MAE 546 Final Project Interferometry-based optical fiber microphone using graphene diaphragm Introduction of conventional microphones and optical fiber microphone Microphone is a kind of device which includes an acoustic-to-electric sensor that converts sound into electrical signals. Conventional microphones use the mechanism of electromagnetic induction (dynamic microphone) or capacitance change (condenser microphone). Microphones have a great many of applications in our daily lives such as telephones, hearing aids, engineering, radio and television broadcasting, speech recognition and so on. Instead of sensing changes in capacitance or magnetic field as with conventional microphones, optical fiber microphone converts acoustic waves into electrical signals by sensing changes in light intensity. It can achieve a large dynamic and frequency range, compared to high fidelity conventional microphones. A great advantage of optical fiber microphone is no reacting to or influenced by any electrical, magnetic, electrostatic or radioactive fields. Therefore it is ideal for use in areas where conventional microphones are ineffective or dangerous, such as industrial turbines or magnetic resonance environment. Also optical fiber microphone is resistant to environmental changes in temperature and humidity, and can be fabricated for any directionality. The distance between the microphone's light source and photodetector can be several kilometers without using any preamplifier or other electrical device, which makes optical fiber microphones suitable for industrial acoustic monitoring. Possessing those qualities, optical fiber microphones are used in some specific applications such as infrasound monitoring and noise-canceling. They have ... ... middle of paper ... ...)/(3r^4 (1-σ^2 )D(∂I/∂X)) The fundamental resonance frequency f of the graphene diaphragm can be expressed as f=t/(2πr^2 ) √(E/(12ρ(1-σ^2))) The microphone sensitivity is given by ∂X/∂P×∂I/∂X and the unit is W/Pa. The displacement sensitivity ∂I/∂X could be determined by the optical properties of fibers and need to be measured. From previous research, the measurement can be done by mounting fibers on a manually controlled micrometer translator and then placed close to a mirror mounted on a piezoelectric transducer. Advantages and Discussion The ultra-small thickness of graphene could significantly improve the pressure sensitivity of the FPI sensors. In addition, graphene has much better mechanical strength than other thin film materials including metal and silica and could bear a static pressure up to MPa. Discussion Shadowing effects of the microphone.
The purpose of this experiment was to determine whether if the sound is affected when it travels through different length pipes. The method used to do this experiment was created by using 5 different PVC pipes in the lengths of 10, 20, 30, 40, and 50 centimeters. Then, using a tuning fork, sound will be produced on one end of the PVC pipe and measured with a decimeter on the other end. This experiment was recorded using 5 trials for each independent level and the average decibels (dB) for each pipe length were recorded.
Although AT&T brought in fiber optic technology in 1979, they weren’t the first company to think of such a creative idea. The conception of interchanging data by making use of light was the idea of by Alexander Graham Bell in 1800s. Bell always thought of the prospective that pulses of light can transfer voice signals, but on no account Bell had a reliable light source to experiment on the idea (Cheo, P. 1990). In 1880, Bell patented-- the Photophone—a phone which operates by means of optical transmission. Unfortunately, Bell’s invention was of no success for the reason that it applies air as the mode of transmitting light instead of the glass fibers that are applied today. Copper wire was basically more dependable than Bell’s device at the point, causing his Photophone to fail (Hecht, J. 1999).
The instrument that will be analysed in this report is the acoustic guitar. An acoustic guitar is any guitar that uses acoustics as a means to transmit the strings vibrational energy to the air to produce a sound. The sound from an acoustic guitar is initiated by the strings. When plucked with the fingers or a plectrum it creates vibrational energy which is then transferred to the soundboard or soundbox. Without the soundboard the string alone would not be able to produce much sound as it would just cut through the air without causing much disturbance, but since the soundboard is large and flat it moves the air easier, this process is called mechanical impedance matching. This increases the systems energy transfer efficiency and produces a much louder sound.
The ideal matching layer thickness is 14 the wavelength.... ... middle of paper ... ... There are many different types of transducers.
