Difference between uds and other speakers english language essay

It is with great enthusiasm and learning spirit that I bring out this final report. I also feel that it is the right opportunity to acknowledge the support and guidance that came in for various quarters during the course of completion of my degree. I express my gratitude to Head of School of Engineering and Computing for rendering me all facilities and guiding me right through the end for the successful completion of the work. I express my gratitude to Mr. Tham Kwong Keong, School of Engineering and Computing for guiding me right through the end for the successful completion of the year and the advice he provide to overcome the troubles I had when I construct the product. Above all I acknowledge lab assistance to help me with the trouble shooting and providing the tools we needed. Despite the best efforts put in by me, it is possible that some unintentional errors might have eluded me. I shall acknowledge with any such errors if pointed out.


” Ultrasonic Directional Speaker” it is a very recent technology, which produce a beam of sound that can ravel trough a straight path. There a simple theory that we have apply for this project which is the non-linearity characteristic of ultrasound. Because of their relatively high amplitude to wavelength ratio, ultrasonic waves commonly display nonlinear propagation behaviour. Using that behaviour we able to produce ultrasound speaker, where the ultrasound acts as a air bone speaker. The sound is better than the normal loud speakers and it is directional. Holosonic Research Labs invented the AudioSpotlight that is made of a sound processor, an amplifier and the transducer. But it is very costly for the consumers for regular use. Ultrasound directional speaker will be a huge commercial market in entertainment and electronic technology. Being the most recent technology and the way we perceive sound Ultrasound directional speaker technology can do many miracles in various fields like, Home audio systems, Navy and military applications, museum displays , library and etc. Thus Ultrasound directional speaker helps us to control where sound comes from and where it goes and the distance.


Chapter One


Project overview

Ultrasonic directional sound is a very recent technology that creates focused beams of Sound same as light beams coming out of a flashlight. Normally for normal speaker systems, the sound beams propagate almost everywhere, when a sound comes from normal speaker; the sound can be heard from every corner of the room. But by using ultrasonic directional speakers the sound beams can be narrowed down by almost straight path like shown in figure 1 below. Producing a directional ultrasound is not simple as producing a directional light beam. Because the light beam can be produced just by using a reflector system around the source, but this technique is nearly impossible for sound. Scientist has a theory that by using ultrasonic sound they can achieve the sound beam. Figure 1. 1 Difference between UDS and other speakersA directional sound will be very helpful for lots of applications and places like in figure 2 bellow museums to give an instruction about the picture they standing in front. The person who standing in front of next picture will not be disturbed and also, give a commercial advertising to a buyer and information about the products in the shops. Figure 1. 2 Use of UDS in MuseumsTo produce a direct line of sound we have to use an ultrasonic sound wave which is define as above 20 kHz, and it will not be able to hear by human ear. To make the sound able to hear we have to use a sound modulation and demodulation techniques. By modulating, we are creating the ultrasonic sound. And according to (Humphrey2007) there is a property of ultrasound that has a non-linear propagation. It will demodulate the ultrasonic sound to sound that humans able to hear. Where using an Air as a medium. This technology has been under development since early 1960s but it has been remained unsuitable for public use due to unfeasibility of both production and operation. Firstly the technology was developed by US NAVY and Soviet NAVY for underwater sonar. In 1980’s this technology has been briefly investigated by Japanese scientist. And again the project has been stopped due to extremely poor quality of sound and high cost. The issues went unsolved until the paper published by Dr. F. Joseph pompei from the Massachusetts institute of Technology in 1998. A full description of working device that have a good fidelity, but the cost was remaining high. So, the product was not able to reach the public for a commercial use. However, very recent development in this technology and the lowering the cost of the product came to great end. They have used the different modulation techniques and digital signal processing to improve the both quality and effectiveness of the sound. In all wave sources, the directivity depends on size of the source compared to the wavelength of the sound. The larger the source compared to the wavelength of the sound wave, the more directional beam results. But this specific field has no impact on the directivity of sound. It is relies in the aperture function of the source according to Huygens-Fresnel principal. At high frequencies the wavelength are quit short, which can result in a narrow distribution of sound from a tweeter in normal loud speaker systems. By making the larger either through dimensionally large speaker, speaker array or panel, higher directivity can be obtained at lower frequencies. Still the maximum directivity of a loud speaker is still very week. Figure 1. 3 Huygens-Fresnel principal. The ultrasonic devices are over the expectation for the scientists. They can create ” virtual” loudspeakers which are physically large and invisible. Because of these reason, making directional sound is possible with any loudspeaker systems. The parametric array is a nonlinear transduction mechanism. It generates narrow beams of low frequency sound. Parametric array generates a low frequency sound trough mixing and interaction of high frequency sound wave. A high frequency sound can be created by modulating a low frequency sound like electromagnetic waves. This method of technology has been used for a communication for long time. To underwater massage sender, underwater diving communicators and a short range communication with submarines. But the massages should be decoded into audible sound by a demodulating ultrasound demodulator receiver. Ultrasound is an any wave which has a frequency above 20 kHz which is a upper limit of human hearing. So as we state above we need a demodulator to extract the information in the ultrasound. So, the dream of direct communication with an ultrasound came to an end in time. But there is a one more property of ultrasound that has a non-linear propagation. Because of their higher amplitude to wave length ratio, ultrasonic waves are display a non-linear propagation. This non-linear propagation can lead the demodulation of modulated ultrasound wave during the propagation tough a medium. Normally the medium is an air. By modulate the sound wave can produce an ultrasound. There are several modulation techniques are available to do and they are; amplitude modulation (AM), dual side band modulation (DSB) modulation, frequency modulation (FM) and pulse width modulation (PWM). Amplitude modulation and dual side band modulation are preferred when considered about loudness of sound but not the quality in other way fidelity of sound. Frequency modulation and pulse width modulation will able to give a good fidelity therefor while the purpose of this project is transfer sound for distance the preferred modulation will be frequency modulation or the pulse width modulation.

