BY NAMIK CIBLAK Department of Mechanical Engineering Yeditepe University Dec 24, 2015ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 1 All images from unless otherwise is indicatedwww.wikipedia.com

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 2 ProductionConsumption Music Box 1600 Phonograph 1899 Compact Cassette Musicassette (MC) Audio Tape (Mechanical) (Magnetic) 1962 Optical Disc Compact disc (CD) DVD, Blu-Ray (Optical) s Digital Audio Recorders Software On-Demand Types 1970s (Semiconductor) Dec 24, 2015

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 3 The acoustic waves are converted into mechanical motion which is then inscribed onto a surface. Mechanical: LP record grooves ( Frances Densmore recording Blackfoot chief Mountain Chief on a cylinder phonograph for the Bureau of American Ethnology (1916) Dec 24, 2015

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 4 The acoustic waves are converted into mechanical motion which is then converted into an electrical signal. Electronic and Magnetic: Microphones Storage MAGNETIC The electrical signal is used to change the magnetization of a tiny region on the surface of a rigid or flexible medium coated with magnetically active material. OPTICAL The electrical signal is used to change the optical properties of the storage medium which is usually has form of a disc. These can be analog or digital. SOLID STATE MEMORY OR SOFTWARE FILE The electrical signal is digitally processed and stored in memory devices using semi-conductor technologies, usually as software files. Dec 24, 2015

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 5 The inscription on a surface mechanically excites a sensor (usually a needle or pin) which, in turn, vibrates a membrane. In music boxes the pins themselves vibrate and generate the sound. Mechanical: Older Phonographs: Two Edison cylinder records (left and right) and their cylindrical cardboard boxes (center) Disc records and cylinders Close-up of the mechanism of an Edison Amberola, manufactured around 1915 Dec 24, 2015

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 6 Electromechanical: Loudspeakers (speakers) Electrical signals are converted into mechanical motion of membranes Woofers Mid-range driver Tweeter Diaphragm (membrane) Suspension (springs) Voicecoil Magnet Dec 24, 2015

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 7 Sound fidelity refers to the degree of closeness of the recorded and replayed sound to its original source, the live performance, in every aspect. The common modern abbreviation is Hi-Fi, referring to “high fidelity”. There are three main contributors, electrical or mechanical, to lower sound fidelity:  Noise. This is an unwanted and meaningless signal, usually random, added to the original signal by the recording and replay components. Sources of may vary from the mechanical or electrical parts of a microphone, to those of speakers, to simple electrical wires, to inaccuracies in LP groves, and so on.  Loss of frequency content. Due to limited dynamics of all involved components, some regions of the frequency spectrum may be modified or lost altogether. For example, even a good microphone or a speaker has operating frequency limits. Further, even in the operating range, not all frequencies are sensed with the same sensitivity.  Distortion. This is again due to the limited dynamics, electrical or mechanical. In this, both frequency spectrum and time-domain intensities are damaged. Dec 24,

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 8 Recording medium has an impact on the sound fidelity. Reel-to-reel audio tape recording: was one of the earliest successes in achieving high sound fidelity. The finest and inexpensive version of this technology is the well known compact cassette. 33⅓ rpm Long Play (LP) microgroove vinyl records. These marked another revolution in music industry. The grooves of modern LPs had a variable size, which acted as an equalizer, reducing volume of low frequencies while increasing the higher ones within the 20 Hz – 20 kHz range. Optical media (analog and digital CDs) was later able to achieve very high fidelity levels. The dynamic range of such modern media is 10 Hz to 22 kHz. Today, there are many digital lossless formats with ability to record beyond the hearing range of humans. However, usually we use lossy formats in an attempt to reduce file sizes. Dec 24, 2015

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 9 PCM, LPCM: [Linear] Pulse-Code Modulation. In this method, the analog signal is simply sampled at certain time intervals and quantized to the closest digital value. This is raw format used in Audio CD, WAV files (Windows), AIFF files (Mac OS), AU files (Sun Microsystems), VOB files (DVD media) Dec 24, 2015 BWF (Broadcast Wave Format). First introduced by European Broadcasting Union, based on WAV. It is now widely used in radio, television, and film industries. The only losses in uncompressed audio file formats occur in the digitization stage, which is reduced by decreasing the sampling time, or, equivalently, by increasing the sample size.

ME485 - Theory & Engineering of Music - Yeditepe University - Namik Ciblak 10 Dec 24, 2015 The uncompressed audio files can be too large for storing and transmission. There are mathematical methods that can compress the a file, which can then be decompressed before replay. Compression may result in some loss of information or may not. LOSSLESSLOSSY FLAC Free Lossless Audio Codec MP3 MPEG Audio Layer III WavPack Free and open source.ra (RealAudio).ape Monkey's Audio VOX (Dialogic ADPCM) Used in digital telephony ALAC Apple Lossless WMA (Windows Media Audio) Lossy and lossless There are many others!