Overview of Recording & Storage

Overview of Recording & Storage - Overview of...

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Unformatted text preview: Overview of Recording Fall 2007 07/24/11 07/24/11 The Science of Music 1 ELECTROSTATIC RUBBINGS Think about this stuff dead cat - 07/24/11 07/24/11 - - + The Science of Music - + - - 2 Electrical Charge The negative charge is identified with electrons. Electrons can be “pushed around” wired (circuits) with the use of a battery. “Resistors” impede this “current” Ohm’s Law: V=iR Electrons are components of atoms. An Atom contains a nucleus of protons and other junk. The protons are the fundamental positive charges. 07/24/11 07/24/11 The Science of Music 3 Various Kinds of Electrical Materials Conductors Electrons move easily Some are poor conductors – Resistors! Insulators 07/24/11 07/24/11 Electrons are held tightly in place by their chemical bonds. The Science of Music 4 Charge stuff Potential Difference or Voltage Current 07/24/11 07/24/11 The work per unit charge required to move a charge from one point to the other The amount of charge that passes a single point in a circuit per unit time (1 sec). The Science of Music 5 Plus … Resistance 07/24/11 07/24/11 The ratio of the potential difference across a resistor (R=Ohms) to the current flowing THROUGH the resistor. This is Ohm’s Law The Science of Music 6 A Magnet S N 07/24/11 07/24/11 The Science of Music +Q OP Survey 7 M agnets come i n al l shapes and si zes. Al most ever y r efr i ger ator door has two to pr ovi de that l ast, snug pul l when i t cl oses. 07/24/11 07/24/11 The Science of Music 8 07/24/11 07/24/11 The Science of Music 9 07/24/11 07/24/11 The Science of Music 10 A Changing Magnetic Field Induces a Current 07/24/11 07/24/11 The Science of Music 11 Magnets Magnets Do NOT attract chages. Magnetism is a very different phenomenon. Magnets have N and S poles Like poles repel Unlike poles attract Where have we seem this before?? 07/24/11 07/24/11 The Science of Music 12 Other Observations A magnet moving into a coil produces an electric current (and voltage!). A wire moving near a magnet will have a current generated in it. There is a “magnetic field” around a wire. A loop of wire acts like a small magnet. 07/24/11 07/24/11 The Science of Music 13 07/24/11 The Science of Music 14 What Reached the Ear? This is an ANALOG signal. The ear doesn’t respond to digital signals. 07/24/11 07/24/11 The Science of Music 15 The Process Analog Source Digital Storage Convert to Analog Retain Analog Speaker 07/24/11 07/24/11 Analog Storage The Science of Music Speaker 16 Storage Methods Analog Storage Mechanical Electrical (Record, cylinder) Magnetic (Tape, Wire) Digital Storage 07/24/11 07/24/11 Magnetic (Tape) Optical (CD) Electrical (MP3 file on your “Flash Memory”) The Science of Music 17 Issues We want the process to be fast. We want to be able to widely distribute the recorded product. We want the product to reproduce, as well as possible, the original sound. We want to ENJOY the final reproduction. 07/24/11 07/24/11 The Science of Music 18 OLDEN DAYS – (Screech of Chalk) d oun S n ma Hu ar E 07/24/11 07/24/11 Bell's ear Phonautograph was a very unusual variation on the basic technology. The recording mechanism was the human ear. By removing a chunk of skull including the inner ear from a human cadaver, and attaching a stylus to the moving parts of the ear, he was able to use this bio­mechanical device to make a recording of the sounds that entered a recording horn. It recorded on a moving glass strip, coated with a film of carbon, so there are probably no original recordings from it. The Science of Music 19 Gramophone The graphophone in its original form was an improved form of the phonograph. One main difference, which Edison would soon adopt, was the use of a cardboard­coated wax cylinder instead of a sheet of tinfoil. The exact construction of the cylinders and the materials used changed considerably in later years, though the basic concept of recording into a soft, plastic material was retained. (image from NMAH) 07/24/11 07/24/11 The Science of Music 20 Development ­ Platter 07/24/11 07/24/11 The Science of Music 21 “HIS MASTERS VOICE” 07/24/11 07/24/11 The Science of Music 22 Western Electric Western Electric's recorder used electronic amplifiers to drive an electromagnetic cutting head, rather than relying on the acoustic horn. The result was a louder, clearer record. 07/24/11 07/24/11 The Science of Music 23 The Need for the Microphone 07/24/11 07/24/11 The Science of Music 24 An Old Carbon Microphone 07/24/11 07/24/11 The Science of Music 25 The Microphone The microphone is a device that received the sound vibrations converts it to an electrical “signal” Which is then sent to the next stage in the process (later). The signal tends to be small and gets weaker as it travels down a long wire. 07/24/11 07/24/11 The Science of Music 26 The Microphone Process MECHANCAL ­­­> ­­­­­­­­­­­­­­­ ELECTRICAL Microphone 07/24/11 07/24/11 The Science of Music Signal on a wire 27 Consider a powder of metal Particles of Metal are pressed closer together. 07/24/11 07/24/11 Resistance is reduced28 The Science of Music How does it work? 07/24/11 07/24/11 The Science of Music 29 The “Crystal” Microphone 07/24/11 07/24/11 The Science of Music 30 The Record 07/24/11 07/24/11 The Science of Music 31 07/24/11 07/24/11 The Science of Music 32 Dynamic Microphone 07/24/11 07/24/11 The Science of Music 33 Movies?? Stretched Horizontally 07/24/11 07/24/11 The Science of Music 34 1920 Wire Recorder 07/24/11 07/24/11 The Science of Music 35 1930s Magnetic Tape 07/24/11 07/24/11 The Science of Music 36 07/24/11 07/24/11 The Science of Music 37 Playback 07/24/11 07/24/11 The Science of Music 38 Today 07/24/11 07/24/11 The Science of Music 39 CD 07/24/11 07/24/11 The Science of Music 40 CD 07/24/11 07/24/11 The Science of Music 41 CD OPERATION 07/24/11 07/24/11 The Science of Music 42 Latest and Greatest Many GB FLASH 07/24/11 07/24/11 The Science of Music 43 How do you squeeze all of that stuff on one iPOD? Compression! Standard CD records about 74 minutes of music. This fills 780 MB … almost a GIG! Compression makes use of what we know about our heads. 07/24/11 07/24/11 The Science of Music 44 What do we know? If there are two tones sounding at the same time and one is much louder than the other, we would only hear the louder one. So omit the data for the softer sound. Omit other sounds that we probably won’t hear. Give up a little in fidelity. This will allow a 5 fold reduction in storage space. 07/24/11 07/24/11 The Science of Music 45 Back to your head 07/24/11 07/24/11 The Science of Music 46 07/24/11 07/24/11 The Science of Music 47 07/24/11 07/24/11 The Science of Music 48 Exploded View 07/24/11 07/24/11 The Science of Music 49 FULL CIRCLE! 07/24/11 07/24/11 The Science of Music 50 ...
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