2013. The. Recording Manual - Construction. [online] Available at: http://www.johnlsayers.com/Recmanual/Titles/Acoustics3.htm [Accessed: 25 Nov 2013].
The sound waves from the caller's voice cause the plastic disk to vibrate, changing the distance between the disks, thus changing the intensity of the electric field. These variations are translated into an electric current which travels across the telephone lines. The receiver of a telephone is composed of a flat ring of magnetic material. Underneath this magnetic ring is a coil of wire where the electric current flows. Here, the current and magnetic field from the magnet cause a diaphragm between the two to vibrate, and replicate the sounds that are transformed into electricity.
Through out the history of music, acoustics have played a major role. After all if it were not for acoustics the quality of sound that we know today would not exist. The word acoustics comes from the Greek word akouein, which means, “to hear”(Encarta Encyclopedia). Since music has to be heard in most cases for enjoyment, acoustics obviously take on a very important role in the pleasure that music brings to the ear. Acoustical architecture and design are two key elements in the way music sounds. For example, an electric guitar played in a concert hall would sound very different compared to the sound produced in a small room. These differences can be explained by the acoustical design of the room and the reverb created by both the instrument and the room in which it is played. These differences signify the importance of acoustics in music.
The history of audio recording first started on 6th December 1877 when Thomas Edison made the very first recording of a human voice singing Mary had a little lamb “on the first tinfoil cylinder phonograph” (Schoenherr, 2005). Later that month John Kruesi built the first practical machine using this equipment from a sketch given by Edison, however it was Edison and his tinfoil phonograph which was the first to succeed in recording the human voice.
Fingering and Acoustic Schematic. n.d. Diagram. University of New South Wales, Faculty of Science. Academic Press, 2001. Web. 13 Sept. 2011.
As transistors get smaller and smaller, silicone transistors are shrinking rapidly to nearly atomic scale. As silicone transistors reach that size, it starts to become ineffective. Transistors has reached a saturation limit, where if made smaller electrons cannot be stopped from source to drain. Graphene now comes into the pictures. Graphene, is the hot topic that every physicists, material scientists, and electrical engineers have been talking about. Why did it garner such popularity in the scientific world, and deserve a Nobel Prize? One, out of many great future application of Graphene is further the shrinkage of transistors. Dominated in a world of silicone transistors, as it is being shrunk to near atomic sizes there emerges many limitations; one of which is the halt of further improvement in transistor speed. Graphene is composed of single carbon atoms bounded together to form a flat hexagonal plane, where one carbon is at each of the six corners. Multiple hexagonal shapes are connected together to form a plane. The “miraculous” physical aspect of this composition allows the e...
Ultrasonic is the universally accepted technique to study the physico-chemical properties of the liquids, liquid mixtures, electrolytic solutions and polymeric solutions. Liquids, liquid-mixtures and solutions find wide applications in medical, pharmaceutical, chemical, lather, textile, nuclear and solvent, solution related industries. The study and understanding of the thermodynamic properties of liquid mixtures and solutions are more essential for their applications in these industries. The measurements of ultrasonic velocity in the combination of density and viscosity have been used to study the molecular interactions in liquid mixtures and solutions.
“Sound or acoustic energy involves the actual vibration of the actual material through which it passes and thus, in general, propagates best through solids and liquids, less well in gasses and not at all in a vacuum” (Wright et al., 1995, p. 70)
This paper is limited to noise nuisance in domestic dwellings and not industrial noise control and the aim is to identify the new technologies for noise control in buildings and how they effectively work to control noise in buildings .
The acoustic speech signal itself can be analysed by creating spectrograms. Each speech signal contains information across multiple frequencies which, when charted on a spectrogram, tend to form bands known as formants. Initial attempts to understand speech percep...
After reading the first paragraphs you may be wondering why are acoustic waves so important in normal life or “why would I ever need this equation?’ Acoustic waves are important because sound is all around us. When you think of the word “acoustic” a few words may come to mind. Guitars, stereos, and many other items involve acoustic waves. For example, when the bass on a stereo is turned all the way up you m...