by the soundbar.

Another advantage of having a soundbar is that if the television is mounted to a wall, the soundbar can be mounted to the wall too, so that the ground can be kept clear for furniture or for movement.

Reference :

How a soundbar works | BUILD. 2014. How a soundbar works | BUILD. [ONLINE] Available at: http://www.build.com.au/how-soundbar-works. [Accessed 15 March 2014].

Samsung Galaxy Note 3 – Review

This week I went to Phones 4u to get hands-on experience with Samsung Galaxy Note 3. It has been there in the stores for several months now but unfortunately I did not get some time to try it out.

First, I will explain the hardware. This mobile phone weighs 168 g and runs Android 4.3 (Jelly Bean) but can be upgraded to Android 4.4.2 (KitKat) after purchase and consists of a 5.7″ FHD (full HD) sAMOLED (Super Active Matrix Organic Light-Emitting Diode) display with a resolution of 1080×1920 pixels. This feature is suitable for a user who enjoys watching movies and playing games on his or her phone. I did not find this really fancy because it is hard to control the screen using just one hand. Note 3 has been manufactured with a Qualcomm Snapdragon 800 chipset and a Krait 400 quad-core processor with a clock speed of 2.3 GHz, so the processing is lighting fast. It also comprises of 3 GB RAM (random access memory), which is ideal for multitasking, and also contains 32 or 64 GB flash memory onboard, so more files can be stored without installing additional storage using microSD cards, although it is possible to expand flash memory up to 64 GB. There is a 13 MP Auto Focus rear camera with features such as Smart Stabilisation, LED flash and Zero Shutter Lag and a front camera of 2 MP. The cameras also feature Dual Shot, Dual Recording and Dual Video Call, so both the cameras can be used simultaneously. The battery installed is a 3200 mAh Standard Battery, which supports up to 11 hours of internet usage time on LTE (Long Term Evolution) and 3G HSPA+, up to 13 hours on WiFi usage and up to 380 hours on standby with LTE, which is impressive. The phone also supports wireless networks such as GSM, GPRS, EDGE and Bluetooth 4.0.

Now I will explain the features in the software. The main feature is Air Command, where a user can hover the stylus known as “S Pen” over the screen and tap the embedded button to open the Air Command, which consists of a list of useful features such as Memo and Scrapbook. Another feature is Action Memo, which allows a user to make a quick handwritten note that instantly activates a function. such as making a call, adding a new contact, creating a To-Do item or email, looking up an address on the map or searching the web [1]. Scrapbook is the third feature that the software contains, which organises photos and videos stored in different places, including online storage, so the user does not have to waste time searching for them. Finally, the S Note, which helps a user to create instant notes, browse through and edit them without having to recreate them. If the user scribbles a chart on S Note, the Easy Chart feature embedded in S Note can transform this in to a professional-looking graph.

In conclusion, this phone is suitable for professionals in the industry of art and design because it is easy to write down notes or ideas and draw sketches on the go using this incredible phone and the S Pen.

Screen Shot 2014-03-08 at 12.04.25

Samsung Galaxy Note 3 with S Pen [1]

References :

[1] Galaxy Note 3 – 4G, 3G, Wi-Fi, NFC, 13MP, 5.7“ FHD, 2.3GHz – Samsung UK – FEATURES. 2014. Galaxy Note 3 – 4G, 3G, Wi-Fi, NFC, 13MP, 5.7“ FHD, 2.3GHz – Samsung UK – FEATURES. [ONLINE] Available at:http://www.samsung.com/uk/consumer/mobile-devices/galaxy-note/smartphones/SM-N9005ZWEBTU-features. [Accessed 08 March 2014].

Samsung Galaxy Note 3 with S Pen [1]

References :

[1] Galaxy Note 3 – 4G, 3G, Wi-Fi, NFC, 13MP, 5.7“ FHD, 2.3GHz – Samsung UK – FEATURES. 2014. Galaxy Note 3 – 4G, 3G, Wi-Fi, NFC, 13MP, 5.7“ FHD, 2.3GHz – Samsung UK – FEATURES. [ONLINE] Available at:http://www.samsung.com/uk/consumer/mobile-devices/galaxy-note/smartphones/SM-N9005ZWEBTU-features. [Accessed 08 March 2014].