Project specification

For producing a sound from ultrasound, the ultrasound must be modulated; there are several modulation techniques Amplitude modulation, frequency modulation, pulse width modulation and etc. We have created the system with pulse width modulation which is has a good fidelity. The whole system can be shown as below block diagram. Piezoelectric TransducersA Half bridge DriverPulse width ModulatorAudio SignalsFigure 1. 4 Block diagram for directional speaker systemsFirstly, the audio signal is pulse width modulated by a pulse width modulator then by using a half bridge driver they drive through an array of piezoelectric transducers. The array consist array of fifty piezoelectric transducers.


The aim of the project is produce an directional invisible air borne speakers by modulate the ultrasonic sound with audio signal and project it through a piezoelectric transducers to specific targeted person or point, where the person only able to hear the sound which we projected.


Firstly, determine the suitable modulation method to design the system that can be stable and with high fidelityDesign a system that modulates the audible sound to high frequency square waveTransmit the square wave output trough a piezoelectric transducersTo enhance the current design so that it can travel further with less noise signal. Personal ObjectiveDetermine the suitable modulation technique. Design controllable system with high frequency modulation. Design a power supply that can produce two different DC voltages to source the device (12V and 24V).

Project Management

Job Allocation

This project is a group project



Risk analysis

Thesis summery

Chapter Two


This has included research papers, journals, various books and other literature in order to get the principles and laws involved in this field. The main literature reviewed may include theory of (Yoneyama and Fujimoto 1983) which explained the theoretical aspects of this project technology. Also we reviewed the various literatures that explain the basic blocks of this technology state below.

