Converting an analog signal to a digital one. Sampling rate 4/6/2018. What is an effective way to transmit information?

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1 What is an effective way to transmit information? Converting an analog signal to a digital one What does the signal look like that is sent? As quick as you can transmit the waveform and then letter-number code telephone game-style V667G893474L If a signal is going to be transmitted over a distance, absorbed and reemitted several times by different devices, what would be an effective way to transmit it? How can a waveform be described by numbers? come up with a method to describe this wave as best they can using only numbers. Code, send and uncodea wave What made a good system? Sampling rate HD vs SD (now probably HD vs 4K) Wav vs mp3 vs flac Record vs CD Analog vs digital What problems did groups have in developing their systems? What could you do to be more accurate in your transmission? Would there be any disadvantages to this? analog waves can be effectively represented by a system of numbers. 1

2 Binary Code and Hexadecimal What are binary #s Binary in 60 sec The Imitation Game, Alan Turing, and The Bombe Hexadecimal 6e6WkFQ More on Enigma Flaw in Enigma Coding HTML of a website (my homepage) HTML to binary Copy a section or all of your HTML code, paste it here, and see the 1 s and 0 s. Adjust your model to account for how the sound of your voice is captured, turned into an electrical wave, and then becomes a digital signal in your phone. What is done to the wave? How? What system is used? Advantages and disadvantages? Wave speed and Sound Review of wave basics Speed of sound and resonance (to supplement the simulation and resonance lab) 2

3 Vibrations and Waves Vibration a wiggle in time Wave a wiggle in space and time ; a disturbance that travels through a medium from one location to another location Back and forth vibratory motion = oscillatory motion. The oscillatory motion of a pendulum is an instance of simple harmonic motion. Period the time of a back and forth swing. (Time/vibrations) Depends only on the length of the pendulum and the acceleration of gravity. A pendulum makes 20 vibrations in 40 seconds. Calculate its period. Wave Description A pendulum swinging over a moving piece of paper will trace out a sine curve. home Wavelength the distance between successive identical parts of the wave (crest to crest, for instance). Frequency how frequently a vibration occurs. A complete back and forth vibration is one cycle. Hertz (Hz) the unit of frequency. One cycle per second = 1 Hz Two cycles per second = 2 Hz Wave Motion The source of all waves is something that vibrates The frequency of the vibrating source and the frequency of the wave it produces is the same. If the frequency is known, then the period can be determined (and vice versa). Frequency = 1/period Period = 1/frequency Waves transfer energy, not matter between two points. The energy is carried by a disturbance in the medium, not by matter moving from one point to the other. What do trials 1-5 tell you? What about trials 6-8? The data convincingly show that wave frequency does not affect wave speed. An increase in wave frequency caused a decrease in wavelength while the wave speed remained constant. Wave Speed The speed of a wave depends on the medium through which it is moving. Sound travels through air at ~ 330 m/s Sound travels 4 times faster in water. Wave speed = frequency x wavelength v = fλ If they are produced at the same time, high frequency sounds (small wavelength) reach your ears at the same time as low frequency sounds (large wavelengths). Wave recap "a waveis a disturbance moving through a medium. Medium could be water, air, a rope, a slinky and are distinguished by their properties (material, density, temperature, elasticity, ect) These properties describe the material not the wave itself Waves are distinguished from each other based on amplitude, frequency, wavelength 3

4 Wave speed wave speed depends upon the medium through which the wave is moving. Only an alteration in the properties of the medium will cause a change in the speed. CYU TRUE or FALSE: Doubling the frequency of a wave source doubles the speed of the waves. FALSE!The speed of a wave is unaffected by changes in the frequency. Solve for wave speed Solve for wave speed 3.5 m/s 3.5 m/s 2.5 m/s 2.5 m/s 2.1 m/s 2.2 m/s CYU increases, its speed will Decrease Remain the same increases, its frequency will Decrease Remain the same CYU increases, its speed will Decrease Remain the same, the speed of a wave is not affected by the wavelength of the wave increases, its frequency will Decrease, wavelength and frequency are inversely proportional to each other Remain the same 4

5 Transverse and Longitudinal Waves Transverse wave the motion of the medium is at right angles to the direction in which the wave travels. Longitudinal wave the motion of the medium is along the same direction in which the medium travels. The Origin of Sound All sounds are produced by the vibrations of material objects. Vibrating material sends a disturbance through a medium (usually air) in the form of a longitudinal wave. Under normal conditions, the frequency of the source = the frequency of the waves produced. Pitch our subjective impression of the frequency of a sound. People with normal hearing can perceive pitches with frequencies from 20 Hz to 20,000 Hz. Infrasonic sound waves with frequencies below 20 Hz. Ultrasonic sound waves with frequencies above 20,000 Hz. Speed of Sound Distance and time Wavelength and frequency Characteristics of the material the sound is traveling in Speed of Sound In air, sound travels about 330 meters per second. Water vapor in the air increases this speed slightly. d temperature also increases this speed. Each degree increase above 0 o C increases the speed of sound by 0.60 m/s. Sound travels 4 times faster in water than in air and 15 times faster in steel than in air. Sound travels faster through elastic materials than inelastic materials. Elasticity the ability of a material to change shape in response to a force and then regain its initial shape. Example: Steel Example of an inelastic material: putty Speed of Sound in Air Sound Travels Faster in Hotter Air v = (0.60 C) At 25 C v = ( ) v = =

6 At -25 C tubes v = ( ) v = ( 15) = Resonance Natural Frequency of Vibration The frequency or frequencies at which an object tends to vibrate with when hit, struck, plucked, strummed or somehow disturbed is known as the natural frequency of the object. Forced Vibration Resonance Chalkboard Tuning Fork 6

7 Tacoma Narrows Bridge Resonance Examples Breaking Wine Glass N0E&feature=related STOMP Resonance w/ Julius Sumner Miller Bn70PpbrM Lab and important equations! Tube Closed at One End Tubes Open at Both Ends wavelength = 4 times the length of the tube λ = 4 L wavelength = 2 times the length of the tube λ = 2 L 7