Technology Overview – History and scientific outline of the technology

Human Hearing – Hearing mechanism of human and hearing range

Ultrasound – The carrier wave of the system

Heterodyning – Digital signal processing method for the system

Modulation – Varies of modulation and the modulation we used (PWM)

Piezoelectric Transducers – Review of speaker which can produce ultrasound

Technology Overview

Normally the speakers produce a sound by directly moving the air molecules. The sound potion of the molecules begins to move all the direction from the point of origin. They do not travel in a straight path, in fact the angle of the audibled sound from a normal loudspeaker is very wide, it almost 360 degrees. It means the sound you hear will be propagate trough an air almost all the directions. To make the sound travel in a straight path, it should have a low beam angle. The beam angle is controlled by a wavelength. And it has proven to say smaller the wavelength, lesser the beam angle. The beam angle is also depends on the aperture size of the speaker. If the source loudspeaker made of several times bigger than the wavelength of the sound transmitting; a fine focused beam can be created by using loudspeaker. But it is not very practical to do. Because the low beam angle only can be achieved by making the wavelength smaller. In here, the ultrasonic sound is helpful to achieve the goal. In 1960’s researchers were developing an underwater sonar system. They were applying a technique which is using a non-linear interaction of high frequency wave to generate a low frequency wave. And in 1975’s an article pointed that there are non-liner effect on air. Following that several large companies including Panasonic and Ricoh trying to develop a loudspeaker using this principal, but it was not a perfect quality of sound. Ultrasonic directional speaker works by emitting ultrasonic energy to create extremely narrow beam of sound that behave like beam of light. And it is a harmless high frequency ultrasonic sound that human ear cannot hear. Ultrasonic sound has a very small wavelength in millimetre range. These sound will produce a new sounds by make use of the non-linearity of an air. These new sound will be in human hearing range. Ultrasonic Direction sound speaker systems have been in use all over the world since 2000. Include American greetings, Best buy, Boston Museum of science, Cisco Systems, the field museum, the Guggenheim, Harvard Peabody Museum, Motorola, Science world BC, Walt Disney and western Union.

Human Hearing

Hearing or audition, it’s an ability to receive sound by vibrating trough an organ such an ear. The vibrations are detected by ear and transduced into nerve impulses that are perceived by the brain. Functional diagram below in figure 6 shows the human ear. The outer ear collects sound waves from environment and channels them into ear drum, a thin sheet of tissue that vibrates in synchronization with the air wave. The middle ear bones transmit these vibrations to the oval window. Cochlea contained 12, 000 nerves cells. During varies of stiffness of the basilar membrane, each nerve only response to narrow range of frequencies, making the ear as a frequency spectrum analyser. Figure 2. 1 Functional diagram of the human earThe ranges of sound pressure levels and frequencies that can be respond without damage to human shown in figure 7 below. The dynamic range of human hearing is ≈ 120 dB. The smallest detectable change in relative level is ≈ 0. 5 dB to 1dB for a wide band noise signals. The frequency range of human hearing is conventionally state as 20 Hz to 20 kHz but it tends to decrease with age. According to (Campell1998) particularly at the age of year 20 the high frequency end, which maybe 16 kHzFigure 2. 2 Human hearing data


Ultrasound is a cyclic sound pressure wave with a frequency which is greater than the upper limit of human hearing range. Thus, ultrasound is not having different physical properties from normal audible sound; only the fact human cannot hear it. Although the limit varies from person to person, it is approximately 20 kilohertz for a healthy young adult. The range of ultrasound is shown in figure 2. 3 below. It starts from 20 kHz to several Gigahertzes. C: UsersSNITERDesktopFYPUltrasound_range_diagram. svg. htm_20130123213845. pngFigure 2. 3 Uses of ultrasoundThe ultrasound is used in many different fields, mainly to penetrate a medium and measure the reflection signature or supply focused energy. The reflection signature can show details about inner structure of the medium we send the ultrasound trough. In real fact, bats use an ultrasound to hunt and make their flee path. Industrial wise ultrasound is used for cleaning and mixing, and to accelerate the chemical process. The most well know process of ultrasound is ultrasonic imaging (sonography) to produce the picture of the human womb. There are many numbers of applications for ultrasound. Figure 2. 4 Uses of ultrasound (Human womb)Ultrasound can be modulated to carry an audio signal (like radio signals are modulated). This is often used to carry message underwater, in underwater diving communicators and short-range communication with submarines, less than five miles. However, due to sound absorb characteristic of sea water, ultrasound cannot be used for a long range communication. The higher the frequency the faster the sound absorbs by sea water, and faster the sound fades. Ultrasonic waves commonly display non-linear propagation because of their high amplitude to wavelength ratio, due to the fact the air molecules takes long time to return to their original density then to be compressed (figure 2. 3. 3). when the sound pressure is high and frequency, maybe a shock wave produced by a returning air molecules colliding with the one being compressed. In fact, an audible sound will be produced. When the frequency of sound rises, the non-linearity characteristic becomes noticeable by an effect called Air viscosity. Figure 2. 5 Non-liner property of ultrasoundThe non-linearity property of ultrasound is used to demodulate the modulated sound in air by a processing called Heterodyning, when two finite amplitude sound waves (primary) having difference frequencies collide with one and other will produce new sound waves (secondary) whose frequencies are summed and differences of the primary waves. This process known as ” nonlinear interaction of sound wave”. Westerved derived an equation which satisfied by the sound pressure of secondary wave produced by non-linear interaction.——————–Eq 2. 1Where,  p is the sound pressure, c_0 is the small signal sound speed, delta is the sound diffusivity, eta is the non-linearity coefficient and 
ho_0 is the ambient density.


Heterodyning is radio signal processing technique invented by Canadian inventor Reginald Fessenden in 1902. This is a new generation of frequencies by mixing two or combining two frequencies. This is useful for placing information into a useful frequency range following modulation and demodulation. The two frequencies are mixed in device such as vacuum tube, transistor or diode, usually called mixer. Heterodyning creates two frequencies one is sum of frequencies and other one is their difference. The new frequency called heterodynes and one of the frequencies is desired. In this case frequency difference is desired. Based on trigonometric identity: In the eq2. 2 the left hand shows the product of the two sine waves and right hand shows result signals. In the result there is sum of two original frequency and difference of them are resulted. In here: The result are one is sum of the two frequencies and other one is difference of the two frequencies. Hence when two or more coherent ultrasound meets in a non-linear material like air they go under heterodyning to produce an audio wave.


Practical implementation and computer simulation has been shown that the quality of the sound or its fidelity can be improved using modulation technique like frequency modulation or pulse width modulation. A pulse width modulation (PWM) is a powerful modulation method for controlling analogue circuits with digital outputs. PWM is has been used in a wide variety of applications, ranging from measurement and communications to power control and conversion. In PWM the width clock pulse is varied according to the amplitude of the signal. so, the time duration and power of each pulse depends on the amplitude of the signal, the larger the amplitude greater the width of the pulse. Figure 2. 6 Generation of PWM signalPWM uses a rectangular pulse wave to get a variation of average value f(t) waveform, where the rectangular wave will be modulated. If we considered a pulse wave f(t), the low value , high value and the duty cycle is D, the average value of waveform is given by; As f(t) is a pulse wave, its value is y_{max} for 0 < t < D. T and y_{min} ford. t < t < T. The above expression then becomes: This expression (Eq2. 5. 2) can be simplified in many cases where as. From this it is safe to say that the average value of the signal ( ) is directly dependant on the duty cycle. Figure 2. 7 Input, output wave diagramWhen the value of the reference signal (the green sine wave in figure 2. 7) is more than the modulation waveform (blue), the PWM signal is (pink) in the high state (1), otherwise is in the low state (0).

Piezoelectric Transducers

Piezoelectric transducer is device that can transform one state of energy to another with a help of using the piezoelectric properties of certain crystals or other materials. When the materials are subjected to force or stress, it generates an electrical potential or voltage proportional to the magnitude of the force. High sensitivity of piezoelectric transducers is very useful in microphones, where they can convert sound pressure into electric voltage and vice versa. Figure 2. 8 the construction of piezoelectric transducersChapter three


The methodology has been divided as two main parts. They are PWM controller design and Voltage regulator. For the PWM controller design the Chosen IC was TL494, which consist of error amplifier, dead-time comparator and PWM comparator. Where the Voltage regulator circuit is a simple circuits using IC7812.

Pulse Width Modulation (PWM)

To design a Pulse width modulation controller, there are no special components needed. Only the TL494 PWM controller circuit used in their standard application circuit shown in figure 3. 1 below. Figure 3. 1 Pin connection of TL494The TL494 has an internal-linear saw tooth oscillator. The frequency of oscillator can be controlled by varying the resister RT and capacitor CT. The approximate oscillation frequency can be determined by given below. For the CT = 0. 1 µF, 0. 01 µF, 0. 001 µF in 15 volt VCC, the changes in frequency versus resister shown below in figure 3. 2. According to the graph bellow the suitable capacitor would be 0. 1 µF. Figure 3. 2 Oscillation frequencies versus resistanceThe output pulse width modulation is produced by comparison of the of the saw tooth waveform across capacitor CT to either of two control signal by comparator inside the Tl494.

Voltage Regulator

The whole sound systems need a two power source to power up the circuits. At first 12 V to supply the PWM modulator and the MOSFET driver IR2111 and another 24 V supply to fed MOSFET so, the piezoelectric transducers will work properly. The chosen voltage regulator is LM7812 3-terminal positive voltage regulator. According to the Data sheet input range of the voltage regulator is 5 volt to 24 volt and the output range is 5 volt to 18 volt. And when the input volt is 24 volt the output volt is approximately 14 volt. Figure 3. 3 pin assignment of LM7812

Half Bridge Driver

Figure 3. 4 Pin allocation of IR2111Chapter Four


The aim of the PWM circuit is produce Pulse width modulated audio signals. Firstly, a loud speaker level input fed in to the intergraded circuit TL494 shown in figure 4. 1 below. The audio is filtered by using 100 nF ceramic capacitor CT to remove any DC from input signal. PWM is created by comparing the input signal with the saw-tooth wave which is created by oscillator. The saw-tooth frequency can be controlled by varying the value of RT at terminal 6. The oscillation frequency decides the frequency of the pulse hence the frequency of the sound produced. The input will apply through the terminal 3 and 4. The PWM comparator compares the input with saw-tooth from oscillator. Figure 4. 1 Block diagram of TL494The output of the comparator then goes through an AND gate for output control. The output from the AND gates drives the transistors which gives an output terminal C1/C2 at pin 8/11 and terminal E1/E2 at pin 9/10 respectively. Figure 4. 2 Internal circuit of IR2111Terminal E1 and E2 are the two outputs (one external output) of this circuit and the chosen terminal E1 applied to the input of half bridge driver IC IR2111(Figure 4. 2 shown below) at the terminal of HIN (high input) and LIN (low input) at pin 10 and 12 respectively. The output of the IC IR2111 at terminal HO (high output) and LO (low output) will be fed in to the MOSFET’s. Figure 4. 3 final CircuitThe schematic of two channel PWM modulator above in figure 4. 3, the circuit has two outputs A and B, each drive an array of piezoelectric transducers. Each output able to drive 200 piezoelectric transducers. In this project have made use of only a one output and fed to drive a only 50 piezoelectric transducers. The gates of the MOSFET control the path of circuit. When the gate voltage is high the channel is open and the current flows. When the gate voltage of transistor Q


Chapter Seven


Chapter Eight